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Introduction IGBT and MOSFET are fully controlled devices and are voltage-driven, that is, the device is turned on or off by controlling the gate voltage. In fact, the structure of the IGBT is an NPN-type MOSFET plus a P-junction, that is, an NPNP structure, which is a P-type BJT driven by MOS in principle. So what is the difference between them? What is the specific connection of them? MOSFET BJT or IGBT - Brief Comparison Catalog Introduction Ⅰ MOSFET & IGBT Review Ⅱ Si IGBT vs SiC MOSFET Ⅲ Different Requirements for Si IGBT and SiC MOSFET 3.1 ON & OFF State 3.2 Short-Circuit Protection 3.3 Interference and Delay Ⅳ IGBT Working Principle by Analogy with MOSFET Ⅴ FAQ Ⅰ MOSFET & IGBT Review MOSFET is a metal-oxide-semiconductor field effect transistor, or metal-insulator-semiconductor. The source and drain of it can be swapped, and they are both N-type regions formed in the P-type backgate. In most cases, these two regions are the same, even if the two ends are reversed, it will not affect the performance of the device. Such devices are considered symmetrical. According to the polarity of its "channel" (working carrier), MOSFET can be divided into two types: N-type and P-type, usually also called NMOSFET and PMOSFET, abbreviations including NMOS, PMOS, etc.IGBT (insulated gate bipolar transistor), is a composite fully controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS. Have the advantages of high input impedance of MOSFET and the low on-voltage drop of the GTR. When the GTR saturation voltage is reduced, the current carrying density is large, but the driving current is large; the MOSFET driving power is small, the switching speed is fast, but the on-state voltage drop is large, and the current carrying density is small. The IGBT combines the advantages of the above two devices, and the driving power is small and the saturation voltage is reduced. In simple terms, an IGBT is equivalent to a thick base PNP transistor driven by a MOS. Figure 1. N-MOSFET Architecture Ⅱ Si IGBT vs SiC MOSFET Since the differences between IGBT and MOSFET in structure, working principle and application range are quite detailed, it is impossible to express clearly in one sentence. Next, we will compare the differences between silicon (Si) IGBTs and silicon carbide (SiC) MOSFETs in detail.The electrical parameters and characteristics of Si IGBT and SiC MOS drivers are quite different. The requirements for driving of SiC MOS are also different from those of traditional silicon devices. They have the characteristics of low on-resistance and small switching loss, which can reduce device loss and improve system efficiency, and more suitable for high frequency circuits. It is widely used in new energy vehicle motor controller, vehicle power supply, solar inverter, charging pile, UPS, PFC power supply and other fields.The difference between the two is mainly reflected in the GS turn-on voltage, GS turn-off voltage, short-circuit protection, signal delay and anti-interference, as follows: Characteristic Si IGBT SiC MOSFET Drive Requirements Switching Frequency Low, >30kHz High, 50~500kHz 1) Use high power gate resistors. 2) Optimize the cooling environment. 3) Improve the efficiency of the DC-DC conversion circuit and reduce the overall loss of driving power. Threshold Voltage 5V-6V 1.6V-4.5V Negative pressure shutdown/Miller clamp to prevent false turn-on Switching Time 300ns 50ns 1) Use digital isolation driver chip, the signal transmission delay can reach 50ns, and it has relatively high consistency, and the transmission jitter is less than 5ns. 2) the low transmission delay push-pull chip is selected. Switching-On Time 15V 15V~22V 1) Priority is given to stabilizing the negative voltage to ensure that the shutdown voltage is stable. 2) A negative voltage clamping circuit is added to ensure that it does not exceed the standard during shutdown. Switching-Off voltage -15V~-5V -5V~0V Short-Circuit Withstand Time <10μs 2~5μs A diode or a resistor string is used to detect short circuits, and the shortest short-circuit protection time is limited to about 1.5μs. CMTI 15kV/μs 100kV/μs 1) The common mode anti-interference ability reaches 100kV/μs to transmit the isolation chip for signal transmission. 2) The optimized isolation transformer design is adopted, and its primary side and the secondary side are shielded to reduce mutual crosstalk. 3) The Miller clamp is used to prevent the influence of the switch of the same bridge arm.   Ⅲ Different Requirements for Si IGBT and SiC MOSFET For a fully-controlled switching device, configuring an appropriate on-off voltage is of great significance for the safety and reliability of the device. Due to the difference between IGBT and MOSFET, the requirements for the two are also different.IGBT is a field-controlled device whose turn-on and turn-off are determined by the voltage between the gate(G) and the emitter(E). The working principle of MOS tube (enhancement mode NMOSFET) is to use VGS to control the amount of "induced charges" to change the condition of the conductive channel, and then to control the drain current. 3.1 ON & OFF State 1) Silicon IGBT: Silicon IGBTs of various manufacturers have the same turn-on and turn-off voltage requirements.· The typical turn-on voltage is required to be 15V.· The shutdown voltage value range is -5V~-15V, and customers can choose the appropriate value according to their needs. The common values are -8V, -10V, -15V.· Prioritize stable positive voltage to ensure stable turn-on.2) Silicon carbide MOSFET: Different manufacturers have different switching voltage requirements:· The turn-on voltage is required to be higher than 22V~15V.· The shutdown voltage is required to be higher -5V~-3V.· Prioritize negative voltage stabilization to ensure stable turn-off voltage.· Increase the negative voltage clamping circuit to ensure that it does not exceed the standard when it is turned off. 3.2 Short-Circuit Protection The switching device has the risk of short circuit during operation, and configuring a suitable short circuit protection circuit can effectively reduce the damage caused by the short circuit during the use of the switching device. Compared to Si IGBTs, SiC MOSFETs have shorter short-circuit withstand times.1) Silicon IGBTThe time of surrender and short-circuit of Si IGBT is generally less than 10μs. When designing the short-circuit protection circuit of it, set the detection delay and corresponding time of short-circuit protection to 5-8μs.2) SiC MOSFETGenerally, the short-circuit withstand capability of SiC MOSFET modules is less than 5μs, and short-circuit protection is required to work within 3μs. A diode or a resistor string is used to detect short circuits, and the protection time is limited to about 1.5μs. 3.3 Interference and Delay 1) The impact of high dv/dt and di/dt on the system.When the switching action is performed under the condition of high voltage and high current, the switching of the silicon carbide MOSFET device will generate high dv/dt and di/dt, which will affect the driver circuit. It is very important to improve the anti-interference ability of the driver circuit for the reliable operation of the system. the following way to achieve.· Add common mode choke coil and filter inductor to the input power supply, which reduce the interference of driver EMI to low voltage power supply.· A low-pass filter is added to the rectification part of the secondary side power supply, which reduce the interference of the driver to the high-voltage side.· Use an isolation chip with a common mode immunity of 100kV/μs for signal transmission.· Optimize the isolation transformer design, and use shielding layer on primary side and secondary side to reduce crosstalk between each other.· Use Miller clamp to prevent the influence of the switch of the same bridge arm. 2) Low transmission delayUsually, the application switching frequency of silicon IGBT is less than 40kHZ, and the recommended application switching frequency of SiC MOSFET is greater than 100kHz. The increase of application frequency makes MOS require the driver to provide lower signal delay time. The transmission delay of the SiC MOSFET drive signal should be less than 200ns, and the transmission delay jitter should be less than 20ns, which can be achieved by the following methods.· Using digital isolation driver chip, the signal transmission delay can reach 50ns, and it has relatively high consistency, and the transmission jitter is less than 5ns.· Select push-pull chips with low transmission delay and short rise & fall time. Due to the conductance modulation effect, the on-state specific resistance of high voltage SiC IGBTs is much lower than that of power SiC MOSs, and does not change much as the blocking voltage rating increases. When the conductance modulation effect is fully exerted, the on-state voltage drop of the IGBT drift region is only related to the bipolar diffusion coefficient and bipolar lifetime of the carriers, and will not change with the increase of the on-current. When the operating temperature changes, the on-state voltage drop of the SiC high voltage IGBT decreases with the increase of the junction temperature. This is mainly because the bipolar lifetime of the extra carriers in the SiC epitaxial layer will increase with the increase of temperature. Although the diffusion coefficient will shrink to some extent with the increase of temperature, the greater prolongation of lifetime will eventually make the the bipolar diffusion length increased, thereby reducing the on-state voltage drop. It is especially true in n-channel devices.This is in sharp contrast to the larger increase in the forward voltage drop of the power MOS at high temperature. Silicon carbide p-channel IGBTs have higher on-state voltage drop than n-channel IGBTs at the same current density due to their larger channel resistance, but their volt-ampere characteristics do not change much with temperature. As for the applications, this is undoubtedly an advantage. Figure 2. Comparison of characteristics between SiC IGBT and power MOS under the Same Condition of Withstand Voltage of 20kV. It is not difficult to calculate from the intersection of the equal power consumption curve in the figure and the on-state characteristic curves of these devices: corresponding to the same power consumption of 300W/cm2, the ratio of the on-state current of the silicon carbide IGBT to the silicon carbide power MOS versus p-channel devices and n-channel devices are different, they are 1.5 and 1.8 at room temperature, respectively, and increase to 2.7 and 3.5 at 225°C, indicating that high-voltage and high-current SiC IGBTs are more suitable for high-temperature applications.In a word, compared with Si IGBT, SiC MOSFET not only improves system efficiency, power density and operating temperature, but also puts forward higher requirements for the driver. In order to make silicon carbide MOSFET better in the system, it is necessary to give SiC MOSFET a appropriate driver.   Ⅳ IGBT Working Principle by Analogy with MOSFET IGBT is a Darlington pair composed of GTR and MOSFET: part of which is MOSFET driver, and the other part is thick-base PNP transistor. Figure 3. IGBT Architecture Its simplified equivalent circuit is shown in the figure below, and RN in the figure is the modulation resistance in the base area of the PNP transistor. It can be clearly seen from this circuit that the IGBT is a composite device of Darlington configuration composed of transistors and MOSFET, where the transistor in the figure is a PNP transistor, and the MOSFET is an N-channel field effect transistor, so the IGBT of this structure is called an N-channel IGBT, and its symbol is N-IGBT. Similarly there are P-channel IGBTs, namely P-IGBTs. Figure 4. Simplified Equivalent Circuit The electrical graphic symbols of the IGBT are shown in the figure. IGBT is a field-controlled device, and its turn-on and turn-off are determined by the voltage UGE between the gate and the emitter. When the gate-emitter voltage UCE is positive and greater than the turn-on voltage UCE (th), a channel is formed in the MOSFET and is a PNP. The N-type transistor provides the base current to turn on the IGBT. At this time, the holes (minority carriers) injected into the N- region from the P+ region modulate the conductance of the N- region, reduce the resistance RN of the N- region, and make the IGBT also has a small on-state voltage drop. When no signal or reverse voltage is applied between the gate and emitter, the channel in the MOSFET disappears, the base current of the PNP transistor is cut off, and the IGBT is turned off. It can be seen that the driving principle of IGBT is basically the same as that of MOSFET.① When UCE is negative: J3 junction is in reverse bias state, and the device is in reverse blocking state.② When UCE is positive: UC< UTH, the channel cannot be formed, and the device is in a forward blocking state; UG> UTH, an N-channel is formed under the insulating gate, and conductance is generated in the N- region due to the interaction of carriers modulation so that the device is conducting forward. Figure 5. Hybrid Switch Using Si IGBT and SiC MOSFET 1) ONThe structure of IGBT silicon is very similar to that of power MOSFET, and the main difference is that JGBT adds a P+ substrate and an N+ buffer layer, in terms of it, one MOS drives two bipolar devices (devices with two polarities). The application of the substrate creates a J junction between the P, and N+ regions of the tube. When the positive gate bias causes the inversion of the P base region under the gate, an N-channel is formed, and an electron flow occurs at the same time, and a current is generated exactly in the manner of a power MOSFET. If the voltage produced by this electron flow is in the range of 0.7V, J1 will be forward biased, some holes will be injected into the N- region, and the resistivity between N- and N+ will be adjusted, which reduces the power conduction the total loss of the pass and initiates a second charge flow. The end result is the temporary emergence of two different current topologies within the semiconductor layer: an electron flow (MOSFET current), and a hole current (bipolar). When UCE is greater than the turn-on voltage UCE(th), a channel is formed in the MOSFET to provide base current for the transistor, and the IGBT is turned on. 2) On-State Voltage DropThe conductance modulation effect reduces the resistance RN and reduces the on-state voltage drop. The so-called on-state voltage drop refers to the tube voltage drop UDS when the IGBT enters the on-state, and this voltage decreases with the rise of UCS. 3) Shut DownWhen a negative bias is applied to the gate or the gate voltage is lower than the threshold value, the channel is disabled and no holes are injected into the N-region. In any case, if the current of the MOSFET decreases rapidly during the switching phase, the collector current decreases gradually. This is because there are still minority carriers in the N layer after the commutation starts. This reduction in residual current value (wake) is entirely dependent on the charge density at turn-off, which in turn is related to several factors, such as the number and topology of dopants, layer thickness and temperature. The decay of minority carriers makes the collector current have a wake waveform. Collector current will cause increased power dissipation and cross-conduction problems, especially on devices that use freewheeling diodes.Considering that the wake is related to the recombination of minority carriers, the current value of the wake should be closely related to the Tc, IC of the chip, and has a close relationship with the mobility of holes. Therefore, depending on the temperature reached, it is feasible to reduce the undesirable effects of this current on the end equipment design. When a back pressure or no signal is applied between the gate and the emitter, the channel in the MOS disappears, the base current of the transistor is cut off, and the IGBT is turned off. 4) Reverse BlockingWhen a reverse voltage is applied to the collector, the junction is reverse biased and the depletion layer expands to the N-region. Because the thickness of this layer is reduced too much, an effective blocking ability will not be obtained, so this mechanism is very important. In addition, if the size of this region is increased too much, the voltage drop will continuously increase. 5) Forward BlockingWhen the gate and emitter are shorted and a positive voltage is applied at the collector terminal, the junction is controlled by the reverse voltage. At this time, the depletion layer of the N drift region is still subjected to the externally applied voltage. 6) LatchICBT has a parasitic PNPN thyristor between the collector and the emitter. Under special conditions, this parasitic device will turn on. This phenomenon increases the amount of current between the collector and the emitter, reduces the controllability of the equivalent MOSFET, and often causes device breakdown problems. The thyristor turn-on phenomenon is known as IGBT latch-up. Specifically, the causes of such defects vary, but are closely related to the state of the devices.   Ⅴ FAQ 1. Are there SiC IGBT?Along with the increasing maturity for the material and process of the wide bandgap semiconductor silicon carbide (SiC), the insulated gate bipolar transistor (IGBT) representing the top level of power devices could be fabricated by SiC successfully. 2. Where are SiC MOSFETs used?The primary automotive applications for SiC power MOSFETs, diodes, and modules are onboard electric vehicle (EV) chargers, DC/DC converters, and drivetrain inverters. Plug-in hybrid EVs and battery EVs (BEVs) use onboard chargers to “refuel” the vehicle battery either at home or at a public charging station. 3. What is SiC MOSFET?Silicon Carbide (SiC) MOSFETs exhibit higher blocking voltage, lower on state resistance and higher thermal conductivity than their silicon counterparts. SiC MOSFETs are designed and essentially processed the same way as silicon MOSFETs. 4. Can MOSFET replace IGBT?Due to the higher usable current density of IGBTs, it can usually handle two to three times more current than a typical MOSFET it replaces. This means that a single IGBT device can replace multiple MOSFETs in parallel operation or any of the super-large single power MOSFETs that are available today. 5. What are the advantages of silicon carbide?Silicon carbide MOSFETs have a critical breakdown strength that is 10x of silicon, and silicon carbide MOSFETs can operate at much higher temperatures, provide higher current density, experience reduced switching losses, and support higher switching frequencies. 6. What are the advantages of silicon carbide (SiC) over silicon (Si)?The advantage of SiC starts in the material itself having a 10x higher dielectric breakdown field strength, 2x higher electron saturation velocity, 3x higher energy bad gap and 3x higher thermal conductivity than Silicon. 7. What is the difference between silicon and silicon carbide?Silicon has a breakdown voltage of around 600V, while silicon carbide can withstand voltages 5-10 times higher. ... Silicon carbide can switch at nearly ten times the rate of silicon, which results in smaller control circuitry. 8. What is SiC in semiconductor?SiC (silicon carbide) is a compound semiconductor composed of silicon and carbide. SiC provides a number of advantages over silicon, including 10x the breakdown electric field strength, 3x the band gap, and enabling a wider range of p- and n-type control required for device construction. 9. Which is better MOSFET or IGBT?When compared to the IGBT, a power MOSFET has the advantages of higher commutation speed and greater efficiency during operation at low voltages. What's more, it can sustain a high blocking voltage and maintain a high current. ... The IGBT is also a three terminal (gate, collector, and emitter) full-controlled switch. 10. Why use an IGBT instead of a MOSFET?The main advantages of IGBT over a Power MOSFET and a BJT are: 1. It has a very low on-state voltage drop due to conductivity modulation and has superior on-state current density. ... It canbe easily controlled as compared to current controlled devices (thyristor, BJT) in high voltage and high current applications. 11. Why is MOSFET preferred?Mosfet provides a very good isolation between the gate and the other two terminals compared to bjt. Mosfet can handle more power compared to BJT. The mosfet has a very low power loss and a high speed. Voltage signals can easily operate a mosfet, so it is used in many digital circuits. 12. Where are MOSFETs used?Power MOSFETs are commonly used in automotive electronics, particularly as switching devices in electronic control units, and as power converters in modern electric vehicles. The insulated-gate bipolar transistor (IGBT), a hybrid MOS-bipolar transistor, is also used for a wide variety of applications. 13. Why IGBT is very popular nowadays?With its lower on-state resistance and conduction losses as well as its ability to switch high voltages at high frequencies without damage makes the Insulated Gate Bipolar Transistor ideal for driving inductive loads such as coil windings, electromagnets and DC motors. 14. How many terminals are in a MOSFET?four terminalsThe MOSFET has four terminals: drain, source, gate, and body or substrate. 15. Why is IGBT bipolar?IGBTs is a bipolar device that utilizes two types of carriers, electrons and holes, resulting from the complex configuration that features a MOSFET structure at the input block and bipolar output, making it a transistor that can achieve low saturation voltage (similar to low ON resistance MOSFETs) with relatively fast. 16. How many types of IGBT are there?two typesInsulated Gate Bipolar Junction Transistor (IGBTs) are normally classified into two types. (ii) Punch Through [PT-IGBT]. These IGBTs are also referred to as symmetrical and asymmetrical IGBTs. These varieties of IGBT differ widely with regard to their fabrication technology, structural details etc. 17. What is full MOSFET?MOSFET stands for metal-oxide-semiconductor field-effect transistor. It is a field-effect transistor with a MOS structure. Typically, the MOSFET is a three-terminal device with gate (G), drain (D) and source (S) terminals. 18. How does an IGBT work as a switch?As defined by being a transistor, an IGBT is a semiconductor with three terminals which work as a switch for moving electrical current. Just as the word “gate” suggests, when voltage is applied to the gate, it opens or “turns on” and creates a path for current to flow between the layers. 19. Can I use transistor instead of MOSFET?It very much depends on the application. BJTs can be cheaper than FETs. This is especially true for high voltage switching where the much larger die area of FETs make them much more expensive. 20. Can IGBT conduct in reverse direction?No. The IGBT cannot conduct current in the reverse direction (from emitter to collector) even with a positive Vge applied to it, because it has a bipolar-type structure. ... However, the gate has no control over this reverse current flow; it is simply the forward biasing of the diode that allows it.

CatalogIntroductionⅠ What is a Microcontroller（MCU）?Ⅱ The History of the Microcontroller (MCU)Ⅲ The Classification and Application of MCUⅣ China MCU Technology and Well-known ManufacturersⅤ  The Basic Functions of MCUⅥ Learning Methods - Using MCUⅦ Six Main Dimensions of MCU Products for Future ImprovementⅧ Programming of MCUⅨ Summary of the MCU Programming EngineerⅩ How to Develop MCU Ⅺ 5 Tips to Solve the Questions About the MCU CrystalⅫ Summary of Chip OperationFAQIntroductionA microcontroller (MCU) is a small computer built on a single metal-oxide-semiconductor (MOS) integrated circuit (IC) chip. A microcontroller is made up of a CPU  (processor core), memory, and programmable input/output peripherals. On chip, a small amount of RAM, as well as ferroelectric RAM, NOR flash, or OTP ROM , is commonly included. Microcontrollers  , in contrast to microprocessors  used in personal computers  or other general-purpose applications, are designed for embedded applications and are made up of a number of discrete chips. This article will delve deeper into the MCU.Ⅰ What is a Microcontroller（MCU）? Microcontroller UnitThe microcontroller unit (MCU) appropriately reduces the frequency and specifications of the CPU  and integrates peripheral interfaces such as memory, counter, USB, A/D conversion, UART, PLC, and DMA. At the same time, even the LCD driver circuit is integrated on a single chip to form a chip-level computer, which can be controlled in different combinations for different applications, such as mobile phones, PC peripherals, remote controls, automotive electronics, industrial stepping motors, machines The control of the arm, etc., can be seen in the MCU.Figure 1 MCU componentsⅡ The History of the Microcontroller (MCU)Microcontroller Unit has a short history, but it has evolved quickly. Its generation and development are roughly synchronized with that of microprocessors  (CPUs). Since Intel Corporation of the United States first introduced 4-bit microprocessors  in 1971, its evolution can be roughly divided into five stages. The following is an overview of the development of Intel's MCU.1971-1976  The initial stage of MCU developmentIn November 1971, Intel introduced the Intel 4004, a 4-bit microprocessor with an integration level of 2000 transistors/chips and equipped with RAM, ROM, and shift registers, which served as the first MCS-4 microprocessor. The Intel 8008 8-bit microprocessor was introduced, followed by other 8-bit microprocessors  from various companies.1976-1980  Low-performance MCU stageThe MCS-48 series, introduced by Intel Corporation in 1976, has a monolithic structure that integrates an 8-bit CPU.  an 8-bit parallel I/O interface, an 8-bit timer/counter, RAM, and ROM on a semiconductor chip. Its addressing range is limited (no more than 4 KB), there is no serial I/O, the RAM and ROM capacity is limited, and the interrupt system is simple, but its functions can meet the needs of general industrial control and intelligent instruments and meters.1980~1983  High-performance MCU stageHigh-performance 8-bit microcontrollers introduced at this stage typically include serial ports, multi-level interrupt processing systems, and multiple 16-bit timers/counters. The capacity of the on-chip RAM and ROM  is increased, and the addressing range can reach 64 KB. A/D conversion interfaces are also available on individual chips. 1983~late 1980s  16-bit microcontroller stage.In 1983, Intel introduced a high-performance 16-bit microcontroller MCS-96  series. The chip integration level was as high as 120,000 transistors/chips due to the use of the most recent manufacturing process.1990sCPUs are developing to a higher level in all directions, such as integration, function, speed, reliability, and application fields. Ⅲ The Classification and Application of MCUMCUs are classified into two types based on their memory type: those with no on-chip ROM  and those with on-chip ROM,  The chip without on-chip ROM  must be used externally with EPROM (typically 8031); the chip with on-chip ROM  is classified as on-chip EPROM (typically 87C51), MASK on-chip mask ROM  (typically 8051), on-chip Flash (typically 89C51), and other types.MCUs are classified into two types based on their intended use: general-purpose and special-purpose. It is classified into4, 8, 16, and 32-bit MCUs based on the width of the data bus and the number of data bytes that can be processed at the same time.Figure 2 MCU product category At present, the most widely used MCU market in China is in the consumer electronics  field, followed by the industrial field and the automotive electronics  market. Consumer electronics  include home appliances, televisions, game consoles, and audio and video systems. Industrial fields include smart homes, automation, medical applications, and new energy generation and distribution. The automotive field includes automotive powertrains and safety control systems. Industrial MCU Industrial MCU products  are primarily used for motor control operation, data acquisition control, and other functions in motor control, instrumentation, low-voltage power distribution, power tools, industrial robots, and other application scenarios.Figure 3 Electric-Vehicle-ChargerThe number of MCU devices is increasing as the complexity of industrial equipment increases. Consider industrial robots: at least ten MCU products  are used in a single industrial robot.Home Appliance MCU MCU is widely used in household appliances, mainly used to realize system control, motor control, panel display control, and other functions.The home appliance market is mainly divided into small household appliances and everyone electricity, small household appliances including kitchen appliances (microwave oven, induction cooker, soybean milk machine, etc.), household appliances (vacuum cleaner, electric fan, electric heater, etc.), personal life small household appliances (electric toothbrush, hairdryer, etc.), everyone electricity mainly for air conditioning, refrigerator, washing machine, and other white appliances.Figure 4 Induction-heating-cooker-app-block-diagramAt the moment, 32-bit MCUs have become the market's mainstream due to their higher specifications and performance, as well as their constantly decreasing cost, and are widely used in automotive electronics.  industrial control/medical, and other fields; however, there are still a large number of application scenarios requiring simple control, and low-value MCUs have cost advantages, so they continue to occupy a large market.BitApplication4Calculator, auto instrument, auto anti-theft device, pager, wireless phone, CD player, LCD dynamic controller, children's toys, scales, chargers, Tire gauge, thermometer, remote control, etc8Electrical appliances, ammeter, motor controller, electric toy machine, pager, fax machine, telephonograph, keyboard and USB, etc16Mobile phones, digital cameras and video recorders, etc32Smart home, IoT, motor and frequency conversion control, security monitoring, fingerprint identification, touch keys, Modem, GPS, STB, Workstation, ISDN telephone, laser printer and color fax machine, etc64Advanced workstation, multimedia interactive system, advanced TV game instrument, advanced terminal, etc.According to IC Insights, the global MCU market is about 16.4 billion dollars in 2019 and could reach about 20 billion dollars by 2023.The scale of China's MCU market was about 25.6 billion yuan in 2019, accounting for about 26% of the global market, with a compound growth rate of 9% from 2015 to 2019.In terms of the global market, the auto circuit accounts for 33% of the global MCU market. According to IC Insights data, the automotive MCU market space will reach $8.1 billion in 2023, the overall growth rate is considerable; At the moment, 32-bit MCUs have become the market's mainstream due to their higher specifications and performance, as well as their constantly decreasing cost, and are widely used in automotive electronics.  industrial control/medical, and other fields; however, there are still a large number of application scenarios requiring simple control, and low-value MCUs have cost advantages, so they continue to occupy a large market.Figure 5  MCU Market StructureFrom the perspective of pattern, the top five global automotive MCU market shares in 2020 were Renesas, NXP, Infineon, Texas Instruments and Microchip, accounting for 87% in total.Ⅳ China MCU Technology and Well-known ManufacturersMCU market is still dominated by overseas leaders, and Chinese high-quality manufacturers are gradually making breakthroughs in the segmented fields, and their share is expected to increase rapidly under the background of accelerated localization in China.The global MCU market is expected to grow further, with the global MCU market size reaching $16.4 billion in 2019 and $20 billion in 2023.On the demand side, improvements in automotive electrification, accelerated IoT  penetration, increased demand for intelligent frequency conversion in home appliances, rapid iteration of wearable devices, and steady growth in industrial control continue to drive the rapid growth of the MCU industry. (Using MCU as an example, the global market compound growth rate from 2020 to 2023 is 7.7 percent, and the market space is expected to be 8.1 billion dollars by 2023)On the supply side, the MCU industry is experiencing a continuous shortage due to the epidemic in 2020. Infineon, NXP.  and ST  , as well as other overseas MCU large factories, have appeared several times to dozens of times the price, with delivery times of more than 50 weeks; persistent shortages are expected to last at least through the end of 2021 and the first quarter of 2022.In terms of circuit barriers, the requirements of automobile circuits in the MCU downstream field are the highest, followed by industrial and home appliance circuits, and the relative requirements of consumer electronics  are slightly lower, according to MCU product environmental temperature, yield, and service life, and other parameters.According to the industry competition pattern, Chinese MCU manufacturers have a low market share, benefit from accelerated replacement due to stock shortages in the short term, and have ample room for improvement in the long term:The global MCU market is more concentrated, with a microchip, ST  MICROELECTRONICS, Renesas, TI, NXP  , Infineon, and other manufacturers occupying more than 80% of the market share; China's MCU market is approximately 25 billion yuan, and the total market share of domestic MCU manufacturers is less than 12%, primarily concentrated in the consumer market, which has ample room for expansion.The shortage of goods leads to the acceleration of the pace of China's MCU manufacturers, in the automotive, industrial, and consumer circuit, the pace of China's MCU certification continues to accelerate. Renesas Electronics - the world's first automotive MCU manufacturer Renesas was founded in 2003 by the merger of Hitachi Semiconductor division and Mitsubishi Electric Semiconductor division. Its main business covers automotive, industrial, communications, and other fields. Renesas is the world's first automotive MCU manufacturer, accounting for 30% of the automotive MCU market in 2020.Renesas MCU has a complete product line covering EV/HEV, powertrain, electric vehicle, vehicle dashboard, vehicle network, chassis control, ADAS, and other application fields.Microchip technology -8 bit MCU main features, acquisition of Atmel to supplement the strength of 32 bit MCUMicrochip Technology Corporation (Microchip) was founded in 1989, Microchip technology is the world's leading supplier of single-chip and analog semiconductors. The company's main business is the microcontroller, memory products, analog interface, and mixed information products, technology licensing, and so on.The products are mainly used in embedded control systems and IoT-related industries, including data processing, Medical Internet + (IoT), smart city, Industry 4.0, intelligent healthcare, etc. Major customers include Intel, Dell, Lockheed Martin, HP, Boeing, etc. STST -ARM architecture MCU king ST was founded in 1987, its products are mainly used in automotive products, computer peripherals, communication systems, consumer products, industrial automation control systems, and other aspects. Its major customers include Apple, blackberry, Bosch, Cisco, Conti, HP, Nokia, Obata, Samsung, and Western Digital.MCU vehicle grade products accounted for 32.13% of the company's revenue. St holds 8.5% of the current MCU market and is the leader in the segmented 32bitMCU  market.ST has been deeply engaged in the automotive semiconductor field for many years, and the company has a complete industrial chain, its products have a very high-cost performance ratio, and occupy a dominant position in the MCU of vehicle regulation level. Its customers include Nissan, Audi, SAIC, Tesla, and many other companies. NXP - the world's leading automotive MCU manufacturer NXP Semiconductor was founded in 2006. It was formerly the semiconductor division of Philips. NXP's main business is MCU, MPU, and other products, which can be widely used in automotive electronics  , industrial control, smart city, smart home, and wearable products. Its MCU/MPU based on the S32 automotive platform has obvious advantages in safety and efficiency and has been adopted by mainstream OEMs around the world.The industry's first crossover MCU was independently developed by NXP: I. MX RT series. Such products have been recognized by many Internet platforms (such as Amazon) for their high integration, cost performance, and security.NXP's acquisition of Freescale (founded by MOTOROLA) in 2015 gives it a deeper presence in the automotive industry. In 2020, 47% of its revenue came from vehicle MCU. At present, the company accounts for 27.8% of the global automotive MCU industry, ranking second in the world. NXP  provides complete semiconductor solutions for intelligent vehicles including automotive entertainment systems, Advanced Driver Assistance Systems (ADAS). Sino Wealth Electronics - China's largest home appliance MCU manufacturer Sino Wealth Electronic Ltd. is an MCU integrated circuit design company, the main products include 8-bit Flash MCU, 8-bit OTP/Mask MCU, 16-bit  DSP , 4-bit OTP/Mask MCU, widely used in household appliances, automotive, industrial control, security, and other fields;In the field of small household appliances, the company's competitors are mainly ABOV from Korea and Holtek from Taiwan. In the field of white household appliances, the company's competitors are mainly from Europe and America, including Renesas, NEC, TI, STM, and so on. Ⅴ The Basic Functions of MCUInternal-function diagramFor most MCUs, the following functions are the most common and basic. The description methods for different MCUs may differ, but the essence is essentially the same.1. Timer: Although there are many different types of Timers, they can be divided into two categories. The first is a Timer with a fixed time interval, which means that its timing is set by the system and cannot be controlled by the user program. The system only provides a few different types of Timers. The user program is given a fixed time interval, such as 32Hz, 16Hz, 8Hz, and so on. Because Timers of this type are relatively common in 4-bit MCUs,they can be used to implement clock, timing, and other related functions.The other type is Programmable Timer. The timing of this type of Timer can be controlled by the user's program. The control methods include the selection of the clock source, the selection of the prescale number, and the setting of the preset number, etc. There are Most MCUs have all three at the same time, and some may have one or both of them. This kind of Timer application is very flexible, and the actual use is also ever-changing. One of the most common applications is to use it to achieve PWM  output.Since the clock source can be freely selected, such Timers are generally combined with the Event Counter.2. IO port: Any MCU has a certain number of IO ports. Without IO ports, the MCU will lose the channel of communication with the outside world. According to the configurable situation of the IO port, it can be divided into the following types:Pure input or pure output : This type of IO port is determined by the MCU hardware design, and can only be input or output, and cannot be set in real-time by software.3. Directly read and write IO port: For example, the IO port of MCS-51 belongs to this type of IO port. When the read IO port command is executed, it is an input port; when the write IO port command is executed, it is automatically an output port.Program programming to set the direction of input and output: the input or output of this type of IO port is set by the program according to the actual needs, the application is more flexible, and can realize some bus-level applications, such as12C bus, various LCD, LED Driver control bus, etc.When using the IO port, this point must be kept in mind: for the input port, there must be a clear level signal to ensure that it cannot be floated (this can be achieved by adding a pull-up or pull-down resistor); and for the output port, the output state level must be Considering its external connection, it should be ensured that there is no source current or sink current in Standby or static state.External interrupts: External interrupts are a basic function of most MCUs. They are commonly used for real-time signal generation, data sampling, and state detection. Rising edge, falling edge, and level triggering are all interrupting methods. In most cases, the external interrupt is handled via the input port. If it is an IO port, the interrupt function will only be enabled when it is set as an input port; if it is set as an output port, the external interrupt function will be automatically closed (with some exceptions in ATMEL's ATiny series, where the output port can also trigger the interrupt function). The application of external interrupt is as follows:Detection of external trigger signals: One is based on real-time requirements, such as thyristor control, detection of sudden signals, and so on, while the other is based on power savings.Measurement of signal frequency:: To ensure that the signal is not missed, an external interrupt is the best option.Decoding data: To reduce design costs in the field of remote control applications, it is frequently necessary to use software to decode various encoded data, such as Manchester and PWM encoding.Button detection and system wake-up: In order for the MCU to enter the Sleep state, it must be woken up via an external interrupt. The most basic form is a button, and the level change is caused by the button's action.4. Communication interface: The communication interface provided by MCU generally includes SPI interface, UART. I2C interface, etc., which are described as follows:SPI interface: This type of interface is the most basic communication method provided by most MCUs. Its data transmission is controlled by a synchronous clock. The signals include SDI (serial data input), SDO (serial data output), SCLK (serial clock), and Ready signal; in some cases, there may be no Ready signal; this type of interface can work in Master mode or Slave mode, the popular saying is to see who provides the clock signal, the party providing the clock is the Master, and the opposite party It is Slaver.UART（Universal Asynchronous Receive Transmit）：It belongs to the most basic asynchronous transmission interface. Its signal lines only have two Rx and Tx lines. The basic data format is: Start Bit + Data Bit(7-bits/8-bits) + Parity Bit(Even， Odd or None) + Stop Bit(1~2Bit). The time occupied by one bit of data is called Baud Rate .For most MCUs, the length of data bits, data check mode (odd check, even check or no check), Stop Bit length and Baud Rate can be flexibly set through program programming. Certainly. The most common way of this type of interface is to communicate with the serial port of the PC.I2C interface: I2C  is a data transmission protocol developed by Philips. It also uses two signals to implement: SDAT (serial data input and output) and SCLK (serial clock). The biggest advantage is that multiple devices can be attached to this bus, and they can be identified and accessed through addresses; one of the biggest advantages of the I2C  bus is that it is very convenient to use software to implement through the IO port, and the data rate of its transmission is completely controlled by SCLK. To control, it can be fast or slow, unlike the UART  interface, which has strict rate requirements.5. Watchdog: Watchdoga basic configuration of most MCUs, can only allow the program to reset it but not close it (some are set when the program is burned in, such as Microchip PIC  series MCUs), while some MCUs are It is determined by a specific method whether it is turned on or not. For example, in Samsung's KS57 series, as long as the program accesses the Watchdog  register, it is automatically turned on and cannot be turned off again. Generally speaking, the reset time of the watchdog can be set by the program. The most basic application of Watchdog  is to provide a self-recovery ability for the MCU to crash due to unexpected failure.Ⅵ Learning Methods - Using MCUThe basic principles and functions of any MCU are similar. The only difference is the configuration and quantity of its peripheral function modules and the instruction system.For the instruction system, although it seems to be different in form, it is only a difference in symbols, and the meanings it represents, the functions to be completed, and the addressing modes are similar.To learn about an MCU, the first thing you need to know is its ROM space, RAM space, number of IO ports, number of timers and timing methods, peripheral function modules (Peripheral Circuit) provided, interrupt sources, operating voltage, and power consumption, etc.After understanding these MCU Features, the next step is to compare the functions of the selected MCU with the required functions of the actual project development and clarify which resources are currently required and which are not used in this project.For the functions that need to be used in the project but are not provided by the selected MCU, it is necessary to carefully understand the relevant information of the MCU, to use an indirect method to achieve it. For example, the developed project needs to communicate with the COM port of the PC, and If the selected MCU does not provide a UART  port, it can be implemented through external interrupts.For the resources needed for project development, you need to carefully understand and read the Manua*, while for the unneeded function modules, you can ignore or browse. For MCU learning, the application is the key and the main purpose.For beginners or designers who use this MCU for the first time, they may encounter a lot of ambiguous descriptions of the functions of the MCU. For this kind of problem, there are two ways to solve it, one is to write a special verification program to understand the functions described in the data; the other can be ignored for the time being. Leave it to modify and improve when debugging. The former method is suitable for projects with loose time and beginners, while the latter method is suitable for those who have some experience in single-chip development or when the project schedule is more urgent.Don't take the time to learn the command system in particular. The instruction system is simply a logical description symbol. During programming, you can only check the relevant instructions in accordance with the logic requirements of the program. As your programming skills improve, you will become more proficient in the instruction system.Ⅶ Six Main Dimensions of MCU Products for Future ImprovementStronger computing performance: MCU towards 500Mhz main frequency, MPU increase more processor cores;Additional wireless connection functions: More RF modules have been integrated.Low power consumption, high energy efficiency ratio: integrated analog chip, and low power analog peripheralsContinued support for hardware accelerators: high integration of algorithms and toolsSafety: improve anti-interference ability and safetyCost-effective: reduce costⅧ Programming of MCUThe programming of MCUs and PCs differ significantly. Although C-based MCU development tools are becoming more popular, assembly language remains the most concise and efficient programming language for designers who are efficient program code and like to use assembly.Circuit diagram to build your own microcontroller programmerThe basic framework for MCU programming is roughly the same, divided into the initialization part (the biggest difference between MCU programming and PC programming), the main program loop body, and the interrupt handler. as shown below:1.Initialization: The most basic and important step in the design of all MCU programs is an initialization, which generally includes the following:Mask all interrupts and set the stack pointer to In general, the initialization section does not want any interruptions to occur.Clearing the system's RAM and displaying the Memory: Although it is not always necessary, it is recommended to develop good programming habits for the sake of reliability and consistency, particularly to avoid accidental errors.IO port initialization: Set the input and output modes of the relevant IO port based on the project's application requirements. Set the pull-up or pull-down resistance for the input port, and the initial resistance for the output port.Interrupt setup: Enable and set interrupt trigger conditions for all interrupt sources required by the project, and close unnecessary interrupts that are not used.Initialization of other functional modules: For all peripheral functional modules of MCU that need to be used, corresponding Settings must be carried out according to the application requirements of the project. For example, Baud Rate, data length, verification mode and Stop Bit length should be set for communication of UART  , and clock source should be set for Programmer Timer. Frequency and Reload Data, etc.Initialization of parameters: after completing the initialization of MCU hardware and resources, the following is the initialization of some variables and data used in the program. This part of initialization needs to be designed according to the specific project and the overall arrangement of the program. For some applications that use EEPROM to store the number of prefab items, it is recommended to copy the relevant data to THE RAM of MCU during initialization to improve the speed of data access and reduce the power consumption of the system (in principle, access to the external EEPROM will increase the power consumption of the power supply).2.Main program loop body: Most MCUs run continuously for a long time, so their main program bodies are basically designed in a looping manner. For applications with multiple working modes, there may be many Each loop body is converted between each other through state flags. For the main program body, the following modules are generally arranged:Calculation procedures: Calculation procedures are generally time-consuming, so it is strongly opposed to processing in any interrupt, especially multiplication and division operations.Processing programs with low or no real-time requirements;Display transfer program: mainly for applications with external LED and LCD Driver.3. Interrupt handler: The interrupt program is mainly used to handle tasks and events with high real-time requirements, such as detection of external sudden signals, detection, and processing of buttons, timing counting, LED display scanning, etc.Under normal circumstances, the interrupt program should keep the code as concise as possible. For functions that do not need to be processed in real-time, the trigger flag can be set in the interrupt, and then the main program executes the specific transaction - this is very important, especially for low-power, low-speed MCUs, is necessary to ensure timely responses to all interrupts.4. There are various MCU processing methods for various task bodies.For example, for low-speed, low-power MCU (Fosc=32768Hz) applications, considering that such projects are handheld devices and use ordinary LCD, the response to buttons and display response requires high real-time performance, so generally Timed interrupts are used to process button actions and data display; for high-speed MCUs, such as Fosc>1MHz applications, since the MCU has enough time to execute the main program loop body at this time, it can only be interrupted at the corresponding Various trigger flags are set in the program, and all tasks are executed in the main program body.5. In MCU programming, special attention should be paid to:Avoid situations where the same variable or data is accessed or set in both the interrupt and the main body. The effective prevention method is to arrange the processing of such data in a module, and decide whether to execute the relevant operation of the data by judging the trigger flag; In other bodies (mainly interrupts), only the trigger flag is set where the processing of the data is required. This ensures that data execution is predictable and unique.Ⅸ Summary of the MCU Programming EngineerTo develop a good habit of summarizing, summarizing is not only a summary of their learning, but also a review and deepening of the learning process, but also to avoid the second error.Before writing the program, we should have a solid understanding of the project so that we can start with a solid idea and a general framework. It is critical to consider the layout and what makes the most sense. To determine which module should be completed first, specific steps for the module, how to name each function, and the relationship with other modules. Take a piece of paper and scribble down significant progress.For C language modular programming, we should first divide each module, a module programming, determine a sequence, and then write the next module based on the success of the previous one. When it comes to header files, write the module's header file after you've finished writing the module.Do not ignore the fact that the program must be unreasonable to comprehend its origins and find a solution. When looking for a source, it should be pertinent; you can search for relevant data on the Internet or consult with others. For example, the primary function of another project was incorporated into this project. Some functions are named multiple times. Step by step analysis of the cause, also according to the experimental phenomenon. When defining the port, the incorrect interface was selected. When you can't solve a problem, it's sometimes good to take a break. Things can go wrong no matter how simple they seemThe problems of code utilization efficiency, anti-interference, and MCU reliability continue to plague MCU application development. Ⅹ How to Develop MCU 1How to reduce program bugsThe following are the over-arching management parameters that should be considered during system operation in order to reduce program bugs.Physical parameters: These are primarily system input parameters that include excitation parameters, acquisition and processing operating parameters, and result parameters at the end of processing.Resource parameters: These are primarily the resources of the system's circuits, devices, and functional units, such as memory capacity, storage unit length, and stacking depth.These application parameters are frequently expressed as the application conditions of some single-chip microcomputers and functional units. The term "process parameter" refers to a parameter that changes in an orderly manner during the system's operation.2How to improve the efficiency of C language programming codeIt is an inevitable trend of the development and application of MCU to use C language to design MCU. If you are programming in C, it is best to be familiar with the C compiler you are using to achieve maximum efficiency. First test the number of statement lines in the assembly language corresponding to each C language compilation, so that you can clearly know the efficiency. When programming in the future, use the statement with the highest compilation efficiency. Each C compiler will have certain differences, so the compilation efficiency will also be different. The code length and execution time of an excellent embedded system C compiler is only 5-20% longer than the same functional degree written in assembly language.C language can be used for complex and time-critical projects, but the premise is that you are very familiar with the C language and C compiler of the MCU system and that you pay special attention to the data types and algorithms that the C compiler system can support. Although C is the most commonly used high-level language, the C language compilation system varies due to MCU manufacturer differences, particularly in the operation of some special function modules. As a result, if you don't understand these features, you'll have a lot of trouble debugging, which will result in lower execution efficiency than assembly language.3 How to Solve the MCU Anti-Interference ProblemThe most effective way to prevent interference is to remove interference sources and cut off interference paths, but this is often difficult to do, so we can only conclude that MCU's anti-interference ability is insufficient. While improving the anti-interference capability of hardware systems, software anti-interference has received increasing attention due to its flexible design, ability to save hardware resources, and high reliability.As for the program run fly, in fact, can also use software trap and watchdog to pull the program back to reset state, so the MCU software anti-interference is the most important to deal with the reset state.In most cases, MCU will have some sign registers that can be used to determine the reason for the reset; alternatively, you can bury some tokens in RAM yourself. Different reset causes can be determined in each program reset by judging these signs. You can also use different flags to jump directly to the corresponding program. In this manner, the program will run indefinitely, and the user will be unaware that it has been reset.4How to test the reliability of the MCU systemWhen a MCU system design is completed, there will be different test items and methods for different MCU system products, but some must be tested:lTest the completeness of the software functions of the MCUlPower-on and power-off testlAging testlTests such as ESD and EFT Sometimes, we can also simulate the damage that may occur in human use. For example, the contact port of the MCU system is intentionally rubbed with the human body or clothing fabric, thereby testing the antistatic ability. Use a high-power electric drill to work close to the MCU system to test the anti-electromagnetic interference ability.To sum up, the MCU has become an important aspect of the development and application of the computer.Most of the functions that must be realized by analog circuits or digital circuits in the past can now be realized by software methods using a single-chip microcomputer. This control technology in which software replaces hardware is also called micro-control technology, which is a revolution of traditional control technology.In addition, in the process of development and application, we must master the skills and improve the efficiency, so as to facilitate its wider use.Ⅺ 5 Tips to Solve the Questions About the MCU CrystalCrystal oscillator for MCUCommon causes of the crystal can not vibratePCB wiring error;Microcontroller quality issues;Crystal vibration quality issues;The load capacitance or matching capacitance does not match the crystal oscillator or the capacitor quality is incorrect;PCB board damp, resulting in impedance mismatch and inability to vibrate;The crystal oscillator circuit is too long;There is a line between the feet of crystal;Influence of peripheral circuit.You are advised to rectify faults one by one as follows: 1Remove the possibility of circuit error so that you can compare the recommended circuit of the corresponding type of microcontroller.2 Rule out the possibility of poor peripheral components; because peripheral components are nothing more than resistance and capacitance.3Rule out the possibility of using a crystal oscillator as a stop oscillator because you will not be experimenting with just one or two crystal oscillators.4Try changing the capacitor at both ends of the crystal; perhaps the crystal oscillator will begin to vibrate; please refer to the crystal oscillator capacitor size instructions.5In PC  B wiring, crystal oscillator circuit wiring should be as short as possible and as close to IC as possible, not between crystal oscillator feet. Ⅻ Summary of Chip OperationThe operation of the chip is mainly the operation of the registers in the chip. The registers in the chip have their unique address mapped on the memory, which is the operation of the corresponding address. To learn the chip, first look at the sequence diagram, then understand the corresponding registers, understand how to operate, define the required port (the program can recognize), write and read the operation program.Cross-sectional-views-of-chip-operationHow data is written to the chip, how it is read out, and through which port it is input or read.When connecting a chip through a bus, the first step is to understand the protocol of the bus. The chip connected to the I2c bus is controlled by the bus.1One 74HC595 lattice is used for column selection, and the other two are used for color selection. The lattice is equivalent to a set of diodes.The diode lights up only when one end is switched to a high level and the other to a low level. Just one end of the selection of different, bright different colors.Timer working mode selection: Set timer T1 in the high four digits and timer T0 in the low four digits. Then the last two characters of each mode set the working mode. When using interrupts, note that after entering the interrupt, the reset should be reset.2Serial port transceiver: Baud rate is generally set in mode 2 (automatic reloading initial value) because different devices have different data processing capabilities, the baud rate is set mainly to take care of low-speed devices and for communication between each other. The interrupt flag bit should be cleared by the software. When setting the serial port interrupt, either sending or receiving can enter the interrupt function, so pay attention to setting the interrupt function. (Self-sense generally sets a function, as the upper machine or lower machine).If you send interrupts, you have to figure out how to enter interrupts the first time, so you send them once and then you can enter interrupts. Only one byte can be sent at a time, and only after TI is set to one can the next byte be sent.3Pcf8591ad conversion, there are four channels of input, read PC  F8591, which channel, read is that channel input voltage, after the conversion of data stored in the chip, then read. Read to write the address of the chip, the son writes device address (0 x40 | channel number) and then reads the data.4Da conversion is to write the device address into the chip first, then write the sub-address (0x40) and then write the digital quantity to be converted. Device address chip information is introduced.5For the liquid crystal display, write data display, he will always display, do not continue to refresh, to change, only re-input.6For THE DS1302 clock chip, reading data is read out of the first data at the falling edge of the eighth clock when writing data, and then prepare for the next output. Pay attention to the writing of the program, but also pay attention to the position of the return value.7In Ds1302, the register is specified first, and then data is written to it. The registers on the chip data indicate the address. 8Initialization is best to write, in case you forget later. When reading or writing, the first operation is the lowest or highest bid, which can be judged according to the sequence diagram.9For the infrared transceiver, receiving, he is according to the length of time between the two falling edges to determine the high level or low level, write a program, first with the timer to determine the length of time, save, and then into binary (the program written to see more, very good).10Stepper motor: mainly used as switches, stepper motor torque decreases with the increase of speed. It is mainly used for automatic feeding of parts processing on machine tools. It can also be used in high-precision control places.Stepper motor is an open-loop control element stepper motor that converts electric pulse signal into angular displacement or linear displacement. In the case of the overload, motor speed, stop position depends only on the pulse signal frequency and pulse number, and are not affected by load change, when the stepper driver receives a pulse signal, it is driving a stepper motor according to set the direction of a fixed Angle, known as the "step Angle", its rotation is based on the Angle of the fixed step by step. The angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning. At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency, achieving the purpose of speed regulation.11Servo motor : Servo motor refers to the engine that controls the operation of mechanical components in a servo system. It is an indirect transmission device for auxiliary motors. Servo motors can control speed, position accuracy is very accurate, voltage signal can be converted into torque and speed to drive the control object. Servo motor rotor speed is controlled by the input signal, and can respond quickly, in the automatic control system, used as an executive element, and has the characteristics of mechanical and electrical time constant is small, high linearity, starting voltage, etc., can receive the electrical signal into the motor shaft angular displacement or angular velocity output. It is divided into DC and AC servo motors. Its main characteristic is that when the signal voltage is zero, there is no rotation phenomenon, and the speed decreases uniformly with the increase of torque.12Chinese Characters overview: To output Chinese characters on display or printer, Chinese characters are designed into a dot matrix graph according to graphic symbols, and corresponding dot matrix codes (glyphs) are obtained.The unified encoding for the representation of Chinese characters in the computer is called the internal code (such as national code), and the internal code is unique (equivalent to the id number of the character). The encoding of Chinese characters formed to facilitate the input of Chinese characters is the input code, which belongs to the external code of Chinese characters. The input code varies with the encoding mode and is diverse. The Chinese character code formed for displaying and printing Chinese characters is the character code, and the computer finds the character code in the character library through the character code and realizes its conversion.Machine code: According to the GB code, each Chinese character has a certain binary code, but this code will conflict with THE ASCII code when handled internally by the computer. To solve this problem, the first byte of each GB code is incremented by 1. Because ASCII code only uses 7 bits, the "1" on the first digit can be used as a symbol to identify Chinese character codes. When the computer processes the code with the first digit of "1", it will be interpreted as the information of Chinese characters, and when it processes the code with the first digit of "0", it will be interpreted as the ASCII code. After such processing, the national code (internal code) is the machine's internal code.If put this "mouth" word graphic "." With "0" instead, you can very vividly get the "mouth" glyphs :0000H 0004H 3FFAH 2004H2004H 2004H2004H 2004H2004H 2004H2004H 2004H 3FFAH 2004H 0000H 0000H. Computer to output "mouth", find shows that character first address, according to the "mouth" machine code after calculation, to find a "mouth" glyph code, and then according to the glyph code (to) in binary character generator, in turn, scan control on the screen, which is where the "0" of the binary empty, is a place where "1" swept out of the window, Then you get the character graph of the mouth.Chinese characters are arranged according to the order of national standard codes and stored in the memory in the form of binary files, which constitute the Chinese character font library, also known as the Chinese character font library, called the Chinese character library1312864 liquid crystal: Each display point corresponds to a binary number, with 1 indicating on and 0 indicating off. The RAM that stores this lattice information is called the display data memory. To display a graph or Chinese character is to write the corresponding lattice information into the corresponding storage unit.When the horizontal address = 0FH, it will be reset to 00H, but it will not automatically add one to the vertical address. Therefore, when writing multiple data in a row, the program needs to determine whether the vertical address needs to be reset14GDRAM: Drawing display RAM provides 128×8 bytes of memory space. When changing the drawing RAM, the horizontal and vertical coordinate values are successively written, and then two bytes of data are written to the drawing RAM. The address counter (AC) will automatically increment the horizontal address (X address) and reset to 00H when the horizontal address is 0XFH. Vertical addresses will not be carried automatically plus 1. The drawing display must be turned off during writing to the drawing RAM,For C, a defined variable is automatically allocated space and its address is the name of the variable. Through this name, the data can be recruited in memory, and the new data can be obtained through an operation. In assembly, the programmer needs to define the storage space and send the data to the accumulator for operation, and the programmer needs to operate every step. In C, this is done by the compiler.FAQ1. What is the main function of microcontroller?Microcontroller is a compressed micro computer manufactured to control the functions of embedded systems in office machines, robots, home appliances, motor vehicles, and a number of other gadgets. A microcontroller is comprises components like - memory, peripherals and most importantly a processor.2. What is an example of a microcontroller?The examples of 8-bit microcontrollers are Intel 8031/8051, PIC1x, and Motorola MC68HC11 families. The 16-bit microcontroller performs greater precision and performance as compared to the 8-bit.3. What are the elements of a microcontroller?Therefore, the microcontroller must also satisfy the five basic elements of input, calculation, storage, output, and control. These are called five elements of microcontrollers.4. Which is best microprocessor or microcontroller?If you need access to large amounts of really fast memory then a microprocessor is likely your best option. A microcontroller is already embedded with memory so the memory choices are fewer than with a microprocessor. The maximum amount of FLASH memory available with most microcontrollers is usually around 2MB.5. What is difference between BIOS and CMOS?The BIOS is the program that starts a computer up, and the CMOS is where the BIOS stores the date, time, and system configuration details it needs to start the computer. ... CMOS is a type of memory technology, but most people use the term to refer to the chip that stores variable data for startup.6. Is CMOS a RAM or ROM?RAM and ROM are the products, but Complimentary Metal Oxide Semiconductor (CMOS) is the process they are built in. CMOS uses two different types of transistors to achieve a lower overall power consumption.7. Whats an RTC battery?The Real Time Clock (RTC) battery provides power for the internal clock/calendar and for maintaining system configuration settings. This error can occur when a machine has been left turned-off for an extended period of time (approximately one to four months), and it is the result of a depleted RTC battery.            

Ⅰ IntroductionThis article focuses on the electronic component known as the Optocoupler. (For the fiber-optic networking component, please refer to Optical Isolators). This guide covers the fundamentals of optocouplers, their working principles, specifications, and practical examples of how to implement them in your circuits.Optocoupler Related VideoVideo: How an Optocoupler Works and Example CircuitⅡ Photocouplers, Opto-couplers & Opto-isolatorsThese devices are known by a variety of names, including optoisolator, photocoupler, and optocoupler.An optocoupler is a semiconductor device that transmits an electrical signal between two isolated circuits using light. This process ensures there is no direct electrical connection between the input (source) and the output (load), effectively protecting sensitive low-voltage components.While often used interchangeably, there is a technical distinction in the industry:Optocoupler: Typically refers to devices used to transfer analog or digital information between circuits with voltage differentials below 5,000 Volts.Optoisolator: Often refers to devices specifically designed to withstand very high voltage differentials (5,000V to 50,000V+) for safety isolation in power systems.Optocouplers are typically housed in small packages ranging from standard DIP (Dual Inline Package) to tiny SMD (Surface Mount Device) packages. Despite their small size, they play a massive role in linking data, optical encoding, and detecting position transitions on encoder wheels.They are also the core technology inside Solid-State Relays (SSR), allowing low-power logic signals to switch high-power AC or DC loads without any mechanical parts.Figure 1: Typical Photocouplers in DIP packagingⅢ Photocoupler / Optocoupler BasicsAn optocoupler consists of two main internal elements encased in a light-tight body:The Emitter: Usually a Near-Infrared LED (Light Emitting Diode) that converts the electrical input signal into light.The Detector: A photosensitive device (such as a phototransistor, photodiode, or TRIAC) that detects the light and generates an electrical output.These two components are separated by a transparent dielectric barrier (glass, plastic, or air gap). Because the connection is made via light photons rather than electrons, the input and output sides are electrically isolated. This isolation prevents high voltages or rapidly changing voltage spikes on one side from damaging components on the other.Ⅳ Optocoupler SymbolIn circuit diagrams, the optocoupler symbol illustrates its internal functionality. The left side typically shows the LED (Emitter), and the right side shows the receiver (Detector).Figure 2: Optocoupler circuit symbol (Phototransistor output)Common Variations:Phototransistor: The most common type for DC signal switching (shown above).Photo-Darlington: Uses a Darlington pair transistor for much higher gain (sensitivity) but slower switching speed.Photo-TRIAC / Photo-SCR: Used for controlling AC power mains.Figure 3: Photo-TRIAC circuit symbol (used for AC control)Ⅴ Optocoupler Specifications to WatchWhen selecting a component, consult the datasheet for these critical parameters:1. Current Transfer Ratio (CTR)This is the equivalent of "gain" (Beta) in a standard transistor. It is the ratio of the output collector current ($I_C$) to the input LED forward current ($I_F$), expressed as a percentage.Standard Phototransistor: CTR ranges from 10% to 100%.Photodarlington: CTR can range from 500% to 5000% (high sensitivity).Design Note - CTR Degradation: The efficiency of the internal LED decreases over time (aging). A good engineering practice is to design your circuit assuming the CTR will drop by 50% over the product's lifespan.2. Bandwidth and SpeedThis determines the maximum data rate.Phototransistors: Generally limited to about 250 kHz.Photodarlingtons: Slower, often limited to < 20 kHz due to long turn-off times.High-Speed Optocouplers: Devices like the 6N137 use a photodiode + logic amplifier architecture and can handle 10 MHz or more.3. Input Current ($I_F$)This is the current required to light up the internal LED. You must calculate a series resistor to limit this current, typically between 5mA and 20mA for standard devices.4. Isolation Voltage ($V_{iso}$)The maximum voltage difference the component can withstand between the input and output pins without electricity jumping the gap. Common ratings are 2500V to 5000V RMS.Ⅵ How It WorksThe operation is straightforward:Current is applied to the input side, flowing through the internal infrared LED.The LED emits infrared light inside the package. The intensity of this light is proportional to the input current.The light strikes the photosensitive base of the output transistor (or Triac).The photosensitive device "turns on" and conducts current.Figure 4: The internal light pathWhy is the Base pin unconnected?In many 6-pin optocouplers (like the 4N25), the base of the transistor is broken out to a pin (Pin 6). However, in most applications, this pin is left floating (unconnected) because the light serves as the base current. Connecting a resistor from the base to the ground can reduce sensitivity but increase switching speed.Figure 5: Effective isolation between Input and OutputⅦ Benefits and TypesPrimary Benefits:Ground Loop Elimination: Breaking the ground path between two circuits prevents hum and noise (critical in audio and instrumentation).Safety: Protects low-voltage microcontrollers (3.3V/5V) from high-voltage spikes (110V/220V).Level Shifting: Allows a 3.3V signal to switch a 24V or 48V circuit effortlessly.Common Types:Photo-Transistor: General-purpose DC switching.Photo-Darlington: High gain for very low input currents.Photo-SCR / Photo-TRIAC: Designed for interfacing with AC power mains.Logic Gate Output: (e.g., 6N137, H11L1) Includes internal logic buffers for high-speed digital communications.Figure 6: Common output configurationsⅧ Typical ApplicationsMicroprocessor I/O: Protecting GPIO pins on Arduinos or PLCs.Switch Mode Power Supplies (SMPS): Used in the feedback loop to maintain voltage regulation while keeping the mains side isolated from the low-voltage side.Motor Driving: Isolating the control logic from the noisy high-current motor drivers.Example: Triac Optocoupler for AC LoadsBy using a device like the MOC3020, a 5V digital signal can trigger a large external Triac, which in turn controls an AC motor or lamp. Many Triac optocouplers feature Zero-Crossing Detection, which ensures the device only switches when the AC voltage is at zero, significantly reducing Electromagnetic Interference (EMI).Figure 7: A basic DC switching configurationⅨ Differences Between Optocouplers and Solid State Relays (SSR)While they operate on the same principle, the distinction lies in power capability and integration.Figure 8: Solid State Relays (SSRs)Optocouplers: Low power. Used for signal transmission. Usually requires external components (external Power Triacs or MOSFETs) to switch heavy loads.Solid State Relays: High power. They contain an optocoupler plus the high-power switching components and protection circuitry inside a single, larger block. They can switch tens of Amps directly.Ⅹ How to Use an Optocoupler with ArduinoConnecting a load directly to an Arduino is risky. If the load is a motor or a solenoid, "flyback" voltage spikes can destroy the microcontroller. Using an optocoupler like the 4N25 or PC817 resolves this.The Circuit Concept:The Arduino drives the internal LED of the optocoupler. The optocoupler's output transistor acts as a switch for the secondary circuit.Figure 9: 4N25 OptocouplerWiring Guide (4N25 to Arduino):1. Input Side: Connect Arduino Pin -> 220Ω Resistor -> Optocoupler Pin 1 (Anode). Connect Pin 2 (Cathode) to Arduino GND.2. Output Side: Connect the device you want to control. Important: If you are using the optocoupler to send a signal into another digital pin, you must use a Pull-up Resistor on the collector (Pin 5) because the phototransistor can only pull voltage down to ground; it cannot "source" voltage effectively.Figure 11: Basic wiring diagram for isolating a signalⅪ FAQ1. What are the disadvantages of an optocoupler?The main disadvantages are speed and power handling. Standard optocouplers have a relatively slow frequency response compared to digital isolators. Also, the output phototransistor cannot handle high currents directly; it usually requires an external transistor or relay to switch heavy loads.2. Is an optocoupler the same as a relay?Not exactly. While both isolate circuits, a mechanical relay uses a physical electromagnet and moving contacts (clicking sound). An optocoupler uses light and has no moving parts. Optocouplers are faster and last longer but handle much less current than relays.3. How do you use an optocoupler for analog signals?While mostly used for digital switching, linear optocouplers exist. To send audio or analog data, you set up a specific bias current (standing current) through the LED and modulate that current with your signal. Specialized "Linear Optocouplers" use feedback photodiodes to linearize the output.4. How do I ensure the optocoupler switches fully (Saturation)?To use an optocoupler as a solid switch, you must drive it into "saturation." This means ensuring the input current ($I_F$) is sufficient and the output collector load resistor is high enough so that the phototransistor turns completely on. Always check the CTR curve in the datasheet.5. Are optocouplers analog or digital?They are fundamentally analog devices (light intensity varies with current), but they are most commonly used in digital applications (On/Off switching). Specialized high-speed digital optocouplers (logic-output) are available specifically for data transmission. ul { margin-bottom: 20px; } li { margin-bottom: 10px; } .caption { text-align: center; font-size: 14px; color: #7f8c8d; margin-top: -15px; margin-bottom: 25px; font-style: italic; } .note-box { background-color: #e8f6f3; border-left: 5px solid #1abc9c; padding: 15px; margin: 20px 0; font-size: 16px; } .warning-box { background-color: #fff3cd; border-left: 5px solid #ffc107; padding: 15px; margin: 20px 0; } strong { color: #d35400; } .faq-item { margin-bottom: 20px; background: #fff; padding: 15px; border: 1px solid #eee; border-radius: 5px; } .faq-question { font-weight: bold; color: #e67e23; font-size: 18px; display: block; margin-bottom: 10px; }

Introduction As a power semiconductor device, IGBT(insulated-gate bipolar transistor) is widely used in the fields of rail transit, smart grid, industrial energy saving, electric vehicles and new energy equipment. It has the characteristics of energy saving, convenient installation and easy maintenance, and stable heat dissipation. It is the core device for energy conversion and transmission. A brief overview, IGBT can be said to be a combination of MOSFET(metal–oxide–semiconductor field-effect transistor) and BJT(bipolar junction transistor). That is, it combines the gate voltage control transistor (high input impedance) of the MOSFET, and uses the dual carriers of the BJT to achieve the purpose of large current (voltage-controlled bipolar device). So what is the internal structure of such a combination? This article will explain in detail with examples. What is IGBT and Its Applications Catalog Introduction Ⅰ IGBT Module Explained Ⅱ IGBT Internal Structure Ⅲ IGBT Internal Current Flow Ⅳ How to Disassemble IGBT Module? Ⅴ FAQ Ⅰ IGBT Module Explained The model of the IGBT module to be disassembled as an example is: FF1400R17IP4. The appearance and equivalent circuit of the module are shown in Figure 1. The length, width and height of this module are: 25cmx8.9cmx3.8cm. The module contains two IGBTs, which are what we often call half-bridge modules. The rated voltage and current of each IGBT are 1.7kV and 1.4kA. Figure 1. FF1400R17IP4 Part 8, 9, 10, 11, and 12 are power terminals and need to be connected to a power circuit.1, 2, 3, 4, and 5 are auxiliary control terminals, which need to be connected to the gate drive circuit.6 and 7 are NTC thermistors, used for temperature detection or over-temperature protection.After having a general understanding of its structure, what can we do with such a black module with this structure? Take an example around us: new electric vehicles, everyone should be familiar with it. Three such black modules can be used as a three-phase motor driver. If it is equipped with a battery, it can drive an electric bus. Of course, this module is also used in many other applications. Figure 2. IGBT in Electric Bus   Ⅱ IGBT Internal Structure After having a preliminary understanding of the external structure and application of the IGBT module, let us enter the subject of this article to see what the inside of this high-tech black module looks like. Figure 3 is the internal picture of the IGBT module with the black casing removed. It should be noted that the most common copper and aluminum are inside the IGBT module. Figure 3. IGBT Internal Structure Figure 4 is a cross-sectional view of the IGBT module. If the black casing and external connection terminals are removed, the IGBT module mainly contains 3 components, the heat dissipation substrate, the DBC substrate and the silicon chip (including the IGBT chip and the Diode chip), and the rest is mainly solder layers and interconnecting wires are used to connect IGBT chips, Diode chips, power terminals, control terminals and DBC(Direct Bond Copper). Below we will briefly introduce each part. Figure 4. IGBT Section View ① Heat Sink SubstrateThe bottom of the IGBT module is the heat dissipation substrate, the main purpose is to quickly transfer the heat generated by the IGBT switching process. Since copper has better thermal conductivity, the substrate is usually made of copper, and the thickness of it is 3-8mm. Of course, there are also substrates made of other materials, such as aluminum silicon carbide (AlSiC), both of which have their own advantages and disadvantages. ② DBCDBC (Direct Bond Copper) is a ceramic surface metallization technology, which contains 3 layers. Have a ceramic insulating layer in the middle and a copper clad layer above and below respectively, as shown in Figure 5(a). Simply put, it is to cover both sides of an insulating material with a copper layer, and then etch a pattern that can carry current on the front side, and the back side must be directly soldered to the heat sink substrate. Figure 5. BDC Base vs PCB The main function of DBC needs to ensure the electrical insulation capacity between the silicon chip and the heat dissipation substrate and good thermal conductivity, while also providing a certain current transmission capacity. The DBC substrate is similar to a 2-layer PCB circuit board. The insulating material in the middle of the PCB is generally FR4, while the commonly used ceramic insulating materials for DBC are aluminum oxide (Al2O3) and aluminum nitride (AlN).For the IGBT module analyzed in this article, there are 6 DBCs inside, and each has 4 IGBT chips and 2 Diode chips. Among them, 2 IGBT chips and 1 Diode chip are used as the upper tube, and the rest are used as the lower tube. As shown in Figure 6. Figure 6. DBC Diagram and Equivalent Circuit ③ IGBT ChipThe IGBT chip model used inside the module is: IGCT136T170. The manual can be downloaded from Infineon official website. Figure 7 shows the top view and basic parameters of the IGBT chip. The gate and emitter of the IGBT are above the chip (front side), and the collector is below (back side). The thickness of the chip is 200um. After the IGBT powers on, the current flows from bottom to top, so the IGBT of this structure can also be called a vertical device. Chip Type VCE ICn1) Die Size IGC136T170S8RH2 1700A 117.5A 17.72×7.7mm2 Figure 7. IGBT Chip Diagram If you make a vertical cut on the 200um chip, you can get the internal structure shown in Figure 8, which is a combination of P-type or N-type semiconductors with different doping. Figure 8 shows the well-known equivalent circuit of an IGBT, which is usually understood as a MOS-controlled PNP transistor. When start to learn about power electronics, you may feel that this picture is a bit strange. Why not draw the collector on the top and the emitter on the bottom? Until you understand that the IGBT current flows from bottom to top, it is not difficult to explain. Figure 8. IGBT Chip Structure and Equivalent Circuit Let’s have a general understanding of the electrical parameters of this IGBT chip. This chip can pass a DC current of 117.5A at 100°C. It can be seen from Figure 4 that a single IGBT device inside the module contains a total of 12 IGBT chips, so the total current is: 117.5*12=1412A, which is basically the same as the 1400A rated current in the IGBT module manual.In order to ensure the current sharing effect between IGBT chips, a 11.5Ω resistor has been integrated inside the gate of each chip. At the same time, considering the current sharing between the DBCs, the two chips on each DBC share a gate resistor externally, as shown in Figure 10. When measuring it with a multimeter, and the resistance is about 4.13Ω. You can calculate it in conjunction with Figure 9 to see if it is consistent with the 1.6Ω in the IGBT module manual. Of course, you can refer to the official manual for more detailed parameters of the IGBT chip. Figure 9. IGBT Equivalent Circuit ④ Diode ChipFigure 10 is a top view of the Diode chip, with the anode on the front and the cathode on the back. The current direction of the diode is from top to bottom, which is exactly the opposite of the current direction of the IGBT. The rated current of the diode chip is 235A, and each IGBT is composed of 6 diodes in parallel, and the total current can reach 1410A, which is basically the same as the 1400A in the module manual. The thickness of diode chip is the same as IGBT, it is also 200um. For more detailed parameters of the diode chip, please refer to the official manual. Chip Type VR IFn1) Die Size SIDC130D170H 1700A 235A 16.3×8mm2 Figure 10. Diode Diagram Such a thin semiconductor material can have kV voltage and hundreds of amperes of current on and off, it’s amazing. This is why the price of high-power semiconductor devices is so very expensive.The upper copper layer interconnection of IGBT chip, Diode chip and DBC is generally realized by bonding wires. Commonly used bonding wires are aluminum wire and copper wire. Among them, the aluminum wire bonding process is mature and the cost is low, but the electrical and thermodynamic properties of the aluminum wire bonding are poor, and the expansion coefficient mismatch is large, which affects the service life of the IGBT. The copper wire bonding process has the advantages of excellent electrical and thermodynamic properties, high reliability, and is suitable for modules with high power density and efficient heat dissipation.   Ⅲ IGBT Internal Current Flow After having a basic understanding of the internal structure of the IGBT module, let us go back and interconnect all the above components to see how the current flows inside the IGBT module. Here we take the upper tube IGBT in one of the DBCs as an example to illustrate the current flow. Red represents the current direction of the upper tube IGBT (S1 and S2), and blue represents the current direction of the diode D1. Figure 11(b) is a left cross-sectional view and a schematic diagram of the current direction of the module of Figure . Figure 11(a). IGBT Current Flow Figure 11(b). IGBT Current   Ⅳ How to Disassemble IGBT Module? Some friends may be curious about how to disassemble this module, but it is actually very simple. You only need to prepare two screwdrivers and a small hammer. Figure 12. IGBT Disassemble Step 1: Unscrew the 4 screws at the bottom of the IGBT module.Step 2: Use a flat-blade screwdriver to pry open all the terminals on the front of the IGBT module. This step is very important. It is necessary to ensure that all the terminals after being pried are vertical to the module substrate.Step 3: You need to fix the IGBT in one place, or use a flat-blade screwdriver to align any position of the connection between the plastic casing of the IGBT module and the substrate, hit the screwdriver with a hammer, and pry the casing from the substrate with the screwdriver. After prying open one position, place something on it, and then pry another position, repeat that, after slowly prying open, just pry open with your hands directly.   Ⅴ FAQ 1. What is IGBT module?An IGBT is a is power semiconductor die and is the short form of insulated-gate bipolar transistor. ... An IGBT power module functions as an electronic switching device. By alternate switching direct current (DC) can be transformed to alternating current (AC) and vice versa. 2. How does IGBT module work?The IGBT combines the simple gate-drive characteristics of power MOSFETs with the high-current and low-saturation-voltage capability of bipolar transistors. The IGBT combines an isolated-gate FET for the control input and a bipolar power transistor as a switch in a single device. 3. What is the purpose of IGBT?The IGBT combines, in a single device, a control input with a MOS structure and a bipolar power transistor that acts as an output switch. IGBTs are suitable for high-voltage, high-current applications. They are designed to drive high-power applications with a low-power input. 4. How many layers are there in IGBT?Working of IGBTIGBT is constructed with 4 layers of semiconductor sandwiched together. The layer closer to the collector is the p+ substrate layer above that is the n- layer, another p layer is kept closer to the emitter and inside the p layer, we have the n+ layers. 5. Which are the terminals of IGBT?The three terminals of IGBT are Gate, Collector and Emitter. 6. How many terminals Mosfet has?four terminalsThe MOSFET has four terminals: drain, source, gate, and body or substrate. 7. What is the function of injecting layer in IGBT?The p+ substrate is also called injector layer because it injects holes into n- layer. The n- layer is called drift region. The next p layer is called the body of IGBT. The n- layer in between the p+ & p region serves to accommodate the depletion layer of pn- junction i.e. J2. 8. Can I replace IGBT with MOSFET?Due to the higher usable current density of IGBTs, it can usually handle two to three times more current than a typical MOSFET it replaces. This means that a single IGBT device can replace multiple MOSFETs in parallel operation or any of the super-large single power MOSFETs that are available today. 9. What are the three terminals of an IGBT and how does it function?The IGBT (insulated gate bipolar transistor) is a three-terminal electronic component, and these terminals are termed as emitter (E), collector(C) and gate(G). Two of its terminals namely collector and emitter are associated with a conductance path and the remaining terminal 'G' is associated with its control. 10. What is an IGBT describe its construction?IGBT – Working, Types, Structure, Operation & Applications. ... The IGBT (Insulated Gate Bipolar Transistor) takes the best parts of both BJT and MOSFET into a single transistor. It takes the input characteristics (high input impedance) of MOSFET (Insulated Gate) and the output characteristics of BJT (Bipolar nature). 11. How does IGBT convert DC to AC?The IGBT act as a switch (when a signal is applied to the gate, they turn on and then turn off when the signal is removed). By closing Q1 and Q4, a positive d.c. supply is applied to the load. Q2 and Q3 will result in a negative d.c. supply across the load. 12. What is the advantage of IGBT?The main advantages of IGBT over a Power MOSFET and a BJT are: It has a very low on-state voltage drop due to conductivity modulation and has superior on-state current density. So smaller chip size is possible and the cost can be reduced. 13. What is drift layer in IGBT?The drift region (electric field or movement of charge) of the IGBT works as a base of the PNP transistor . The current gain of the transistor depends upon the width and doping level of the transistor. 14. What is the structure of IGBT?The structure of IGBT is very much similar to that of PMOSFET, except one layer known as injection layer which is p+ unlike n+ substrate in PMOSFET. This injection layer is the key to the superior characteristics of IGBT. Other layers are called the drift and the body region. The two junctions are labeled J1 and J2. 15. What are the advantages of IGBTs?Advantages of IGBT:Simple drive circuitLow on-resistanceHigh voltage capacityFast switching speedEasy of driveLow switching lossLow on stage power dissipationLow gate drive requirement 16. Why IGBT is very popular nowadays?With its lower on-state resistance and conduction losses as well as its ability to switch high voltages at high frequencies without damage makes the Insulated Gate Bipolar Transistor ideal for driving inductive loads such as coil windings, electromagnets and DC motors. 17. Why diode is used in IGBT?We know that MOSFET or IGBT is a unidirectional device, they only conduct current in forward bias and block the current in reverse bias. ... For this reason, an external diode is connected across the MOSFET or IGBT or SCR to provide a path for reverse current.

Introduction An oscillator is an electronic component used to generate an oscillating signal. The circuit composed of it is called an oscillating circuit, which can convert direct current into an electronic circuit or device with a certain frequency of alternating current signal. It is widely used in electronics industry, medical treatment, scientific research, etc. Catalog Introduction Ⅰ Oscillator Basics 1.1 Oscillator Meaning 1.2 Classification Rules Ⅱ Examples: RC Oscillator, LC Oscillator and Crystal Oscillator 2.1 RC Oscillator 2.2 LC Oscillator 2.3 Crystal Oscillator Ⅲ Selection Rules Ⅳ FAQ Ⅰ Oscillator Basics 1.1 Oscillator Meaning The oscillator is simply a frequency source and generally used in a phase-locked loop. In detail, it is a device that can convert DC power into AC power without external signal excitation. Generally divided into two types: positive feedback and negative resistance. The so-called oscillation, its meaning alludes to AC, and the oscillator includes a process and function starting from scratch. In other words, it can complete the conversion from DC power to AC power, such a device can be called an oscillator. 1.2 Classification Rules Oscillators are widely used, and there are many types:According to the oscillation frequency: high frequency oscillator, and low frequency oscillator.According to the oscillation waveform: sine wave oscillator, and non-sine wave oscillator.According to the oscillation feedback: positive feedback oscillator, and negative resistance oscillator.   Ⅱ Examples: RC Oscillator, LC Oscillator and Crystal Oscillator Electronic Oscillators || RC, LC, Crystal 2.1 RC Oscillator In a resistance-capacitance oscillator or short for RC oscillator, by using RC components in the feedback branch, a phase shift occurs between the input of the RC network and the output from the same network. The input is again moved through the second inverting stage, giving a phase shift, which is the same as providing the required positive feedback. It is suitable for low frequency oscillation, and is generally used to generate low frequency signals of 1Hz to 1MHz. The circuit is composed of four parts: amplifying circuit, frequency selection network, positive feedback network, and amplitude stabilization. The main advantages of it are simple structure, economic and convenient, and belong to the audio frequency oscillator. Figure 1. RC Oscillator Circuit (1) Vibration ProcessWhen the power is just turned on, there are various electrical disturbances in the circuit, and a relatively large feedback voltage is generated through feedback through the frequency selection network. Passing through the continuous loop of linear amplification and feedback, the oscillation voltage will continue to increase.(2) Oscillation FrequencyThe oscillation frequency is determined by the phase balance condition., Only meets the phase balance condition at f0, the oscillation frequency is .Changing R and C can change the oscillation frequency.(3) Conditions for Start-up and Stable OscillationTaking into account the starting conditions of AuF>1, generally Rt should be selected slightly larger than 2R1. If this value is too large, it will cause serious distortion of the oscillation waveform.The RC series-parallel sine-wave oscillator circuit composed of an op amp does not rely on the transistor inside the op amp to enter the nonlinear region to stabilize the amplitude, but to achieve the purpose of amplitude stabilization by introducing negative feedback from the outside.(4) Stable AmplitudeThe growth process of the oscillation amplitude cannot continue forever, when the amplifier gradually enters the saturation or cut-off zone from the amplification zone. Working in a non-linear state, its gain gradually decreases. When the amplifier gain decreases and the loop gain decreases to 1, the amplitude increase process will stop and the oscillator will reach equilibrium.For the RC oscillator circuit, increasing the resistance can reduce the oscillation frequency, and it does not need to increase the cost. The frequency of the sine wave generated by the commonly used LC oscillation circuit is relatively high. If a low frequency sine oscillation is to be generated, the oscillation circuit must have a larger inductance and capacitance. This will not only cause the components to be bulky, heavy, and inconvenient to install, but also difficult to manufacture with high cost. Therefore, the sinusoidal oscillation circuit below 200kHz generally adopts an RC oscillation circuit with a lower oscillation frequency.   2.2 LC Oscillator LC oscillator is also called LC oscillating circuit, resonance circuit, tank circuit or tuning circuit. It consists of a capacitor and a parallel coil. The circuit has an inductor L and a capacitor C. Capacitors store energy in the form of electrostatic fields and generate potential on their plates, while inductance coils store energy in the form of electromagnetic fields. By placing the switch in a specific position, the capacitor is charged to the DC supply voltage. When the capacitor is fully charged, the switch is switched to a certain position, and the charged capacitor is connected in parallel to the inductor coil, so the capacitor starts to discharge itself through the coil. Figure 2. LC Oscillator Circuit The LC circuit is not only used to generate a specific frequency signal, but also used to separate a specific frequency signal from a more complex signal. They are key components in many electronic equipment, especially radio equipment, used in oscillators, filters, tuners and mixer circuits.The inductive circuit is an idealized model because it assumes that there is no energy dissipated due to resistance. The actual realization of any LC circuit will include the loss caused by the small but non-zero resistance of the components and connecting wires. The purpose of an LC circuit is usually to minimize oscillations, so the resistance is made as small as possible. Although there is no lossless circuit in practice, studying the ideal form of this circuit is beneficial to study physical phenomenon.When electromagnetic oscillation occurs in an oscillating circuit, if there is no energy loss and no external influences, the period and frequency of it at this time are called the natural frequency and natural period of the oscillating circuit. The natural period can be obtained by the following formula: Where, the time constant is L/R. What are LC Oscillations? 2.3 Crystal Oscillator Some electronic devices require an AC signal with a highly stable frequency, but the LC oscillator has poor stability and the frequency is easy to drift (that is, the frequency of the generated AC signal is easy to change). A special component-quartz crystal is used in the oscillator, which can generate a highly stable signal. This kind of oscillator that uses a quartz crystal is called a crystal oscillator. It is mainly composed of a crystal and peripheral components. In a crystal oscillator, the main frequency determining element is a quartz crystal. Due to the inherent characteristics of the quartz crystal oscillator, it has extremely high frequency stability. Temperature compensation may be related to the crystal oscillator to improve the thermal stability. Because it is a fixed frequency oscillator, stability and accuracy are the basic considerations when use it. Figure 3. Crystal Oscillator Circuit The crystal oscillator has a piezoelectric effect, that is, the crystal will deform when a voltage is applied to the two poles of the wafer. Conversely, if an external force deforms the wafer, the metal sheets on the two poles will generate voltage. If an appropriate alternating voltage is applied to the chip, the chip will resonate (the resonance frequency is related to the tilt angle of the quartz slope, etc., and the frequency is constant). The crystal oscillator uses a crystal that can convert electrical energy and mechanical energy into each other. It can provide stable and accurate single-frequency oscillation when working in a resonance state. Under normal working conditions, the absolute accuracy of ordinary crystal oscillator frequencies can reach 50 parts per million. Using this feature, the crystal oscillator can provide a more stable pulse, which is widely used in the clock circuit of the microchip. In addition, the wafers are mostly quartz semiconductor materials, and the shell is encapsulated with metal.The main parameters of the crystal oscillator include nominal frequency, load capacitance, frequency accuracy, frequency stability, etc. These parameters determine the quality and performance of the crystal oscillator. Therefore, in practical applications, an appropriate crystal oscillator should be selected according to specific requirements. For example, systems such as communication networks and wireless data transmission require high-precision crystal oscillators. However, since the higher the performance of the crystal oscillator is, the more expensive it is, so you can choose a crystal that meets the requirements when buying.   Ⅲ Selection Rules Oscillators are used in many electronic products. In order to ensure the normal operation of electronic products, the selection of oscillators is important. The following summarizes the five selection rules for reference.1) Appearance InspectionBy checking the appearance of the product, whether the marking text is clear and standard, whether there are cracks on the surface of the appearance, and whether the pins have been soldered. If the product is found to be imperfect on the outside, it should not be used.2) FrequencyChoose the appropriate frequency according to the actual product requirements. The frequency is the most important, and it cannot be replaced casually. Negotiations must be conducted after passing the qualification verification or professional test. If the frequency required by the actual circuit is 5MHZ, do not replace it with a similar frequency without any original replacement.3) Output ModeWhen choosing a oscillator, consider the type of oscillator output required by the circuit, which generally divided into level output and differential output. As for level output, CMOS is the most commonly used type, and in terms of differential output, LVPECL(Low Voltage Positive Emitter-Couple Logic) and LVDS (Low-Voltage Differential Signaling) are commonly used differential output type. Different output types cannot be changed randomly, especially differential and ordinary oscillators.4) ModelTo use the oscillator, you must see the model mark of the shell. The model number indicates its multiple parameters. According to the product requirements, the corresponding product parameters can be found, and the same model can be found later. If the crystal oscillator model is not selected properly, it will cause errors in the application.5) ReplacementIf an oscillator is damaged, it should be replaced by the original model in principle. When the original model is not available, it is best to consider replacing it with another model or other type of oscillator after testing.   Ⅳ FAQ 1. What is oscillator and its types?An oscillator is a type of circuit that controls the repetitive discharge of a signal, and there are two main types of oscillator; a relaxation, or an harmonic oscillator. This signal is often used in devices that require a measured, continual motion that can be used for some other purpose. 2. What are the types of oscillator in electronics?There are two main types of electronic oscillator – the linear or harmonic oscillator and the nonlinear or relaxation oscillator. 3. How many types of oscillations are there?There are 3 main types of Oscillation – Free, damped, and forced oscillation. When a body vibrates with its own frequency, it is called a free oscillation. 4. What is RC and LC oscillator?The oscillation frequency is proportional to the inverse of the capacitance or resistance, whereas in an LC oscillator the frequency is proportional to inverse square root of the capacitance or inductance. So a much wider frequency range can be covered by a given variable capacitor in an RC oscillator. 5. What is the principle of oscillator?There are many types of electronic oscillators, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback. 6. What are the three types of oscillator?The main types of Oscillators include: Wien Bridge Oscillator. RC Phase Shift Oscillator. Hartley Oscillator. 7. What is the use of LC oscillator?LC oscillators are used in heating with high-frequency, RF generators, radios, TV receivers, etc. These types of oscillators use tank circuits including the components like a capacitor (C) and an inductor (L). 8. What does RC oscillator do?RC oscillators are a type of feedback oscillator; they consist of an amplifying device, a transistor, vacuum tube, or op-amp, with some of its output energy fed back into its input through a network of resistors and capacitors, an RC network, to achieve positive feedback, causing it to generate an oscillating. 9. What is RC phase oscillator?RC phase-shift oscillators use resistor-capacitor (RC) network to provide the phase-shift required by the feedback signal. They have excellent frequency stability and can yield a pure sine wave for a wide range of loads. ... Further, the circuit also shows three RC networks employed in the feedback path. 10. What are the advantages of RC oscillator?The RC phase shift oscillator gives good Frequency stability. The output of this circuit is sinusoidal that is quite distortion free.. It is suitable for lower frequencies and this lower limit exists in as low as 1Hz. RC phase shift oscillators don't require any negative feedback and stabilization arrangements. 11. What is a crystal oscillator used for?A crystal oscillator is an electronic oscillator circuit that is used for the mechanical resonance of a vibrating crystal of piezoelectric material. It will create an electrical signal with a given frequency. 12. What are the advantages of crystal oscillator?The Advantages of a Crystal OscillatorStability. Stability is one of the most important requirements of any oscillator.High Q. The Q factor or quality factor describes how 'underdamped' oscillators are.Frequency Customization and Range.Low Phase Noise.A Crystal Oscillator Is Compact and Inexpensive. 13. What is crystal oscillator explain?A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a constant frequency. ... Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz.

Introduction The rectifier diode is a semiconductor device that converts AC into DC. Usually it contains a PN junction with two terminals, a positive electrode and a negative electrode. The most important characteristic is unidirectional conductivity. In electronic circuits, its breakdown voltage is high, the reverse leakage current is small, and the high temperature performance is good. Generally, it can be made of materials such as semiconductor germanium or silicon. In addition, high-voltage and high-power rectifier diodes are made of high-purity single crystal silicon (it is easy to reverse breakdown when there is more doping). This kind of device has a large junction area and can pass a large current (up to thousands of amperes), but the operating frequency is not high, generally below tens of KHz. Rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits. If require full-wave rectification, several diodes need to be connected to form a rectifier bridge. What is a Rectifier? (AC to DC) Catalog Introduction Ⅰ Common Parameters Ⅱ Rectifier Diodes Selection Ⅲ Rectifier Common Failures Ⅳ Rectifier Diodes Detection Ⅴ Rectifier Diode Replacement 5.1 Replacing Rules 5.2 Commonly Used Rectifier Models List Ⅵ Rectifier Diode Circuit Types 6.1 Half-Wave Rectifier Circuit 6.2 Full-Wave Rectifier Circuit 6.3 Bridge Rectifier Circuit Ⅶ High-frequency Rectifier Diodes Ⅷ FAQ Ⅰ Common Parameters The rectifier diode uses the unidirectional conductivity of the PN junction to convert alternating current into pulsating direct current. Rectifier diodes have a large leakage current, and most of them are diodes packaged with surface mount materials. The parameters of the rectifier diode include the maximum rectifier current, which refers to the maximum current value allowed by the rectifier diode for long-term operation. It is the main parameter of the rectifier diode and the main basis for the option of the rectifier diode. Except it, other important parameters are introduced here.(1) Maximum average rectified current IF: It refers to the maximum forward average current allowed to pass through the diode during long-term operation. The current is determined by the PN junction area and the heat dissipation conditions. It should be noted that the average current passing through the diode cannot be greater than this value, and has heat dissipation.(2) Maximum reverse working voltage VR: It refers to the maximum reverse voltage allowed to be applied across the diode. If it is greater than this value, the reverse current (IR) will increase sharply, and the unidirectional conductivity of the diode will be destroyed, causing reverse breakdown. Usually take half of the reverse breakdown voltage VB as VR.(3) Maximum reverse current IR: It is the reverse current allowed to flow through the diode under the highest reverse working voltage. This parameter reflects the quality of the unidirectional conductivity of the diode. Therefore, the smaller the current value, the better the diode quality.(4) Breakdown voltage VB: It refers to the voltage value at the sharp bend point of the reverse volt-ampere characteristic curve of the diode. When the reverse is a soft characteristic, it refers to the voltage value under a given reverse leakage current condition.(5) The highest operating frequency fm: It is the highest operating frequency of the diode under normal conditions. It is mainly determined by the junction capacitance and diffusion capacitance of the PN junction. If the operating frequency exceeds fm, the unidirectional conductivity of the diode will not be well reflected.(6) Reverse recovery time trr: It refers to the reverse recovery time under the specified load, forward current and maximum reverse transient voltage.(7) Zero-bias capacitor CO: It refers to the sum of the capacitance of the diffusion capacitance and the junction capacitance when the voltage across the diode is zero. It is worth noting that, due to the limitation of the manufacturing process, even the same type of diode has a large dispersion of its parameters. The parameters given in the manual are often within a range. If the test conditions change, the corresponding parameters will also change. For example, the IR of the 1N5200 series silicon plastic rectifier diode measured at 25°C is less than 10uA, and at 100°C IR becomes less than 500uA.     Ⅱ Rectifier Diodes Selection Rectifier diodes are generally planar silicon diodes, which are used in various power rectifier circuits. When selecting a rectifier diode, the parameters such as its maximum rectifier current, maximum reverse working current, cut-off frequency and reverse recovery time should be mainly considered.The rectifier diode used in the ordinary series stabilized power supply circuit does not require high reverse recovery time of the cut-off frequency. The rectifier diode with the maximum rectified current and maximum reverse working current should meet the requirements of the circuit.The rectifier diode used in the rectifier circuit of the switching regulated power supply and the pulse rectifier circuit should be a rectifier diode with a higher operating frequency and shorter reverse recovery time (such as RU series, EU series, V series, 1SR series, etc.) or select fast recovery diodes, or Schottky rectifier diode.     Ⅲ Rectifier Common Failures (1) Inadequate lightning protection and poor overvoltage protection. The rectifier device is not equipped with lightning protection and overvoltage protection devices. Or insufficient routine maintenance of the equipment.(2) Poor operating conditions. In the indirect drive generator set, because the calculation of the speed ratio is incorrect or the ratio of the diameters of the two belt pulleys does not meet the requirements of the speed ratio, the generator runs at a high speed for a long time, so the rectifier is at a higher voltage for a long time. It accelerates the rectifier aging, and was damaged by premature breakdown.(3) Poor operation management. The load failure or diode breakdown doesn’t fixed in time.(4) Poor equipment installation or manufacturing process. The generator set has been operating under large vibration for a long time, which affects the rectifier tube operation. At the same time, because the generator set speed is unstable, the working voltage of the rectifier tube also fluctuates, which greatly accelerate the aging and damage of the rectifier tube.(5) The specifications and models of the rectifier tube do not match. When replacing a new rectifier tube, wrongly replace the tube whose working parameters do not meet the requirements or the wiring is wrong, causing the rectifier tube to breakdown and damage.(6) The safety margin of the rectifier tube is too small. The overvoltage and overcurrent safety margin of the rectifier tube is too small, so that the rectifier tube cannot withstand the overvoltage or the peak value of the overcurrent transient process that occurs in the generator excitation circuit and is damaged. Figure 1. Diode as Rectifier Symbol     Ⅳ Rectifier Diodes Detection Here is a more general and simple method. Remove all the rectifier diodes in circuit, use the 100×R or 1000×R ohm range of a multimeter to measure the two lead wires of the rectifier diode (adjust and test twice). If the resistance values measured twice are very different, for example, the resistance value is as high as a few hundred kΩ to infinity, or the resistance value is only a few hundred Ω or less, indicating that the diode is good (except under special circumstances). If the resistance value measured twice is almost the same and the resistance value is very small, it means that the diode has been broken down and cannot be used. In addition, if the resistance values measured twice are both infinite, it means that the diode has been internally disconnected and cannot be used.     Ⅴ Rectifier Diode Replacement   5.1 Replacing Rules After the rectifier diode is damaged, you should replace with the same model or another model with the same parameters.Generally, rectifier diodes with high withstand voltage (reverse voltage) can be substituted for rectifier diodes with low withstand voltage, while rectifier diodes with low withstand voltage cannot be replaced with rectifier diodes with high withstand voltage. A diode with a high rectification current value can be substituted for a diode with a low rectification current value, while a diode with a low rectification current value cannot be substituted for a diode with a high rectification current value.   5.2 Commonly Used Rectifier Models List Material Model Reverse Voltage Operation (peak) Average Rectified Current   Silicon Rectifier Diode 1N4001 50V 1A (Ir=5uA,Vf=1V,Ifs=50A) 1N4002 100V 1A 1N4003 200V 1A 1N4004 400V 1A 1N4005 600V 1A 1N4006 800V 1A 1N4007 1000V 1A 1N4148 75V 4PF, Ir=25nA,Vf=1V 1N5391 50V 1.5A (Ir=10uA,Vf=1.4V,Ifs=50A) 1N5392 100V 1.5A 1N5393 200V 1.5A 1N5394 300V 1.5A 1N5395 400V 1.5A 1N5396 500V 1.5A 1N5397 600V 1.5A 1N5398 800V 1.5A 1N5399 1000V 1.5A 1N5400 50V 3A (Ir=5uA,Vf=1V,Ifs=150A) 1N5401 100V 3A 1N5402 200V 3A 1N5403 300V 3A 1N5404 400V 3A 1N5405 500V 3A 1N5406 600V 3A 1N5407 800V 1A (Ir=5uA,Vf=1V,Ifs=50A) 1N5408 1000V 1A   Ⅵ Rectifier Diode Circuit Types The power grid supplies users with alternating current, and various electrical devices require direct current. Rectification is the process of converting AC into DC. Utilizing the device with unidirectional conductivity, the current of alternating direction and magnitude can be converted into direct current. The following introduces three main rectifier circuits composed of crystal diodes.   6.1 Half-Wave Rectifier Circuit Figure 2. Half-Wave Rectifier Circuit The figure shows the simplest rectifier circuit. It is composed of power transformer B, rectifier diode D and load resistor Rfz. The transformer transforms the voltage into the required alternating voltage e2, and then D transforms the AC into pulsating DC.The transformer threshold voltage e2 is a sine wave voltage whose direction and magnitude change with time, and its waveform is shown in Figure (a). In the 0~K time, e2 is a positive half cycle, that is, the upper end of the transformer is positive and the lower end is negative. At this time, the diode is in forward conductive conduction, and e2 is added to the load resistor Rfz through it. Within π~2π, e2 is in negative half cycle, the lower end of the transformer secondary is positive, and the upper end is negative. At this time, D bears the reverse voltage and does not conduct, and there is no voltage on Rfz. In the time of π~2π, the process of 0~π time is repeated, and in the time of 3π~4π, the process of π~2π time... half-cycle through Rfz, a single right direction voltage is obtained on Rfz (up positive and lower negative), as shown in Figure (b), which achieves the purpose of rectification. But the load voltage Usc, and the load current also changes with time, so it is usually called pulsating DC. Figure 3. Half-Wave Rectifier Wave This rectification method of removing the first half week and leaving half a week is called half wave rectification. It is not difficult to note that the half-wave rectification is at the expense of consuming half of the AC in circuit, and the current utilization rate is very low. According to it, half-wave rectifier diode is commonly used in high voltage and small current occasions, and is rarely used in general radio devices.   6.2 Full-Wave Rectifier Circuit Figure 4. Full-Wave Rectifier Circuit If some adjustments are made to the structure of the rectifier circuit, a full-wave rectifier circuit that can be obtained. The figure above is the electrical schematic diagram of the full-wave rectifier circuit.The full-wave rectifier circuit can be regarded as a combination of two half-wave rectifier circuits. A tap needs to be drawn in the middle of the secondary coil of the transformer to divide the secondary coil into two symmetrical windings, so as to get two voltages e2a and e2b of equal size but opposite polarity to form two energized circuits.The working principle of the full-wave rectifier circuit can be illustrated by the waveform diagram. Between 0 and π, e2a is a positive voltage to Dl, D1 is turned on, and a up positive and down negative voltage is obtained on Rfz. e2b is a reverse voltage to D2, and D2 is not conductive (see Figure(b) ). In the time of π-2π, e2b is a positive voltage to D2, D2 is turned on, and the voltage obtained on Rfz is still up positive and down negative voltage, therefore e2a is a reverse voltage to D1, and D1 is not conductive (see figure (c). Figure 5. Full-Wave Rectifier Circuit Wave Repeated this way, because the two rectifier elements D1 and D2 conduct electricity in turn, the result is that the load resistor Rfz has the same direction of current at the positive and negative half cycles, as shown in Figure(b). This is full-wave rectification, which not only uses the positive half-cycle, but also cleverly uses the negative half-cycle. Full-wave rectifier greatly improves the rectification efficiency. Figure 6. Full-Wave Rectifier Circuits This circuit requires the transformer to have a secondary center tap that makes the two ends symmetrical, which brings a lot of trouble to the production. In addition, in this circuit, the maximum reverse voltage that each rectifier diode can withstand is twice the maximum value of the transformer secondary voltage, so diodes should withstand higher voltages.   6.3 Bridge Rectifier Circuit Figure 7. Bridge Rectifier Circuit The bridge rectifier circuit is the most used rectification circuit. It has the advantages of a full-wave rectifier circuit as long as two diode ports are connected to form a bridge structure, so its shortcomings are overcome to a certain extent.The bridge rectifier circuit is as follows: Figure 8. Bridge Rectifier Circuit (a) When e2 is a positive half cycle, D1, D3 and the direction voltage, D1, D3 are turned on; D2, D4 are applied with reverse voltage, they are turned off. E2, Dl, Rfz, and D3 are energized a loop in the circuit. On Rfz, a positive and negative half-wave washing voltage is formed. When e2 is a negative half cycle, a positive voltage is applied to D2 and D4, and they are turned on; Apply reverse voltage to D1 and D3, they are cut off. E2, D2Rfz, and D4 are energized a loop in the circuit, and the other half-wave rectified voltage is also formed on Rfz. Figure 9. Bridge Rectifier Circuit (b) If repeated, a full-wave rectified voltage at Rfz is made. The waveform diagram is the same as the full-wave rectifier. It is not difficult to see from the figure that the reverse voltage of each diode in the bridge circuit is equal to the maximum value of the secondary voltage of the transformer, which is half smaller than the full-wave cleaning circuit.     Ⅶ High-frequency Rectifier Diodes The rectifier diode in the switching power supply must have the characteristics of low forward voltage reduction and fast recovery, and should also have sufficient output power. The following three types of high-frequency diodes can be used: fast recovery rectifier, ultra-fast recovery rectifier, and Schottky diode rectifier.Fast recovery and ultra-fast recovery rectifier diodes have moderate and high forward voltage drop, and the range is from 0.8 to 1.2V. These two types of rectifier diodes also have higher cut-off voltage parameters. Therefore, they are particularly suitable for use in low-power auxiliary power circuits with output voltages around 12V.Compared with general rectifier diodes, the reverse recovery time difference between fast recovery rectifier diodes and ultra-fast recovery rectifier diodes is reduced to the nanosecond level, thus greatly improving the efficiency of the power supply. According to experience, when choosing a fast recovery rectifier diode, its reverse recovery time should be at least 1/3 of the rise time of the switching transistor. These two kinds of rectifier diodes also reduce the switching voltage spike, because it will affect the ripple of the output DC voltage.Whether fast recovery rectifier diodes and ultra-fast recovery rectifier diodes used in switching power supplies need a heat sink, which depends on the maximum power of the circuit. Under normal circumstances, the allowable junction temperature is 175°C during manufacture. The manufacturer has a technical parameters provided for the designer to calculate the maximum output operating current, voltage, and case temperature. Even under the action of a large forward current, the forward voltage drop of Schottky rectifier diodes is very low, only about 0.4V. Moreover, as the junction temperature increases, its forward voltage drop decreases. Therefore, Schottky rectifier diodes are particularly suitable for low-voltage output circuits around 5V. Its reverse recovery time is negligible, because this device is a semiconductor device with majority carrier. During the switching process of the device, there is no need to remove the stored charge of the minority carrier.Schottky rectifier diodes have two major shortcomings: First, the reverse cut-off voltage tolerance is low, about 100V; second, the reverse leakage current is large, making the device more susceptible to have heat breakdown than other types of rectifier devices. Of course, these shortcomings can also be overcome by adding a transient overvoltage protection circuit and appropriately controlling the junction temperature.     Ⅷ FAQ 1. How does a rectifier diode work?A rectifier is a device that converts an Alternating Current (AC) into a Direct Current (DC) by using one or more contact diodes. ... In simple words, a diode allows current in just one direction. This unique property of the diode allows it to act sort of a rectifier by converting an alternating current to a DC source.   2. What is a function of rectifier diode?A rectifier diode is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC).   3. What is the function of diode in rectifier circuit?A characteristic of diodes is that current flows (forward direction) or current does not flow (reverse direction) depending on the direction of applied voltage. This works to convert alternating current (AC) voltage to direct current (DC).   4. Which is used as rectifier?We know that the core use of rectifier is to convert AC current into DC current. The rectifier consists of semiconductor diodes to do this function.   5. What is the limitation of a diode rectifier?Disadvantages of Full Wave Bridge RectifierIt needs four diodes. The circuit is not suitable when a small voltage is required to be rectified. It is because, in this case, the two diodes are connected in series and offer double voltage drop due to their internal resistance.   6. What is the ideal rectifier diode efficiency?It is the ratio of DC output power to the AC input power. The rectifier efficiency of a full-wave rectifier is 81.2%.   7. What is a fast recovery rectifier?Definition: Fast Recovery Diode is a semiconductor device which possesses short reverse recovery time for rectification purpose at high frequency. A quick recovery time is crucial for rectification of high-frequency AC signal. Diodes are mostly used in rectifiers because they possess ultra-high switching speed.   8. Which diode is fast recovery diode?FRD stands for fast recovery diodes. They offer high-speed support and generally have a trr of approximately 50 to 100 ns. With a VF of approximately 1.5V, it is rather large when compared to general rectifying diodes. Another generic term for the FRD type would be a “High-speed Diode.”   9. What is ultra fast recovery diode?A fast diode is a faster-than-standard current rectifier. ... A fast rectifier typically recovers ten times faster than a standard rectifier, and an ultrafast designation is usually applied to rectifiers designed to beat the standard rectifier recovery by being more than fifty times faster.   10. What is the difference between a Schottky diode and a rectifier diode?Schottky diode, also known as barrier diode is mainly used in low voltage circuits because the forward voltage drop of Schottky diode(Vf) is less than a rectifier diode. The forward voltage drop of a Schottky diode is typically in the range of . 25 to 0.5 V whereas the Vf of a rectifier diode is around 0.7 volts.   11. What is Schottky barrier rectifier?The Schottky diode or Schottky Barrier Rectifier is named after the German physicist Walter H. Schottky, is a semiconductor diode designed with a metal by the semiconductor junction. It has a low-forward voltage drop and a very rapid switching act. ... Actually, it is one of the oldest semiconductor devices in reality.