The Kynix Blog

The diode and the negative end of the power supply are connected in series to monitor the current, and the fixed range digital multimeter (DMM) is used to detect the current. This simple design example can realize the current monitoring from a number of μA to 100mA in a single range. This design example has proved to be very useful and simple. Only 3 to 4 modules are needed to monitor the current from the μA over to 100mA in a single range.   Home Energy Monitor Project: Current   As defined by the diode formula IF≅I0 × exp (eVF/kT), the voltage on the diode increases with the logarithmic current flowing through it. Where IF is a forward current, IO is a reverse saturation current, the charge is (1.602 × 10 ~ (-19) C) V _ F is a forward voltage T is the temperature (K), k is the Boltzmann constant (1.380 × 10 ~ (-23) J/K). Depending on the purpose, the following formulas can be extracted: VF∝logIF（temperature fixed）       Catalog   I Shunt Diode II Adding Extra Diodes III. LTspice IV Conclusion FAQ     I Shunt Diode Now let ' s look at a diode with a measuring instrument . When the current is low , it indicates the milliampere ( mA ) level current that flows through the meter rather than the diode; while in a large current it displays the voltage on the diode, and the logarithm of the current thus derived ( imagining the diode as a self-adjusting shunt ) . Therefore the bottom of the meter scale is therefore quite linear and the top has enough logarithmic properties and the middle is a transition phase , so the entire range is very useful. As shown in Fig.1, using a Schottky rectifier, a 100μA/1.7kΩ meter and an appropriate series resistor can monitor the current from 10 μA to over 100mA within a single range, and the indicated speed is limited to the pendulum speed of the meter. Fig. 1 Schottky rectifier, 100 μ A / 1.7 kΩ meter and suitable series resistance This simple circuit often has more problems than the number of components, in addition to the high-precision calibration process, the circuit also has two main drawbacks: series voltage drop and temperature stability. The diode voltage drop is as high as 400mV, so it is best to use a new or charged battery when monitoring, otherwise your measured components may show that the battery is low. Or treat the circuit as a convenient low-voltage test circuit that might add a short-circuit switch.   II Adding Extra Diodes At the bottom of the scale, almost all current flows through the instrument, which is limited by the machine and magnetic temperature coefficients, and the measured temperature coefficient is very low. But at large currents, a voltage drop can be seen on the diode, which will drop at a rate of about 2mV/K, as predicted by the diode formula. This not only affects the slope of low of logarithm, but also affects the transition point from linear to logarithmic. In addition, the meter windings account for a large part of the total series resistance, and the TCR of copper at room temperature is 3930 ppm/kg. Fig.2 shows the relation curves of deviation and current of 1N5817 at 0℃, 25℃ and 50℃. These curves take into account the TCR of the measuring circuit and the temperature coefficient of the diode, but ignore the self-heating effect of the latter, but there is no problem at relatively stable temperature. Fig. 2 Deviation and current curve Self-heating mainly exists in D1 will have no impact on current. Suppose the current flowing through is 100mA, the voltage drop D1 is 400mV—that's 40mW. According to the manual, the basic thermal resistance of a D0-41 1N5815 with a slightly longer pin and a large amount of radiating copper is 50 K/W. When these data are taken into account, the temperature rise of the node is only 2℃ at 100mA, which is equivalent to the reduction of VF by about 4mV, or the error of about 1% at full scale. Try to keep the diode to a short pin and high thermal quality, noting that there may be high transient currents during conduction, as these can lead to errors until the temperature of the node cools again. Fig. 3 An improved version of the offset temperature coefficient Fig. 4 The bias and current curve after adding a diode Fig. 4 shows the curve of the circuit. Note that most of the curve is now in logarithmic form, and that extra diode effectively suppresses the initial linear region. However, the selection of this diode is critical because the forward voltage of D2 should be slightly lower than that of D1, but other features should match.   III LTspice D1 using 10MQ060N and D2 using BAT54—this is the first pair of components emulated. Both are cheap, modeled by LTspice and are therefore recommended components. A pair of 10MQ060N works almost consistently (but a pair of BAT54 is inconsistent). In most of the time, this group combines with other components showing worse temperature variations and strange indications, so it is necessary to  model the circuit before building it. If the sensitivity and resistance of the instrument are appropriate, R1 can be omitted. On the same thermal properties, the D1 and D2 can track mutual temperature changes. Silicon P-N junction diodes generally have a very straight (log IF) / VF relation, while Schottky's straight line is not. This is because their structures have higher series resistance, are more closed to linear than logarithmic at very low currents, and have protection loops to control the potential gradient of P-N diodes that are parallel to Schottky nodes. Therefore, in practice, the exact logarithmic law will change with the current and the type of component. Although a used diode may be fine for the first pair, due to the inevitable inaccuracy of the circuit, the double diode design still needs to be carefully selected. Schottky diodes can provide more reference resources. 100 μ A /1700 Ω indicators, which are very common, very tightly connected, very useful, and their linear and structure are well consistent with units, just match the 35mm × 14mm aperture, so select them. The calibration points used in Fig.5 are generated by arranging a series of combinations of monitors, batteries, fixed and variable resistors, and the DMM series. Existing test scales are marked at the appropriate points and then removed and scanned, which are used as templates for the final layout.  The simulation results are used to generate the reference point in Fig.5 (left), and the results well reflect the actual operation, although the multimeter is poor. These scales can save time, but are not as accurate as they are newly made (obviously these measuring structures need different scales), and R1 can be calibrated slightly (the instrument is set at ±20%). Both scales consider the non-linearity of the instrument structure. Fig.5 The calibration point (right) of the monitor, battery, fixed and variable resistor, and DMM combination IV Conclusion Whatever, now that these circuits are embedded in most of my development projects and even in production testing devices, they are effective in finding a variety of faults and problems, from power lines short-circuiting to the pull-up pins of miscoding. In order to facilitate the monitoring of the current, it is necessary to connect the appropriate diode with the negative end of the power supply and monitor its forward voltage drop. After some simple calibration, you can monitor the supply current in full sync with the other parameters you want to detect.   FAQ   1. What is a shunt diode? In electronics, a shunt is a device that creates a low-resistance path for electric current, to allow it to pass around another point in the circuit. ... The origin of the term is in the verb 'to shunt' meaning to turn away or follow a different path.   2. What is shunt and its uses? shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path. A shunt (aka a current shunt resistor or an ammeter shunt) is a high precision resistor which can be used to measure the current flowing through a circuit.   3. How does a shunt diode work? The shunt regulator operates by maintaining a constant voltage across its terminals and it takes up the surplus current to maintain the voltage across the load. One of the most common examples of the shunt regulator is the simple Zener diode circuit where the Zener diode acts as the shunt element.   4. What are the disadvantages of shunts? a. It has poor efficiency for large load currents. b. It has high output impedance. c. The output DC voltage is not absolutely constant because both VBB and VZ voltages decrease with increase in room temperature.   5. Where is shunt used? The shunt is used in the galvanometer for measuring the large current. It is connected in parallel to the circuit of the galvanometer. The galvanometer is the current sensing devices. The direction of flow of current inside the circuit is determined by the pointer of the galvanometer.   6. Why shunt is always connected in parallel? A shunt resistance should be connected in parallel to the galvanometer so as to keep its resistance low. Such low resistance galvanometer ( ammeter) is used in series with the circuit to measure the strength of current through the circuit.   7.How is shunt current calculated? How to Calculate a Shunt: a. Write down the Ohm's law expression of "V = I * R" where "V" is the voltage drop across shunt resistor, "I" is the current flowing through shunt and "R" is the shunt resistance. b. Substitute value of voltage "V" and current "I" in the Ohm's law expression.   8. What size shunt do I need for battery monitor? A 100 amp shunt would be plenty if you are only using 12v devices like water pump, furnace blower and lights. We have an inverter and pass up to 200 amps sometimes. The shunt that came with our monitor is good for 500 amps. It doesn't hurt to have a shunt larger than you need.   9. Why shunt is used in galvanometer? Since galvanometer is a very sensitive instrument that it can not measure the heavy currents . to do so A shunt is connected with parallel with galvanometer to convert it into ammeter. ... so after that it can measure heavy currents in the circuit.   10. Is a shunt a resistor? A shunt is a low-ohm resistor that can be used to measure current. Shunts are always employed when the measured current exceeds the range of the measuring device.

IntroductionThe application of communication power source centralized monitoring technology in communication power supply indicates that the maintenance and management of communication power supply is changing from manual management mode to machine mode. The following is its purposes: (1) adapt to the development of communication technology; improve the maintenance and management of communication power supply equipment.(2)improve the power supply quality of communication power supply, making the power supply system have higher reliability and economy.(3) take full advantage of the computer technology to make the management of power supply equipment more automatic and intelligent.(4) realize less manual work of communication power supply equipment monitoring.(5) improve the maintenance efficiency and reduce maintenance costs. At present, the development of communication power centralized monitoring technology and the implementation of the monitoring system have entered a new era.As for function, in order to meet the requirement of machine monitoring than manual work, it emphasizes the quick response and fault alarm accuracy to the fault events of the power equipment. At present, the power supply monitoring system is continuously improved and developed based on its basic functions, such as telecontrol, teleindication and telemetering, monitoring information query, data storage and recording, real-time historical trend, system configuration, remote operation, password management, support for networking, etc. 1. Intelligent Device AccessBecause there are many kinds of communication power supply equipment, for intelligent equipment, even the same kind of equipment also have different protocols because of different manufacturers, in addition, there are many suppliers of power supply equipment, thus there are more kinds of protocols. In the process of implementation of the monitoring system, to make better use of the resources of intelligent equipment, the intelligent device is directly connected to its monitoring system through the conversion of the communication interface and protocol. The communication interface conversion basically belongs to the hardware conversion between RS-232, RS-485 and CAN, which is easy to realize. In the past, the conversion of communication protocols has always been a thorny problem in the implementation of monitoring systems. At present, this problem has been preliminarily resolved. On the one hand, most power supply equipment manufacturers can provide the communication protocol of their equipment actively, on the other hand, the intelligent equipment receives agreement officially. Both of them make the protocol conversion easily. At present, if the protocol and communication interface conversion is based on protocol converter, this method is connecting a protocol converter between an intelligent device and station monitoring host. One end is connected with the serial port of the intelligent device, another is connected with the serial port of the station monitoring host computer, thus the conversion of communication protocol and the communication interface is completed.In short, the protocol converter is a microcomputer system with CPU, EPROM, RAM, serial communication port and so on. The protocol conversion generally has two conditions: firstly, there are at least two serial ports which match with the serial ports of the converted intelligent device and the local station monitoring sovereignty respectively; secondly, the conversion software is solidified in the EPROM of the protocol conversion when the communication protocol of the intelligent device is converted into the host protocol of the local station monitoring. This method is more effective for multiple intelligent devices with different protocols connected to one monitoring host at the same time. Another way is putting the protocol conversion function in the station monitoring host, this method is not often used in practice because it is only suitable for connecting intelligent devices with a single subject protocol to a monitoring host. If there are too many kinds of protocols in a monitoring host, the monitoring host will be overburdened and its normal work will be affected. At the same time, it will bring about problems for the development of to monitoring host software. In addition, the unified communication protocol provides a better solution for intelligent device access. 2. Reliability of the Monitoring SystemAs a result of new-technology and high-quality devices are more widely used in the production of communication power supply equipment, the reliability and automation of the monitoring system have been greatly improved. For example, switching power supply equipment, UPS, diesel generator sets and other intelligent devices, as well as non-intelligent devices such as VRLA storage batteries which are widely used now. All have high reliability to improve the monitoring management and provide better conditions for the purpose of less manual work. Therefore, based on the continuous improvement of the performance of the power supply monitoring system, the reliability of the monitoring system should be improved. 3. Perfecting the Self-checking Function of the Monitoring SystemIn order to make the monitoring system play its role more effectively, it is necessary to continuously improve the basic functions of the monitoring system, meanwhile, pay attention to the use of the advantages of computer data processing, developing and improving the high intelligent performance. Fundamentally change the traditional maintenance mode, using the monitoring technology effectively.The implementation of the monitoring system is based on the new maintenance mode. That is, taking the region as the monitoring management center to monitor and manage the corresponding stations and stations. Urban monitoring and management center unifies its regions and manages them. The difference between the manual and mechanized management modes except for the maintenance, the greater difference is computer realize the automatically real-time monitoring. For example, when the power supply equipment fails, The monitoring system will make a quick response and timely report to the corresponding management center. To adapt to this kind of computer monitoring and management mode, it is necessary to change the traditional maintenance mode fundamentally. Using the computer monitoring system, which is characterized by the real-time monitoring of the power supply equipment, but it requires to read the meter at intervals within the period of time, which is stored and printed in the form of a daily report form. These statements should also be kept for two to three years. This method takes up the large resources of the monitoring system, and the data is rarely used in practice. In the face of these problems, the monitoring system in certain functions should be reconsidered:(1) On the basis of continuously improving the reliability of the controlled equipment (power supply equipment), the safety and reliability of the monitoring system can be improved comprehensively.(2) From the overall consideration of the controlled equipment and the monitoring system, since the security and reliability of the power supply equipment can be basically guaranteed (the reliability requirements of power supply equipment are: switching rectifier MTBF> 50,000h, VRLA battery MTBF> 350,000h. the reliability index of AC/DC distribution equipment is higher as required, and the reliability index of the monitoring system should be MTBF> 100000h), the implementation of the monitoring system should be simplified, practical and highly intelligent. At the same time, it should ensure the accuracy and rapidity of the alarm and warning performance of the monitoring system, also with the intelligent optimization of statistical analysis. The continuous improvement of the function makes the reading meter within time period become less significant.(3) renew the traditional maintenance concept and establish a new maintenance system.Therefore, another important task of the future monitoring system is to fundamentally change the traditional maintenance mode. Making more effective use of monitoring technology to impel the power monitoring system play a greater role in the management of communication power supply maintenance. 4. Network Access Detection of the Monitoring SystemTesting the monitoring system is difficult and will be limited by the following conditions:(1) to carry out the inspection of the monitoring system, it is necessary to have a standard basis for the items, indicators, conditions, and methods. And there are some technical requirements of the monitoring system at present, but as the standard basis of monitoring system detection is far from enough.(2) compared with the general power supply equipment, the monitoring system adopts more computer technology, and emphasizes the network and function of the system, and the real time of the system software, so it is difficult to evaluate the technical performance of monitoring system.(3) A monitoring system is a large real-time network system, which has certain capacity features (including software and hardware capacity). The realization of various performance indicators is meaningful only when the capacity is full, but it is impossible to establish a full capacity system when having these detecting indices.(4) restricted by the mode of communication, communication conditions and other aspects. ConclusionFrom the above situation, we can see that the implementation of the monitoring system is indeed facing great difficulties. Even that, the monitoring system is tested through certain methods to reach the maximum approximation. It is necessary and meaningful to describe and evaluate the performance index of the monitoring system.You May Also LikeList of Basic Electronic ComponentsSwitching Power Supply Tutorial: 4V～16VWhat is A MCU’s internal Structure: Single Chip Micro-ComputerPCB Wring Tutorial: A/D converterDIY Community: Let's Make MonitoringHydroponic Grenhouse Monitoring and Control System

The circuit that converts analog signals into digital signals is called analog-to-digital converter (abbreviated as a/d converter or adc, analog to digital converter). The function of A/D conversion is to convert time-continuous and continuous-amplitude analog quantities It is converted into a digital signal with discrete time and discrete amplitude. Therefore, A/D conversion generally involves four processes: sampling, holding, quantization, and encoding. In actual circuits, some of these processes are combined. For example, sampling and holding, quantization and coding are often implemented simultaneously during the conversion process. A short video introducing a/d converter: Electronic Basics: ADC (Analog to Digital Converter)    Catalog   I What is A/D converter? II Wiring Layout of Successive   Approximation A/D Converter III Wiring Layout of High-precision ∑-△   A/D Converter IV Conclusion FAQ   I What is A/D converter? The process of converting analog to digital is called the analog-to-digital converter, and the circuit that completes the conversion is called the A/D converter (abbreviate  ADC). Its function is making the analog signal whose time and amplitude are continuously converted to discrete digital signal whose time and amplitude are also discrete.  Fig. 1 Basic operation of an A/D converter The conversion accuracy of monolithic integrated A/D converters is described by resolution and conversion errors, and the layout of A/D converter is also changing as the conversion accuracy of AD converters increases. Specifically, the resolution rate of A/D converter refers to the number of discrete digital signals that can be output for analog signals within the allowable range, and the conversion error is usually given in the form of the maximum output error. In general, it represents the difference between the actual output of the A/D converter and the theoretical output. The multiples of the lowest significant bits are commonly represented it. For example, the relative error between −1/2 LSB and +1/2 LSB, shows that the error between the actual output digital quantity and the theoretical output digital quantity should be less than half a word of the lowest bit. Fig. 2 Relationship between analog input and digital output   At first, A/D converters originated in the analog paradigm, in which most of the physical silicon was analog. With the development of new design topology, this paradigm has evolved into a digital component as the main part in low-speed A/D converters. Although the leading role of the A/D converter change from analogue to digital, the wiring criterion of it has not changed. When cabling designers design mixed-signal circuits, basic wiring knowledge is still needed to achieve efficient wiring. In this paper, we take the successive approximation A/D converters and ∑-type A/D converters as examples to discuss the PCB routing strategy for the A/D converters.  Fig. 3  An 8-level ADC coding scheme   II Wiring Layout of Successive Approximation A/D Converter The successive approximation A/D converters have 8-bit, 10-bit, 12-bit, 16-bit, and 18-bit resolution. Initially, the process and structure of these converters were bipolar with R-2R trapezoidal resistor networks. However, these devices have been transferred to the CMOS process by using the capacitance-charge distribution topology recently. But this migration does not change the system routing strategy of these converters. Except for high resolution devices, the basic wiring methods are consistent. For these devices, special care is needed to prevent digital feedback from converter serial or parallel output interfaces. From the point of view of circuits and on-chip resources dedicated to different fields, analog plays a dominant role in successive approximation A/D converters. Fig. 4 is a block diagram of a 12-bit CMOS successive approximation A/D converter. Fig. 4 Block diagram of a 12-bit CMOS successive approximation A/D converter This converter uses the charge distribution formed by the capacitor array. In this block diagram, most of the sample/hold, comparator, digital-to-analog converter (DAC) and 12-bit successive approximation A/D converter are simulated. The rest of the circuit is digital. Therefore, most of the energy and current needed for this converter are used in internal analog circuits. This device requires very small digital current, only D/A converters and digital interfaces will have a small amount of switch-on and off. In addition, these types of converters can have multiple ground and power connection pins. The names of pin are often misunderstood because pin labels used to distinguish analog and digital connections. These labels are not intended to describe system connections to PCB, but to determine how digital and analog currents flow out of the chip. Knowing that this information and main resources consumed in the chip are analog, you will understand the significance of connecting the power supply and the ground pin on the same plane, such as the analog plane. Fig. 5 The successive approximation A/D converter, regardless of its resolution, usually has at least two connecting ends: AGND and DGND. Take Microchip's A/D converters, MCP3201 and MCP3008, as the examples in this article. Fig. 5 Pin configurations for typical 10-bit and 12-bit converters More details about these devices, two grounding pins are usually pulled out of the chip: AGND and DGND. The power supply has one lead, when using these chips for PCB wiring, AGND and DGND should be connected to the analog ground plane. And the analog and digital power pins should also be connected to the analog power plane or at least to the analog power rail, in general, every power pin is connected closely to an appropriate bypass capacitor as close as possible. But the devices such as MCP3201 have only one ground pin and one positive power pin, the only reason for this is due to the limitation of the number of packaged pins. However, isolating the grounding can improve the converter's performance and the repeatable accuracy. For the power strategy of all these converters, the analog plane should connect all ground, positive and negative power pins. Also, a “COM” pin or an “IN” pin associated with an input signal should be connected as close to the signal grounding as possible. For higher-resolution successive approximation A/D converters (16-bit and 18-bit converters), separate digital noise from "quiet" analog converters and power supply planes requires additional attention. So external digital buffers should be used for noise-free operation when these devices are interfaced with single-chip computers. Although these types of successive approximation A/D converters usually have internal double buffers on the digital output side, external buffers are still needed to further isolate the analog circuits in the converters from the digital bus noise.  Fig. 6 Correct power policy for this system   For high-resolution successive approximation A/D converters, the power and grounding of the converter should be connected to the analog plane. Then, the digital output of the A/D converter should be buffered with external tristate output buffers. These buffers have the function of isolating the analog and digital sides in addition to the high-drive capability.   Fig. 7 Layout block diagram of successive approximation A/D converter   III Wiring Layout of High-precision ∑-△ A/D Converter Fig. 8  Schematic diagram of high-precision ∑-△ type A/D converter The main part of a silicon board in high precision ∑-△ type A /D converter is digital. In the early stage of converter production, the shift in the example prompted users to use PCB planes to isolate digital and analog noise. Like successive approximation A/D converters, these types of A/D converters may have multiple analog grounding, digital grounding, and power pins. Digital or analog design engineers tend to separate the pins and connect them to different planes. However, this is wrong, especially if you try to solve the serious noise problem of 16-bit to 24-bit precision devices. For a high-resolution ∑-△ type A/D converter with 10Hz data rate, the clock (internal or external) added to the converter may be 10MHz or 20MHz. This high-frequency clock is used for switching modulators and over-sampling engines. For these circuits, the AGND and DGND pins are connected on the same ground plane as the successive approximation A/D converters. Also, analog and digital power pins are best connected on the same plane. The requirement of analog and digital power plane is the same as that of high-resolution successive approximation A/D converter. There must be a ground plane, which means that at least two panels are required. On this double panel, the ground plane should cover at least 75% of the total panel area. The purpose of the ground plane layer is to reduce the grounding impedance and inductance, and to provide shielding that against electromagnetic interference (EMI) and radio frequency interference (RFI). If an internal connection line is required on the ground plane side of the circuit board, the line should be as short as possible and perpendicular to the earth current loop. IV Conclusion For low-precision A/D converters, such as six-bit, eight-bit or maybe even 10-bit A/D converters, the analog and digital pins are not separated. But when the converter accuracy and resolution of the selected converters increase, wiring requirements become more stringent. High-resolution successive approximation A/D converters and ∑-△ type A/D converters need to be directly connected to low-noise analog ground and power plane.   FAQ   1. How does an AD converter work? Analog-to-Digital converters (ADC) translate analog signals, real world signals like temperature, pressure, voltage, current, distance, or light intensity, into a digital representation of that signal. This digital representation can then be processed, manipulated, computed, transmitted or stored.   2. What are ad DA converters used for? DACs are commonly used in music players to convert digital data streams into analog audio signals. They are also used in televisions and mobile phones to convert digital video data into analog video signals. These two applications use DACs at opposite ends of the frequency/resolution trade-off.   3. What is the main role of an ADC? In more practical terms, an ADC converts an analog input, such as a microphone collecting sound, into a digital signal. An ADC performs this conversion by some form of quantization – mapping the continuous set of values to a smaller (countable) set of values, often by rounding.   4. What is the difference between AD and DA converters? A D/A converter takes a precise number (most commonly a fixed-point binary number) and converts it into a physical quantity (example: voltage or pressure). ... An ideal D/A converter takes abstract numbers from a sequence of impulses that are then processed by using a form of interpolation to fill in data between impulses.   5. Why is a DAC needed? Any time you want to listen to a digital audio signal (like an MP3 or the audio from a digital video) through an analog output (like wired headphones and speakers), you need a DAC to convert the digital signal from the source into an analog signal at the point of connection. ... This is why you need a separate DAC.   6. How are AD converters categorized? Main Types of ADC Converters. Successive Approximation (SAR) ADC. Delta-sigma (ΔΣ) ADC. Dual Slope ADC. Pipelined ADC.   7. Which is fastest ADC? flash ADC. The flash ADC is the fastest type available. A flash ADC uses comparators, one per voltage step, and a string of resistors. A 4-bit ADC will have 16 comparators, an 8-bit ADC will have 256 comparators.   8. What is better analog or digital signal? The smooth analog signal matches the recorded sound wave better than the steps of a digital recording. However, the analog medium (vinyl or magnetized tape) the recording is imprinted on can have tiny imperfections that cause cracking and popping noise.   9. Why are ADC and DAC required in an embedded system? An embedded system uses the ADC to collect information about the external world (data acquisition system.) The input signal is usually an analog voltage, and the output is a binary number.   10. Why ADC is used in microcontroller? An analog-to-digital converter (ADC) is used to convert an analog signal such as voltage to a digital form so that it can be read and processed by a microcontroller. Most microcontrollers nowadays have built-in ADC converters. It is also possible to connect an external ADC converter to any type of microcontroller.  

This article would introduce MCU in details, including analysis its internal structure, and elaborate some important concepts, especially would put emphasis on the concept of memory decoding.   Catalog I. What is MCU? II. Some Basic Concepts 2.1 The Meaning of Rom 2.2 The Meaning of Bit 2.3 The Meaning of Bytes III. The Working Principle of Memory IV. MCU Circuit v. Memory Decoding FAQ   I. What is MCU?   MCU(microcomputer) is an integrated circuit chip. It integrates the microprocessor(CPU), which has data-handling technology such as arithmetic, logic and data transfer, etc, random access data memory(RAM), read-only program memory(ROM), input and output circuit (I/O port) that using the very large scale processing-data technology and may also include a timing counter, serial communication port (SCI), display drive circuit (LCD or LED drive circuit), pulse width modulation circuit (PWM), analog multiplexer and A/D converter, which form a minimum but perfect computer system.   Under the control of software, these circuits can complete the tasks specified by the program designer accurately, quickly, and efficiently. From this point of view, the single-chip microcomputer has the function which the microprocessor does not have, it has intelligent control functions which the modern industry control request separately. And this is the single-chip microcomputer's biggest characteristic.       II. Some Basic Concepts   2.1 The Meaning of Rom Let's think about a problem: when we write instruction in a programmer into an MCU and then take off it, the MCU can execute the instruction, so the instruction must be stored somewhere in the MCU. And this place can still maintain this instruction not to be lost after it power-off. What place is this? This place is the internal ROM of MCU, which is the read-only program memory. Why do you call it read-only memory? We use the programmer, external equipment, to write to the ROM operation under special conditions. In the MCU normal working conditions,  the data can only read but can’t write in, so we call it ROM.   2.2 The Meaning of Bit From the experiment above, we already know that the level of a lamp or a line can represent two states: 0 and 1. In fact, this is a binary bit, thus we call a line a bit, expressed in BIT.   2.3 The Meaning of Bytes A line can represent 0 and 1, two lines can express 00, 01, 10, 11 four states, that is, it can express 0 to 3, and three can express 0 to 7. The computer usually put with eight lines together, counting at the same time, can represent 0 to 255, for a count of 256 states. These eight lines or 8-bit is called a byte (BYTE).   III. The Working Principle of Memory   Structure All the instructions that a single-chip microcomputer can execute are the instructional systems of it. Different kinds of single-chip computers have different instructional systems. In order for a single-chip microcomputer to automatically complete a specific task, the problems to be solved must be programmed into a series of instructions (these instructions must be recognized and executed by the selected single-chip microcomputer). These instructions integrated into the program, and the program needs to be stored in memory—a storage unit.    The memory consists of many storage units (the smallest unit of storage), just as a building has many rooms, each room in a large building is assigned a unique room number. Each storage unit must also be assigned a unique address number, which is known as the address of the storage unit so that the address of the storage cell is known. The instructions are stored in these units. The storage unit can be found, where the stored instructions can be taken out and then executed.   Memory is the place where data is stored. It uses the electricity level to store the data, that is, it actually stores the electrical level, not the number of 1234 that we are used to thinking of. A memory is like a small drawer. If there are eight small drawers in a small drawer, each one is used to store the "charge," and the charge is passed in or released through the wire attached to it. You can think of a wire as a pipe, and the charge in the grid is like water, so it's easy to understand it. Each small drawer in memory is a place for data, which we call a ''bit''.   With this structure, we can start storing data. If we want to put in a data 12, that is 00001100, and we just have to fill the second and third squares with the charge, and the other cells are free of the charges. But the problem is that memory has a lot of cells, and the lines are parallel, and when you put the charge in it, you put the charge in all the cells, and when you release the charge, you release the charge from each cell. In the case of it, no matter how many cells the memory has, it can only be put in the same number, which is certainly not what we want.    A little bit to change structurally,  there's a control line on each unit, and if you want to put the data in the unit, give a signal to the control line of the unit. Therefore, the control line turns on the switch so that the charge can flow freely. And there is no signal on the other unit control lines, so the switch turns off and will not be affected, so that if you handle the control lines of different units, you can write different data to each unit. Similarly, if you want to take data from one unit, just turn on the corresponding control switch.     IV. MCU Circuit   A circuit is always made up of components connected by wires. In analog circuits, wiring is not a problem, because there is usually a serial relationship between the devices, and there are not many connections between the devices, but the computer circuits are different. The microprocessor is the core for it, each device must be connected to the microprocessor, the work of each device must be coordinated, so it needs a lot of connections.   If still like analog circuits, there will be an amazing number of lines between microprocessors and devices, so the concept of a bus has been introduced into the microprocessor, and each device has shared the connection. All 8 data lines are connected to eight common lines, that is, the equivalent of each device is in parallel, but this is not enough. If there are two devices delivering data at the same time, one is 0 and the other is 1, what exactly does the receiver get? This situation is not allowed, so control through the control line to make the device working time-sharing, at any time there can be only one device to send data ( multiple devices can receive at the same time).      V. Memory Decoding   So how do we control the control lines of each unit? It is not that simple to lead the control lines of each unit out of the integrated circuit. There are 65,536 units in a model 27512 memory, and if each line is drawn out, the integrated circuit must have more than 60,000 feet, so it is necessary to find a way to reduce the number of lines. We have a way called decoding, briefly introduce: one line can represent two states and two lines can represent four states and three lines can represent eight kinds, and so on, thus we only need 16 lines to represent 65536 states.   Since the decoding problem solved, let's focus on another problem. Where did the eight lines in each unit come from? Actually, it is connected to the computer, in general, the eight wires not only for memory but also connected to other devices. The problem arises in this way. Because these eight wires are not dedicated to the memory and the computer, it is not good if a unit is always connected to the eight wires. For example, if the value in this memory cell is 0FFH but there one unit is OOH, then what the line set at a high level or a low level?   Thus we have to separate them. The solution is: when the outside wire is connected to the pin of the integrated circuit, it does not directly attach to the units, but a set of switches is added to the middle. Normally we leave the switch off, and if we really want to write data to this memory, or read the data out of the memory, just turn the switch on. This set of switches is selected by three leads: read control, write control, and chip selector.    To write data into the chip, select the chip first, then send a write signal, the switch turns on, and the incoming data (charge) is written into the film chip. If you want to read, select the film chip first, and then send out the read signal, the switch turns on, and the data is sent out. The read and write signals are also connected to another memory at the same time, but the chip selector ends are different.   Although there is a read or write signal, there is no chip selection signal, so the other memory will not "misunderstand" and result in a conflict. What will happen if you pick two chips at the same time? Actually, this can’t be happening because the system is designed and controlled by computer, not by the human. If any, there’s something wrong with the circuit.     From the introduction above, we have seen that the eight lines used to transmit data are not dedicated, but shared by many devices, so we call it data bus. The data line of the device is called the data bus, and all the control lines of the device are called the control bus. There are memory cells in the internal or external memory and other devices of a single chip. Units must be assigned addresses before they can be used. Of course, the assigned addresses are also given in the form of electrical signals. Because there are too many memory cells, there are many lines for address allocation, which are called address buses. Sixteen address lines are also connected, called address buses.   FAQ   1. What are the characteristics of microcomputer? a. Small size and low cost. b. One user. c. Easy to use. d. Low computing power. e. Commonly used for personal application.   2. What are the advantages of microcomputer? a. This computer is widely used today. b. The microcomputer is small in size. c. The microcomputer is used to design different software and app. d. This type of computer is a low cost, so all the users can easily buy. e. No need for highly trained staff for operating microcomputer to office work.   3. Why microcontrollers are often called single chip computers? Single-chip computers are mainly of the form known as Microcontroller chips (the most commonly known are the PIC range by Microchip inc) and used in embedded devices. They provide much more basic functionality but are far simpler to work with as they don't require any external chips in order to function.   4. What is single chip microcomputer that has everything inbuilt? This is a microcomputer built using separate components (CPU, Memory, etc.). ... For some specific applications, we also have single chip computers in a VLSI chip. This single chip microcomputer will have a CPU, memory and I/O interfaces, timers, ADC/DACs etc. on a single chip itself.   5. What is difference between microprocessor and microcomputer? The main difference between Microprocessor and Microcomputer is that the Microprocessor is a computer processor contained on an integrated-circuit chip and Microcomputer is a small, relatively inexpensive computer. ... Microprocessors contain both combinational logic and sequential digital logic.   6. Is Raspberry Pi a microcomputer? The Raspberry PI is a microcomputer that's often used by hobbyists to create projects like animated LED displays or bird watchers.   7. Which is a feature of a single chip microcomputer? A single-chip microcomputer is a major branch of a microcomputer. The biggest feature of the structure is that the CPU, memory, timer and various input/output interface circuits are integrated on a very large-scale integrated circuit chip. In terms of its composition and function, a single chip is a computer.   8. What are the components of microcomputer? The main components are: (1) the central processing unit (CPU), (2) input devices, (3) output devices, and (4) memory. The CPU of a microcomputer performs all the arithmetic, logic, and data handling functions of the microcomputer.   9. Is microcontroller a microcomputer? A Microcontroller is a small and low-cost microcomputer, which is designed to perform the specific tasks of embedded systems like displaying microwave information, receiving remote signals etc.   10. What is the definition of microcomputer? Microcomputer, an electronic device with a microprocessor as its central processing unit (CPU). Microcomputer was formerly a commonly used term for personal computers, particularly any of a class of small digital computers whose CPU is contained on a single integrated semiconductor chip.   You May Also Like Transformers Basics: Construction, Types, Materials and Design Switched Mode Power Supply Tutorial: Principles & Functions of SMPS Circuits List of Basic Electronic Components Switching Power Supply Tutorial: 4V～16V

In the design of circuit systems, we often encounter things like this: when a circuit program is copied from the book completely, the result of the experiment is not correct. Why is it that? The reason is interference. We must do a good job of anti-interference in the process of the electronic circuit and program design.     Catalog I. Three Basic Element of Interference II. Suppressing Interference Sources     2.1 Common Measures to Suppress Interference Sources     2.2 Common Measures to Cut off the Path of Interference Propagation     2.3 Improve the Anti-interference Performance of Sensitive Devices III. Experience and Advice FAQ   I. Three Basic Element of Interference   a. Interference Source: Refers to the components, devices, or signals that cause interference, as described in mathematical terms as follows: some places where the figure of du/dt(voltage regulator factor) or di/dt(current rate of charge) is large may be the interference source. Also the lightning, relays, SCR, motor, high-frequency clock and so on may become interference sources.   b. Propagation Path: Refers to A path or medium in which interference travels from an interference source to a sensitive device. The typical path of interference propagation is the conduction of wires and the radiation of space.    c. Sensitive Device: Refers to an object that is susceptible to interference. Such as A/D or D/A converter, single-chip microcomputer, digital IC, weak signal, and so on. The basic principle of anti-jamming design is to suppress the interference source, cut off the path of interference propagation, and improve the anti-jamming performance of sensitive devices.   II. Suppressing Interference Sources   Suppressing interference sources is to minimize the du/dt and di/dt of interference sources as much as possible. Reduce the du/dt of the interference source by paralleling capacitors at both ends of the interference source; reduce the di/dt of the interference source by using the series inductance or resistance in the interference source loop and adding the freewheel diode. This is the highest priority and the most important principle in anti-interference design.   2.1 Common Measures to Suppress Interference Sources are as follows: (1) Add freewheel diode to the relay coil to eliminate the interference when disconnecting the coil. Only having a freewheel diode will delay the break time of the relay, therefore adding an extra more Zener diode will increase the number of operating times of the relay in unit time.   (2) Connect spark suppression circuit at both ends of relay contact(is usually RC; resistor is selected from several kΩ to dozens of kΩ; capacitance selects 0.01uF), so as to reduce the interference.   (3) Add filter circuit to the motor, pay attention to the capacitance, and inductance lead should be as short as possible.   (4) each IC on the circuit board should be connected with a high-frequency capacitor of 0.01 μ F to 0.1 μ F to reduce the influence of IC to the power supply. Pay attention to the wiring of high-frequency capacitance. The connection should be close to the power supply and should be as short as possible. Otherwise, it will increase the equivalent series resistance of the capacitance, which will affect the filtering effect.   (5) Avoid 90 degree fold line and reduce high-frequency noise when wiring.   (6) Connect the RC suppression circuit to both ends of the thyristor to reduce the noise caused by the thyristor (ps: if the noise is serious may break down the thyristor).   According to the path of interference, it can be divided into two types: conduction interference and radiation interference. Conduction interference is the interference that propagates through the wire to the sensitive device. The high-frequency interference noise is different from the useful signal in the frequency band, which can be cut off by adding a filter to the conductor, and sometimes it can be solved by isolating the optical coupling. Power noise is the most harmful, we should pay special attention to handling. Radiation interference refers to the interference which propagates through the space radiation to the sensitive device. The general solution is to increase the distance between the interference sources and the sensitive devices, to isolate them with grounding wires, and mask the sensitive devices.     2.2 Common Measures to Cut off the Path of Interference Propagation (1) Consider the influence of power supply on single-chip computers. A good power supply helps solve the majority of the jamming problems in circuit design. Many single-chip computers are sensitive to the noise of the power supply, so it is necessary to add a filter circuit or voltage stabilizer to the power supply of a single-chip microcomputer to reduce the interference. For example, a π-shaped filter circuit composed of magnetic beads and capacitors, in addition, a 100Ω resistor can be used to replace magnetic beads when the conditions are not high.   (2) If the I/O port of the single-chip microcomputer is used to control the noise devices such as motors, the I/O port, and the noise source should be isolated.（ adding a π-shaped filter circuit）   (3) Pay attention to the crystal wiring. The crystal oscillator and single-chip microcomputer pin should as close as possible; the clock area should be isolated by grounding wire, crystal oscillator shell should be grounded and fixed. This measure can solve many difficult problems.   (4) Make reasonable partitions of the circuit board. Such as strong signal and weak signal, digital signal, and analog signal. Interference sources (such as motors and relays) and sensitive elements (such as microcontroller) should be isolated as far as possible.   (5) Separate the digital area from the analog area by landlines, and finally, connect to the power at one point. This principle is taken into account when the manufacturer makes the A/D and D/A chip pins arrangement.   (6) Single-chip microcomputer and large ground wire should be grounded separately to reduce mutual interference. High-power devices should be placed on the edge of the circuit board as far as possible.   (7) Use the anti-interference components such as magnetic beads, magnetic rings, power filters, and shielding covers in key places such as I / O portion, power lines, and circuit board connectors, which can significantly improve the anti-interference performance of the circuit.   2.3 Improve the Anti-interference Performance of Sensitive Devices To improve the anti-jamming performance of sensitive devices is to reduce the picking up of interference noise from the interference sources and to recover from abnormal state as soon as possible. The Usual Measures are as Follows: (1) Reduce the area of the loop in order to reduce the inductive noise.   (2) Power and ground wires should be as thick as possible, besides reducing the pressure drop, it is more important to reduce the coupling noise.   (3) The idle I / O port of SCM shouldn’t suspend, but connecting the ground or power supply. And the idle ends of other IC should be grounded or connected to power without changing the logic of the system.   (4) Using the power source monitoring and watchdog timer, such as IMP809, IMP706, IMP813, X25043, X25045, and so on, can greatly improve the anti-interference performance of the whole circuit.   (5) Under the condition that the speed can meet the requirement, the crystal oscillator of the single chip microcomputer is reduced and the low-speed digital circuit is chosen as far as possible.   (6) IC device is welded directly to the circuit board as far as possible.   III. Experience and Advice Software 1. Clearing the code space that is not commonly used, because this is equivalent to the NOP, can help programs recover when appearing program fleet.   2. Adding several NOP before the jump instruction, the same purpose as 1.   3. When there is no hardware WatchDog, an analog one can be used through software to monitor the operation of the program.   4. Dealing with the adjustment or setting of external device parameters, the parameters can be re-transmitted periodically in order to prevent the external device from making mistakes due to interference, so that the external device can be restored correctly as soon as possible.   5. Adding additive data to check anti-interference in Communication.   6. When there are communication lines, such as I2C or a three-wire system, it is found that the anti-interference effect of the Data line is better than that of the low one.   Hardware 1. The layout of grounding and power supply wires.   2. The decoupling of the circuit.   3. The separation of digital ground wire and analog ground wire.   4. Each digital element needs 104 capacitors between the grounding and the power supply.   5. In the applications with relays, especially in the case of high current, a 104 and diode can be combined between the relay coils to prevent the contact spark interference of the relay, and 472 capacitors installed at the contact point and the normal beginning.   6. To prevent the crosstalk of I / O port, the I / O port can be isolated by diode isolation, gate isolation, optocouple isolation, electromagnetic isolation, and so on.   7. Multi-layer board anti-jamming is certainly better than single-layer board, but its cost is several times higher.   8. Choosing an anti-jamming device is more effective than any other method.   FAQ   1. What is Circuit interference? Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.   2. What causes electrical interference? What Causes Interference? Interference occurs when undesired radio signals or electromagnetic "noise" sources are picked up by consumer electronics products -most often telephones, audio equipment, VCRs or TVs. It usually results in noise, unwanted voices or distorted TV pictures. In most cases, the source is nearby.   3. What is meant by circuit design? As circuit design is the process of working out the physical form that an electronic circuit will take, the result of the circuit design process is the instructions on how to construct the physical electronic circuit.   4. What is circuit design theory? In integrated circuit design automation, the term "circuit design" often refers to the step of the design cycle which outputs the schematics of the integrated circuit. Typically this is the step between logic design and physical design.   5. Which software is best for circuit design? a. Eagle b. Altium c. Proteus d. KiCad e. Cadence OrCAD PCB Designer f. DesignSpark g. Protel h. Cadstar i. Sprint-Layout j. PADS PCB   6. How does circuit design work? Digital electronic circuit design takes the electrical signals in the form of discrete values. The data are represented in the form of zeros and ones. Digital circuits extensively use transistors, interconnected to give create logic gates that provide the function of Boolean logic.   7. How long does it take to design a circuit? Programming the Micro-controller. Division of labor will make the work more efficient and specializations and expertise are more focused. Normally, it only takes hours to program the microcontroller of a simple circuit but complex circuit diagrams may take 2 to 3 days.   8. Is circuit design difficult? Designing a circuit is easy if you the basic working principle of each & every electronics components you're going to use. But making it efficient is a bit time-consuming. Once you know the rules, it's normally not too difficult. Of course, some circuits are more difficult than others.   9. What are the types of circuit? There are 5 Main Types of Electric Circuit – Close Circuit, Open Circuit, Short Circuit, Series Circuit and Parallel Circuit.   10. What is the process of a circuit? The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit. ... Typically this is the step between logic design and physical design.   You May Also Like Can We Manage to Recycle PCB Boards for Avoiding Harming the Environment? 10 Things to Consider While choosing a PCB Prototype Service Some Guides for Beginners Before You Create A Printed Circuit Board(PCB) Industrial Chain and Development Trend of PCB in China

The insulated gate bipolar transistor (hereinafter referred to as IGBT) is a composite device of MOSFET and GTR. Thus it has the advantages of MOSFET and GTR, it is an ideal switch device to replace GTR, which is widely used at present with its ability to turn off, and it’s also widely used in all kinds of solid-state power supply.     Catalog   I. What is IGBT? II. The Driving Requirement of IGBT III. The Overcurrent Protection Analysis of IGBT IV. Simulation and Experiment FAQ   I. What is IGBT?   The insulated gate bipolar transistor (hereinafter referred to as IGBT) is a composite device of MOSFET and GTR. Thus it has the advantages of MOSFET, including fast operation speed, high switching frequency, high input impedance, simple drive circuit, and good thermal temperature; it also contains the advantages of GTR, like large current-carrying capacity and high blocking voltage. It is an ideal switch device to replace GTR, which is widely used at present with its ability to turn off and is also widely used in all kinds of solid-state power supply.   And it requires a reasonable drive circuit, but its improper control may cause damage, such as IGBT damage due to overcurrent, and affects the performance of the whole machine. In a word, the drive circuit is very important to IGBT. So this paper mainly discusses the driving and short-circuit protection of IGBT, based on the analysis of its working principle, then designs and simulates the overcurrent protection of the drive circuit.     Electronic Basics #28: IGBT and when to use them     II. The Driving Requirement of IGBT   Driving Requirement IGBT is a voltage-type control device. To make IGBT turn on and off safely and reliably, the driving circuit must meet the following conditions.  And the gate capacitance of IGBT is much larger than that of MOSFET. To increase the switching speed, it is necessary to have a suitable gate bias voltage and gate series resistance.   Gate Voltage In any case, the gate drive voltage in the open state can not exceed the limited value (generally 20V) given by the parameter table, and the optimal gate forward-bias voltage is 15 V ±1.5V. This value is sufficient to allow IGBT to reach saturation and then getting conduction, which can minimize the conduction loss. In the case of gate voltage is cutting off with the value of zero, to reduce the turn-off time and improve the withstand voltage and anti-interference ability of IGBT, a reverse voltage of -5 ~ -15 V can be added between the gate and the source electrode when the IGBT is in a blocking state.   Gate Series Resistance Core The selection of appropriate gate series resistance (RG) is very important for the drive of IGBT. The effect of RG on switching loss is shown in Fig.1. Fig. 1 The Effect of RG on Switching Loss It is the dynamic current of charging and discharging the input capacitance rather than the DC current that is required in a static state, and the input impedance of IGBT is up to 109 ~ 1011. In this case, the DC gain can reach 108 ~ 109, almost without any power consumption.   To decrease the steepness of the front and rear edges of the control pulse, prevent oscillation and reduce the voltage tip pulse with a large IGBT collector, it is necessary to add a gate series resistor RG. When the RG increases, the on-off time will prolong and the energy consumption of the IGBT will increase; in turn, the RG reduces, the di/dt will increase and may damage IGBT.   Thus, according to the current capacity and voltage rating, and switching frequency of IGBT, it is necessary to select a suitable RG, usually from dozens of ohms to hundreds of ohms. To get a more specific value of RG, it is suggested to refer to the device manual. Fig.2 Main Circuit of Inverter Power Supply   Requirements for Driving Power The switching process of IGBT consumes a certain amount of power from the driving power supply. The difference between the gate forward bias voltage and the reverse bias voltage is the △VGE; working frequency is f, the gate capacitance is CGE; and the minimum peak current of the power supply is:     Overcurrent Protection for IGBT The overcurrent protection of IGBT is limiting the short-circuit current and its I-V track to the short circuit safe working area when the device overflows, and the IGBT is turned off before the device is damaged to avoid the damage of the switch tube. When the upper and lower arms conducting, the power supply voltage is almost all added to the two ends of the switch, at this time, the larger the short circuit current is, the smaller the saturation voltage drop will be, during this time, the device would be damaged due to the large current.     III. The Overcurrent Protection Analysis of IGBT   Based on the above analysis, an IGBT drive circuit which contains isolated optocoupler and over-current protection has been put forward in this article, as shown in Fig.3. Fig.3 The Drive and Overcurrent Protection Circuit of IGBT  In Fig.3, the high-speed optocoupler 6N137 realizes the electrical isolation of the input and output signals, which is suitable for high-frequency applications. The main drive circuit adopts push-pull output mode, which effectively reduces the output impedance of the drive circuit, improves the driving ability, and makes it suitable for the drive of high power IGBT.   The over-current protection circuit uses the principle of desaturation of the collector. When an over-current occurs, the IGBT will be turn off. The V1, V3and V4 constitute the driving pulse amplifier circuit; V1 and R5 constitute an emitter follower. The emitter follower provides a fast current source, which reduces the turn-off time. Using the collector desaturation principle, D1, R6, R7, and V2 form a short-circuit signal detection circuit. D1 is a fast recovery diode, to prevent the high voltage on the collector from running into the driving circuit when IGBT is turned off.   In order to prevent the power device from being misled by static electricity, bidirectional voltage regulators D3 and D4 are connected in parallel between the gate sources.   Normal When the control circuit sends a high-level signal, the optocoupler 6N137 turns on, V1, V2 turns off, V3 turns on and V4 turns off. And the drive circuit provides IGBT a driving voltage of +15V to turn it on. When the control circuit sends a low level signal, the optocoupler 6N137 turns off, V2 and V3 conduct, and the drive circuit provides a voltage of -5v to IBGT, making IGBT shut down.   Overcurrent When a short-circuit fault exists, the voltage of 15V is almost all added to the IGBT. At this time, the voltage of V2 cuts off in the short circuit detection circuit, and the electric potential of point A depends on the partial voltage of D1, R6, R7, and VCES.  When the main circuit works normally and the IGBT is on, the A point is kept low, which is lower than the B point potential. All A1 output low level, this time V5 cuts off, and the C point is high level.   So when operating normally, the input to the optocoupler 6N137 is always consistent with the output. When overcurrent occurs, the IGBT collector is desaturated, A point potential rises, when it is higher than B potential ( the setting potential), that is, when the current exceeds the designed fixed value, the A1 overturns and outputs a high level, meanwhile, V5 is switched on, thereby making C in a low potential state. The input signal to the optocoupler 6N137 is always low level regardless of whether the control circuit is sent to a high level or a low level to turn off the power tube. Thus, over-current protection is achieved until the circuit is troubleshot and then restarted.   Fig. 4 Strong Driving Circuit of IGBT with Short-Circuit Protection   IV. Simulation and Experiment   Input to the drive circuit with a high level of 15V and a low level of -5V square wave signal. The output waveform of IGBT is shown in Fig.5  Fig.5 IGBT Output Signal According to the above principle and analysis, the actual output waveform of the circuit is shown in Fig.6  Fig.6 Actual Circuit Output Waveform Conclusion (1) Providing -5V and +15V driving voltage for IGBT to ensure IGBT's turn on and off. (2) Having over-current protection to prevent the IGBT from being damaged when the current is overcurrent. (3) Using in a wide range because the circuit can dynamically adjust the maximum current according to the load. (4) Adopting discrete components as the driving circuits to reduce the cost of the whole system.     FAQ   1. How does an insulated gate bipolar transistor 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.   2. Which insulated gate bipolar transistor? IGBTs are widely used as switching devices in the inverter circuit (for DC-to-AC conversion) for driving small to large motors. IGBTs for inverter applications are used in home appliances such as air conditioners and refrigerators, industrial motors, and automotive main motor controllers to improve their efficiency.   3. How do I trigger IGBT?   An IGBT is simply switched “ON” and “OFF” by triggering and disabling its Gate terminal. A constant +Ve voltage i/p signal across the 'G' and the 'E' will retain the device in its “ON” state, while deduction of the i/p signal will cause it to turn “OFF” like BJT or MOSFET.   4. 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. So smaller chip size is possible and the cost can be reduced.   5. Why IGBT is used an inverter? The Insulated Gate Bipolar Transistor (IGBT) is used in VFD inverter modules as the preferred electronic power switch for the following reasons. ... The IGBT has a fast switching speed. This minimises switching losses and allows for high switching frequencies which is good for motor harmonic and noise reduction.   6. What is difference between IGBT and SCR? SCR is a silicon control rectifier and igbt is a insulated gate bipolar transistor. ... scr has anode ,cathode and gate and igbt has base ,emitter, gate ,and collector. In the both devices gate terminal is used for triggering. Scr has only one insultive layer but igbt has 2 insulated silicon layers.   7. What is IGBT principle? IGBT Principle of Operation：IGBT requires only a small voltage to maintain conduction in the device unlike in BJT. The IGBT is a unidirectional device, that is, it can only switch ON in the forward direction. This means current flows from the collector to the emitter unlike in MOSFETs, which are bi-directional.   8. What causes IGBT failure? The failure modes for the IGBT are in the form of degradation of certain key electrical parameters (e.g., leakage current, threshold voltage) or the loss of functionality (inability to turn-off). The failure causes can be due to environmental conditions or operating conditions.   9. Is IGBT unipolar or bipolar? 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.   10. Which IGBT used in VFD? IGBT (insulated gate bipolar transistor) provides a high switching speed necessary for PWM VFD operation. IGBTs are capable of switching on and off several thousand times a second. A VFD IGBT can turn on in less than 400 nanoseconds and off in approximately 500 nanoseconds.   11. Can we use IGBT instead of 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.   12. How fast can an IGBT switch? The typical switching time of IGBT is about hundreds of nanoseconds and the value varies with load current, junction temperature, and other factors [17–20]. However, the change of IGBT switching time is very small [4,5] (range from several to tens of nanoseconds) when the health status of the IGBT module changes.   13. Is IGBT faster than Mosfet? When compared to the IGBT, a power MOSFET has the advantages of higher commutation speed and greater efficiency during operation at low voltages. ... The IGBT combines the simple gate-drive characteristics found in the MOSFET with the high-current and low-saturation-voltage capability of a bipolar transistor.   14. How many IGBT are in a VFD? Six IGBTs. In a typical six pulse drive there are six IGBTs pulsing voltage up to 15,000 times per second. Since their introduction in the 1980's, IGBTs have literally switched up the market and now play a large role in many modern day power electronics applications where speed and process control are needed.   15. What is the function 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.   16. Is IGBT a rectifier? IGBTs have a pretty good current handling capacity when compared to standard BJTs (Bipolar junction transistor) and MOSFETs (metal–oxide–silicon transistor). IGBTs are devices whose switching is fully controlled electronically. Most standard rectifiers in the market are typically 6-pulse rectifiers.   17. How many types of IGBT are there? two types. The IGBT is classified as two types based on the n+ buffer layer, the IGBTs that are having the n+ buffer layer is called the Punch through IGBT (PT-IGBT), the IGBTs that does not have an n+ buffer layer are called the Non-Punch Through- IGBT (NPT- IGBT).   18. How do you prevent IGBT failure? IGBT turn-off requires that the IGBT be driven to the cutoff region of operation so that it can successfully block the reverse high voltage across it once the high-side IGBT has turned on. In principle this can be achieved by reducing the IGBT gate-emitter voltage to 0 V.   19. What is the difference between unipolar and bipolar devices? As their name implies, Bipolar Transistors are “Bipolar” devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a “Unipolar” device that depends only on the conduction of electrons (N-channel) or holes (P-channel).   20. What is IGBT and Igct? GTO stands for Gate Turn-Off Thyristor, IGCT stands for Insulated Gate Commutated Thyristor and IGBT stands for Insulated Gate Bipolar Transistor. The comparison between the three devices are derived with respect to symbol, characteristic, advantages, disadvantages and applications.   You May Also Like The First Fully 2D FETs Lead A Faster Electronic Future The First Printed 2D Transistor Is Discovered by Researchers The First Chemical Circuit Developed Smarter transistors could be three times more efficient