The Kynix Blog - General electronic semiconductor

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

This paper introduces a switching power supply with the half-bridge circuit. Its input voltage is AC 220V ±20V, the output voltage is DC 4V ~16V, the maximum current is 40A, and the working frequency is 50kHz. And its design idea, working principle, and characteristics of the power supply are introduced emphatically. 12V 10A switching power supply (with schematic and explanation)   Catalog   I. Introduction II. Main Technical Indicators III. Main Functions Description 3.1 AC EMI Filter and Rectifier Filter Circuit 3.2 Half-bridge Power Converter 3.3 Design of Power Transformer 3.4 Design of Auxiliary Power Supply 3.5 Drive Circuit 3.6 Fan Wind Speed Control Circuit 3.7 PWM Control Circuit 3.8 Current Fold back Circuit FAQ       I. Introduction Power supplies with the voltage of 5~15V and current at 5~40A are most commonly used in scientific research, production, experiments and other applications. The maximum current of the general experimental power supply is only 5A or 10A, For this purpose, a switching power supply with continuously adjustable voltage at 4V~16V and maximum output current of 40A has been developed. It adopts half-bridge circuit, with power MOS transistor as switching device and the switching frequency is 50kHz. Light weight, small volume and low cost are advantages of it.   II. Main Technical Indicators   1) Output Voltage: AC 220V±20％  2) Input Voltage: DC 4～16V(adjustable) 3) Output Current: 0~40A 4) Output Voltage Adjustment Rate: ≤1％ 5) Ripple Voltage Up: p≤50mV 6) Current / Voltage Display Function and Fault Alarm Indication   Basic Working Principles and Schematic Diagrams The schematic block diagram of the power supply is shown in Fig.1. After 220V AC voltage is filtered by EMI and rectifier, about 300V DC voltage is added to the half-bridge converter to drive the power MOS tube with the dual pulse signal generated by the pulse width modulation(PWM) circuit. The quasi-square-wave voltage is gained by coupling and isolating the power transformer, and a stable DC output voltage can be obtained by rectifying filter feedback control. Fig. 1 Working Block Diagram of Integral Power Supply   III. Main Functions Description   3.1 AC EMI Filter and Rectifier Filter Circuit Fig.2 AC EMI Filter and Input Rectifier Filter Circuit The power line of the electronic equipment is an important way of electromagnetic interference (EMI) to get into or out of the electronic equipment, but installing the power line filter at the entrance of the power line of the equipment can effectively cut off the transmission path of EMI. And it composed of IEC plug power filter and PCB power filter.   The main purpose of the IEC plug power filter is to prevent the interference from the power grid from entering the power supply box, and for PCB power filter the purpose is to suppress the high frequency noise generated when the power switch is switched. Bridge rectifier circuit is used when AC input voltage is 220V, if JTI jumper is short-connected, then 110V is suitable.   Because the input voltage is high and the capacitor capacity is large, the surge impulse current will be produced at the moment when the power network is switched on, and the general surge current value is tens of times that of the steady current.   This may result in the damage of rectifier bridge and input fuse, or the saturation damage to power devices of high frequency transformer cores, and the reduction of the service life of high voltage electrolytic capacitors, etc. So the input soft start circuit composed of resistance R1 and relay K1 is added in front of rectifier bridge to avoid those damages.   3.2 Half-bridge Power Converter The power supply uses half-bridge converter circuit, as shown in Fig.3, its operating frequency is 50kHz, the main parts on the primary side are power transistors: Q4 and Q5, and capacitors: C34 and C35. Q4 and Q5 alternately conduct and cutoff, A positive and negative square wave pulse voltage of U1/2 is generated through the primary winding N1 of a high frequency transformer. The energy is transferred from transformer to the output, and Q4 and Q5 use IRFP460 power MOS transistor. Fig.3 Switching Power Supply Schematic   3.3  Design of Power Transformer   1) Setting of the Working Frequency The working frequency has a great influence on the volume, weight and circuit characteristics of the power supply. The output filter inductance and capacitance volume decrease with high working frequency, but the switching loss increases, the heat quantity increases and the radiator volume increases. Therefore, according to the factors such as components and cost performance, optimizing the operating frequency of power supply, the formula is fs=50kHz, T=1/fs=1/50kHz=20μs.   2)Core Selection ①Selecting the EE type ferrite core made of R2KB ferrite material, has many advantages, such as versatility, large lead space, convenient wiring operation, economics, and so on. ②Determination of Working Magnetic Induction Intensity: Bm The saturation magnetic induction intensity of R2KB soft magnetic ferrite material is Bs=0.47T, considering that Bs will decrease at high temperature, and in order to prevent the saturation of high-frequency transformer at the moment of closing,  selecting Bm=1 / 3Bs= 0.15T ③Calculation and Determination of Core Type The geometric cross-sectional area S and the window area Q of the magnetic core have a certain functional relationship with the output power Po. For half-bridge converters, when the pulse waveform is an approximately square wave, having SQ= (1) η—Efficiency j—Current density, generally 300~500A/cm2 kc—Fill factor of magnetic core, ferrite core kc=1 Ku—Filling coefficient of copper, related to the wire diameter, winding process, winding number, and so on, is generally about 0.1~0.5. The units of each parameter: Po—W，S—cm2, Q—cm2, Bm—T, fs—Hz, j—A/cm2. The values each parameter:  Po=640W，Ku=0.3,j=300A/cm2,η=0.8,Bm=0.15T, plugging these into formula(1) to get SQ=4.558cm4. From the manufacturer manual of EE55 magnetic core: S=3.54cm2, Q=3.1042cm2, calculating SQ=10.9cm4, the SQ value of EE55 magnetic core is larger than the calculated value. EE55 magnetic core is the option.   3) Calculating Turns of Primary and Secondary Side Windings Calculate the primary number turns of windings according to the lowest input voltage and the full load(the duty ratio is maximum). It is known that the DC input voltage of Umin=176V after rectifying and filtering is Udmin=1.2 × 176 = 211.2V. For the half-bridge circuit, the voltage applied on the primary winding of the power transformer is equal to half of the input voltage, that is Upmin=Udmin/2=105.6V, assuming Dmax=0.9(the maximum duty ratio), getting tonmax= T × Dmax= 20 × 0.9 μs.   Design of an Output Voltage 4~16V Switching Power Supply   Fig.4 Schematic Diagram of Auxiliary Power Supply Upmin×tonmax×104=105.6×9.0×10－6×104, plugging into formula N1=8.9 turns,  the maximum output voltage is Uomax=16V when calculating secondary turns; the secondary circuit uses full wave rectifier, Us as the inductive voltage on the secondary winding and Uo as the output voltage and Uf as the rectifier diode voltage drop, taking 1 V as the voltage drop, Uz is filter inductor equal circuit voltage drop taking 0.3V, getting Us=19.22V×N2=N1×8.9=1.8 turns; For the convenience of winding the transformer, if the secondary winding is 2 turns, then the primary winding will be corrected to N1=N2=10 turns.   4) Selected Wire Diameter When selecting the wire diameter of the winding, the skin effect of the wire should be considered. It is generally required that the wire diameter be less than two times the penetration depth, and the penetration depth Δ is determined by formula (2), Δ= (2), and the unit of penetration depth Δ is m. In formula ω is the angular frequency: ω=2πfs; μ is magnetic conductivity, for the relative permeability of copper wire: μr=1 , 则μ=μ0×μr=4π×10－7H/m; γ is the conductivity of copper, γ = 58 × 10 —6Ωm. The operating frequency of the transformer is 50kHz, and the penetration depth of the copper conductor is Δ=0.2956mm at this frequency, thus the diameter of the winding wire must be copper wire whose diameter is less than 0.59mm. In addition, the current density of copper wire is generally 3 ~ 6 A / mm2, the 0.56mm enamelled wire with 8 strands in parallel for the primary is 10 turns, and the thick 0.15mm flat copper strip with 2 turns in the secondary.   3.4 Design of Auxiliary Power Supply The auxiliary power supply using RCC converter (Ringing Choke Converter), is shown in Fig.4. The input voltage is AC 220 V, as rectifier filter voltage, and the output DC voltage is 12.5 V, the output DC current is 0.5 A. In the circuit, Q8 and transformer primary winding N1 and feedback winding N3 constitute self-excited oscillation. R72 is starting resistance. Q9, R77 constitutes primary overcurrent protection of auxiliary power supply. D20, C81, ZD1, Q11, R75, N76 constitutes voltage detection and voltage stabilizing circuit. The DC component of the base current of Q 8 keeps the output voltage constant, and the transformer is made of EE19 material and LP3 material. The primary is 180 turns, the feedback winding is 5.5 turns, the secondary is 11 turns, the primary inductance is 2.6 MHz, the core gap is 0.4mm.   3.5 Drive Circuit The drive circuit is shown in Fig.5. TL494 outputs the pulse signal of 50kHz and drives the power MOS transistor through the coupling of a high-frequency pulse transformer. The secondary pulse voltage is a timing MOS switch, during which Q7 ends, and the drain circuit formed by it does not work. Q7 conducts when the second pulse voltage is 0, rapidly releasing the gate charge of MOS, and accelerating MOS cutoff. R70 is the spike to suppress the driving pulse, R68, D15, R67 used to speed up driving and suppress the oscillation caused by driving pulse, D17, and the connected pulse transformer windings form a demagnetization circuit.  Fig.5 Driving Circuit Schematic Diagram 3.6 Fan Wind Speed Control Circuit Fan wind speed control circuit is shown in Fig.6. Based on the decreasing trend of diode forward tube pressure drop with increasing temperature, D9 and D10 are used as radiator temperature samplers close to the radiator. When the temperature of the radiator rises with the increase of output power, the level of the positive phase input of the operational amplifier N2A decreases, the output low level causes the transistor Q3 to start conducting, and the voltage on the fan rises.   The rotational speed rises and finally reaches the maximum speed. When the load is lighter and the radiator temperature is lower than 50 ℃, the output of N2A is high level, Q3 is not conductive, and auxiliary electricity 12.5V stepped down by resistance R57 supplying to fan, thus the fan is running at low speed and low noise. The circuit can improve the working life of the fan, increase the reliability of the circuit and reduce the noise caused by the fan in the case of a small load.   Fig.6 Fan Wind Speed Control Circuit 3.7 PWM Control Circuit The general pulse width modulator (TL494,) used in the control circuit has the advantages of generality and low cost, as shown in Fig.7. The output voltage is sampled by R40, RV2, RV1, R41 and then sent to the TL494 pin 1 after the R5 impedance matching. RV1 installed in power front panel to realize the output voltage adjustment. R103 and C14 sample the output inductor L1 front signal which delivering through R5 to TL494 pin 1 to improve power supply stability and eliminate the influence of L1 on loop stability.   3.8 Current Foldback Circuit In order to enhance the reliability of the power supply, this power supply adopts two-stage over-current protection: primary and secondary. Current transformer CT1 is initially used to detect the primary transformer current. The detected current signal is converted from R60 to voltage signal, then filtered by D2~D4 and C9, and then the voltage is divided by potentiometer RV3, and inverted by N3, finally added to the Q 1 tube base. When the primary current is abnormal, the inverter reverses the Q1 switch and adds a high level of VREF=5V to the TL494 pin 4 (the TL494 dead-zone control pin, which is turned off at a high level), TL494 is off. Overcurrent protection on the main output DC line uses R45-R56 resistance as the sampling resistance. When the output current increases, the level of pin15 becomes lower. When the output current is greater than 105% of 40A, the internal operational amplifier of TL494 acts. The pin3 level rises, limiting the increase of the output pulse width, and the power supply is in the limiting state. FAQ   1. How does a switching power supply work? The “switch” in a switching power supply is actually a semiconductor – a MOSFET that is either off or on – driven into its saturation range to transfer power across nearly zero resistance. It does this many thousands of times per second, creating the high-frequency AC intermediary.   2. What is difference between linear and switching power supply? Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges.   3. What is a switching power supply 12v? Switching regulated 12VDC power supplies, sometimes referred to as SMPS power supplies, switchers, or switched mode power supplies, regulate the 12VDC output voltage using a complex high frequency switching technique that employs pulse width modulation and feedback. Acopian switching regulated power supplies also employ extensive EMI filtering and shielding to attenuate both common and differential mode noise conducted to the line and load. Galvanic isolation is standard in our 12VDC switchers, affording our users input to output and output to ground isolation for maximum versatility. Acopian switching regulated power supplies are highly efficient, small and lightweight, and are available in both AC-DC single and wide-adjust output and DC-DC configurations.   4. What is a DC switching power supply? A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor.   5. When should you use a switching power supply? Switching power supplies are primarily used in digital systems such as telecommunication devices, computing equipment, audio equipment, mobile phone chargers, medical test devices, arc welding equipment and automotive chargers.   6. Is a switching power supply regulated? A switch mode power supply regulates an output voltage with pulse width modulation (PWM). This process creates high-frequency noise but it provides a high-efficiency rating in a small form factor. ... The low DC voltage is finally converted into a steady DC output with another set of diodes, capacitors, and inductors.   7. Is a switching power supply DC? A switching power supply takes an AC input, but rectifies and filters into DC first, is converted back into AC at some high switching frequency, steps down the voltage with a transformer, then is rectified and filtered into a DC output.   8. How do I know if my power supply is regulated? You can generally stick one probe into the middle of the connector, and hold the other against the outside. With a few exceptions, the middle is positive, so use the red lead there, and use the black lead on the outside shell. Regulated supplies, without any load, should measure very close to the target voltage of 12v.   9. Can I use a switching power supply to drive a DC motor? A simple unregulated analog power supply may be easier and be able to supply the large starting under load current more that the switching one. DC motors are not too fussy about the supply, and will usually run quite well on unfiltered DC.   10. What are the 3 types of power supply? There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages.   You May Also Like Learn Some Basic Knowledge about Capacitor Voltage Transformer The Latest Development of Electric Vehicle Power Management Technology Design a Momentary Pushbutton in the Circuit of Laching Power Switch

The devices or components commonly used in electronic circuits include: resistors, capacitors, inductors, sensors, potentiometers, transformers, diodes, bipolar junction transistors (BJTs), photoelectric switches, resonators, oscillators, filters, silicon controlled rectifiers (SCRs), relays, dual inline package (DIP) switches, fuse holders, bridge rectifiers, emitters, reed switches, common mode chokes and ferrite beads, magnetic rings, etc. This article contains a lot of commonly used electronic components figures, and I hope you will find this information useful.A Simple Guide to Electronic Components FAQ1. What are basic electronic components?You will work with a number of basic electronic components when building electronic circuits, including resistors, capacitors, diodes, transistors, and integrated circuits. 2. What are electronic components called?They are also called Electrical elements or electrical components. e.g. Resistors, Capacitors, Diodes, Inductors. 3. What are the 3 classification of electronic components?Classification of Electronic Components: Components can be classified as passive, active, or electro-mechanic components.Active components are devices that can amplify an electric signal and produce power.Passive components can't introduce net energy into the circuit. 4. What are the two types of electronic components?These are of 2 types: Passive and Active Components. 5. What is passive electronic components?A passive element is an electrical component that does not generate power, but instead dissipates, stores, and/or releases it. Passive elements include resistances, capacitors, and coils (also called inductors). These components are labeled in circuit diagrams as Rs, Cs and Ls, respectively. 6. How do I choose electronic components?How to select electronic components?Manufacturers.Application Circuit Complexity.Electrical Parameters [voltage, current, power, accuracy, response time, speed, resolution, etc.]Mechanical Parameters [dimension, package, weight, etc.]Consideration w.r.t Manufacturing / Testing. 7. What is difference between active and passive components?Active components are the elements or devices which are capable of providing or delivering energy to the circuit. Passive components are the ones that do not require any external source for the operation and are capable of storing energy in the form of voltage or current in the circuit. 8. How to Test Electric Components with a Multimeter?Continuity tests measure if electricity can flow through the part.Resistance tests how much current is lost as electricity flows through a component or circuit.The third common test is for voltage, or the force of the electric pressure. 9. What are passive components?A passive component is an electronic component which can only receive energy, which it can either dissipate, absorb or store it in an electric field or a magnetic field. ... Passive components cannot amplify, oscillate, or generate an electrical signal. Common examples of passive components include: Resistors. Inductors. 10. How do I choose a PCB component?6 tips for choosing PCB componentsThink about component footprint decisions.Use good grounding practices.Assign virtual parts footprints.Ensure you have complete BOM Data.Sort reference designators.Check spare gates. Relevant information about "List of Basic Electronic Components"About the article "List of Basic Electronic Components", If you have better ideas, don't hesitate to write your thoughts in the following comment area. You also can find more articles about electronic semiconductor through Google search engine, or refer to the following related articles:Rectifiers and Filters NotesCharacteristics and Functions of DiodesReview and Application of Electronic skinSwitched Mode Power Supply Tutorial: Principles & Functions of SMPS CircuitsTransformers Basics: Construction, Types, Materials and Design

Warm hint: The word in this article is about 1000 words and reading time is about 5 minutes     This article introduces you some basic and simple rectifiers and their waveforms and working principle and more.   Catalog I. Introduction 1.1 Composition of DC Stabilized Power Supply 1.2 Basic Concepts II. Detail & Analysis 2.1 Half-Wave Rectifier 2.2 Full-Wave Rectifier 2.3 Bridge Rectifier 2.4 Capacitor Filter 2.5 Inductor Filter FAQ   I. Introduction   1.1 Composition of DC Stabilized Power Supply FIG.1   2. Basic Concepts   AC voltage (current): both amplitude and direction change periodically with time. FIG.2 Sinusoidal Voltage/Current Waveform (AC): alternating voltage/current whose amplitude and direction both change sinusoidally and periodically over time. It is often called AC for short.   Effective value: the direct voltage/current thermally equivalent to the alternating voltage/current is called the effective value of the AC (voltage or current).   Peak value: the maximum instantaneous value of AC (voltage or current).   Frequency: the number of times that AC (voltage or current) changes periodically every second.   Direct voltage/current: voltage/current whose value and direction do not change with time. In fact, the direction can be guaranteed not to change over time, but it is impossible for the value to act the same way all the time. So the alternating voltage/current whose direction is always the same and the numerical value changes over time can be explained as a superposition of DC (voltage or current) and AC (voltage or current) whose amplitude and direction change with time. II. Detail & Analysis   2.1 Half-Wave Rectifier The circuit diagram and the waveforms of half-wave rectifier are shown as the following figures. FIG.3 Average value: FIG.4 Effective value: Turns ratio: According to this, the required output voltage can be obtained by selecting the appropriate N1 and N2.   2.2 Full-Wave Rectifier The following figures are the circuit diagram and the waveform of full-wave rectifier. FIG.5 FIG.6 Average value: Effective value: Transformer: The number of turns of the primary winding is N1, and the number of turns of the secondary winding is N2a=N2b. Turns ratio: According to this, the required output voltage can be obtained by selecting the appropriate N1, N2a and N2b.   2.3 Bridge Rectifier The following figures are the circuit diagram and the waveform of bridge rectifier. FIG.7 FIG.8 Average value: Effective value: Transformer: The number of turns of the primary winding is N1, and the number of turns of the secondary winding is N2. Turns ratio: According to this, the required output voltage can be obtained by selecting the appropriate N1 and N2.   2.4 Capacitor Filter The following figures are the circuit diagram and the waveform of capacitor filter. FIG.9 Filtering principles: a~b: u2=uc=u0, the capacitor C is charged in a sine wave; b~c: u2≈uc = u0, the capacitor C discharges in an exponential curve, but the sinusoidal waves of u2 basically coincide. c~d: u2＜uc=u0, the capacitor C continues to discharge exponentially, and u2 to drop in a sine wave. FIG.10 The effects of RL and C on filtering are shown in the following figure. FIG.11 （1）Basic knowledge of capacitors   Definition:   Basic equations:  Energy equation:  FIG.12 （2）Charging the capacitor Where  It is a time constant, and the initial values of current is  FIG.13 （3）Discharging the capacitor Where It is a time constant, and the initial values of current is FIG.14 （4）Output voltage   After the filtered voltage waveform is linearized, the following approximate waveform is obtained: FIG.15 Based on the relationship of similar triangles, there is And  So we have When There is  FIG.16 Rectifier diode: The current and the conduction angle of the rectifier diode in the capacitor filter circuit are shown in the following figure: FIG.17 Where iD is the current of the rectifier diode when the current is switched on, and io is the current in the load.   2.5 Inductor Filter In heavy current load, if a filter capacitor is used, the capacitance of it and the inrush current of the rectifier both will be very large. But if an industrial-frequency inductor is in series with it for filtering after the rectification, then we can solve these problems very well. The following figure is the circuit diagram of the inductor filter. FIG.18 From the energy point of view, the effects of the inductive filter and the capacitive filter are the same. Therefore, the volt-ampere characteristics of the inductive filter is similar to that of the capacitive filter, see the figure below. FIG.19 The quantitative analysis of inductive filter is more complex, so we should do it with the help of the previous analyzed results for the capacitive filter. If  then we have When the inductor filter is used, the waveform of the terminal voltage and current of the inductor and the conduction angle of the rectifier diode are shown in the following figure. Because the rectifier diode is connected in series with an inductor, the conduction angle of it can reach 180°. Therefore, in situations where harmonics are not demanding, we can use inductive filter to meet PFC (Power Factor Correction) requirements. FIG.20 （1）Basic concepts of inductor FIG.21 Definition:  Basic equations: Energy equation: （2）When inductor stores energy   After the switch is closed, here we have According to the initial conditions, the solution is Where It is a time constant, and the initial voltage is FIG.22 （3）When inductor releases energy FIG.23 After the switch is closed, here we have According to the initial conditions, here we have: Where It is a time constant, and the initial voltage is FIG.24 How Amplifiers Work: Rectifiers and Filter Capacitors   FAQ   1. What are the types of rectifiers? The Different Types of Rectifiers: a. Single Phase & Three Phase Rectifiers. b. Half Wave & Full Wave Rectifiers. c. Bridge Rectifiers. d. Uncontrolled & Controlled Rectifiers.   2. What is Rectifier used for? A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC).   3. What is an example of rectifier? Thyristors are commonly used in place of diodes to create a circuit that can regulate the output voltage. Many devices that provide direct current actually generate three-phase AC. For example, an automobile alternator contains six diodes, which function as a full-wave rectifier for battery charging.   4. Is Zener diode a rectifier? A Zener diode is a special type of rectifying diode that can handle breakdown due to reverse breakdown voltage without failing completely. Here we will discuss the concept of using diodes to regulate voltage drop and how the Zener diode operates in reverse-bias mode to regulate voltage in a circuit.   5. What is the working principle of rectifier? Principle: A junction diode offers a low resistance to current in one direction(when forward biased) and a high resistance in the other direction(when reverse biased). Thus, the diode acts as a rectifier.   6. Why zener diode is not used in Rectifier? No, we don't prefer to use a Zener Diode in a rectifier circuit because for a rectifier circuit a high maximum peak inverse voltage is required. Unlike the normal p-n junction diode, a Zener diode has a low peak inverse voltage. This is an undesirable property for the rectifier circuit.   7. What are the signs of a bad Rectifier? You'll note signs right away like poor starts, fluctuating meter readings, and dimmed headlights. around 13 volts, the bike will start to drain the battery. When this happens, it's only a matter of time before the engine stops completely.   8. What causes a rectifier to fail? Ground connections are important for good voltage, and if there is faulty voltage, the regulator rectifier can run hot. Bad grounding, corroded battery connection and poor or loose battery connections will cause faulty voltage.   9. Will a bad rectifier cause no spark? A bad regulator/ rectifier will result in a dead battery, and once the battery is competely dead you will not get a spark.   10. What is the difference between diode and rectifier? A diode is a switching device, while a rectifier is generally used for the conversion of AC voltage to DC voltage. ... A diode allows the flow of current only when it is forward biased. The diode blocks the reverse flow of current. A rectifier, on the other hand, consists of a transformer, a diode, and a filter circuit.   You May Also Like: Transformers Basics: Construction, Types, Materials and Design Characteristics and Functions of Diodes Switched Mode Power Supply Tutorial: Principles & Functions of SMPS Circuits

Warm hints: The word in this article is about 3000 words and reading time is about 12 minutes.     This article would introduce you different kinds of power supply circuits.   Catalog   I. Circuit Arrangement of Switching Power Supply II. The Principle of the Input Circuit and the Common Circuits 2.1 Principle of AC Input Rectifier Filter Circuit 2.1.1 Lightning Protection Circuit 2.1.2 Input Filter Circuit 2.1.3 Rectifier Filter Circuit 2.2 Principle of DC Input Filter Circuit 2.2.1 Input Filter Circuit 2.2.2 The Anti-surge Circuit III. Power Conversion Circuits 3.1 The Working Principle of MOS Tube 3.2  Common Schematic Diagram 3.3 Working Principle 3.4 Push-pull Power Conversion Circuit 3.5 Power Conversion Circuit with Transformer Driver IV. Output Rectifier Filter Circuit 4.1 Forward Rectifier Circuit 4.2 Flyback Fectifier Circuit 4.3 Synchronous Rectifier Circuit V. Principles of Steady-voltage Loop 5.1 Schematic Diagram of Feedback Circuit 5.2 Working Principles VI. Short Circuit Protection Circuits 6.1 Current-limiting Circuit 6.2 Short Circuit Protection for Low-power Circuit 6.3 Short Circuit Protection for Medium-power Circuit 6.4  Common Current-limiting, Short-circuit Protection Circuit 6.5 Current Transformer Sampling Current Protection Circuit VII. Output Current Limiting Protection VIII. Output Overvoltage Protection Circuits 8.1 SCR Trigger Protection Circuit 8.2 Optocoupler Protection Circuit 8.3 Output Voltage Limiting Protection Circuit 8.4 Output Overvoltage Lockout Circuit IX. Power Factor Correction Circuit (PFC) 9.1 Schematic Diagram of PFC Circuit 9.2 The Working Principles X. Input Under-voltage and Overvoltage Protection 10.1 Schematic Diagram 10.2 The Working Principles FAQ       I. Circuit Arrangement of Switching Power Supply   The main circuit of the switch-mode power supply is composed of an input EMI filter, rectifier filter circuit, power conversion circuit, and PWM controller circuit, output rectifier filter circuit. The auxiliary circuits include the input & output Undervoltage protection circuit, the output overcurrent protection circuit, the output short circuit protection circuit, and so on.   The block diagram of switching power supply circuit arrangement is as follows:   FIG.1 Block diagram of switching power supply circuit arrangement   II. The Principle of the Input Circuit and the Common Circuits   2.1 Principle of AC Input Rectifier Filter Circuit 2.1.1    Lightning Protection Circuit When there is a lightning strike, the circuit composed of MOV1, MOV2, MOV3, F1, F2, F3, and FDG1 is used to provide protection against the resulting high voltage introduced into the power supply through the electrical grid.   When the voltage applied to the two ends of the piezoresistor exceeds its operating voltage, the resistance value will decrease, making the high voltage energy be consumed on the piezoresistor; if the current is too large, the F1, F2, and F3 will burn out to protect the following circuits. 2.1.2     Input Filter Circuit The double Pi filter network composed of C1, L1, C2 and C3 is mainly used to suppress the electromagnetic noise and clutter signal of the input power supply to prevent its interference to the power supply, and also to prevent the interference of the high-frequency clutters generated by the power supply itself to the electrical grid. The C5 will start to be charged when the power is turned on, producing a large instantaneous current, which is called surge current, but with an RT1 (thermistor) it can be effectively prevented. Because the instantaneous energy is all consumed on the RT1, after a certain time the resistance of RT1 will decrease as the temperature rises (RT1 is a negative temperature coefficient device) and the energy consumed by RT1 will be very small at this time, to make sure the following circuits work normally.     2.1.3   Rectifier Filter Circuit After the AC voltage is rectified by BRG1 and filtered by C5, a purer DC voltage can be obtained. If the C5 capacity becomes smaller, the output AC ripples increase with it.     2.2 Principle of DC Input Filter Circuit FIG.3 The schematic of rectifier circuit   2.2.1   Input Filter Circuit The double Pi filter network composed of C1, L1and C2 is mainly used to suppress the electromagnetic noise and clutter signal of the input power supply to prevent its interference to the power supply, and also to prevent the interference of the high-frequency clutters generated by the power supply itself to the electrical grid. C3 and C4 are Safety Capacitors and the L2, L3 are Differential Mode Inductors.   2.2.2   The Anti-surge Circuit This anti-surge circuit is composed of R1, R2, R3, Z1, C6, Q1, Z2,  R4, R5, Q2, RT1 and C7. At the instant of switch-on, Q2 does not conduct due to the presence of C6, and the current forms a loop through the RT1. Q2 turns on when the voltage on C6 is charged to Z1's steady voltage value. If C8 leaks or the following circuits are short-circuited, the voltage drop generated by the instantaneous current at the instant of switch-on on RT1 causes the Q1 conducted, so that Q2 does not have a gate voltage and does not conduct, making the RT1 burnt out in a very short time to protect the following circuits.   III. Power Conversion Circuits   3.1   The Working Principle of MOS Tube At present, the most widely used insulated gate FET is MOSFET, which uses the electroacoustic effect that occurs on the semiconductor surface to work, making it also known as surface field effect transistor. Because its gate is in a nonconducting state, the input resistance can be greatly increased up to 105 ohms. The MOSFET uses the gate-source voltage to change the amount of charge induced on the semiconductor surface to control the drain current.   3.2   Common Schematic Diagram FIG.4 Schematic of power conversion circuit    3.3  Working Principle The buffer composed of R4, C3, R5, R6, C4, D1, and D2 are connected in parallel with the MOS transistor switches, so that the voltage stress of the switch transistor and EMI are reduced, without secondary breakdown occurring. When the switch Q1 is turned off, the primary coil of the transformer is prone to generate peak voltages and spike currents. These components are combined to absorb the peak voltage and current well. The peak current signal measured from R3 participates in the duty cycle control of the current operating cycle and is therefore the current limit of the current operating cycle. When the voltage on R5 reaches 1V, the UC3842 stops working and switch Q1 turns off immediately.   The junction capacitances CGS and CGD in R1 and Q1 together form an RC network. The charge and discharge of the capacitor directly affects the switching speed of the switch. If R1 is too small, it will cause oscillation and electromagnetic interference will be great. If R1 is too large, the switching speed of the switching tube will be reduced. Z1 usually limits the GS voltage of the MOS transistor to less than 18V, thus protecting the MOS transistor.   The gate-controlled voltage of Q1 is a saw wave. The larger the duty cycle is, the longer the Q1 conduction time is, the more energy the transformer stores. When Q1 is turned off, the transformer releases energy through D1, D2, R5, R4, and C3 and at the same time, it also achieves the goal of resetting the magnetic field, which prepares the transformer for the next storage and transfer of energy. According to the output voltage and current, the IC adjusts the duty cycle of 6-pin sawtooth wave, thus stabilizing the output current and voltage of the complete machine.   C4 and R6 are voltage surge absorption loops.   3.4  Push-pull Power Conversion Circuit Fig.5 Schematic diagram of push-pull power conversion circuit Q1 and Q2 will be turned on in turn.   3.5  Power Conversion Circuit with Transformer Driver FIG.6 Schematic diagram of power conversion circuit with transformer driver T2 is the transformer driver, T1 is the switch-mode transformer, TR1 is the current loop .   IV. Output Rectifier Filter Circuit   4.1   Forward Rectifier Circuit FIG.7 Schematic diagram of forward rectifier circuit T1 is a switch-mode transformer, its primary and secondary sides are in a same phase. D1 is a rectifier diode, D2 is a flyback diode and R1, C1, R2 and C2 form a despiker circuit. L1 is a freewheeling inductor and C4, L2, and C5 form a π filter.   4.2  Flyback Fectifier Circuit FIG.8 Schematic diagram of flyback fectifier circuit T1 is a switch-mode transformer, and the primary and secondary sides are opposite. D1 is a rectifier diode, and R1 and C1 form a despiker circuit. L1 is a a freewheeling inductor, R2 is adummy load and C4, L2 and C5 form a π type filter.   4.3   Synchronous Rectifier Circuit FIG.9 Schematic diagram of synchronous rectifier circuit Working principle: When the upper end of the secondary winding of transformer is positive, the current through C2, R5, R6 and R7 makes Q2 turned on and form a loop. Q2 is the rectifier and the Q1 gate is turned off due tothe reverse bias. When the lower end of second wingding is positive, the current through C3, N4 and R2 makes Q1 conducted as a freewheeling diode. The Q2 gate is turned off due to the reverse bias. L2 is a freewheeling inductor, C6, L1 and C7 form a π filter and R1, C1, R9 and C4 form a despiker circuit.   V.  Principles of Steady-voltage Loop   5.1  Schematic Diagram of Feedback Circuit FIG.10 Schematic diagram of feedback circuit 5.2  Working Principles When the output U0 is increased, the voltage of pin 3 of U1 chip is increased either after dividing voltage with these sampling resistors R7, R8, R10 and VR1, until exceeding the reference voltage of pin 2 of U1 chip, it begins to output a high level, turning the Q1 and photoelectric triode on, and lighting the optocoupler OT1 and LED. Accordingly, the potential of pin 1 of UC3842 becomes lower and therefore decreases the duty cycle of pin 6 of U1 chip and U0.    On the contrary, when the output U0 is decreased, the voltage of pin 3 of U1 chip is decreased either until it exceeds the reference voltage of pin 2 of U1 chip, it begins to output a low level, Q1 and photoelectric triode are not conducting, and optocoupler OT1 and LED do not shine. Accordingly, the potential of pin 1 of UC3842 becomes higher and therefore increases the duty cycle of pin 6 of U1 chip and U0. Repeatedly, so that the output voltage remains stable. Regulating VR1 can change the output voltage.   Feedback loop is an important circuit that affects the stability of switching power supply. If the feedback resistors and capacitors are wrong, missed or false soldered, self-excited oscillations will occur, resulting in fault phenomena, such as abnormal waveforms, oscillations within empty or full load condition and unstable output voltage.   VI. Short Circuit Protection Circuits   6.1  Current-limiting Circuit In the case of short circuit at the output end, PWM control circuit can limit the output current within a safe range. There are many ways to  realize the current limiting. When the current limiting circuit does not work in short circuit, all we can do is to add additional circuits.   6.2  Short Circuit Protection for Low-power Circuit FIG.11 Schematic diagram of low-power short-circuit protection circuit When the output circuit is shorted, the output voltage disappears, the optocoupler OT1 does not turn on, the voltage of pin 1 of UC3842 rises to about 5V, and the partial voltages of R1 and R2 exceed the TL431 reference, making it conductive, the VCC potential of pin 7 of UC3842 is pulled down, and the IC stops operating. After UC3842 stopped working, the potential of pin 1 disappeared, TL431 did not conduct, and the potential of UC38427 increased, making UC3842 restart, and go round and begin again, until the short-circuit phenomenon disappears, then the circuit automatically returns to normal operation.   6.3  Short Circuit Protection for Medium-power Circuit FIG.12 Schematic diagram of medium-power short-circuit protection circuit When the output is short-circuited, the voltage of pin of UC3842 rises. When the potential of pin 3 of U1 chip is higher than that of pin 2, the comparator inverts the output high level of pin 1 to charge C1. When the voltage across C1 exceeds the pin 5 reference voltage, the pin 7 of U1 chip outputs low level. The voltage of pin 1 of UC3842 begins to be lower than 1V and UC3842 stops working, making the output voltage be zero, and go round and begin again, until the short-circuit phenomenon disappears, and the circuit begins to work normally. R2 and C1 are charge and discharge time constants respectively, and the short circuit protection will not work if the resistance is not correct.   6.4  Common Current-limiting, Short-circuit Protection Circuit FIG.13 Schematic diagram of protection circuit 1 When the output circuit is short-circuited or overcurrent, the primary current of the transformer increases, the voltage drop across R3 increases, the voltage at pin 3 increases, and the duty cycle of pin 6 of UC3842 increases. When the voltage at pin 3 exceeds 1V, the UC3842 turns off and without output.   6.5  Current Transformer Sampling Current Protection Circuit The current transformer sampling current protection circuit which has low power consumption but high cost, and the circuit is often complicated. FIG.14 Schematic diagram of protection circuit 2 The larger the output current is (the extreme case refers to short circuit), the higher the voltage sensed by the TR1 secondary coil. When the voltage of pin 3 of UC3842 exceeds 1 volt, the UC3842 stops working. Go round and begin again, until the short-circuit or overload disappears, the circuit recovers itself.   VII. Output Current Limiting Protection FIG.15 Schematic diagram of protection circuit 3 The above is a common output current limiting protection circuit, and its working principle is as follows:   When the output current is too high, the voltage across the RS (manganese copper wire) rises, the voltage of pin 3 of the U1 chip is higher than the reference voltage of pin 2. Pin 1 of the U1 chip outputs a high voltage, which makes Q1 turned on, and the optoelectronic effect occurs on the optocoupler, the voltage of pin 1 of UC3842 is reduced, together with the output voltage, to achieve the goal of overload protection or current limiting.     VIII. Output Overvoltage Protection Circuits   The role of the output overvoltage protection circuit is to limit the output voltage to a safe value when the output voltage exceeds the design value.    When an internal voltage regulator loop of a switching power supply fails or an overvoltage occurs due to a user's improper operation, an overvoltage protection circuit is used to protect against damage to downstream electrical equipment.   The most commonly used overvoltage protection circuits are as follows:   8.1  SCR Trigger Protection Circuit FIG.16 Schematic diagram of protection circuit 4 As shown above, when the output of Uo1 rises, the Zener diode (Z3) breaks down and it is pulled into conduction, letting the control terminal of the Silicon Controlled Rectifier reach the trigger voltage, so the SCR turns on and the Uo2 is shorted to ground. Then the overcurrent or short circuit protection circuit will work and stop the operation of the entire power supply circuit. When the overvoltage condition on the output terminals is eliminated, the trigger voltage of the control terminal of the thyristor is discharged to the ground through R, and the thyristor returns to the off state.   8.2  Optocoupler Protection Circuit FIG.17 Schematic diagram of protection circuit 5A FIG.18 Schematic diagram of protection circuit 5B As shown in the above figure, when an phenomenon of overvoltage occurs in the Uo, the Zener breaks down and conducts current through the optocoupler (OT2) and R6 to the ground, lightening the light-emitting diode of the photocoupler, which causes the phototransistor of the photocoupler to conduct. The base of Q1 is turned on and the voltage of pin 3 of UC3842 is reduced, turning off the IC and the entire power supply while Uo is zero, and go round and begin again.   8.3  Output Voltage Limiting Protection Circuit FIG.19 Schematic diagram of protection circuit 6 The output voltage limiting protection circuit is shown in the diagram. When the output voltage rises, zener and optocoupler are on, and the base of Q1 turns on either due to a driving voltage according. The voltage of pin 3 of UC3842 rises and the output drops. When the zener is not conducting, the voltage of pin 3 of UC3842 drops and the output voltage rises. As time goes by, the output voltage will be stable within a range (depending on the zener's value).   8.4  Output Overvoltage Lockout Circuit FIG.20 Output overvoltage lockout circuit A FIG.21 Output overvoltage lockout circuit B The working principle is shown in Figure A is that when the output voltage Uo rises, the Zener and optocoupler turn on, and then go with the base of Q2, because of which the base of Q1 is on due to the drop of voltage.   Q2 is on all the time after the voltage of Vcc is through R1, Q1, and R2, making the pin 3 of UC3842 always be conducted with high level and therefore stop working.   In Figure B, the voltage of pin 3 of the U1 chip raises due to big rises of Uo, and pin 1 outputs a high level. Because of the presences of D1 and R1, the pin 1 of U1 chip is always on and outputs a high level, so it is always low and then it stops working. Is it positive feedback?     IX. Power Factor Correction Circuit (PFC)   9.1 Schematic Diagram of PFC Circuit FIG.22 Schematic diagram of PFC circuit 9.2  The Working Principles The input voltage is rectified by an EMI filter composed of L1, L2, L3, and so on and a BRG1, one part of which is then fed into the PFC inductor and another part of which is fed into the PFC controller as the sampling of the input voltage to adjust the duty cycle of the control signal before divided by R1 and R2, that is to change them on and off time of Q1 and to stabilize the output voltage of PFC.   L4 is a PFC inductor that stores energy when Q1 is on and releases energy when Q1 is switched off. D1 is the start diode. D2 is the PFC rectifier diode, and C6, C7 are filtered. One part of the PFC voltage is sent to the downstream circuit, and another part of it is fed into the PFC controller as the sampling of the output voltage before divided by R3 and R4, to adjust the duty cycle of the control signal and to stabilize the output voltage of PFC.     X. Input Under-voltage and Overvoltage Protection   10.1  Schematic Diagram FIG.23 Schematic diagram of input undervoltage and overvoltage protection circuit   10.2  The Working Principles The input under-voltage and overvoltage protection principles of the switching power supply of AC input and DC input are almost the same. The sampling voltages of the protection circuits all come from the same input filtered voltage.   The sampling voltage is divided into two ways, one way is fed into pin 3 of the comparator after divided by R1, R2, R3, and R4. If the sampling voltage is higher than the reference voltage of pin 2, then pin 1 of the comparator will output a high level to control the main controller and make the main controller turned off, so there is no power output. The other way is fed into pin 6 of the comparator before it is divided by R7, R8, R9, and R10.   If the sampling voltage is lower than the reference voltage of pin 5, then pin 7 of the comparator will output a high level to control the main controller and make it turned off, so there is no power output.   How To Make a Switching Power Supply     FAQ   1. What are the 3 types of power supply? There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages.   2. What is meant by switch mode power supply? A switch mode power supply is a power converter that utilises switching devices such as MOSFETs that continuously turn on and off at high frequency; and energy storage devices such as the capacitors and inductors to supply power during the non-conduction state of the switching device.   3.What are the advantages and disadvantages of switch mode power supply? Advantages & disadvantages of switch mode power supply (SMPS) a. The switch mode power supply has a smaller in size. b. The SMPS has light weight. c. It has a better power efficiency typically 60 to 70 percent. d. It has a strong anti interference. e. SMPS has wide output range. f. Low heat generation in SMPS.   4. What is a DC switching power supply? A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor.   5. What is the difference between a switching power supply and a linear power supply? Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges.   6. Do I need a switching power supply? The switching power supply implies higher efficiency due to the high switching frequency, enabling it to use a smaller, less-costly high-frequency transformer as well as lighter, less-costly filter components. Switching power supplies contain more overall components, therefore are usually more expensive.   7. Is a switching power supply regulated? A switch mode power supply regulates an output voltage with pulse width modulation (PWM). This process creates high-frequency noise but it provides a high-efficiency rating in a small form factor. ... The low DC voltage is finally converted into a steady DC output with another set of diodes, capacitors, and inductors.   8. How do I know if my power supply is regulated? You can generally stick one probe into the middle of the connector, and hold the other against the outside. With a few exceptions, the middle is positive, so use the red lead there, and use the black lead on the outside shell. Regulated supplies, without any load, should measure very close to the target voltage of 12v.   9. Can I use a switching power supply to drive a DC motor?   A simple unregulated analog power supply may be easier and be able to supply the large starting under load current more that the switching one. DC motors are not too fussy about the supply, and will usually run quite well on unfiltered DC.   10. Are switch mode power supplies any good? Switch mode power supplies, SMPS provide improved efficiency & space saving over traditional linear supplies, but care has to be taken to ensure noise on the output is low. Switch mode power supplies are widely used because of the advantages they offer in terms of size, weight, cost, efficiency and overall performance.   You May Also Like: Transformers Basics: Construction, Types, Materials and Design Modeling and Control of Full Bridge Push-Pull Bi-Directional DC/DC Converter Review and Application of Electronic skin How to Drive Thermostat by Using Solid State Relay