A PFC control circuit

Abstract

The utility model discloses a kind of PFC control circuit, it is related to voltage adjustment field, the PFC control circuit includes: EMC filter module, for the electromagnetic interference in the input alternating current is filtered and inhibited, and prevent the noise produced by native from straying into power grid;The beneficial effects of the utility model are: the utility model is through ingenious circuit design, in the case where not depending on special PFC control chip, using zero-crossing sampling and logic control, has realized that PFC circuit is only in the controllable work of alternating current source zero-crossing point vicinity;Effectively improve the power factor (PF value) of input power supply, while significantly reduce the voltage stress and heating problem of power device under wide voltage input range;Its overall structure is simple, all adopt general conventional device, not only greatly reduce system cost, improve the consistency and reliability of circuit, also provide strong support for the industrialization popularization of this technology in air conditioner and other high-power household appliances.

Description

Technical Field

[0001] This utility model relates to the field of voltage regulation, specifically a PFC control circuit. Background Technology

[0002] With the increasing prevalence of high-power home appliances such as air conditioners, the requirements for power factor correction (PFC) performance in power supply circuits are becoming increasingly stringent. Traditional PFC control circuits typically employ dedicated control chips to shape the input current waveform and improve the power factor. However, these chip-based control solutions suffer from high costs, circuit complexity, and sensitivity to component parameters. Especially in applications with a wide voltage input range (e.g., 110V to 360V), power devices experience significant voltage stress and heat generation, leading to decreased system reliability and shortened lifespan, necessitating improvements. Utility Model Content

[0003] The purpose of this invention is to provide a PFC control circuit to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution:

[0005] A PFC control circuit, comprising:

[0006] The EMC filter module is used to filter out and suppress electromagnetic interference in the input AC power and prevent noise generated by the unit from entering the power grid.

[0007] The zero-crossing sampling module is used to detect the zero-crossing point of AC current through optocoupler isolation and to provide the zero-crossing signal Zero_C to the MCU.

[0008] The PFC control module is used to receive the drive signal PFC_D from the MCU, drive the IGBT transistor M1 to turn on and off through the optocoupler, control the inductor current to improve the input current waveform and increase the power factor (PF value).

[0009] The soft-start module is used to receive the control signal RY from the MCU and control the relay to switch the connection and short circuit of the current-limiting thermistor, so as to prevent the inrush current during power-on.

[0010] The overcurrent protection module is used to sample the current of IGBT M1 in real time. When the current exceeds the set threshold, the drive signal PFC_D is quickly turned off through the comparator and optocoupler to protect the circuit.

[0011] The EMC filtering module is connected to the zero-crossing sampling module, the PFC control module, and the soft-start module, while the overcurrent protection module is connected to the PFC control module.

[0012] As a further improvement of this utility model: the zero-crossing sampling module includes an optocoupler U3. The A terminal of the optocoupler U3 is connected to the EMC filter module in sequence through resistors R13 and R10. The K terminal of the optocoupler U3 is connected to the EMC filter module. The C terminal of the optocoupler U3 is connected to a 5V voltage and one end of resistor R19. The E terminal of the optocoupler U3 is connected to one end of resistor R21. The other end of resistor R21 is connected to one end of resistor R22 and the base of transistor Q3. The other end of resistor R22 is connected to the common point DGND. The emitter of transistor Q3 is connected to the common point DGND. The collector of transistor Q3 is connected to the other end of resistor R19 and one end of resistor R20. The other end of resistor R20 is connected to one end of capacitor C11 and the MCU. The other end of capacitor C11 is connected to the common point DGND.

[0013] As a further improvement of this utility model: the PFC control module includes an optocoupler U1, an IGBT M1, a transistor Q1, and a transistor Q2. The base of transistor Q1 receives the drive signal PFC_D from the MCU through resistor R5. The collector of transistor Q1 is connected to a 5V voltage through resistor R4. The emitter of transistor Q1 is connected to the first terminal of optocoupler U1. The third terminal of optocoupler U1 is connected to the collector of transistor Q2. The emitter of transistor Q2 is connected to the common point DGND. The base of transistor Q2 is connected to one end of resistor R14. The other end of resistor R14 is connected to one end of resistor R11 and the overcurrent protection module. The other end of resistor R11 is connected to a 5V voltage. The sixth terminal of optocoupler U1 is connected to a 15V voltage. The fourth terminal of optocoupler U1 is connected to the common point GND-IGBT. The fifth terminal of optocoupler U1... One end of resistor R8 is connected to the gate (G) of IGBT M1, the negative terminal of Zener diode ZD1, and one end of resistor R7. The emitter (E) of IGBT M1 is connected to the positive terminal of Zener diode ZD1, the other end of resistor R7, one end of capacitor C3, one end of resistor R9, and the common point GND-IGBT. The collector (C) of IGBT M1 is connected to one end of resistor R6, one end of varistor ZR1, and one end of the output terminal of rectifier DB2. The other end of resistor R6 is connected to the other end of capacitor C3. The other end of resistor R9 is connected to the other end of varistor ZR1, the other end of the output terminal of rectifier DB2, and the overcurrent protection module. One end of the input terminal of rectifier DB2 is connected to the EMC filter module through reactor L2, and the other end of the input terminal of rectifier DB2 is connected to the EMC filter module.

[0014] As a further improvement of this utility model: the soft start module includes a relay RY1, one end of which is connected to a 12V voltage, and the other end of which receives the control signal RY from the MCU.

[0015] As a further embodiment of this utility model: the overcurrent protection module includes a comparator U4 and an optocoupler U2. The fourth terminal of the comparator U4 is connected to the PFC control module through a resistor R16. The third terminal of the comparator U4 is connected to one end of a resistor R17 and one end of a resistor R18. The other end of the resistor R17 is connected to a 15V voltage. The other end of the resistor R18 is connected to the common point GND-IGBT. The first terminal of the comparator U4 is connected to one end of a resistor R15 and the K terminal of the optocoupler U2. The other end of the resistor R15 is connected to a 15V voltage. The A terminal of the optocoupler U2 is connected to a 15V voltage through a resistor R12. The E terminal of the optocoupler U2 is connected to the common point DGND. The C terminal of the optocoupler U2 is connected to the PFC control module.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows: Through ingenious circuit design, this utility model achieves controllable operation of the PFC circuit only near the zero-crossing point of the AC power supply without relying on a dedicated PFC control chip, by utilizing zero-crossing sampling and logic control; it effectively improves the power factor (PF value) of the input power supply, while significantly reducing the voltage stress and heat generation of power devices under a wide voltage input range (such as 110V to 360V); its overall structure is simple, and it uses all common and conventional components, which not only greatly reduces the system cost and improves the consistency and reliability of the circuit, but also provides strong support for the industrialization and promotion of this technology in high-power home appliances such as air conditioners. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of a PFC control circuit. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0019] Please see Figure 1 A PFC control circuit, comprising:

[0020] The EMC filter module is used to filter out and suppress electromagnetic interference in the input AC power and prevent noise generated by the unit from entering the power grid.

[0021] The zero-crossing sampling module is used to detect the zero-crossing point of AC current through optocoupler isolation and to provide the zero-crossing signal Zero_C to the MCU.

[0022] The PFC control module is used to receive the drive signal PFC_D from the MCU, drive the IGBT transistor M1 to turn on and off through the optocoupler, control the inductor current to improve the input current waveform and increase the power factor (PF value).

[0023] The soft-start module is used to receive the control signal RY from the MCU and control the relay to switch the connection and short circuit of the current-limiting thermistor, so as to prevent the inrush current during power-on.

[0024] The overcurrent protection module is used to sample the current of IGBT M1 in real time. When the current exceeds the set threshold, the drive signal PFC_D is quickly turned off through the comparator and optocoupler to protect the circuit.

[0025] The EMC filtering module is connected to the zero-crossing sampling module, the PFC control module, and the soft-start module, while the overcurrent protection module is connected to the PFC control module.

[0026] In a specific embodiment: Please refer to Figure 1 In the EMC filter module, the AC voltage input passes through the EMC filter circuit (choke L1) to filter out interference, and the AC current charges the electrolytic capacitor E1 through the rectifier bridge DB1. At the same time, the positive half-cycle of the AC current AC1 charges the electrolytic capacitor E2, and the voltage is doubled at this time.

[0027] In this embodiment: Please refer to Figure 1 The zero-crossing sampling module includes an optocoupler U3. The A terminal of the optocoupler U3 is connected to the EMC filter module in sequence through resistors R13 and R10. The K terminal of the optocoupler U3 is connected to the EMC filter module. The C terminal of the optocoupler U3 is connected to a 5V voltage and one end of resistor R19. The E terminal of the optocoupler U3 is connected to one end of resistor R21. The other end of resistor R21 is connected to one end of resistor R22 and the base of transistor Q3. The other end of resistor R22 is connected to the common point DGND. The emitter of transistor Q3 is connected to the common point DGND. The collector of transistor Q3 is connected to the other end of resistor R19 and one end of resistor R20. The other end of resistor R20 is connected to one end of capacitor C11 and the MCU. The other end of capacitor C11 is connected to the common point DGND.

[0028] When the AC current crosses zero, the LED inside the optocoupler U3 does not emit light, so the C and E terminals of the optocoupler U3 are not conducting, the transistor Q3 is cut off, and the collector of the transistor Q3 is at a high level, which is fed back to the MCU.

[0029] In this embodiment: Please refer to Figure 1The PFC control module includes an optocoupler U1, an IGBT M1, a transistor Q1, and a transistor Q2. The base of transistor Q1 receives the drive signal PFC_D from the MCU through resistor R5. The collector of transistor Q1 is connected to a 5V voltage through resistor R4. The emitter of transistor Q1 is connected to the first terminal of optocoupler U1. The third terminal of optocoupler U1 is connected to the collector of transistor Q2. The emitter of transistor Q2 is connected to the common point DGND. The base of transistor Q2 is connected to one end of resistor R14. The other end of resistor R14 is connected to one end of resistor R11 (overcurrent protection module). The other end of resistor R11 is connected to a 5V voltage. The sixth terminal of optocoupler U1 is connected to a 15V voltage. The fourth terminal of optocoupler U1 is connected to the common point GND-IGBT. The fifth terminal of optocoupler U1 is connected to resistor R8. One end of resistor R8 is connected to the gate (G) of IGBT M1, the negative terminal of Zener diode ZD1, one end of resistor R7, the emitter (E) of IGBT M1 is connected to the positive terminal of Zener diode ZD1, the other end of resistor R7, one end of capacitor C3, one end of resistor R9, the common point GND-IGBT, the collector (C) of IGBT M1 is connected to one end of resistor R6, one end of varistor ZR1, one end of the output terminal of rectifier DB2, the other end of resistor R6 is connected to the other end of capacitor C3, the other end of resistor R9 is connected to the other end of varistor ZR1, the other end of the output terminal of rectifier DB2, and the overcurrent protection module. One end of the input terminal of rectifier DB2 is connected to the EMC filter module through reactor L2, and the other end of the input terminal of rectifier DB2 is connected to the EMC filter module.

[0030] After the MCU receives the zero-crossing information, it outputs the drive signal PFC_D, which turns on transistor Q1. At this time, the base of transistor Q2 is at a high level, and transistor Q2 also turns on, triggering optocoupler U1 to turn on. The 5th pin of optocoupler U1 outputs a high level, controlling IGBT M1 to turn on, so that current is generated on reactor L2, adjusting the sinusoidal nature of the input AC current and improving the power factor (PF value).

[0031] In this embodiment: Please refer to Figure 1 The soft start module includes a relay RY1. One end of the relay RY1 is connected to a 12V voltage, and the other end of the relay RY1 receives the control signal RY from the MCU.

[0032] When the circuit starts up, initially relay RY1 is not working, the control switch is open, and thermistor RT1 is connected to the circuit. After a short time following power-on, the MCU controls the RY signal to go low, creating a voltage difference across relay RY1. Relay RY1 then powers on and controls the corresponding switch to close, short-circuiting thermistor RT1 and reducing the impedance in the circuit. By adding a thermistor during circuit startup, damage to the circuit from the large current instantaneous upon power-on is avoided.

[0033] In this embodiment: Please refer to Figure 1 The overcurrent protection module includes comparator U4 and optocoupler U2. The fourth terminal of comparator U4 is connected to the PFC control module through resistor R16. The third terminal of comparator U4 is connected to one end of resistor R17 and one end of resistor R18. The other end of resistor R17 is connected to a 15V voltage. The other end of resistor R18 is connected to the common point GND-IGBT. The first terminal of comparator U4 is connected to one end of resistor R15 and the K terminal of optocoupler U2. The other end of resistor R15 is connected to a 15V voltage. The A terminal of optocoupler U2 is connected to a 15V voltage through resistor R12. The E terminal of optocoupler U2 is connected to the common point DGND. The C terminal of optocoupler U2 is connected to the PFC control module.

[0034] When IGBT M1 is turned on, a certain first voltage is generated in resistor R9. The voltage division of resistors R17 and R18 serves as the second voltage. The first and second voltages are input to comparator U4. Under normal power conditions, the first voltage is less than the second voltage, so the first terminal of comparator U4 outputs a high level, optocoupler U2 is not conducting, and transistor Q2 remains on. Under abnormal power conditions, the voltage across resistor R9 increases, and the first voltage is greater than the second voltage. The first terminal of comparator U4 outputs a low level, optocoupler U2 conducts, pulling down the base voltage of transistor Q2, transistor Q2 is turned off, optocoupler U1 is not conducting, preventing the PFC control module from being driven and protecting the circuit.

[0035] The working principle of this utility model is as follows: The EMC filtering module is used to filter and suppress electromagnetic interference in the input AC power and prevent noise generated by the machine from entering the power grid; the zero-crossing sampling module is used to detect the zero-crossing point of the AC power through optocoupler isolation and provide the zero-crossing signal Zero_C to the MCU; the PFC control module is used to receive the drive signal PFC_D from the MCU, drive the IGBT transistor M1 to turn on and off through optocoupler, control the inductor current to improve the input current waveform and increase the power factor (PF value); the soft-start module is used to receive the control signal RY from the MCU, control the relay to switch the connection and short-circuit of the current-limiting thermistor, and realize the function of preventing inrush current during power-on; the overcurrent protection module is used to sample the current of the IGBT transistor M1 in real time, and when the current exceeds the set threshold, it quickly turns off the drive signal PFC_D through comparator and optocoupler to protect the circuit.

[0036] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0037] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A PFC control circuit, characterized in that, The PFC control circuit includes: The EMC filter module is used to filter out and suppress electromagnetic interference in the input AC power and prevent noise generated by the unit from entering the power grid. The zero-crossing sampling module is used to detect the zero-crossing point of AC current through optocoupler isolation and to provide the zero-crossing signal Zero_C to the MCU. The PFC control module receives the drive signal PFC_D from the MCU, drives the IGBT transistor M1 to turn on and off via an optocoupler, controls the inductor current to improve the input current waveform and increase the power factor. The soft-start module is used to receive the control signal RY from the MCU and control the relay to switch the connection and short circuit of the current-limiting thermistor, so as to prevent the inrush current during power-on. The overcurrent protection module is used to sample the current of IGBT M1 in real time. When the current exceeds the set threshold, the drive signal PFC_D is quickly turned off through the comparator and optocoupler to protect the circuit. The EMC filtering module is connected to the zero-crossing sampling module, the PFC control module, and the soft-start module, while the overcurrent protection module is connected to the PFC control module.

2. The PFC control circuit according to claim 1, characterized in that, The zero-crossing sampling module includes an optocoupler U3. The A terminal of the optocoupler U3 is connected to the EMC filter module in sequence through resistors R13 and R10. The K terminal of the optocoupler U3 is connected to the EMC filter module. The C terminal of the optocoupler U3 is connected to a 5V voltage and one end of resistor R19. The E terminal of the optocoupler U3 is connected to one end of resistor R21. The other end of resistor R21 is connected to one end of resistor R22 and the base of transistor Q3. The other end of resistor R22 is connected to the common point DGND. The emitter of transistor Q3 is connected to the common point DGND. The collector of transistor Q3 is connected to the other end of resistor R19 and one end of resistor R20. The other end of resistor R20 is connected to one end of capacitor C11 and the MCU. The other end of capacitor C11 is connected to the common point DGND.

3. The PFC control circuit according to claim 1, characterized in that, The PFC control module includes an optocoupler U1, an IGBT M1, a transistor Q1, and a transistor Q2. The base of transistor Q1 receives the MCU's drive signal PFC_D through resistor R5. The collector of transistor Q1 is connected to a 5V voltage through resistor R4. The emitter of transistor Q1 is connected to the first terminal of optocoupler U1. The third terminal of optocoupler U1 is connected to the collector of transistor Q2. The emitter of transistor Q2 is connected to the common point DGND. The base of transistor Q2 is connected to one end of resistor R14. The other end of resistor R14 is connected to one end of resistor R11 (overcurrent protection module). The other end of resistor R11 is connected to a 5V voltage. The sixth terminal of optocoupler U1 is connected to a 15V voltage. The fourth terminal of optocoupler U1 is connected to the common point GND-IGBT. The fifth terminal of optocoupler U1 is connected to resistor R8. One end of resistor R8 is connected to the gate (G) of IGBT M1, the negative terminal of Zener diode ZD1, one end of resistor R7, the emitter (E) of IGBT M1 is connected to the positive terminal of Zener diode ZD1, the other end of resistor R7, one end of capacitor C3, one end of resistor R9, the common point GND-IGBT, the collector (C) of IGBT M1 is connected to one end of resistor R6, one end of varistor ZR1, one end of the output terminal of rectifier DB2, the other end of resistor R6 is connected to the other end of capacitor C3, the other end of resistor R9 is connected to the other end of varistor ZR1, the other end of the output terminal of rectifier DB2, and the overcurrent protection module. One end of the input terminal of rectifier DB2 is connected to the EMC filter module through reactor L2, and the other end of the input terminal of rectifier DB2 is connected to the EMC filter module.

4. The PFC control circuit according to claim 1, characterized in that, The soft start module includes a relay RY1. One end of the relay RY1 is connected to a 12V voltage, and the other end of the relay RY1 receives the control signal RY from the MCU.

5. The PFC control circuit according to claim 3, characterized in that, The overcurrent protection module includes comparator U4 and optocoupler U2. The fourth terminal of comparator U4 is connected to the PFC control module through resistor R16. The third terminal of comparator U4 is connected to one end of resistor R17 and one end of resistor R18. The other end of resistor R17 is connected to a 15V voltage. The other end of resistor R18 is connected to the common point GND-IGBT. The first terminal of comparator U4 is connected to one end of resistor R15 and the K terminal of optocoupler U2. The other end of resistor R15 is connected to a 15V voltage. The A terminal of optocoupler U2 is connected to a 15V voltage through resistor R12. The E terminal of optocoupler U2 is connected to the common point DGND. The C terminal of optocoupler U2 is connected to the PFC control module.

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