PFC overcurrent protection circuit and PFC circuit

Abstract

The invention discloses a PFC overcurrent protection circuit and a PFC circuit. The PFC overcurrent protection circuit comprises a current sampling module, a reference voltage generation module, an overcurrent comparison module, a hardware protection module, a software protection module, a PFC driving module and a reset signal output module. And the reset signal output module is respectively connected with the output end of the software protection unit and the input end of the overcurrent comparison module. According to the PFC overcurrent protection circuit, when overcurrent occurs in the PFC circuit, two protection modes of hardware protection and software protection can be combined, the reference voltage is not liable to be interfered, and the reliability of PFC overcurrent protection is improved.

Description

Technical Field

[0001] The present invention belongs to the field of PFC circuit applications, and in particular relates to a PFC overcurrent protection circuit and a PFC circuit. Background Art

[0002] At present, common PFC overcurrent protection circuits usually include PFC drive circuits, sampling circuits, comparison circuits, and signal holding circuits. When overcurrent occurs, the shutdown method of the PFC drive is usually one of software shutdown or hardware shutdown. The shutdown process is not fast enough and a single shutdown method cannot guarantee the reliability of overcurrent protection. The output of the reference voltage is not stable enough and is easily disturbed. In addition, common PFC overcurrent protection circuits do not have a fault holding function and may continue to conduct when the circuit is still in a fault state, affecting the service life of the IGBT.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] An object of the present invention is to overcome the deficiencies of the prior art and to provide a PFC overcurrent protection circuit which has rapid shutdown, high reliability of overcurrent protection and good protection effect on IGBT.

[0005] A second object of the present invention is to provide a PFC circuit using the PFC overcurrent protection circuit.

[0006] To achieve the first purpose, the basic concept of the technical solution adopted by the present invention is:

[0007] A PFC overcurrent protection circuit comprises a current sampling module, a reference voltage generating module, an overcurrent comparison module, a hardware protection module, a software protection module, a PFC driving module and a reset signal output module; the current sampling module is respectively connected to the output end of the PFC circuit and the input end of the overcurrent comparison module, the reference voltage generating module is connected to the other input end of the overcurrent comparison module, the output end of the overcurrent comparison module is respectively connected to the input end of the software protection unit and the input end of the hardware protection unit, the output end of the hardware protection unit is connected to the input end of the PFC driving module, the output end of the software protection unit is connected to the control end of the PFC driving module, the output end of the PFC driving module is connected to the control end of the PFC circuit, and the reset signal output module is respectively connected to the output end of the software protection unit and the input end of the overcurrent comparison module.

[0008] Preferably, the current sampling module includes a first capacitor, a third diode, a fourth resistor, and a seventh resistor; one end of the fourth resistor is connected to the output end of the PFC circuit, and the other end is grounded; one end of the seventh resistor is connected to the output end of the PFC circuit, and the other end is divided into two paths, the first path is grounded via the first capacitor, and the second path is connected to the input end of the overcurrent comparison module via the third diode.

[0009] Preferably, the reference voltage generating module includes a working power supply, a follower, an eighth resistor, and a ninth resistor; one end of the eighth resistor is connected to the working power supply input terminal, and the other end is divided into two paths, the first path is grounded via the ninth resistor, and the second path is connected to the non-phase input terminal of the follower; the output terminal of the follower is divided into two paths, the first path is connected to the inverting input terminal of the follower, and the second path is connected to the input terminal of the overcurrent comparison module.

[0010] Preferably, the overcurrent comparison module includes a comparator and a tenth resistor; one end of the tenth resistor is connected to the output end of the comparator, and the other end is connected to the non-inverting input end of the comparator; the output end of the comparator is divided into two paths, the first path is connected to the input end of the hardware protection module, and the second path is connected to the input end of the software protection module; the non-inverting input end of the comparator serves as the input end of the current sampling module connected to the overcurrent comparison module, and the inverting input end of the comparator serves as the reference voltage generation module connected to the input end of the overcurrent comparison module.

[0011] Preferably, the hardware protection module includes a fifth resistor, a sixth resistor, and a transistor; the base of the transistor serves as the input end of the hardware protection module, and is connected to the output end of the comparator via the fifth resistor; the collector of the transistor serves as the output end of the hardware protection module, and is connected to the input end of the PFC driving module; the emitter of the transistor is grounded, one end of the sixth resistor is connected to the output end of the fifth resistor, and the other end is grounded.

[0012] Preferably, the software protection module includes a microprocessor; the input end of the microprocessor is connected to the output end of the comparator, and the output end of the microprocessor is divided into two paths, the first path is connected to the control end of the PFC drive module, and the second path is connected to the input end of the reset signal output module.

[0013] Preferably, the PFC driving module includes a working power supply, a driving power supply, a first resistor, a second resistor, a third resistor, and a driving chip; the anode of the primary diode of the driving chip serves as the input end of the PFC driving module, and the cathode of the primary diode of the driving chip serves as the control end of the PFC driving module; one end of the first resistor is connected to the working power supply input end, and the other end is connected to the cathode of the primary diode of the driving chip; one end of the second resistor is connected to the working power supply input end, and the other end is connected to the anode of the primary diode of the driving chip; the upper tube emitter of the secondary transistor of the driving chip is connected to the driving power supply input end, and the lower tube emitter of the secondary transistor of the driving chip is grounded; one end of the third resistor is connected to the collector of the secondary transistor of the driving chip, and the other end is connected to the control end of the PFC circuit.

[0014] Preferably, the reset signal output module includes a second diode; an anode of the second diode is connected to the output end of the microprocessor, and a cathode of the second diode is connected to the inverting input end of the comparator.

[0015] To achieve the second purpose, the basic concept of the technical solution adopted by the present invention is:

[0016] A PFC circuit uses the above-mentioned PFC overcurrent protection circuit.

[0017] Preferably, the PFC circuit includes a filter / pre-charging circuit, a rectifier bridge, an energy storage inductor, a switch tube, an AC power supply, a first diode and a capacitor group; the control end of the switch tube serves as the control end of the PFC circuit, and the output end of the switch tube serves as the output end of the PFC circuit; the two input ends of the filter / pre-charging circuit are connected to the AC power supply, the two input ends of the rectifier bridge are connected to the two output ends of the filter / pre-charging circuit, the positive output end of the rectifier bridge is connected to one end of the energy storage inductor, the other end of the energy storage inductor and the anode of the first diode are commonly connected to the input end of the switch tube, the cathode of the first diode is connected to the positive electrode of the capacitor group, and the negative electrode of the capacitor group is connected to the negative output end of the rectifier bridge.

[0018] After adopting the above technical solution, the PFC overcurrent protection circuit and PFC circuit provided by the present invention have the following beneficial effects compared with the prior art:

[0019] (1) The PFC overcurrent protection circuit and PFC circuit provided by the present invention combine the two protection modes of hardware protection and software protection, thereby improving the reliability of PFC overcurrent protection; a follower is provided in the reference voltage generation module to buffer the signal, so that the output reference voltage is not interfered by other circuits and the voltage output is stable; the reset signal output module has a fault recovery function, thereby improving the convenience of the application of this circuit.

[0020] (2) The PFC overcurrent protection circuit and PFC circuit provided by the present invention use a resistor sampling method to perform current sampling, and at the same time, a diode is connected in series at the non-inverting end of the comparator. If the protection current needs to be increased, there is no need to replace the sampling resistor, and the sampling voltage signal of the sampling resistor can be directly amplified, thereby improving the convenience of the application of this circuit.

[0021] (3) The PFC overcurrent protection circuit and PFC circuit provided by the present invention are provided with a follower in the circuit for generating the reference voltage, which provides high input impedance and low output impedance to buffer the signal, so that the reference voltage signal is not interfered by other circuits and the voltage output is stable.

[0022] (4) The PFC overcurrent protection circuit and PFC circuit provided by the present invention have a fault holding function to prevent the circuit from being turned on in a fault condition, thereby increasing the service life of the IGBT.

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the accompanying drawings described below are only some embodiments. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0025] In the attached picture:

[0026] Figure 1 It is a circuit principle diagram of the PFC overcurrent protection circuit and the PFC circuit described in the present invention.

[0027] It should be noted that the drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0029] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] The present invention proposes a PFC circuit, such as Figure 1 As shown, the PFC circuit 1 includes a filter / pre-charge circuit, a rectifier bridge BR1, an energy storage inductor L1, a switch tube Q1, an AC power source AC, a first diode D1 and a capacitor group. The two input ends of the filter / pre-charge circuit are connected to the AC power source AC, the two input ends of the rectifier bridge BR1 are connected to the two output ends of the filter / pre-charge circuit, the positive output end of the rectifier bridge BR1 is connected to one end of the energy storage inductor L1, the other end of the energy storage inductor L1 and the anode of the first diode D1 are connected to the input end of the switch tube Q1, the cathode of the first diode D1 is connected to the positive electrode of the capacitor group, and the negative electrode of the capacitor group is connected to the negative output end of the rectifier bridge BR1. Specifically, Figure 1 In the embodiment, the switch tube Q1 is an IGBT, the input end of the switch tube Q1 is the collector of the IGBT, the control end of the switch tube Q1 is the gate of the IGBT, and the output end of the switch tube Q1 is the emitter of the IGBT.

[0032] The present invention proposes a PFC overcurrent protection circuit, such as Figure 1 As shown, it includes a current sampling module 3, a reference voltage generating module 4, an overcurrent comparison module 5, a hardware protection module 6, a software protection module 8, a PFC driving module 2, and a reset signal output module 7.

[0033] The current sampling module 3 includes a first capacitor C1, a third diode D3, a fourth resistor R4, and a seventh resistor R7; one end of the fourth resistor R4 is connected to the output end of the switch tube Q1, and the other end is connected to the ground GND2; one end of the seventh resistor R7 is connected to the output end of the switch tube Q1, and the other end is connected to the anode of the third diode D3, and the other end of the seventh resistor R7 is also connected to the ground GND2 via the first capacitor C1; the cathode of the third diode D3 is connected to the input end of the overcurrent comparison module 5.

[0034] The fourth resistor R4 is a sampling resistor, which samples the output current of the PFC circuit and transmits it to the input end of the overcurrent comparison module 5; the overcurrent signal is sampled by resistor sampling. When increasing the protection current, the resistance of the sampling resistor needs to be reduced, which leads to an increase in the power consumption and temperature rise of the resistor, which is not conducive to the reliability of the circuit. In this embodiment, the third diode D3 is connected in series at the non-inverting input end of the comparator of the overcurrent comparison module 5. Without changing the original comparison voltage, the sampling resistor does not need to be replaced, and the sampling voltage signal of the sampling resistor is directly amplified to increase the protection current. The sampling current is output to the third diode D3. Since the overcurrent and overvoltage capacity of the diode is very poor, it cannot work normally if reliable protection measures are not taken. Therefore, a first-order RC absorption circuit composed of a seventh resistor R7 and a first capacitor C1 is set between the fourth resistor R4 and the third diode D3 to avoid excessive sampling current, which causes overcurrent and damages the diode.

[0035] The reference voltage generating module 4 includes a working power supply VCC, a follower U2, an eighth resistor R8, and a ninth resistor R9; one end of the eighth resistor R8 is connected to the working power supply VCC, the other end of the eighth resistor R8 and one end of the ninth resistor R9 are connected to the in-phase input end of the follower U2, the other end of the ninth resistor R9 is grounded GND1, the output end of the follower U2 is connected to the input end of the overcurrent comparison module 5, and the output end of the follower U2 is also connected to the inverting input end of the follower U2.

[0036] Because the voltage value of the working power supply VCC is relatively high, the working power supply VCC is divided by setting the eighth resistor R8 and the ninth resistor R9. The voltage value obtained after the voltage division is transmitted to the non-inverting input terminal of the follower U2. The follower U2 is the follower of the comparator in the overcurrent comparison module 5. It provides high input impedance and low output impedance to buffer the signal so that the output reference voltage is not interfered by other circuits and the voltage output is stable. The output terminal of the follower U2 outputs the reference voltage Vref obtained after dividing the working power supply VCC, and outputs the reference voltage Vref to the input terminal of the overcurrent comparison module 5.

[0037] The overcurrent comparison module 5 includes a comparator U1 and a tenth resistor R10; one end of the tenth resistor R10 is connected to the output end of the comparator U1, and the other end is connected to the non-inverting input end of the comparator U1; the overcurrent comparison module 5 has two input ends, namely the non-inverting input end and the inverting input end of the comparator U1, the non-inverting input end of the comparator U1 is used as the input end of the current sampling module 3 connected to the input end of the overcurrent comparison module 5, and the inverting input end of the comparator U1 is used as the reference voltage generation module 4 connected to the input end of the overcurrent comparison module 5; the output end of the comparator U1 is divided into two paths, the first path is connected to the input end of the hardware protection module 6, and the second path is connected to the input end of the software protection module 8.

[0038] The comparator U1 compares the two voltage values ​​inputted at the non-inverting input terminal and the inverting input terminal. When the PFC circuit does not have an overcurrent, the voltage at the non-inverting input terminal is less than the voltage at the inverting input terminal, and the output terminal of the comparator U1 outputs a low-level signal; when the PFC circuit has an overcurrent, the voltage at the non-inverting input terminal is greater than the voltage at the inverting input terminal, and the output terminal of the comparator U1 outputs a high-level fault FO signal. The tenth resistor R10 is the feedback resistor of the comparator U1, and divides the voltage outputted from the output terminal of the comparator U1 to the non-inverting input terminal of the comparator U1.

[0039] The hardware protection module 6 includes a fifth resistor R5, a sixth resistor R6, and a transistor Q2; the base of the transistor Q2 serves as the input end of the hardware protection module 6, and is connected to the output end of the comparator U1 via the fifth resistor R5; the collector of the transistor Q2 serves as the output end of the hardware protection module 6, and is connected to the input end of the PFC driving module 2; the emitter of the transistor Q2 is grounded GND1, one end of the sixth resistor R6 is connected to the output end of the fifth resistor R5, and the other end is grounded GND1.

[0040] Specifically, in this embodiment, the transistor Q2 is an NPN transistor.

[0041] The fifth resistor R5 is a current limiting resistor, which prevents the input voltage of the base of the transistor Q2 from being too high and burning the transistor Q2; the sixth resistor R6 is a pull-down resistor. When there is no overcurrent in the PFC circuit, the sixth resistor R6 always pulls the base of the transistor Q2 down to a low level; when the base of the transistor Q2 is at a low level, the transistor Q2 is cut off, and the collector of the transistor Q2 is at a high level; when an overcurrent occurs in the PFC circuit, the base level of the transistor Q2 is reversed from a low level to a high level, the transistor Q2 is turned on, and the collector of the transistor Q2 becomes a high level.

[0042] The software protection module 8 includes a microprocessor MCU, the input end of the microprocessor MCU is connected to the output end of the comparator U1, and the output end of the microprocessor MCU is divided into two paths, the first path is connected to the control end of the PFC drive module 2, and the second path is connected to the input end of the reset signal output module 7.

[0043] When there is no overcurrent in the PFC circuit, the comparator U1 continuously outputs a low level, and the PWM drive signal output by the microprocessor MCU is a low level; when there is an overcurrent in the PFC circuit, the comparator U1 outputs a high level, and the microprocessor MCU stops outputting the PWM drive signal; after the microprocessor MCU stops outputting the PWM drive signal for a period of time, it starts to output a high-potential reset REST signal that is greater than the voltage at the same-phase input terminal of U1 until the PFC circuit resumes normal operation, and the microprocessor MCU outputs a low-level PWM drive signal again.

[0044] The PFC driving module 2 includes a working power supply VCC, a driving power supply VDD, a first resistor R1, a second resistor R2, a third resistor R3, and a driving chip; specifically, the driving chip is a driving chip IC1 in the PFC overcurrent protection circuit provided in this embodiment; the anode of the primary diode of the driving chip IC1 serves as the input end of the PFC driving module 2, and the cathode of the primary diode of the driving chip IC1 serves as the control end of the PFC driving module 2; one end of the first resistor R1 is connected to the working power supply VCC input end, and the other end is connected to the cathode of the primary diode of the driving chip IC1; one end of the second resistor R2 is connected to the working power supply VCC input end, and the other end is connected to the anode of the primary diode of the driving chip IC1; the upper tube emitter of the secondary transistor of the driving chip IC1 is connected to the driving power supply VDD input end, and the lower tube emitter of the secondary transistor of the driving chip IC1 is grounded GND2; one end of the third resistor R3 is connected to the collector of the secondary transistor of the driving chip IC1, and the other end is connected to the control end of the PFC circuit 1.

[0045] When the PFC circuit does not have an overcurrent, the anode of the primary diode of the driver chip IC1 is at a high level, the cathode of the primary diode of the driver chip IC1 is at a low level, the primary diode of the driver chip IC1 is turned on, the transistor of the driver chip IC1 is turned on, and the PFC circuit is driven to work normally. When the PFC circuit has an overcurrent, the transistor Q2 is turned on, the anode of the primary diode of the driver chip IC1 becomes a low level; the microprocessor MCU stops outputting the PWM drive signal, and the cathode of the primary diode of the driver chip IC1 becomes a high level; both of these situations will cause the primary diode of the driver chip IC1 to be cut off, the secondary transistor of the driver chip IC1 to be cut off, and the PFC circuit is driven to shut down. The first resistor R1 is a pull-up resistor, which can always pull up the anode of the primary diode of the driver chip IC1 to a high level when the PFC circuit does not have an overcurrent; the second resistor R2 is a pull-up resistor, which can always pull up the cathode of the primary diode of the driver chip IC1 to a high level when the PFC circuit has an overcurrent; the third resistor R3 is the gate resistor of the IGBT, which has the function of eliminating gate oscillation and adjusting the on-off speed of the switch tube Q1.

[0046] The reset signal output module 7 includes a second diode D2, an anode of the second diode D2 is connected to the output end of the microprocessor MCU as the input end of the reset signal output module 7, and a cathode of the second diode D2 is connected to the inverting input end of the comparator U1.

[0047] Since the diode has unidirectional conductivity, in order to prevent the microprocessor MCU output terminal from being directly connected to the reference voltage Vref input terminal, thereby affecting the microprocessor MCU, a second diode D2 is set between the microprocessor MCU output terminal and the reference voltage Vref input terminal to cut off the current output from the reference voltage Vref input terminal; the microprocessor MCU outputs a high-level reset REST signal that is transmitted to the inverting terminal of the follower U1 through the second diode D2. At this time, the second diode D2 is turned on, causing the levels of the in-phase input terminal and the inverting input terminal of the comparator U1 to be reversed.

[0048] The difference between ground GND1 and ground GND2 is that the voltage to ground is different. To prevent electrical interference between different modules and loops, electrical isolation measures should be set between the two grounds.

[0049] The working principle of the above-mentioned PFC overcurrent protection circuit is as follows:

[0050] When the PFC circuit 1 works normally and no overcurrent occurs, the current sampling module 3 samples the output current of the PFC circuit 1 and transmits the sampled current to the non-inverting input terminal of the comparator U1. The reference voltage Vref is input to the inverting input terminal of the comparator U1. The voltage at the non-inverting input terminal of the comparator U1 is less than the voltage at the inverting input terminal. The comparator U1 continuously outputs a low level, turning off the transistor Q2. At the same time, the microprocessor MCU normally outputs a low-level PWM drive signal. The transistor Q2 is turned off, so that the anode of the primary diode of the driver chip IC1 is at a high level; the microprocessor MCU normally outputs a low-level PWM drive signal, so that the cathode of the primary diode of the driver chip IC1 is at a low level; the primary diode of the driver chip IC1 is turned on, so that the secondary transistor of the driver chip IC1 is turned on, and the PFC circuit 1 is driven to work normally.

[0051] When an overcurrent occurs in the PFC circuit, the current sampling module 3 samples the overcurrent output by the PFC circuit 1, and transmits the overcurrent to the non-inverting input terminal of the comparator U1. The reference voltage Vref is input to the inverting input terminal of the comparator U1. The voltage at the non-inverting input terminal of the comparator U1 is greater than the voltage at the inverting input terminal. The comparator U1 outputs a high-level fault FO signal, and the high-level fault FO signal is transmitted to the base of the transistor Q2, so that the base level is reversed, and the transistor Q2 is turned on to reach a saturation state, and the voltage of the anode of the primary diode of the driver chip IC1 is pulled down to a low level, so that the primary diode of the driver chip IC1 is cut off, the secondary transistor of the driver chip IC1 is turned off, and the PFC drive is turned off, so that the PFC circuit 1 stops working. This shutdown process is hardware protection.

[0052] On the other hand, the high-level fault FO signal will also be transmitted to the microprocessor MCU, and the microprocessor MCU will stop outputting the PWM drive signal to the cathode of the primary diode of the driver chip IC1, so that the cathode of the primary diode of the driver chip IC1 becomes a high level, the primary diode of the driver chip IC1 is cut off, the secondary transistor of the driver chip IC1 is turned off, and the PFC drive is turned off, so that the PFC circuit 1 stops working. This shutdown process is software protection.

[0053] At the same time, the high-level fault FO signal output by the comparator U1 is transmitted to the non-inverting input terminal of the comparator U1 through the voltage division of the tenth resistor R10. The third diode D3 cuts off the high-level signal at the non-inverting input terminal of the comparator U1, so that the non-inverting input terminal of the comparator U1 continues to maintain a high level, that is, the voltage at the non-inverting input terminal of the comparator U1 continues to be greater than the voltage at the inverting input terminal. The comparator U1 continues to output a high-level fault FO signal to realize the fault holding function.

[0054] In addition, after receiving the high-level fault FO signal, the microprocessor MCU will process the received fault FO signal. If the fault is restored, a high-level reset REST signal greater than the voltage of the non-inverting input terminal of the comparator U1 will be sent. This signal is transmitted to the inverting input terminal of the comparator U1 through the second diode D2. At this time, the second diode D2 is turned on, so that the levels of the non-inverting input terminal and the inverting input terminal of the comparator U1 are reversed, and the comparator U1 changes to output a low level and stops outputting a high-level fault FO signal, and the PFC circuit 1 resumes normal operation.

[0055] This PFC overcurrent protection circuit has fault holding and fault recovery functions, which can prevent the circuit from continuing to conduct multiple times under fault conditions, thereby increasing the service life of the IGBT.

[0056] Compared with software protection, the shutdown process of hardware protection eliminates the process of detecting, processing fault signals and judging overcurrent through software, which can protect IGBT devices more timely. Moreover, the reliability of PFC overcurrent protection is improved through the dual protection of hardware protection and software protection.

[0057] After adopting the above technical solution, the PFC overcurrent protection circuit and PFC circuit provided by the present invention have the following beneficial effects compared with the prior art:

[0058] (1) The PFC overcurrent protection circuit and PFC circuit provided by the present invention combine the two protection modes of hardware protection and software protection, thereby improving the reliability of PFC overcurrent protection; a follower is provided in the reference voltage generation module to buffer the signal, so that the output reference voltage is not interfered by other circuits and the voltage output is stable; the reset signal output module has a fault recovery function, thereby improving the convenience of the application of this circuit.

[0059] (2) The PFC overcurrent protection circuit and PFC circuit provided by the present invention use a resistor sampling method to perform current sampling, and at the same time, a diode is connected in series at the non-inverting end of the comparator. If the protection current needs to be increased, there is no need to replace the sampling resistor, and the sampling voltage signal of the sampling resistor can be directly amplified, thereby improving the convenience of the application of this circuit.

[0060] (3) The PFC overcurrent protection circuit and PFC circuit provided by the present invention are provided with a follower in the circuit for generating the reference voltage, which provides high input impedance and low output impedance to buffer the signal, so that the reference voltage signal is not interfered by other circuits and the voltage output is stable.

[0061] (4) The PFC overcurrent protection circuit and PFC circuit provided by the present invention have a fault holding function to prevent the circuit from being turned on in a fault condition, thereby increasing the service life of the IGBT.

[0062] The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content suggested above without departing from the scope of the technical solution of the present invention. The implementation scheme in the above embodiment can be further combined or replaced. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the solution of the present invention.

Claims

1. A PFC overcurrent protection circuit, characterized in that: It includes a current sampling module, a reference voltage generation module, an overcurrent comparison module, a hardware protection module, a software protection module, a PFC drive module and a reset signal output module; The current sampling module is connected to the output end of the PFC circuit and the input end of the overcurrent comparison module respectively, the reference voltage generation module is connected to the other input end of the overcurrent comparison module, the output end of the overcurrent comparison module is connected to the input end of the software protection unit and the input end of the hardware protection unit respectively, the output end of the hardware protection unit is connected to the input end of the PFC driving module, the output end of the software protection unit is connected to the control end of the PFC driving module, and the output end of the PFC driving module is connected to the control end of the PFC circuit; The reference voltage generating module includes a follower, which provides high input impedance and low output impedance.

2. The PFC overcurrent protection circuit according to claim 1, characterized in that: The current sampling module includes a first capacitor, a third diode, a fourth resistor, and a seventh resistor; One end of the fourth resistor is connected to the output end of the PFC circuit, and the other end is grounded; one end of the seventh resistor is connected to the output end of the PFC circuit, and the other end is divided into two paths, a first path is grounded via the first capacitor, and a second path is connected to the input end of the overcurrent comparison module via the third diode.

3. The PFC overcurrent protection circuit according to claim 1, characterized in that: The reference voltage generating module also includes a working power supply, an eighth resistor and a ninth resistor; One end of the eighth resistor is connected to the working power input terminal, and the other end is divided into two paths, the first path is grounded via the ninth resistor, and the second path is connected to the non-inverting input terminal of the follower; the output end of the follower is divided into two paths, the first path is connected to the inverting input terminal of the follower, and the second path is connected to the input terminal of the overcurrent comparison module.

4. The PFC overcurrent protection circuit according to claim 1, characterized in that: The overcurrent comparison module includes a comparator and a tenth resistor; One end of the tenth resistor is connected to the output end of the comparator, and the other end is connected to the non-inverting input end of the comparator; the output end of the comparator is divided into two paths, the first path is connected to the input end of the hardware protection module, and the second path is connected to the input end of the software protection module; the non-inverting input end of the comparator is connected to the input end of the overcurrent comparison module as the current sampling module, and the inverting input end of the comparator is connected to the input end of the overcurrent comparison module as the reference voltage generation module.

5. The PFC overcurrent protection circuit according to claim 1, characterized in that: The hardware protection module includes a fifth resistor, a sixth resistor, and a triode; The base of the transistor serves as the input end of the hardware protection module and is connected to the output end of the comparator via the fifth resistor; the collector of the transistor serves as the output end of the hardware protection module and is connected to the input end of the PFC driving module; the emitter of the transistor is grounded, one end of the sixth resistor is connected to the output end of the fifth resistor, and the other end is grounded.

6. The PFC overcurrent protection circuit according to claim 1, characterized in that: The software protection module includes a microprocessor; The input end of the microprocessor is connected to the output end of the comparator. The output end of the microprocessor is divided into two paths, the first path is connected to the control end of the PFC drive module, and the second path is connected to the input end of the reset signal output module.

7. The PFC overcurrent protection circuit according to claim 1, characterized in that: The PFC driving module includes a working power supply, a driving power supply, a first resistor, a second resistor, a third resistor, and a driving chip; The anode of the primary diode of the driver chip serves as the input end of the PFC driver module, and the cathode of the primary diode of the driver chip serves as the control end of the PFC driver module; one end of the first resistor is connected to the working power input end, and the other end is connected to the cathode of the primary diode of the driver chip; one end of the second resistor is connected to the working power input end, and the other end is connected to the anode of the primary diode of the driver chip; the upper tube emitter of the secondary transistor of the driver chip is connected to the driving power input end, and the lower tube emitter of the secondary transistor of the driver chip is grounded; one end of the third resistor is connected to the collector of the secondary transistor of the driver chip, and the other end is connected to the control end of the PFC circuit.

8. The PFC overcurrent protection circuit according to claim 1, characterized in that: It also includes a reset signal output module, the reset signal output module is respectively connected to the output end of the software protection unit and the input end of the overcurrent comparison module, and the reset signal output module includes a second diode; An anode of the second diode is connected to the output terminal of the microprocessor, and a cathode of the second diode is connected to the inverting input terminal of the comparator.

9. A PFC circuit, characterized in that: A PFC overcurrent protection circuit as described in any one of claims 1 to 8 is used.

10. The PFC circuit according to claim 9, characterized in that: The PFC circuit includes a filter / pre-charge circuit, a rectifier bridge, an energy storage inductor, a switch tube, an AC power supply, a first diode and a capacitor group; The control end of the switch tube serves as the control end of the PFC circuit, and the output end of the switch tube serves as the output end of the PFC circuit; the two input ends of the filter / pre-charging circuit are connected to the AC power supply, the two input ends of the rectifier bridge are connected to the two output ends of the filter / pre-charging circuit, the positive output end of the rectifier bridge is connected to one end of the energy storage inductor, the other end of the energy storage inductor and the anode of the first diode are connected to the input end of the switch tube, the cathode of the first diode is connected to the positive electrode of the capacitor group, and the negative electrode of the capacitor group is connected to the negative output end of the rectifier bridge.

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