阅读说明：本技术 一种igbt过流保护电路 (IGBT overcurrent protection circuit ) 是由 杨凯 余文毅 柳岸明 定渊博 杨帆 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种IGBT过流保护电路,包括解耦保护电路、基准电平生成电路、故障信号生成电路和硬件封锁电路；解耦保护电路用于根据采集的IGBT下管的栅极和漏极电压生成保护电压信号；故障信号生成电路将保护电压信号与基准电压信号进行比较,当保护电压信号大于基准电压信号时形成故障信号；硬件封锁电路在故障信号的触发下将下管的栅极电压钳位至下管驱动电源的负电源,使下管关断；本发明采用分离的模拟电路器件配置可解耦的过流保护电路的三种工作模式,在IGBT发生过流故障时、正常工作时、不工作时的三种现实工况中灵活切换,在不使用驱动芯片的情况下实现过流保护,并可通过调节电路参数来调节执行电压范围和响应时间值。(The invention discloses an IGBT overcurrent protection circuit, which comprises a decoupling protection circuit, a reference level generation circuit, a fault signal generation circuit and a hardware lockout circuit, wherein the decoupling protection circuit is connected with the reference level generation circuit; the decoupling protection circuit is used for generating a protection voltage signal according to the collected grid and drain voltage of the IGBT lower tube; the fault signal generation circuit compares the protection voltage signal with the reference voltage signal and forms a fault signal when the protection voltage signal is greater than the reference voltage signal; the hardware locking circuit clamps the grid voltage of the lower tube to a negative power supply of the lower tube driving power supply under the trigger of the fault signal to turn off the lower tube; the invention adopts three working modes of a decoupled over-current protection circuit configured by separated analog circuit devices, flexibly switches among three practical working conditions of over-current fault occurrence, normal working and non-working of the IGBT, realizes over-current protection without using a driving chip, and can adjust the execution voltage range and the response time value by adjusting circuit parameters.)

1. An IGBT overcurrent protection circuit is characterized by comprising a decoupling protection circuit, a reference level generation circuit, a fault signal generation circuit and a hardware lockout circuit;

the decoupling protection circuit is respectively connected with the grid and the drain of the IGBT lower tube, and generates a protection voltage signal according to the collected grid voltage and drain voltage of the IGBT lower tube;

the reference level generating circuit is used for providing a reference voltage signal;

the fault signal generating circuit is respectively connected with the decoupling protection circuit, the reference level generating circuit and the hardware locking circuit, compares the protection voltage signal provided by the decoupling protection circuit with the reference voltage signal provided by the reference level generating circuit, and forms a fault signal and sends the fault signal to the hardware locking circuit when the value of the protection voltage signal is greater than the reference voltage signal;

and the hardware blocking circuit is connected with the grid of the IGBT lower tube, and clamps the grid voltage of the IGBT lower tube to a negative power supply of the lower tube driving power supply under the triggering of the fault signal, so that the IGBT lower tube is turned off.

2. The IGBT overcurrent protection circuit of claim 1, wherein the decoupling protection circuit comprises a first diode, a first resistor, a second diode, a fourth resistor, a third diode, a fifth resistor;

the negative electrode of the first diode is connected with the drain electrode of the IGBT lower tube, and the negative electrode of the first diode is connected with the positive electrode of the second diode through the first resistor; the cathode of the second diode outputs a protection voltage signal;

the fourth resistor is connected with the third diode in parallel, a first end of the fourth resistor and the anode of the third diode are connected with the anode of the first diode, and a second end of the fourth resistor and the cathode of the third diode are connected with the gate of the lower tube of the IGBT;

and the first end of the fifth resistor is connected with a negative power supply of the lower tube driving power supply, and the second end of the fifth resistor is connected with the anode of the second diode.

3. The IGBT overcurrent protection circuit of claim 2, wherein the decoupling protection circuit has three modes of operation:

when the IGBT lower tube does not act, the drain voltage of the IGBT lower tube breaks down the first diode, and the fourth resistor is connected with a negative power supply of the lower tube driving power supply to clamp; the breakdown energy of the first diode is discharged to a negative power supply of the lower tube driving power supply through the third diode and the fifth resistor; the protection voltage signal output by the second diode is limited to (-V2-V)_D2+ X); wherein, -V2 represents the negative supply of the lower tube drive supply, V_D2The conduction voltage of the second diode is represented, and the size of X depends on the resistance values of the first resistor, the fourth resistor and the fifth resistor;

when the IGBT lower tube acts and short circuit does not occur, the drain voltage of the IGBT lower tube is the conduction voltage drop of the IGBT lower tube, the first diode is not broken down, the second end of the fourth resistor and the negative electrode of the third diode are connected with the positive power supply of the lower tube driving power supply, and the protection voltage signal output by the second diode is limited to (-V2-V)_D2)；

When the IGBT lower tube acts and short circuit occurs, the drain voltage of the IGBT lower tube breaks down the first diode, the second end of the fourth resistor and the negative electrode of the third diode are connected with the positive power supply of the lower tube driving power supply, and the breakdown energy of the first diode is discharged to the negative power supply of the lower tube driving power supply through the fifth resistor; the protection voltage signal output by the second diode is limited to (V2+ X Y/Udc-V)_D2) (ii) a Where V2 represents the positive supply of the down tube drive supply, Udc represents the bus voltage, and Y represents the drain voltage of the IGBT down tube.

4. The IGBT overcurrent protection circuit according to claim 1, wherein the reference voltage generation circuit includes a second resistor and a fifth diode; one end of the second resistor is used for outputting a reference voltage of a tube driving power supply, and the other end of the second resistor is connected with the cathode of the fifth diode; and the anode of the fifth diode is connected with a negative power supply of the lower tube driving power supply.

5. The IGBT overcurrent protection circuit according to claim 1, wherein the fault signal generation circuit includes a first comparator, an eighth resistor, a sixth diode, and a ninth resistor;

the positive phase input end of the first comparator is used for receiving a protection voltage signal, and the negative phase input end of the first comparator is used for receiving a reference voltage signal;

the eighth resistor and the sixth diode are connected in series between the positive phase input end and the output end of the first comparator, the fault voltage signal output by the output end of the first comparator is converted into a corresponding fault current signal through the ninth resistor and is transmitted to the hardware locking circuit.

6. The IGBT overcurrent protection circuit of claim 1, wherein the hardware lockout circuit comprises a first triode, a twenty-first resistor, a MOS (metal oxide semiconductor) transistor, an eighteenth resistor and a seventh capacitor;

a base electrode of the first triode receives a fault signal output by the fault signal generating circuit, a collector electrode of the first triode receives a reference voltage of a lower tube driving power supply, and an emitter electrode of the first triode is connected with a negative power supply of the lower tube driving power supply through the twenty-first resistor;

the grid electrode of the MOS tube is connected with the emitting electrode of the first triode, the source electrode of the MOS tube is connected with the negative power supply of the lower tube driving power supply, and the drain electrode of the MOS tube is connected with the grid electrode of the IGBT lower tube after being sequentially connected with the eighteenth resistor and the seventh capacitor in series.

7. The IGBT over-current protection circuit according to any one of claims 1-6, further comprising a filter circuit; the input end of the filter circuit is connected with the decoupling protection circuit, and the output end of the filter circuit is connected with the fault signal generation circuit;

the filter circuit carries out filtering and voltage division processing on the protection voltage signal output by the decoupling protection circuit so as to output a protection voltage signal matched with the input resistance range of the fault signal generation circuit.

8. The IGBT overcurrent protection circuit according to any one of claims 1 to 6, further comprising a controller and a reset circuit;

the controller is connected with the fault signal generating circuit, generates a reset signal according to the fault signal output by the fault signal generating circuit and sends the reset signal to the reset circuit;

the output end of the reset circuit is connected with the fault signal generating circuit, and the protection voltage signal in the fault signal generating circuit is clamped to the negative power supply of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is released to the negative power supply of the lower tube driving power supply, and the fault signal is removed.

9. The IGBT overcurrent protection circuit according to claim 8, further comprising an interference elimination circuit for comparing the fault signal output from the fault signal generation circuit with the reference voltage signal and sending the comparison result as a valid fault signal to the controller;

the interference elimination circuit comprises a sixteenth resistor, a sixth capacitor and a second comparator;

the sixteenth resistor and the sixth capacitor form a first-order RC low-pass filter circuit for filtering fault voltage signals generated by the fault signal generating circuit;

the positive phase input end of the second comparator is used for receiving the fault voltage signal after filtering processing, the negative phase input end of the second comparator is used for receiving the reference voltage signal, and the output end of the second comparator is connected and controlled to send the effective fault signal to the controller.

10. The IGBT overcurrent protection circuit of any one of claims 1-9, further comprising an IGBT drive circuit for controlling turn-on and turn-off of an upper IGBT tube and a lower IGBT tube;

the IGBT driving circuit comprises a first capacitor, a third resistor, a fourth diode, a seventh resistor, a second capacitor and a sixth resistor;

the first capacitor and the third resistor are connected in parallel to form an IGBT switching-on circuit for adjusting the switching-on speed of the IGBT; the seventh resistor and the fourth diode are connected in series and then are connected in parallel with the first capacitor and the third resistor, and the seventh resistor and the fourth diode are connected in series to form an IGBT turn-off circuit; the common connecting end of the first capacitor, the third resistor and the seventh resistor is connected with the grid of the upper IGBT tube or the lower IGBT tube;

after the second capacitor and the sixth resistor are connected in parallel, the first end of the second capacitor is connected with the common connecting end of the first capacitor, the third resistor and the seventh resistor, the second end of the second capacitor is grounded, and the third end of the second capacitor is connected with the source electrode of the IGBT upper tube or the IGBT lower tube.

Technical Field

The invention belongs to the technical field of electronic circuits, and particularly relates to an IGBT overcurrent protection circuit for a frequency converter, which is realized by adopting discrete device hardware.

Background

With the popularization of frequency conversion technology, more and more IGBT overcurrent protection circuits are applied to power supply circuits, the existing IGBT overcurrent protection circuits are generally designed by using controlled direct current sources in driving chips, and the software protection mode has the defects that the execution voltage range is protected, and the response time is protected and is fixed and unadjustable. After the power module of the high-power frequency converter is bare-filmed and connected in parallel or the IGBT module is changed into the silicon carbide module, the original protection scheme based on the driving chip can not meet the requirement of response time any more, and the protection voltage range can not be set independently.

Disclosure of Invention

In view of at least one of the drawbacks and needs of the prior art, the present invention provides an IGBT over-current protection circuit that can adjust the range of protection implementation voltage and set response time through RC network parameters and diode profile selection changes.

In order to achieve the above object, according to one aspect of the present invention, there is provided an IGBT overcurrent protection circuit, including a decoupling protection circuit, a reference level generation circuit, a fault signal generation circuit, and a hardware lockout circuit;

the decoupling protection circuit is respectively connected with the grid and the drain of the IGBT lower tube, and generates a protection voltage signal according to the collected grid voltage and drain voltage of the IGBT lower tube;

the reference level generating circuit is used for providing a reference voltage signal;

the fault signal generating circuit is respectively connected with the decoupling protection circuit, the reference level generating circuit and the hardware locking circuit, compares the protection voltage signal provided by the decoupling protection circuit with the reference voltage signal provided by the reference level generating circuit, and forms a fault signal and sends the fault signal to the hardware locking circuit when the value of the protection voltage signal is greater than the reference voltage signal;

and the hardware blocking circuit is connected with the grid of the IGBT lower tube, and clamps the grid voltage of the IGBT lower tube to a negative power supply of the lower tube driving power supply under the triggering of the fault signal, so that the IGBT lower tube is turned off.

Preferably, in the IGBT overcurrent protection circuit, the decoupling protection circuit includes a first diode D1, a first resistor R1, a second diode D2, a fourth resistor R4, a third diode D3, and a fifth resistor R5;

the cathode of the first diode D1 is connected with the drain of the lower tube of the IGBT, and the cathode is connected with the anode of a second diode D2 through the first resistor R1; the cathode of the second diode D2 outputs a protection voltage signal;

the fourth resistor R4 is connected in parallel with the third diode D3, the first end of the fourth resistor R4 and the anode of the third diode D3 are connected with the anode of the first diode D1, and the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected with the gate of the lower tube of the IGBT;

the first end of the fifth resistor R5 is connected with the negative power supply of the lower tube driving power supply, and the second end is connected with the anode of the second diode D2.

Preferably, in the IGBT overcurrent protection circuit, the decoupling protection circuit has three operating modes:

when the IGBT lower tube does not act, the drain voltage of the IGBT lower tube breaks down the first diode D1, and the fourth resistor R4 is connected with the negative power supply of the lower tube driving power supply for clamping; the breakdown energy of the first diode D1 is discharged to the negative power supply of the down tube driving power supply through the third diode D3 and the fifth resistor R5; the protection voltage signal output by the second diode D2 is limited to (-V2-V)_D2+ X); wherein, -V2 represents the negative supply of the lower tube drive supply, V_D2Representing the turn-on voltage of the second diode D2, the magnitude of X depends on the resistances of the first, fourth and fifth resistors R1, R4 and R5;

when the IGBT down tube operates and short circuit does not occur, the drain voltage of the IGBT down tube is the conduction voltage drop of the IGBT down tube, the first diode D1 is not broken down, the second end of the fourth resistor R4 and the negative electrode of the third diode D3 are connected with the positive power supply of the down tube driving power supply, and the protection voltage signal output by the second diode D2 is limited to (-V2-V)_D2)；

When the IGBT down tube is operated and short circuit occurs, the drain voltage of the IGBT down tube breaks down the first diode D1, the second end of the fourth resistor R4 and the negative electrode of the third diode D3 are connected with the positive power supply of the down tube driving power supply, and the first diode D1The breakdown energy is discharged to a negative power supply of the lower tube driving power supply through a fifth resistor R5; the protection voltage signal output by the second diode D2 is limited to (V2+ X Y/Udc-V)_D2) (ii) a Where V2 represents the positive supply of the down tube drive supply, Udc represents the bus voltage, and Y represents the drain voltage of the IGBT down tube.

Preferably, in the IGBT overcurrent protection circuit, the reference voltage generation circuit includes a second resistor R2 and a fifth diode D5; one end of the second resistor R2 is used for lowering the reference voltage of the tube driving power supply, and the other end of the second resistor R2 is connected with the cathode of the fifth diode D5; the anode of the fifth diode D5 is connected with the negative power supply of the lower tube driving power supply.

Preferably, in the IGBT overcurrent protection circuit, the fault signal generation circuit includes a first comparator, an eighth resistor, a sixth diode, and a ninth resistor;

the positive phase input end of the first comparator is used for receiving a protection voltage signal, and the negative phase input end of the first comparator is used for receiving a reference voltage signal;

the eighth resistor and the sixth diode are connected in series between the positive phase input end and the output end of the first comparator, a fault voltage signal output by the output end of the first comparator is transmitted to the interference elimination circuit, and the fault voltage signal is converted into a corresponding fault current signal through the ninth resistor and is transmitted to the hardware blocking circuit.

Preferably, in the IGBT overcurrent protection circuit, the hardware blocking circuit includes a first triode Q1, a twenty-first resistor R21, a MOS transistor Q3, an eighteenth resistor R18, and a seventh capacitor C7;

a base electrode of the first triode Q1 receives a fault signal output by the fault signal generating circuit, a collector electrode of the first triode Q1 receives a reference voltage of a lower tube driving power supply, and an emitter electrode of the first triode Q1 is connected with a negative power supply of the lower tube driving power supply through the twenty-first resistor R21;

the gate of the MOS transistor Q3 is connected with the emitter of the first triode Q1, the source is connected with the negative power supply of the lower tube driving power supply, and the drain is connected with the gate of the lower tube of the IGBT after being sequentially connected with the eighteenth resistor R18 and the seventh capacitor C7 in series.

Preferably, the IGBT overcurrent protection circuit further includes a filter circuit; the input end of the filter circuit is connected with the decoupling protection circuit, and the output end of the filter circuit is connected with the fault signal generation circuit;

the filter circuit carries out filtering and voltage division processing on the protection voltage signal output by the decoupling protection circuit so as to output a protection voltage signal matched with the input resistance range of the fault signal generation circuit.

Preferably, in the IGBT overcurrent protection circuit, the filter circuit includes a tenth resistor R10, a fifth capacitor C5, a thirteenth resistor R13, and an eleventh resistor R11;

the first end of the tenth resistor R10 is connected with the output end of the decoupling protection circuit and receives a protection voltage signal, and the second end of the tenth resistor R10 is connected with the eleventh resistor R11; the other end of the eleventh resistor R11 is used as the output end of the filter circuit;

after the fifth capacitor C5 is connected in parallel with the thirteenth resistor R13, one end of the fifth capacitor C5 is connected with the second end of the tenth resistor R10, and the other end of the fifth capacitor C5 is connected with the gate of the lower tube of the IGBT;

the tenth resistor R10, the fifth capacitor C5 and the thirteenth resistor R13 form a first-order RC filter circuit and a resistor voltage dividing circuit, and filter and divide a protection voltage signal output by the decoupling protection circuit; the eleventh resistor R11 is an output matching resistor, which ensures that the output protection voltage signal matches the input resistance range of the fault signal generating circuit.

Preferably, the IGBT overcurrent protection circuit further includes a controller and a reset circuit;

the controller is connected with the fault signal generating circuit, generates a reset signal according to the fault signal output by the fault signal generating circuit and sends the reset signal to the reset circuit;

the output end of the reset circuit is connected with the fault signal generating circuit, and the protection voltage signal in the fault signal generating circuit is clamped to the negative power supply of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is released to the negative power supply of the lower tube driving power supply, and the fault signal is removed.

Preferably, in the IGBT overcurrent protection circuit, the reset circuit includes an optocoupler and a second transistor Q2;

a first input end of the optocoupler receives a reset signal output by the controller, a second input end of the optocoupler is grounded, a first output end of the optocoupler is connected with a base electrode of a second triode Q2, and a second output end of the optocoupler is connected with an emitting electrode of a second triode Q2; and the emitter of the second triode Q2 is connected with the negative power supply of the lower tube driving power supply, and the collector of the second triode Q2 is connected with the positive-phase input end of the first comparator in the fault signal generating circuit.

Preferably, the IGBT overcurrent protection circuit further includes an interference elimination circuit;

the interference elimination circuit is used for comparing the fault signal output by the fault signal generation circuit with the reference voltage signal and sending the comparison result to the controller as an effective fault signal.

Preferably, in the IGBT overcurrent protection circuit, the interference elimination circuit includes a sixteenth resistor R16, a sixth capacitor C6, and a second comparator U1B;

the sixteenth resistor R16 and the sixth capacitor C6 form a first-order RC low-pass filter circuit for filtering fault voltage signals generated by the fault signal generating circuit;

the positive phase input end of the second comparator U1B is used for receiving the filtered fault voltage signal, the negative phase input end is used for receiving the reference voltage signal, and the output end is connected with the controller so as to send the effective fault signal to the controller.

Preferably, the IGBT overcurrent protection circuit further includes an IGBT drive circuit for controlling the on and off of an IGBT upper tube and an IGBT lower tube;

the IGBT driving circuit comprises a first capacitor C1, a third resistor R3, a fourth diode D4, a seventh resistor R7, a second capacitor C2 and a sixth resistor R6;

the first capacitor C1 and the third resistor R3 are connected in parallel to form an IGBT (insulated gate bipolar transistor) turn-on circuit for adjusting the turn-on speed of the IGBT; the seventh resistor R7 is connected with the fourth diode D4 in series and then is connected with the first capacitor C1 and the third resistor R3 in parallel, and the seventh resistor R7 and the fourth diode D4 are connected in series to form an IGBT turn-off circuit; the common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7 is connected with the grid of an upper IGBT tube or a lower IGBT tube;

after the second capacitor C2 is connected with the sixth resistor R6 in parallel, the first end of the second capacitor C2 is connected with the common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7, the second end of the second capacitor C2 is grounded, and the third end of the second capacitor C2 is connected with the source electrode of the upper IGBT tube or the lower IGBT tube;

the sixth resistor R6 and the second capacitor C2 form an IGBT internal capacitance-inductance network compensation circuit, and the circuit is used for adjusting the switching waveform of an IGBT upper tube or an IGBT lower tube and ensuring the reliable turn-off of the IGBT upper tube or the IGBT lower tube.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

the IGBT overcurrent protection circuit provided by the invention adopts three working modes of a decoupled overcurrent protection circuit configured by separated analog circuit devices, flexibly switches among three practical working conditions of overcurrent fault occurrence, normal working and non-working of the IGBT, realizes overcurrent protection without using a driving chip, and can adjust an execution voltage range and set a response time value by adjusting circuit parameters and diode selection.

Drawings

Fig. 1 is a power circuit diagram of a conventional frequency converter;

fig. 2 is a schematic structural diagram of a first IGBT overcurrent protection circuit provided in an embodiment of the present invention;

FIG. 3 is a schematic circuit diagram of an upper tube driving circuit and a lower tube driving circuit according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a decoupling protection circuit provided in an embodiment of the present invention;

fig. 5 is a schematic diagram of three different operation modes of the decoupling protection circuit provided in the embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a filter circuit according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a reference voltage generating circuit according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of a fault signal generating circuit according to an embodiment of the present invention;

FIG. 9 is a block diagram of a hardware lockout circuit according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a second IGBT overcurrent protection circuit according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of a reset circuit according to an embodiment of the present invention;

FIG. 12 is a schematic diagram of a structure of a de-jamming circuit according to an embodiment of the present invention;

fig. 13 is a schematic diagram of the position of the inverter half-bridge drive signals when driven in parallel.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a power circuit diagram of a conventional frequency converter, and referring to fig. 1, an IGBT overcurrent protection circuit designed for upper and lower transistors of an a-phase half bridge is taken as an example to be described, and the IGBT overcurrent protection circuit needs to use state signals D1 (upper tube drain voltage signal), G1 (upper tube gate voltage signal), S1 (upper tube source voltage signal), D2 (lower tube drain voltage signal), G2 (lower tube gate voltage signal), and S2 (lower tube source voltage signal) of the upper and lower tubes of the a-phase half bridge.

Fig. 2 is a schematic diagram of a composition structure of the IGBT overcurrent protection circuit provided in this embodiment, and as shown in fig. 2, the IGBT overcurrent protection circuit includes an upper tube driving circuit and a lower tube driving circuit, the upper tube driving circuit is used for controlling the on and off of an upper tube of the IGBT, and the lower tube driving circuit is used for controlling the on and off of a lower tube of the IGBT.

Fig. 3 is a schematic circuit diagram of the upper tube driving circuit and the lower tube driving circuit provided in this embodiment, and as shown in fig. 3, the topology of the upper tube driving circuit and the topology of the lower tube driving circuit are the same, and the following description is given by taking the upper tube driving circuit as an example.

The upper tube driving circuit comprises a first capacitor C1, a third resistor R3, a fourth diode D4, a seventh resistor R7, a second capacitor C2 and a sixth resistor R6;

the first capacitor C1 and the third resistor R3 are connected in parallel to form an IGBT (insulated gate bipolar transistor) switching-on circuit for adjusting the switching-on speed of the IGBT; the seventh resistor R7 is connected with the fourth diode D4 in series and then is connected with the first capacitor C1 and the third resistor R3 in parallel, and the seventh resistor R7 and the fourth diode D4 are connected in series to form an IGBT turn-off circuit; among them, the fourth diode D4 preferably employs a schottky diode below the 100ns response level. The common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7 is connected with the grid of the upper tube of the IGBT;

after the second capacitor C2 is connected with the sixth resistor R6 in parallel, the first end of the second capacitor C2 is connected with the common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7, the second end of the second capacitor C2 is grounded, and the third end of the second capacitor C2 is connected with the source electrode of the upper tube of the IGBT; the sixth resistor R6 and the second capacitor C2 form an IGBT internal capacitance-inductance network compensation circuit, and the circuit is used for adjusting the switching waveform of an IGBT upper tube and ensuring that the IGBT upper tube is reliably turned off when the driving signal G1 is high-resistance.

The IGBT overcurrent protection circuit also comprises a decoupling protection circuit, a reference level generation circuit, a fault signal generation circuit and a hardware lockout circuit as a core part of overcurrent protection;

the decoupling protection circuit is used for acquiring the grid voltage and the drain voltage of the lower tube of the IGBT and generating a protection voltage signal according to the grid voltage and the drain voltage;

the reference level generating circuit is used for providing a reference voltage signal;

the fault signal generating circuit is used for comparing the protection voltage signal with the reference voltage signal and forming a fault signal when the value of the protection voltage signal is greater than the reference voltage signal;

and the hardware blocking circuit is used for clamping the grid voltage of the IGBT lower tube to a negative power supply of the lower tube driving power supply under the triggering of the fault signal, so that the IGBT lower tube is switched off, and overcurrent protection is realized.

Fig. 4 is a schematic structural diagram of the decoupling protection circuit provided in this embodiment, and referring to fig. 4, the decoupling protection circuit includes a first diode D1, a first resistor R1, a second diode D2, a fourth resistor R4, a third diode D3, and a fifth resistor R5;

the cathode of the first diode D1 is connected with the drain of the lower tube of the IGBT, and the cathode is connected with the anode of the second diode D2 through a first resistor R1; the cathode of the second diode D2 outputs a protection voltage signal SignalA;

the fourth resistor R4 is connected in parallel with the third diode D3, the first end of the fourth resistor R4 and the anode of the third diode D3 are connected with the anode of the first diode D1, and the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected with the gate of the lower tube of the IGBT;

the fifth resistor R5 has a first terminal connected to the negative power supply of the down tube driving power supply and a second terminal connected to the anode of the second diode D2.

Referring to fig. 5, in the present embodiment, the decoupling protection circuit has three operation modes:

working mode 1: when the IGBT lower tube does not act, the voltage value of the drain voltage VD2 of the IGBT lower tube is close to the voltage value Udc of the bus voltage, the drain voltage of the IGBT lower tube breaks down the first diode D1, and the fourth resistor R4 is connected with a negative power supply-V2 of a lower tube driving power supply for clamping; the voltage value of the state signal S is ensured not to reach the protection limit voltage value through the voltage division regulation of R4 and R1. The breakdown energy of the first diode D1 is discharged to the negative power supply of the down tube driving power supply through the third diode D3 and the fifth resistor R5; finally, the voltage value of the state signal S is limited to be near-V2 + X, and the protection voltage signal SignalA output by the second diode D2 is limited to (-V2-V)_D2+ X); wherein, -V2 represents the negative supply of the lower tube drive supply, V_D2Representing the turn-on voltage of the second diode D2, the magnitude of X depends on the resistances of the first, fourth and fifth resistors R1, R4 and R5;

the working mode 2 is as follows: when the IGBT low tube operates and short circuit does not occur, the drain voltage VD2 of the IGBT low tube is the conduction voltage drop when the IGBT is conducted, generally is very small and close to 0, so that the voltage value of the drain voltage VD2 of the IGBT low tube is close to the reference value group 2 of the low tube driving power supply, at this time, the first diode D1 is not broken down, the second end of the fourth resistor R4 and the negative electrode of the third diode D3 are connected with the positive power supply of the low tube driving power supply, and the state signal SThe voltage value of the second diode D2 is close to the negative power supply-V2 of the lower tube driving power supply, and the protection voltage signal SignalA output by the second diode D2 is limited to (-V2-V)_D2)；

Working mode 3: when the IGBT lower tube acts and overcurrent short circuit occurs, information needing overcurrent protection is sent to the controller MCU; at this time, the drain voltage VD2 of the IGBT lower tube is a certain larger value Y smaller than the bus voltage Udc, the first diode D1 is broken down, the second end of the fourth resistor R4 and the negative electrode of the third diode D3 are connected to the positive power supply of the lower tube driving power supply, and the breakdown energy of the first diode D1 is discharged to the negative power supply of the lower tube driving power supply through the fifth resistor R5; finally, the voltage value of the status signal S is limited to (V2+ X Y/Udc), and the protection voltage signal output by the second diode D2 is limited to (V2+ X Y/Udc-V)_D2) (ii) a Where V2 represents the positive supply of the down tube drive power supply and Y represents the drain voltage of the IGBT down tube.

In summary, under normal operation, the operating state of the decoupling protection circuit switches between the operating mode 1 and the operating mode 2, and the protection voltage signal at SignalA is (-V2-V)_D2) To (-V2-V)_D2+ X).

The circuit application condition of this example [ bus voltage UDC: 600V, lower tube driving positive supply V2 (with respect to reference voltage group 2): 15V), lower tube driving negative supply-V2 (with respect to reference voltage group 2): -4V, the conduction voltage V of the second diode D2_D2：0.3V]；

In this example, by configuring the resistance values of the first resistor R1, the fourth resistor R4, and the fifth resistor R5 to configure X as 6V, the protection voltage signal at SignalA varies from-4.3V to 1.7V (reference and group 2) under normal operating conditions.

If overcurrent faults occur when the IGBT is switched on, the decoupling protection circuit works in a mode 3, and the protection voltage signal at the SignalA position is limited to 15.6V at the moment.

According to the circuit topology configuration mode, the protection voltage signal SignalA is divided into clear voltage areas according to the working condition of the IGBT.

As a preferred example, the IGBT overcurrent protection circuit further includes a filter circuit; the filter circuit is used for filtering and dividing the protection voltage signal SignalA output by the decoupling protection circuit so as to output a protection voltage signal A matched with the input resistance range of the fault signal generation circuit.

Fig. 6 is a schematic circuit structure diagram of the filter circuit provided in this embodiment, and referring to fig. 6, the filter circuit includes a tenth resistor R10, a fifth capacitor C5, a thirteenth resistor R13, and an eleventh resistor R11;

the first end of the tenth resistor R10 is connected with the output end of the decoupling protection circuit and receives the protection voltage signal SignalA, and the second end of the tenth resistor R10 is connected with the eleventh resistor R11; the other end of the eleventh resistor R11 is used as the output end of the filter circuit;

after the fifth capacitor C5 is connected in parallel with the thirteenth resistor R13, one end of the fifth capacitor C5 is connected to the second end of the tenth resistor R10, and the other end of the fifth capacitor C5 is connected to the gate of the lower tube of the IGBT;

the tenth resistor R10, the fifth capacitor C5 and the thirteenth resistor R13 form a first-order RC filter circuit and a resistor voltage dividing circuit, and the protection voltage signal SignalA output by the decoupling protection circuit is filtered and subjected to voltage dividing; the eleventh resistor R11 is an output matching resistor, which ensures that the output protection voltage signal a matches the input resistance range of the fault signal generation circuit.

As a specific example, the filter circuit performs voltage division filtering on the protection voltage signal SignalA through a resistor R10, a resistor R13 and a capacitor C5, the resistance value of R10 is equal to R13, and R11 is regarded as the driving resistor of the lower-stage comparator circuit, at this time, the voltage value of the signal a output by the filter circuit is-2.15V to 0.85V under the normal operation condition, the voltage value is 7.8V under the fault condition, and the voltage value of the filtered protection voltage signal is transited among the three voltage values under the mode transition condition, and the transition range is (-2.15V to 7.8V).

Fig. 7 is a schematic circuit configuration diagram of the reference voltage generating circuit provided in the present embodiment, referring to fig. 7, the reference voltage generating circuit is used to set a voltage threshold range, and includes a second resistor R2 and a fifth diode D5; one end of the second resistor R2 is used for lowering the reference voltage of the tube driving power supply, and the other end is connected with the cathode of the fifth diode D5; the anode of the fifth diode D5 is connected to the negative power-V2 of the lower tube driving power supply, the fifth diode D5 is a zener diode, and the reference voltage signal B (e.g., 3V) relative to the group 2 is generated through the second resistor R2 and the zener diode D5.

Fig. 8 is a schematic circuit configuration diagram of a fault signal generating circuit provided in the present embodiment, and referring to fig. 8, the fault signal generating circuit includes an operational amplifier U1A, an eighth resistor R8, a sixth diode D6, and a ninth resistor R9;

the non-inverting input terminal of the operational amplifier U1A is configured to receive the protection voltage signal a, and the inverting input terminal is configured to receive the reference voltage signal B; when the voltage value of the protection voltage signal A is larger than the reference voltage signal B, the overcurrent fault is considered to occur;

the eighth resistor R8 and the sixth diode D6 are connected in series between the non-inverting input terminal and the output terminal of the operational amplifier U1A, the output terminal of the operational amplifier U1A outputs a Fault voltage signal C, and the Fault voltage signal C is converted into a corresponding Fault current signal Fault2 through the ninth resistor R9 and transmitted to the hardware lockout circuit.

Fig. 9 is a schematic circuit structure diagram of the hardware lockout circuit provided in this embodiment, and referring to fig. 9, the hardware lockout circuit includes a first transistor Q1, a twenty-first resistor R21, a MOS transistor Q3, an eighteenth resistor R18, and a seventh capacitor C7;

the base electrode of the first triode Q1 receives a Fault current signal Fault2 output by the Fault signal generating circuit, the collector electrode of the first triode Q1 receives a reference voltage group 2 of the lower tube driving power supply, and the emitter electrode of the first triode Q8925 is connected with a negative power supply-V2 of the lower tube driving power supply through a twenty-first resistor R21;

the gate of the MOS transistor Q3 is connected to the emitter of the first triode Q1, the source is connected to the negative power supply-V2 of the lower tube driving power supply, and the drain is connected in series with the eighteenth resistor R18 and the seventh capacitor C7 in sequence and then to the gate of the lower tube of the IGBT.

The Fault current signal Fault2 output by the Fault signal generating circuit drives the hardware blocking circuit to enable a first triode Q1 in the circuit to be conducted, the grid voltage of an MOS tube Q3 is 5V2 through a resistor R21, an MOS tube Q3 is conducted, a lower tube grid signal is clamped to-V2, the lower tube is guaranteed to be turned off, the IGBT tube is turned off before a final confirmation signal is sent to the controller MCU, the safety of the IGBT is guaranteed, and damage is avoided. Wherein, the effect of R18 and C7 is to realize soft turn-off, so that the IGBT is not damaged by generating excessive voltage spike.

In the embodiment, the range of the protection execution voltage is changed by adjusting the resistance values of the resistors R4, R1 and R5 in the decoupling protection circuit, and the response time is set by adjusting the resistance values of the R9 in the fault signal generation circuit and the R21 and R18 in the hardware lockout circuit.

Referring to fig. 10, as a preferred embodiment, the IGBT overcurrent protection circuit further includes a controller MCU and a reset circuit;

the controller MCU is used for generating a reset signal according to a fault voltage signal C output by the fault signal generating circuit and sending the reset signal to the reset circuit;

the reset circuit is used for clamping a protection voltage signal in the fault signal generating circuit to a negative power supply-V2 of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is discharged to the negative power supply of the lower tube driving power supply to remove the fault signal.

Fig. 11 is a schematic circuit structure diagram of the reset circuit provided in this embodiment, and referring to fig. 11, the reset circuit includes an optocoupler U507 and a second transistor Q2;

a first input end 1 of the optocoupler U507 receives a RESET signal RESET _ Sig output by the controller MCU, a second input end 2 is grounded, a first output end 4 is connected with a base electrode of a second triode Q2, and a second output end 5 is connected with an emitter electrode of a second triode Q2; the emitter of the second triode Q2 is connected with the negative power supply-V2 of the lower tube driving power supply, and the collector is connected with the non-inverting input end of the operational amplifier U1A in the fault signal generating circuit.

When the controller MCU tries to perform software RESET, if an overcurrent fault disappears, the RESET circuit transmits a fault instruction RESET _ Sig sent by the MCU to a triode Q2 through a resistor R19, a capacitor C8, an optocoupler U507, a resistor R17, a resistor R20 and a capacitor C9 to conduct the triode Q2, at the moment, a protection voltage signal A is pulled down to-V2, a fault voltage signal C in the fault signal generation circuit discharges energy to a negative power supply-V2 of a lower tube driving power supply through the resistor R8 and a diode D6, and the fault voltage signal C finally falls to-V2, so that the overcurrent fault is removed.

Further, in order to avoid the influence of interference, the IGBT overcurrent protection circuit provided in this embodiment further includes an interference elimination circuit; the interference elimination circuit is used for comparing the fault voltage signal output by the fault signal generation circuit with the reference voltage signal and sending the comparison result to the controller as an effective fault signal.

Fig. 12 is a schematic circuit structure diagram of the interference cancellation circuit provided in this embodiment, and referring to fig. 12, the interference cancellation circuit includes a sixteenth resistor R16, a sixth capacitor C6, and a second comparator U1B;

the sixteenth resistor R16 and the sixth capacitor C6 form a first-order RC low-pass filter circuit for filtering the fault voltage signal C generated by the fault signal generating circuit;

the comparator U1B has a positive input terminal for receiving the filtered fault voltage signal C, a negative input terminal for receiving the reference voltage signal B, and an output terminal connected to the controller MCU for sending an effective fault signal D (high level effective) to the controller to confirm that an overcurrent fault has occurred.

Fig. 13 is a schematic diagram of positions of half-bridge driving signals of frequency converters during parallel driving, as shown in fig. 13, when multiple tubes are connected in parallel, a lower tube state signal D2 is separated into D21 and D22, and according to the structure of the decoupling protection circuit, the same IGBT overcurrent protection circuits are respectively built for D21, G2, S2, D22, G2, and S2, wherein the circuit structures and signal processing manners of the decoupling protection circuit, the reference level generation circuit, the fault signal generation circuit, the hardware lockout circuit and the like are completely the same as those described above, and the plurality of IGBT overcurrent protection circuits use the same controller MCU and send fault signals to the controller MCU through an or gate.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.