阅读说明：本技术 Igbt模块驱动及保护电路 (IGBT module driving and protecting circuit ) 是由 汪扬 朱天宇 周安健 周洪波 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种IGBT模块驱动及保护电路,包括隔离驱动电路和辅助电源电路；隔离驱动电路包括微处理器、隔离驱动芯片U1、驱动电流放大电路、IGBT和IGBT的集电极和发射极的检测电路；隔离驱动芯片U1分别与微处理器、驱动电流放大电路、IGBT和IGBT的集电极和发射极的检测电路电连接；辅助电源电路包括电源管理集成芯片U3、欠压保护电路、MOS管Q4、MOS管Q5、变压器T1、电压整流电路和输出滤波电路；变压器T1有三个绕组,分别为原边绕组N1、原边绕组N2和副边绕组P1；电源管理集成芯片U3分别与欠压保护电路、MOS管Q4和MOS管Q5连接,MOS管Q4与原边绕组N1连接,MOS管Q5与原边绕组N2连接,副边绕组P1分别与电压整流电路和输出滤波电路连接。本发明可靠性高,设计简洁。(The invention discloses a driving and protecting circuit of an IGBT module, which comprises an isolation driving circuit and an auxiliary power circuit; the isolation driving circuit comprises a microprocessor, an isolation driving chip U1, a driving current amplifying circuit, an IGBT and a detection circuit of a collector and an emitter of the IGBT; the isolation driving chip U1 is respectively and electrically connected with the microprocessor, the driving current amplifying circuit, the IGBT and the detection circuit of the collector and emitter of the IGBT; the auxiliary power supply circuit comprises a power supply management integrated chip U3, an undervoltage protection circuit, an MOS tube Q4, an MOS tube Q5, a transformer T1, a voltage rectification circuit and an output filter circuit; the transformer T1 has three windings, which are a primary winding N1, a primary winding N2 and a secondary winding P1; the power management integrated chip U3 is respectively connected with the undervoltage protection circuit, the MOS tube Q4 and the MOS tube Q5, the MOS tube Q4 is connected with the primary winding N1, the MOS tube Q5 is connected with the primary winding N2, and the secondary winding P1 is respectively connected with the voltage rectification circuit and the output filter circuit. The invention has high reliability and simple design.)

1. The utility model provides a IGBT module drive and protection circuit which characterized in that: the circuit comprises an isolation driving circuit and an auxiliary power supply circuit;

the isolation driving circuit comprises a microprocessor, an isolation driving chip U1, a driving current amplifying circuit, an IGBT and a detection circuit of a collector and an emitter of the IGBT; the isolation driving chip U1 is respectively and electrically connected with the microprocessor, the driving current amplifying circuit, the IGBT and the detection circuit of the collector and emitter of the IGBT; the IGBT is also electrically connected with the driving current amplifying circuit; the isolation driving circuit drives the waveform to carry out isolation transmission through an isolation driving chip U1, and then amplifies driving power through a driving current amplifying circuit to drive the grid of the IGBT;

the auxiliary power supply circuit comprises a power supply management integrated chip U3, an undervoltage protection circuit, an MOS tube Q4, an MOS tube Q5, a transformer T1, a voltage rectifying circuit and an output filter circuit; the transformer T1 comprises three windings, namely a primary winding N1, a primary winding N2 and a secondary winding P1; the power management integrated chip U3 is respectively connected with the under-voltage protection circuit, the MOS tube Q4 and the MOS tube Q5, the MOS tube Q4 is connected with the primary winding N1, the MOS tube Q5 is connected with the primary winding N2, and the secondary winding P1 is respectively connected with the voltage rectification circuit and the output filter circuit; the auxiliary power supply circuit is used for supplying power to the isolation driving chip U1, and the primary side and the secondary side of the power supply are isolated through a transformer T1.

2. The IGBT module driving and protection circuit according to claim 1, wherein: the driving current amplifying circuit comprises a resistor R4, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R14, a resistor R15, a triode Q1 and a triode Q3;

the resistor R4, the resistor R7, the resistor R9 and the resistor R11 are connected in parallel, a connecting point of the resistor R4, the resistor R7, the resistor R9 and the resistor R11 is connected with the grid of the IGBT, the other connecting point of the resistor R4, the resistor R7, the resistor R9 and the resistor R11 is connected with one end of the resistor R8, the other end of the resistor R8 is connected with the isolation driving chip U1 through the resistor R10, and the other end of the resistor R8 is further connected with the isolation driving chip U1 through the resistor R12;

the triode Q1 and the triode Q3 form a class-A-B push-pull complementary circuit, the triode Q1 is an NPN type triode, the triode Q3 is a PNP type triode, bases of the two triodes are directly connected, an emitter of the triode Q1 is connected with an emitter of the triode Q3, a collector of the triode Q1 is connected with a power VCC2, a resistor R14 and a resistor R15 are connected in parallel, a connecting point of the resistor R14 and the resistor R15 is connected with an isolation driving chip U1, and the other connecting point of the resistor R14 and the resistor R15 is connected with a collector of the triode Q3.

3. The IGBT module driving and protection circuit according to claim 2, wherein: the IGBT collector and emitter detection circuit comprises a diode D1, a diode D2, a diode D3, a resistor R1, a resistor R2, a resistor R3 and a capacitor C1, wherein one end of the resistor R2 is connected with an isolation driving chip U1 through the resistor R3, and the other end of the resistor R2 is connected with an isolation driving chip U1; a pin 1 of the diode D3 is connected with a connection point of the resistor R2 and the resistor R3 through the capacitor C1, a pin 2 of the diode D3 is connected with the isolation driving chip U1, and a pin 3 of the diode D3 is connected with the HV through the resistor R1, the diode D1 and the diode D2 in sequence.

4. The IGBT module driving and protecting circuit according to any one of claims 1 to 3, characterized in that: the isolation driving circuit further comprises a phase inverter U2, the input end of the phase inverter U2 is connected with the microprocessor, the output end of the phase inverter U2 is connected with the isolation driving chip U1, when the microprocessor outputs PWM waves, the pin 8 of the isolation driving chip U1 is at a low level, a diode between the pin 7 and the pin 8 of the isolation driving chip U1 is conducted, and the pin 11 of the isolation driving chip U1 outputs a high level; when the microprocessing output is at a low level, the pin 8 of the isolation driver chip U1 is at a high level, the diode between the pin 7 and the inside of the pin 8 of the isolation driver chip U1 is turned off, and the pin 11 of the isolation driver chip U1 is at a low level.

5. The IGBT module driving and protection circuit of claim 4, wherein: the undervoltage protection circuit comprises a resistor R17, a resistor R23, a resistor R28, a voltage regulator tube Z2 and a capacitor C23; the resistor R28, the voltage regulator tube Z2 and the capacitor C23 are connected in parallel, a connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is grounded, and the other connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is sequentially connected with the VCC1 through the resistor R23 and the resistor R17.

6. The IGBT module driving and protection circuit of claim 5, wherein: the auxiliary power supply circuit further comprises a loop compensation circuit, the loop compensation circuit comprises a resistor R30 and a capacitor C26, the resistor R30 is connected with the capacitor C26 in parallel, a connecting point of the resistor R30 and the capacitor C26 is grounded, and the other connecting point of the resistor R30 and the capacitor C26 is connected with the power management integrated chip U3.

7. The IGBT module driving and protection circuit of claim 6, wherein: the auxiliary power supply circuit further comprises a resistor R19, a resistor R20, a resistor R24, a resistor R29, a resistor R26 and a resistor R33, wherein the resistor R19 and the resistor R20 are current-limiting resistors, one end of the resistor R19 is connected with the power management integrated chip U3, the other end of the resistor R19 is connected with the transformer T1, one end of the resistor R20 is connected with the power management integrated chip U3, and the other end of the resistor R20 is connected with the transformer T1;

the resistor R24 and the resistor R29 are driving resistors, one end of the resistor R24 is connected with the MOS transistor Q4, the other end of the resistor R24 is connected with the power management integrated chip U3, one end of the resistor R29 is connected with the MOS transistor Q5, and the other end of the resistor R29 is connected with the power management integrated chip U3;

the resistor R26 and the resistor R33 are discharge resistors, two ends of the resistor R26 are respectively connected with the source and the gate of the MOS transistor Q4, and two ends of the resistor R33 are respectively connected with the source and the gate of the MOS transistor Q5.

8. The IGBT module driving and protection circuit according to claim 7, wherein: the voltage rectifying circuit comprises a diode D5, a diode D6 and a diode D7, wherein the anode of the diode D5 is connected with VEE2, the cathode of the diode D5 is connected with one end of a secondary winding P1, and the other end of the secondary winding P1 is connected with VCC2 through a diode D6 and a diode D7 in sequence.

9. The IGBT module driving and protection circuit according to claim 8, wherein: the auxiliary power supply circuit further comprises a capacitor C7 and a capacitor C8, the capacitor C7 and the capacitor C8 are blocking capacitors, the capacitor C7 and the capacitor C8 are connected in parallel, a connecting point of the capacitor C7 and the capacitor C8 is connected with the negative electrode of the diode D5, and the other connecting point of the capacitor C7 and the capacitor C8 is connected with the negative electrode of the diode D6.

10. The IGBT module driving and protection circuit according to claim 9, wherein: the output filter circuit comprises a capacitor C9-a capacitor C19, wherein the capacitor C9-the capacitor C14 are connected in parallel, a connecting point of the capacitor C9-the capacitor C14 is connected with VEE2, the other connecting point of the capacitor C9-the capacitor C14 is connected with VE, and the output filter circuit is an output filter capacitor of-8V; the capacitor C15-the capacitor C19 are connected in parallel, one connecting point of the capacitor C15-the capacitor C19 is connected with VE, and the other connecting point of the capacitor C15-the capacitor C19 is connected with VCC2, and is a +15V output filter capacitor.

Technical Field

The invention belongs to the technical field of automobile motor control systems, and particularly relates to an IGBT module driving and protecting circuit.

Background

The motor controller is used as a core component of the electric automobile and provides driving force for the whole automobile. An IGBT (insulated gate bipolar transistor) plays a very important role as a core component of a motor controller. The performance and reliability of the electric automobile are directly affected by the performance and reliability of the drive circuit of the IGBT. Therefore, how to design a high-performance and high-reliability IGBT driving circuit is particularly important.

The existing IGBT is mainly driven by two types, wherein one type is direct drive, and the other type is isolation drive. Since the operating voltage on an electric vehicle is high, the current is large. The driving of the IGBT is mainly realized by a PWM (pulse width modulation) method, and the PWM belongs to a weak signal system, and the IGBT and the weak signal system need to be electrically isolated for safety and reduction of interference of a high-voltage circuit part on the weak signal circuit. Therefore, the isolation driving circuit exhibits higher reliability and safety.

At present, a driving circuit of a motor controller generally adopts a combination of an auxiliary power supply and a driving chip, the auxiliary power supply generally adopts a relatively conventional flyback topology structure, a driving part generally adopts a minimum basic circuit, and the driving circuit can meet the use requirements, but still has the problems of complex design, more devices and poor performance, and has no advantage in cost.

Therefore, it is necessary to develop a driving and protecting circuit of the IGBT module.

Disclosure of Invention

The invention aims to provide an IGBT module driving and protecting circuit which is high in reliability and simple in design.

The invention relates to an IGBT module driving and protecting circuit, which comprises an isolation driving circuit and an auxiliary power circuit;

the isolation driving circuit comprises a microprocessor, an isolation driving chip U1, a driving current amplifying circuit, an IGBT and a detection circuit of a collector and an emitter of the IGBT; the isolation driving chip U1 is respectively and electrically connected with the microprocessor, the driving current amplifying circuit, the IGBT and the detection circuit of the collector and emitter of the IGBT; the IGBT is also electrically connected with the driving current amplifying circuit; the isolation driving circuit drives the waveform to carry out isolation transmission through an isolation driving chip U1, and then amplifies driving power through a driving current amplifying circuit to drive the grid of the IGBT;

the auxiliary power supply circuit comprises a power supply management integrated chip U3, an undervoltage protection circuit, an MOS tube Q4, an MOS tube Q5, a transformer T1, a voltage rectifying circuit and an output filter circuit; the transformer T1 comprises three windings, namely a primary winding N1, a primary winding N2 and a secondary winding P1; the power management integrated chip U3 is respectively connected with the under-voltage protection circuit, the MOS tube Q4 and the MOS tube Q5, the MOS tube Q4 is connected with the primary winding N1, the MOS tube Q5 is connected with the primary winding N2, and the secondary winding P1 is respectively connected with the voltage rectification circuit and the output filter circuit; the auxiliary power supply circuit is used for supplying power to the isolation driving chip U1, and the primary side and the secondary side of the power supply are isolated through a transformer T1.

Optionally, the driving current amplifying circuit includes a resistor R4, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R14, a resistor R15, a transistor Q1, and a transistor Q3;

the resistor R4, the resistor R7, the resistor R9 and the resistor R11 are connected in parallel, a connecting point of the resistor R4, the resistor R7, the resistor R9 and the resistor R11 is connected with the grid of the IGBT, the other connecting point of the resistor R4, the resistor R7, the resistor R9 and the resistor R11 is connected with one end of the resistor R8, the other end of the resistor R8 is connected with the isolation driving chip U1 through the resistor R10, and the other end of the resistor R8 is further connected with the isolation driving chip U1 through the resistor R12;

the triode Q1 and the triode Q3 form a class-A-B push-pull complementary circuit, the triode Q1 is an NPN type triode, the triode Q3 is a PNP type triode, bases of the two triodes are directly connected, an emitter of the triode Q1 is connected with an emitter of the triode Q3, a collector of the triode Q1 is connected with a power VCC2, a resistor R14 and a resistor R15 are connected in parallel, a connecting point of the resistor R14 and the resistor R15 is connected with an isolation driving chip U1, and the other connecting point of the resistor R14 and the resistor R15 is connected with a collector of the triode Q3.

Optionally, the collector and emitter detection circuit of the IGBT includes a diode D1, a diode D2, a diode D3, a resistor R1, a resistor R2, a resistor R3, and a capacitor C1, one end of the resistor R2 is connected to the isolated driving chip U1 through a resistor R3, and the other end of the resistor R2 is connected to the isolated driving chip U1; a pin 1 of the diode D3 is connected with a connection point of the resistor R2 and the resistor R3 through the capacitor C1, a pin 2 of the diode D3 is connected with the isolation driving chip U1, and a pin 3 of the diode D3 is connected with the HV through the resistor R1, the diode D1 and the diode D2 in sequence.

Optionally, the undervoltage protection circuit includes a resistor R17, a resistor R23, a resistor R28, a regulator tube Z2, and a capacitor C23; the resistor R28, the voltage regulator tube Z2 and the capacitor C23 are connected in parallel, a connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is grounded, and the other connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is sequentially connected with the VCC1 through the resistor R23 and the resistor R17.

Optionally, the isolation driving circuit further includes an inverter U2, an input end of the inverter U2 is connected to the microprocessor, an output end of the inverter U2 is connected to the isolation driving chip U1, when the microprocessor outputs the PWM wave, an 8-pin of the isolation driving chip U1 is at a low level, a diode between an internal 7-pin and an internal 8-pin of the isolation driving chip U1 is turned on, and an 11-pin output of the isolation driving chip U1 is at a high level; when the microprocessing output is at a low level, the pin 8 of the isolation driver chip U1 is at a high level, the diode between the pin 7 and the inside of the pin 8 of the isolation driver chip U1 is turned off, and the pin 11 of the isolation driver chip U1 is at a low level.

Optionally, the auxiliary power supply circuit further includes a loop compensation circuit, the loop compensation circuit includes a resistor R30 and a capacitor C26, the resistor R30 and the capacitor C26 are connected in parallel, a connection point of the resistor R30 and the capacitor C26 is grounded, and another connection point of the resistor R30 and the capacitor C26 is connected to the power management integrated chip U3.

Optionally, the auxiliary power supply circuit further includes a resistor R19, a resistor R20, a resistor R24, a resistor R29, a resistor R26, and a resistor R33, where the resistor R19 and the resistor R20 are current-limiting resistors, one end of the resistor R19 is connected to the power management integrated chip U3, the other end of the resistor R19 is connected to the transformer T1, one end of the resistor R20 is connected to the power management integrated chip U3, and the other end of the resistor R20 is connected to the transformer T1;

the resistor R24 and the resistor R29 are driving resistors, one end of the resistor R24 is connected with the MOS transistor Q4, the other end of the resistor R24 is connected with the power management integrated chip U3, one end of the resistor R29 is connected with the MOS transistor Q5, and the other end of the resistor R29 is connected with the power management integrated chip U3;

the resistor R26 and the resistor R33 are discharge resistors, two ends of the resistor R26 are respectively connected with the source and the gate of the MOS transistor Q4, and two ends of the resistor R33 are respectively connected with the source and the gate of the MOS transistor Q5.

Optionally, the voltage rectifying circuit includes a diode D5, a diode D6, and a diode D7, an anode of the diode D5 is connected to the VEE2, a cathode of the diode D5 is connected to one end of the secondary winding P1, and the other end of the secondary winding P1 is connected to the VCC2 through a diode D6 and a diode D7 in sequence.

Optionally, the auxiliary power supply circuit further includes a capacitor C7 and a capacitor C8, the capacitor C7 and the capacitor C8 are dc blocking capacitors, the capacitor C7 and the capacitor C8 are connected in parallel, a connection point of the capacitor C7 and the capacitor C8 is connected to a negative electrode of the diode D5, and another connection point of the capacitor C7 and the capacitor C8 is connected to a negative electrode of the diode D6.

Optionally, the output filter circuit comprises a capacitor C9-a capacitor C19, wherein the capacitor C9-the capacitor C14 are connected in parallel, a connection point of the capacitor C9-the capacitor C14 is connected to VEE2, and another connection point of the capacitor C9-the capacitor C14 is connected to VE, which is an output filter capacitor of-8V; the capacitor C15-the capacitor C19 are connected in parallel, one connecting point of the capacitor C15-the capacitor C19 is connected with VE, and the other connecting point of the capacitor C15-the capacitor C19 is connected with VCC2, and is a +15V output filter capacitor.

The invention has the following advantages:

(1) the power supply design is simplified, and two paths of voltages of +15V and-8V for driving the IGBT can be realized only by providing a push-pull drive and a three-winding transformer, namely a secondary winding; the power supply adopts an open-loop design, the voltage stabilization can be realized without a complex negative feedback loop, and the reliability of the circuit is high.

(2) The IGBT isolation driving chip is adopted, the safety of the driving board is guaranteed, meanwhile, the power amplification circuit is designed, the driving capability of the circuit is improved, the overall design of the circuit is simplified under the condition of complete functions, the number of devices is small, and the cost is reduced.

Drawings

FIG. 1 is a circuit diagram of an isolation driving circuit in the present embodiment;

fig. 2 is a circuit diagram of the auxiliary power circuit in the present embodiment.

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in fig. 1 and fig. 2, in the present embodiment, an IGBT module driving and protecting circuit includes an isolation driving circuit and an auxiliary power circuit; the isolation driving circuit comprises a microprocessor, an isolation driving chip U1 (U1 type: ACPL-344JT, AVAGO of manufacturer), a driving current amplifying circuit, an IGBT and a detection circuit of a collector electrode and an emitter electrode of the IGBT; the isolation driving chip U1 is respectively and electrically connected with the microprocessor, the driving current amplifying circuit, the IGBT and the detection circuit of the collector and emitter of the IGBT; the IGBT (namely Q2 in figure 1) is also electrically connected with a driving current amplifying circuit; the isolation driving circuit drives the waveform to carry out isolation transmission through an isolation driving chip U1, amplifies driving power through a driving current amplifying circuit, drives a grid electrode of the IGBT, and controls the on-off of a driving signal by utilizing the characteristic that the saturation voltage drop between a collector electrode and an emitter electrode rises along with the increase of the on-state current of the IGBT when the IGBT is on so as to realize the overcurrent protection of the IGBT. The auxiliary power supply circuit comprises a power supply management integrated chip U3, an undervoltage protection circuit, an MOS tube Q4, an MOS tube Q5, a transformer T1, a voltage rectifying circuit and an output filter circuit; the transformer T1 comprises three windings, namely a primary winding N1, a primary winding N2 and a secondary winding P1; the power management integrated chip U3 is respectively connected with the under-voltage protection circuit, the MOS tube Q4 and the MOS tube Q5, the MOS tube Q4 is connected with the primary winding N1, the MOS tube Q5 is connected with the primary winding N2, and the secondary winding P1 is respectively connected with the voltage rectification circuit and the output filter circuit; the auxiliary power supply circuit is used for supplying power to the isolation driving chip U1, and the primary side and the secondary side of the power supply are isolated through a transformer T1.

In this embodiment, because the power is magnetic isolation, the isolation driving chip U1 is optical coupling isolation, thereby electrically isolating the IGBT driving from the preceding weak signal system.

In this embodiment, the pins 1, 2 (empty pins) and 4 (empty pins) of the isolation driver chip U1 are the low-voltage common ground VEE, and are directly grounded. The 3 feet of the isolation driving chip U1 is the primary side power supply end of U1, and is connected with the anode of an external power supply, namely the input voltage side of an auxiliary power supply, and is generally the anode of a small battery. The pin 5 of the isolation driving chip U1 is an under-voltage signal pin, the pin 6 of the isolation driving chip U1 is a failure signal pin, the pin 5 of the isolation driving chip U1 is connected to an IO port of the microprocessor through a pull-up resistor R5, the pin 6 of the isolation driving chip U1 is connected to the IO port of the microprocessor through a pull-up resistor R6, and a connection point of a resistor R5 and a resistor R6 is connected to the anode of the bias power supply. The pin 7 of the isolation driving chip U1 is the anode of the U1 internal diode, the pin 7 of the isolation driving chip U1 is always connected with the positive pole of the bias voltage, and the pin 8 of the isolation driving chip U1 is the cathode of the U1 internal diode.

The pin 9 of the isolation driving chip U1 is a negative voltage power supply end of the isolation output end of the driving chip, and the pin 9 of the isolation driving chip U1 is connected with VEE2 (-8V) in a power supply circuit and used for providing reverse bias voltage for the IGBT and improving the anti-jamming capability of the gate pole of the IGBT. The 10 pins of the isolation driving chip U1 are soft turn-off pins of the isolation driver, the 10 pins of the isolation driving chip U1 are directly connected to the gate of the IGBT (Q2), and the 11 pins of the isolation driving chip U1 are output terminals of the driving chip, that is, 8-pin signals of the isolation driving chip U1 are output from the pins after being isolated. The 12 pin (VCC 2 pin) of the isolation driver chip U1 is the power supply terminal of the isolation driver driving terminal and is connected with VCC2 in the power supply circuit. And when the voltage Vce is greater than the threshold voltage 7V, the 6 pin (Fault) of the isolation driving chip U1 is set to be low level, and the driving waveform signal is closed. The 15 pins of the isolation driving chip U1 are self detection pins of the isolation driving chip U1, and are suspended during use, and the 16 pins of the isolation driving chip U1 are negative voltage input pins and are in short circuit with the 9 pins of the isolation driving chip U1.

As shown in fig. 1, in this embodiment, the collector and emitter detection circuit of the IGBT includes a diode D1, a diode D2, a diode D3, a resistor R1, a resistor R2, a resistor R3, and a capacitor C1, one end of the resistor R2 is connected to the isolated driving chip U1 through a resistor R3, and the other end of the resistor R2 is connected to the isolated driving chip U1; a pin 1 of the diode D3 is connected with a connection point of the resistor R2 and the resistor R3 through the capacitor C1, a pin 2 of the diode D3 is connected with the isolation driving chip U1, and a pin 3 of the diode D3 is connected with the HV through the resistor R1, the diode D1 and the diode D2 in sequence. When the IGBT is turned on, the voltage between the collector and the emitter is increased along with the increase of the voltage flowing through the IGBT, when the voltage between the collector and the emitter is greater than 7V, the overcurrent function of the isolation driving chip U1 is triggered, the voltage of the 6 pin of the isolation driving chip U1 is set to be zero, and the driving signal is turned off.

As shown in fig. 1, in the present embodiment, the driving current amplifying circuit includes a resistor R10, a resistor R12, a resistor R8, a resistor R4, a resistor R7, a resistor R9, a resistor R11, a resistor R14, a resistor R15, a transistor Q1, and a transistor Q3, where the resistor R4, the resistor R7, the resistor R9, and the resistor R11 are connected in parallel. The triode Q1 and the triode Q3 form a class-A-B push-pull complementary circuit, the triode Q1 is an NPN type triode, and the triode Q3 is a PNP type triode. The bases of the two transistors are directly connected, and the emitter of the transistor Q1 is connected with the emitter of the transistor Q3. The collector of the transistor Q1 is connected with a power supply VCC2, and the collector of the transistor Q3 is connected with a negative power supply VEE2 through a resistor R14 and a resistor R15.

As shown in fig. 1, in this embodiment, the isolation driving circuit further includes an inverter U2 (model number is SN74LVC1G 08), an input end of the inverter U2 is connected to the microprocessor, an output end of the inverter U2 is connected to the isolation driving chip U1, when the microprocessor outputs a PWM wave, that is, outputs a high level, after passing through the inverter U2, a pin 8 of the isolation driving chip U1 is at a low level, since an anode of the light emitting diode is at a high level and a cathode of the light emitting diode is at a low level, a diode between the pin 7 and the pin 8 of the isolation driving chip U1 is turned on, a pin 11 of the isolation driving chip U1 outputs a high level, and at this time, the transistor Q1 is turned on, and the transistor Q3 is turned off, so that a gate of the IGBT is at a high level, and the IGBT is turned on quickly. When the microprocessing output is at a low level, after passing through the inverter U2, the pin 8 of the isolation driving chip U1 is at a high level, the light emitting diode is in a cut-off state because the anode and the cathode of the light emitting diode are at high levels, the pin 11 output of the isolation driving chip U1 is at a low level, at this time, the triode Q1 is turned off, the triode Q3 is turned on, so that the gate of the IGBT is at a low level, and the negative voltage VEE2 provides current to rapidly turn off the IGBT. This process realizes the transmission of the PWM wave.

As shown in FIG. 2, in this embodiment, a power management integrated circuit U3 (model LM 25037/-Q1) is used for changing the power supply to generate two output voltages of +15V and-8V. Wherein, the resistor R17, the resistor R23, the resistor R28, the voltage regulator tube D4 and the capacitor C23 form an undervoltage protection circuit, and when the input voltage is lower than a set value, the LM25037/-Q1 stops working. The resistor R28, the voltage regulator tube Z2 (BZX 84-5V 1) and the capacitor C23 are connected in parallel, a connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is grounded, and the other connecting point of the resistor R28, the voltage regulator tube Z2 and the capacitor C23 is sequentially connected with the VCC1 through the resistor R23 and the resistor R17.

As shown in fig. 2, in this embodiment, the resistor R30 and the capacitor C26 form a loop compensation circuit, wherein the resistor R30 and the capacitor C26 are connected in parallel, a connection point of the resistor R30 and the capacitor C26 is grounded, and another connection point of the resistor R30 and the capacitor C26 is connected to the power management integrated chip U3. The power supply is an open loop design so the FB pin is connected to ground, resistor R31 is connected between pin 5 and ground, and resistor R31 is used to set the dead time. Resistor R32 is connected between pin 7 and ground, and resistor R32 is used to set the operating frequency. The auxiliary power supply circuit further comprises a resistor R19, a resistor R20, a resistor R24, a resistor R29, a resistor R26 and a resistor R33, wherein the resistor R19 and the resistor R20 are current-limiting resistors, one end of the resistor R19 is connected with the power management integrated chip U3, the other end of the resistor R19 is connected with the transformer T1, one end of the resistor R20 is connected with the power management integrated chip U3, and the other end of the resistor R20 is connected with the transformer T1. The resistor R24 and the resistor R29 are driving resistors, one end of the resistor R24 is connected with the MOS transistor Q4, the other end of the resistor R24 is connected with the power management integrated chip U3, one end of the resistor R29 is connected with the MOS transistor Q5, and the other end of the resistor R29 is connected with the power management integrated chip U3. The resistor R26 and the resistor R33 are discharge resistors; two ends of the resistor R26 are respectively connected with the source and the gate of the MOS transistor Q4, and two ends of the resistor R33 are respectively connected with the source and the gate of the MOS transistor Q5.

As shown in fig. 2, in the present embodiment, the transformer T1 has three windings, namely, a primary winding N1, a primary winding N2 and a secondary winding P1. The auxiliary power supply circuit further comprises a capacitor C7 and a capacitor C8, the capacitor C7 and the capacitor C8 are blocking capacitors, the capacitor C7 and the capacitor C8 are connected in parallel, a connecting point of the capacitor C7 and the capacitor C8 is connected with the negative electrode of the diode D5, and the other connecting point of the capacitor C7 and the capacitor C8 is connected with the negative electrode of the diode D6. The output filter circuit comprises a capacitor C9-a capacitor C19, wherein the capacitor C9-the capacitor C14 are connected in parallel, a connecting point of the capacitor C9-the capacitor C14 is connected with VEE2, the other connecting point of the capacitor C9-the capacitor C14 is connected with VE, and the output filter circuit is an output filter capacitor of-8V; the capacitor C15-the capacitor C19 are connected in parallel, one connecting point of the capacitor C15-the capacitor C19 is connected with VE, and the other connecting point of the capacitor C15-the capacitor C19 is connected with VCC2, and is a +15V output filter capacitor. In the circuit, the primary side voltage is a constant value, when a MOS tube Q4 is switched on and a MOS tube Q5 is switched off (LM 25037/-Q1 has two-way driving and has a phase difference of 180 degrees), a primary side winding N1 and a secondary side winding P1 form a transformer, a diode D5 is switched on, diodes D6 and D7 are switched off, the voltage on the secondary side winding P1 charges capacitors C9-C14, and the capacitor voltage is the peak voltage (-8V) of the secondary side winding P1 in a steady state. When the MOS transistor Q4 is cut off and the MOS transistor Q5 is switched on, the primary winding N2 and the secondary winding P1 form a transformer, at the moment, the diode D5 is cut off, square wave voltage on the secondary winding P1 passes through the capacitor C7 and the capacitor C8, then is rectified by the diode D7, the capacitors C15-C19 are charged, and the capacitor voltage is the peak voltage (+ 15V) of the capacitor winding P1 in a steady state. The winding turn ratio of the transformer is N1: N2: P1=7:4:4 (in the embodiment, the primary side input voltage is required to be +15V, and if the input voltage changes, the winding of the transformer should be changed correspondingly).

In the embodiment, the power circuit is improved, and the push-pull circuit is matched, so that the driving current of the IGBT can be increased, the switching speed and the switching frequency can be improved, and the reliability of the driving circuit can be improved.