Driving circuit for optimizing switching characteristics of silicon carbide MOSFET

Abstract

The invention discloses a driving circuit for optimizing switching characteristics of a silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and belongs to the technical field of power electronics. After an input voltage VCC is isolated and converted by the isolation power supply unit, the input voltage VCC is input to the driving power supply unit for level conversion, and then a driving positive voltage and a driving negative voltage required by the work of the silicon carbide MOSFET are output. An input voltage VIN signal, a pulse signal VPWM, a driving positive voltage and a driving negative voltage pass through the driving signal unit to output a driving signal of the silicon carbide MOSFET; the outputs of the driving signal unit and the driving power supply unit are jointly input into the crosstalk suppression unit for crosstalk suppression, and a switching signal is output to the silicon carbide MOSFET. According to the invention, stable driving positive voltage and driving negative voltage required for switching on and switching off the silicon carbide MOSFETs can be output without being influenced by fluctuation of power supply voltage output by the isolation power supply unit, meanwhile, the rising or falling speed of driving voltage spikes generated when the silicon carbide MOSFETs work in series can be effectively inhibited, and the response speed is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a driving circuit for optimizing the switching characteristics of a silicon carbide MOSFET. Background Art

[0002] Power semiconductor devices have always been considered as key components of power electronic devices. With the widespread application of power electronics technology in industries such as industry, medical care, transportation, and consumption, power semiconductor devices based on silicon materials have always played an important role. However, over time, power silicon devices have gradually become unsuitable for high voltage, high temperature, high efficiency, and high power density due to the limitations of their own physical properties. Silicon carbide materials have been a hot topic of concern in recent years due to their superior physical properties, especially in the development and application of silicon carbide MOSFETs. Compared with silicon MOSFETs of the same power level, silicon carbide MOSFETs have greatly reduced on-resistance and switching losses, making them suitable for higher switching frequencies.

[0003] The device characteristics of silicon carbide MOSFET are quite different from those of traditional silicon MOSFET. For example, the driving voltage range of silicon carbide MOSFET is smaller than that of silicon MOSFET. Therefore, the driving voltage safety threshold of silicon carbide MOSFET is very small, and a voltage spike in the driving circuit may break through the oxide layer between the gate (G) and the drain (S). At the same time, the switching speed of silicon carbide MOSFET is significantly faster than that of silicon MOSFET. The high-speed switching characteristics bring about the gate crosstalk problem of the upper and lower tubes of silicon carbide MOSFET. Among the existing technologies, some use the silicon MOSFET driving circuit design, but do not do anything to deal with the gate crosstalk, and the application risk is relatively high. Others suppress the gate crosstalk by using a driver chip with a Miller clamp, but because the response speed of the driver chip with a Miller clamp still lags behind the switching speed of the silicon carbide MOSFET, the driver chip with a Miller clamp has little optimization effect on the gate crosstalk, and the silicon carbide MOSFET still has the risk of device failure. Summary of the invention

[0004] In view of the defects of the prior art, the present invention outputs stable driving positive / negative voltage required for turning on and off the silicon carbide MOSFET through a voltage regulator and a level conversion chip, thereby solving the problem of a small safety threshold range of the driving voltage. At the same time, a clamping circuit is designed to solve the crosstalk problem existing between the upper and lower tubes of the silicon carbide MOSFET, effectively suppressing the peak of the driving voltage and reducing the failure risk of the silicon carbide MOSFET.

[0005] In order to achieve the above object, the present invention provides a driving circuit for optimizing the switching characteristics of silicon carbide MOSFET, comprising: an input voltage V CCAfter being isolated and transformed by the isolation power supply unit, the voltage signal of the driving power supply unit is input to the driving power supply unit for level conversion and outputs two levels of driving positive voltage and driving negative voltage required for the operation of the silicon carbide MOSFET;

[0006] Input voltage V IN Signal, pulse signal V PWM The driving positive voltage and the driving negative voltage output by the driving power supply unit are output as driving signals of the silicon carbide MOSFET through the driving signal unit;

[0007] The output of the driving signal unit and the output of the driving power supply unit are input into the crosstalk suppression unit for crosstalk suppression, and a switching signal is output to the silicon carbide MOSFET.

[0008] Furthermore, the driving power supply unit includes a level conversion chip, a resistor R2, a resistor R4, a resistor R5 and a voltage regulator tube D1;

[0009] The input voltage V of the driving power supply unit 总 is the voltage output by the isolated power supply unit, and the output is the driving positive voltage V + and driving negative pressure V - ; Resistor R2 and voltage regulator D1 are connected in series and then in parallel to the input voltage V of the driving power supply unit. 总 The resistor R2 and the voltage regulator D1 are connected to the source S of the silicon carbide MOSFET, and the other end of the voltage regulator D1 is connected to the negative voltage driver V - Resistor R4 and resistor R5 are connected in series and then connected in parallel to the driving positive voltage V + The source S of the silicon carbide MOSFET is connected to the resistor R4, and the end connected to the resistor R5 is connected to the reference end of the level conversion chip; the input end of the level conversion chip is connected to one end of the resistor R2, and the output end is connected to the driving positive voltage V + connected.

[0010] Furthermore, the input voltage V 总 The two ends of the drive power supply unit input voltage V 总 One end of the drive positive voltage V + Between the input end of the level conversion chip and the source S of the silicon carbide MOSFET, between the source S of the silicon carbide MOSFET and the negative driving voltage V - Between the source S of the SiC MOSFET and the positive driving voltage V + Between the reference end of the level conversion chip and the source S of the silicon carbide MOSFET, between the reference end of the level conversion chip and the negative driving voltage V - Between the reference end of the level conversion chip and the output end of the level conversion chip, and the driving positive voltage V + and driving negative pressure V -Any resistor, capacitor or diode can be added in between.

[0011] Further, the crosstalk suppression unit is composed of a driving resistance circuit, an absorption circuit, and a clamping circuit;

[0012] The output signal DRV_G of the driving signal unit is connected to the gate G of the silicon carbide MOSFET through a driving resistor circuit;

[0013] The absorption circuit is connected in parallel between the gate G and the source S of the silicon carbide MOSFET;

[0014] The clamp circuit is composed of a resistor R8, a resistor R9, a diode D3, a diode D4, a capacitor C5 and a capacitor C6; one end of the resistor R8 is connected to the positive driving voltage V output by the driving power supply unit. + The anode of diode D3 is connected to the cathode of diode D4 and connected to the gate G of silicon carbide MOSFET; one end of resistor R9 is connected to the anode of diode D4, and the other end is connected to the negative voltage V - one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is connected to the source S of the silicon carbide MOSFET; one end of the capacitor C6 is connected to the anode of the diode D4, and the other end is connected to the source S of the silicon carbide MOSFET.

[0015] Furthermore, the driving resistance circuit is composed of at least one resistor R7.

[0016] Furthermore, a circuit consisting of a diode D2 and a resistor R6 connected in series can be connected in parallel at both ends of the resistor R7, and the anode of the diode D2 is connected to the resistor R6 or the cathode of the diode D2 is connected to the resistor R6.

[0017] Furthermore, the absorption circuit has at least a capacitor C7 and a resistor R connected in parallel. 11 composition.

[0018] Furthermore, in the absorption circuit, the capacitor C7 branch is also connected in series with a resistor R 11 ;

[0019] Capacitor C7 and resistor R 11 A resistor, a capacitor or a diode can be arbitrarily added to the branch or between the gate G and the source S of the silicon carbide MOSFET.

[0020] Further, the isolated power supply unit includes a power supply module and an isolation circuit connected in sequence;

[0021] The input voltage Vcc supplies power to the power module, and the power module outputs a current for driving the silicon carbide MOSFET switch to the isolation circuit;

[0022] The isolation circuit is implemented by a transformer, and the voltage required to drive the silicon carbide MOSFET is output on the secondary side of the transformer by relying on the turns ratio between the primary and secondary sides of the transformer.

[0023] Further, the driving signal unit includes a driving chip and a push-pull transistor Q1 and a push-pull transistor Q2 connected in sequence;

[0024] Its input terminal includes the input voltage signal V IN , pulse signal V PWM And the positive driving voltage V output by the driving power supply unit + and driving negative pressure V - ; The first output terminal of the driver chip and the driving positive voltage V + connected to the 2nd pin of the push-pull transistor Q1; the second output terminal of the driver chip is connected to the negative voltage V - The third output terminal of the driving chip is connected to the push-pull transistor Q1 and the pin 1 of the push-pull transistor Q2; the pins 3 of the push-pull transistor Q1 and the push-pull transistor Q2 are connected and serve as the output signal DRV_G of the driving signal unit.

[0025] Beneficial effects of the present invention:

[0026] The driving power supply unit of the present invention can output stable driving positive voltage and driving negative voltage required for turning on and off the silicon carbide MOSFET through a voltage regulator tube and a level conversion chip, and is not affected by the power supply voltage fluctuation output by the isolation power supply unit. The crosstalk suppression unit can effectively suppress the rising or falling speed of the driving voltage spike generated when the silicon carbide MOSFET works in series through a clamping circuit and an RCD absorption circuit, and the response speed is faster, so that the silicon carbide MOSFET will not be mis-turned on or the device will not fail due to too low a driving voltage.

[0027] The circuit structure of the present invention is simple, does not require the introduction of additional active devices, has low cost, and has higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the driving circuit structure for optimizing the switching characteristics of silicon carbide MOSFET according to an embodiment of the present invention.

[0029] Figure 2 The figure is a schematic diagram of the circuit structure of a driving power supply unit according to an embodiment of the present invention.

[0030] Figure 3 The figure is a schematic diagram of a specific driving power supply unit circuit structure according to an embodiment of the present invention.

[0031] Figure 4 The figure is a schematic diagram of the circuit structure of a crosstalk suppression unit according to an embodiment of the present invention.

[0032] Figure 5 The figure is a schematic diagram of the circuit structure of a crosstalk suppression unit according to an embodiment of the present invention.

[0033] Figure 6 FIG. 4 is a schematic diagram of another driving resistor circuit (example 1) according to an embodiment of the present invention.

[0034] Figure 7 Schematic diagram of another driving resistor circuit (Example 2) according to an embodiment of the present invention.

[0035] Figure 8 Schematic diagram of an absorption circuit according to an embodiment of the present invention.

[0036] Fig. 9 Schematic diagram of the structure of a driving signal unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] like Figure 1 As shown, an embodiment of the present invention provides a driving circuit for optimizing the switching characteristics of a silicon carbide MOSFET, including: an isolation power supply unit, a driving power supply unit, a driving signal unit and a crosstalk suppression unit.

[0039] Input voltage V CC After the isolation power supply unit is isolated and transformed, it is input to the driving power supply unit for level conversion and outputs the voltage signals of the positive driving voltage and negative driving voltage required for the operation of the silicon carbide MOSFET. IN Signal and pulse signal V PWM The driving signal of the silicon carbide MOSFET is output through the driving signal unit. The output of the driving signal unit and the output of the driving power supply unit are input to the crosstalk suppression unit for crosstalk suppression, and the switching signal is output to the silicon carbide MOSFET through conditioning.

[0040] like Figure 2 As shown, the driving power supply unit includes a level conversion chip, a resistor R2, a resistor R4, a resistor R5 and a voltage regulator D1. The input voltage V 总 is the voltage output by the isolation power supply unit; the resistor R2 and the voltage regulator D1 are connected in series and then in parallel to the input voltage V of the driving power supply unit. 总 The resistor R2 and the voltage regulator D1 are connected to the source S of the silicon carbide MOSFET, and the other end of the voltage regulator D1 is connected to the negative voltage driver V - Resistor R4 and resistor R5 are connected in series and then connected in parallel to the driving positive voltage V +The source S of the silicon carbide MOSFET is connected to the resistor R4, and the end connected to the resistor R5 is connected to the reference end of the level conversion chip; the input end of the level conversion chip is connected to one end of the resistor R2, and the output end is connected to the driving positive voltage V + The input voltage of the driving power supply unit is V 总 The two ends of the drive power supply unit input voltage V 总 One end of the drive positive voltage V + Between the input end of the level conversion chip and the source S of the silicon carbide MOSFET, between the source S of the silicon carbide MOSFET and the negative driving voltage V - Between the source S of the SiC MOSFET and the positive driving voltage V + Between the reference end of the level conversion chip and the source S of the silicon carbide MOSFET, between the reference end of the level conversion chip and the negative driving voltage V - Between the reference end of the level conversion chip and the output end of the level conversion chip, and the driving positive voltage V + and driving negative pressure V - Any resistor, capacitor or diode can be added in between.

[0041] Figure 3 A specific embodiment circuit of a driving power supply unit is given. In which, the resistor R1 is connected in parallel with the input voltage V 总 The resistors R2 and R3 are connected in series and then in parallel to the input voltage V of the driving power supply unit. 总 The other end of R2 is connected to one end of R1, the other end of resistor R3 is connected to the other end of resistor R1, the end connected to resistor R2 and resistor R3 is connected to the source S of silicon carbide MOSFET, and capacitor C1 and capacitor C2 are connected in series and in parallel to the input voltage V of the driving power supply unit. 总 The other end of capacitor C1 is connected to one end of resistor R1, the other end of capacitor C2 is connected to the other end of resistor R1, the end of capacitor C1 and capacitor C2 connected is connected to the source S of silicon carbide MOSFET, and resistor R4 and resistor R5 are connected in series and then in parallel to the driving positive voltage V + The source S of the silicon carbide MOSFET is connected to the resistor R4, and one end of the resistor R5 is connected to the reference end of the level conversion chip, and the other end of the resistor R4 is connected to the positive driving voltage V + The other end of R5 is connected to the source S of the silicon carbide MOSFET, the input end of the level conversion chip is connected to one end of the resistor R1, and the output end is connected to the driving positive voltage V + One end of the voltage regulator D1 is connected to the source S of the silicon carbide MOSFET, and the other end of the voltage regulator D1 is connected to the driving negative voltage V - One end of capacitor C3 is connected to the positive voltage V +The other end of capacitor C3 is connected to the source S of the silicon carbide MOSFET, one end of capacitor C4 is connected to the source S of the silicon carbide MOSFET, and the other end of capacitor C4 is connected to the negative driving voltage V - One end of the input voltage of the driving power supply unit is connected to the driving negative voltage V - The capacitor C8 is connected in parallel between the positive driving voltage V+ and the negative driving voltage V - Both ends.

[0042] Specifically, resistors R1, R2 and R3 are the input voltage V of the driving power supply unit. 总 The dummy load is used to avoid no-load operation. Capacitors C1, C2, C3 and C4 are supporting capacitors. The voltage regulator D1 is used to stabilize the negative voltage V - The voltage value set by the parameter will not be exceeded for a long time. The resistors R4 and R5 are matched resistors. Through the ratio of the resistance values ​​of the resistors R4 and R5, and the reference voltage of the reference end of the level conversion chip, a stable driving positive voltage V is given. + , the voltage at the input of the driving power supply unit is V 总 Within the allowable voltage value range, the driving positive voltage V + and driving negative pressure V - will not be affected by the input voltage V 总 The impact of changes in the voltage of the silicon carbide MOSFET is ensured to always maintain the driving voltage within the safety threshold.

[0043] like Figure 4 As shown, the crosstalk suppression unit is composed of a driving resistance circuit, an absorption circuit and a clamping circuit.

[0044] The clamping circuit is composed of resistor R8, resistor R9, diode D3, diode D4, capacitor C5 and capacitor C6, which is used to suppress the crosstalk between silicon carbide MOSFETs. One end of resistor R8 is connected to the positive driving voltage V output by the driving power supply unit. + The anode of diode D3 is connected to the cathode of diode D4 and connected to the gate G of silicon carbide MOSFET; one end of resistor R9 is connected to the anode of diode D4, and the other end is connected to the negative voltage V - one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is connected to the source S of the silicon carbide MOSFET; one end of the capacitor C6 is connected to the anode of the diode D4, and the other end is connected to the source S of the silicon carbide MOSFET.

[0045] Specifically, when the SiC MOSFET is turned off, the gate G of the SiC MOSFET is connected to the negative driving voltage V -When the voltage VS of the source S of the SiC MOSFET has a transient positive voltage spike, the voltage VS is higher than the negative driving voltage V - When the voltage drops across capacitors C5 and C6, C5 is discharged and C6 is charged. By configuring the parameters of resistor R8, capacitor C5, capacitor C6 and resistor R9, the rising slope of the instantaneous forward voltage spike can be adjusted, thereby suppressing the voltage VS impact amplitude of the source S of the silicon carbide MOSFET, and controlling the forward voltage spike within a safe threshold range without affecting the normal operation of the silicon carbide MOSFET. Similarly, when the silicon carbide MOSFET is turned off, the gate G of the silicon carbide MOSFET is connected to the driving negative voltage V-. When the voltage VS of the source S of the silicon carbide MOSFET has an instantaneous negative voltage spike, making the voltage VS lower than the driving negative voltage V-, a voltage drop will also occur across capacitors C5 and C6, charging C5 and discharging C6. By configuring the parameters of resistor R8, capacitor C5, capacitor C6 and resistor R9, the falling slope of the instantaneous negative voltage spike can be adjusted, thereby suppressing the impact amplitude of the voltage VS of the source S of the silicon carbide MOSFET, and controlling the negative voltage spike within a safe threshold range, which does not affect the normal operation of the silicon carbide MOSFET. Diode D3 is used to clamp the voltage VG of the gate G of the silicon carbide MOSFET at the driving positive voltage V + Below, so that it will not be higher than the driving positive voltage V for a long time + , diode D4 is used to clamp the gate voltage VG of the SiC MOSFET to the negative driving voltage V - Above, so that it will not be lower than the driving negative pressure V for a long time - .

[0046] The output signal DRV_G of the driving signal unit is connected to the gate G of the silicon carbide MOSFET through a driving resistor circuit, and the driving resistor circuit is used to configure the on-resistance and off-resistance of the silicon carbide MOSFET. The driving resistor circuit includes at least one resistor R7. The two ends of the resistor R7 can also be connected in parallel to a circuit consisting of a diode D2 and a resistor R6 in series, where the anode of the diode D2 is connected to the resistor R6 or the cathode of the diode D2 is connected to the resistor R6. Figure 6 , Figure 7 shown.

[0047] like Figure 8 As shown, the absorption circuit at least includes a capacitor C7 and a resistor R connected in parallel. 11 , used to suppress the voltage spike and fluctuation generated when the SiC MOSFET is turned off and stabilize the output voltage. 11 It is the electrostatic discharge resistor between the gate G and source S of the silicon carbide MOSFET, which is used to protect the silicon carbide MOSFET from being damaged by static electricity. A resistor R can also be connected in series on the capacitor C7 branch.10 . Capacitor C7 and resistor R 11 Any resistor, capacitor or diode can be added to the branch or between the gate G and source S of the silicon carbide MOSFET.

[0048] Specifically, one end of capacitor C7 is connected to the gate G of the silicon carbide MOSFET, and the other end is connected to the gate G of the silicon carbide MOSFET through a resistor R 10 Connected to the source S of the SiC MOSFET; resistor R 11 One end is connected to the gate G of the silicon carbide MOSFET, and the other end is connected to the source S of the silicon carbide MOSFET.

[0049] The isolated power supply unit includes a power module and an isolation circuit connected in sequence. The input voltage Vcc supplies power to the power module, and the power module outputs the current that drives the switch action of the silicon carbide MOSFET to the isolation circuit power module. The isolation circuit is usually implemented by a transformer. The current that drives the switch action of the silicon carbide MOSFET is input to the primary side of the transformer. Depending on the turns ratio of the primary and secondary sides of the transformer, the voltage required to drive the silicon carbide MOSFET is output on the secondary side of the transformer.

[0050] like Fig. 9 As shown, the driving signal unit includes a driving chip and a push-pull transistor Q1 and a push-pull transistor Q2, and its input end includes an input voltage signal V IN , pulse signal V PWM And the positive driving voltage V output by the driving power supply unit + and driving negative pressure V - The first output terminal of the driver chip is connected to the positive driving voltage V + connected to the 2nd pin of the push-pull transistor Q1; the second output terminal of the driver chip is connected to the negative voltage V - The third output terminal of the driver chip is connected to the pin 1 of the push-pull transistors Q1 and Q2. The pins 3 of the push-pull transistors Q1 and Q2 are connected and serve as the output signal DRV_G of the drive signal unit. The input voltage signal V IN Used to power the driver chip, the pulse signal V PWM It is used to provide the switching signal required by silicon carbide MOSFET. The driver chip has two functions: isolation and drive signal generation. The isolation function is to electrically isolate the front-stage control circuit of the driver chip from the back-stage power conversion circuit. The drive signal generation function is to convert the pulse signal V PWMAfter processing and outputting the switching signal of the silicon carbide MOSFET, the silicon carbide MOSFET has reliable opening and closing capabilities. The function of the push-pull transistor is to improve the driving ability of the driver chip. Since the current required for instantaneous charging and discharging of the capacitor between the gate and source of the silicon carbide MOSFET is relatively large, the push-pull transistor can realize the rapid charging of the capacitor between the gate and source of the silicon carbide MOSFET, and can also effectively reduce the switching loss of the silicon carbide MOSFET.

[0051] The specific embodiments of the present invention are described above in conjunction with the accompanying drawings. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A driving circuit for optimizing the switching characteristics of a silicon carbide MOSFET, characterized in that: Input voltage V CC After being isolated and transformed by the isolation power supply unit, the voltage signal of the driving power supply unit is input to the driving power supply unit for level conversion and outputs two levels of driving positive voltage and driving negative voltage required for the operation of the silicon carbide MOSFET; Input voltage V IN Signal, pulse signal V PWM The driving positive voltage and the driving negative voltage output by the driving power supply unit are output as driving signals of the silicon carbide MOSFET through the driving signal unit; The output of the driving signal unit and the output of the driving power supply unit are input into the crosstalk suppression unit for crosstalk suppression, and a switching signal is output to the silicon carbide MOSFET.

2. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 1, characterized in that: The driving power supply unit includes a level conversion chip, a resistor R2, a resistor R4, a resistor R5 and a voltage regulator tube D1; The input voltage V of the driving power supply unit 总 is the voltage output by the isolated power supply unit, and the output is the driving positive voltage V + and driving negative pressure V - ; Resistor R2 and voltage regulator D1 are connected in series and then in parallel to the input voltage V of the driving power supply unit. 总 The resistor R2 and the voltage regulator D1 are connected to the source S of the silicon carbide MOSFET, and the other end of the voltage regulator D1 is connected to the negative voltage driver V - Resistor R4 and resistor R5 are connected in series and then connected in parallel to the driving positive voltage V + The source S of the silicon carbide MOSFET is connected to the resistor R4, and the end connected to the resistor R5 is connected to the reference end of the level conversion chip; the input end of the level conversion chip is connected to one end of the resistor R2, and the output end is connected to the driving positive voltage V + connected.

3. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 2, characterized in that: The input voltage V of the driving power supply unit 总 The two ends of the drive power supply unit input voltage V 总 One end of the drive positive voltage V + Between the input end of the level conversion chip and the source S of the silicon carbide MOSFET, between the source S of the silicon carbide MOSFET and the negative driving voltage V - Between the source S of the SiC MOSFET and the positive driving voltage V + Between the reference end of the level conversion chip and the source S of the silicon carbide MOSFET, between the reference end of the level conversion chip and the negative driving voltage V - Between the reference end of the level conversion chip and the output end of the level conversion chip, and the driving positive voltage V + and driving negative pressure V - Any resistor, capacitor or diode can be added in between.

4. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 1, characterized in that: The crosstalk suppression unit is composed of a driving resistance circuit, an absorption circuit, and a clamping circuit; The output signal DRV_G of the driving signal unit is connected to the gate G of the silicon carbide MOSFET through a driving resistor circuit; The absorption circuit is connected in parallel between the gate G and the source S of the silicon carbide MOSFET; The clamp circuit is composed of a resistor R8, a resistor R9, a diode D3, a diode D4, a capacitor C5 and a capacitor C6; one end of the resistor R8 is connected to the positive driving voltage V output by the driving power supply unit. + The anode of diode D3 is connected to the cathode of diode D4 and connected to the gate G of silicon carbide MOSFET; one end of resistor R9 is connected to the anode of diode D4, and the other end is connected to the negative voltage V - one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is connected to the source S of the silicon carbide MOSFET; one end of the capacitor C6 is connected to the anode of the diode D4, and the other end is connected to the source S of the silicon carbide MOSFET.

5. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 4, characterized in that: The driving resistance circuit is composed of at least one resistor R7.

6. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 5, characterized in that: The two ends of the resistor R7 can also be connected in parallel with a circuit consisting of a diode D2 and a resistor R6 connected in series, where the anode of the diode D2 is connected to the resistor R6 or the cathode of the diode D2 is connected to the resistor R6.

7. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 4, characterized in that: The absorption circuit at least has a capacitor C7 and a resistor R connected in parallel with each other. 11 composition.

8. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 7, characterized in that: In the absorption circuit, the capacitor C7 branch is also connected in series with a resistor R 11 ; Capacitor C7 and resistor R 11 A resistor, a capacitor or a diode can be arbitrarily added to the branch or between the gate G and the source S of the silicon carbide MOSFET.

9. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 1, characterized in that: The isolated power supply unit comprises a power supply module and an isolation circuit connected in sequence; The input voltage Vcc supplies power to the power module, and the power module outputs a current for driving the silicon carbide MOSFET switch to the isolation circuit; The isolation circuit is implemented by a transformer, and the voltage required to drive the silicon carbide MOSFET is output on the secondary side of the transformer by relying on the turns ratio between the primary and secondary sides of the transformer.

10. The driving circuit for optimizing the switching characteristics of silicon carbide MOSFET according to claim 1, characterized in that: The driving signal unit includes a driving chip and a push-pull transistor Q1 and a push-pull transistor Q2 connected in sequence; Its input terminal includes the input voltage signal V IN , pulse signal V PWM And the positive driving voltage V output by the driving power supply unit + and driving negative pressure V - ; The first output terminal of the driver chip and the driving positive voltage V + connected to the 2nd pin of the push-pull transistor Q1; the second output terminal of the driver chip is connected to the negative voltage V - The third output terminal of the driving chip is connected to the push-pull transistor Q1 and the pin 1 of the push-pull transistor Q2; the pins 3 of the push-pull transistor Q1 and the push-pull transistor Q2 are connected and serve as the output signal DRV_G of the driving signal unit.

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