Soft shutdown circuit and method for SiC MOSFET

Abstract

The technical solution of the present application provides a soft-shutdown circuit and method for SiC MOSFET, the soft-shutdown circuit comprising: an output-side logic control module, for receiving and outputting a drive pulse signal of the SiC MOSFET, and also for outputting a control signal synchronized with the drive pulse signal; an output-stage power amplifier circuit, electrically connected to the output-side logic control module, and configured to amplify the drive pulse signal and output it to the SiC MOSFET; a soft-shutdown module, electrically connected to the output-side logic control module and the output-stage power amplifier circuit, and configured to gradually reduce the drive pulse voltage after a short circuit or overcurrent fault occurs in the SiC MOSFET, so as to achieve delayed shutdown of the drive pulse signal. The soft-shutdown circuit and method of the technical solution of the present application can achieve delayed shutdown of the SiC MOSFET when a short circuit or overcurrent fault occurs in the SiC MOSFET.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a soft shutdown circuit and method for a SiC MOSFET. Background Art

[0002] As an important device for the utilization of electric energy, power electronic power converters play an important role in production and life. The core of power electronic power converters is power semiconductor devices, which largely determine the performance of power electronic power converters. At present, most power semiconductor devices are Si semiconductor materials, whose characteristics are close to the theoretical limit, becoming a bottleneck for the further development of power electronic power converters. Compared with Si power devices, SiC power devices have more excellent characteristics: SiC power devices have higher switching speeds, can operate at higher junction temperatures, and can achieve high frequency, high voltage and high current at the same time. These characteristics can significantly improve the performance of semiconductor power converters, obtain higher power conversion efficiency, achieve higher power density, and reduce system costs.

[0003] In power electronic converters, the control signal sent by the microcontroller is a weak signal and cannot directly drive the power semiconductor device. It is necessary to set a drive circuit between the microcontroller and the power semiconductor device. The drive circuit mainly shapes and amplifies the weak current control signal sent by the microcontroller to realize the on-off control of the power semiconductor device; when a fault occurs in the power semiconductor device and the circuit in which it is located, the drive circuit must also transmit the fault information back to the microcontroller. Therefore, the drive circuit is a bridge for the interaction between the weak current control signal and the strong current power circuit. The reliability of the drive circuit directly affects the overall reliability of the power electronic converter.

[0004] SiC MOSFET is mainly used in high-voltage applications, which require high reliability. If a short circuit or overcurrent fault occurs in the circuit, it will cause serious consequences. Therefore, it must be shut down after a short circuit or overcurrent fault is detected. Currently, hard shutdown is commonly used, and the drive circuit will immediately shut down the gate drive voltage of the SiC MOSFET. This practice often has the risk of causing the SiC MOSFET to fail due to overvoltage. Summary of the invention

[0005] The technical problem to be solved by the present application is to provide a soft shutdown circuit and method for SiC MOSFET, which can achieve delayed shutdown of SiC MOSFET when a short circuit or overcurrent fault occurs in SiC MOSFET.

[0006] To solve the above technical problems, the present application provides a soft shutdown circuit for SiC MOSFET, comprising: an output side logic control module, used to receive and output a drive pulse signal of the SiC MOSFET, and also used to output a control signal synchronized with the drive pulse signal; an output stage power amplifier circuit, electrically connected to the output side logic control module, and configured to amplify the drive pulse signal and output it to the SiC MOSFET; a soft shutdown module, electrically connected to the output side logic control module and the output stage power amplifier circuit, and configured to gradually reduce the drive pulse voltage after a short circuit or overcurrent fault occurs in the SiC MOSFET, so as to achieve delayed shutdown of the drive pulse signal.

[0007] In some embodiments of the present application, the soft shutdown module is configured to perform the following operations after a short circuit or overcurrent fault occurs in the SiCMOSFET: in a first stage, the drive pulse voltage is reduced from a first positive voltage to a second positive voltage; in a second stage, the drive pulse voltage is reduced from the second positive voltage to a third positive voltage; and when the drive pulse signal output by the output stage power amplifier circuit is a shutdown signal, the third stage is performed to reduce the drive pulse voltage from the third positive voltage to a negative voltage.

[0008] In some embodiments of the present application, the soft shutdown module includes: a fourth MOS tube, the gate of the fourth MOS tube is electrically connected to the output side logic control module, and the source end is electrically connected to the output side ground; an eighth capacitor, the first end of the eighth capacitor is electrically connected to the output side ground; a thirteenth resistor, the first end of the thirteenth resistor is electrically connected to the drain end of the fourth MOS tube, and the second end is electrically connected to the second end of the eighth capacitor; a fourteenth resistor, the first end of the fourteenth resistor is electrically connected to the DC positive voltage, and the second end is electrically connected to the second end of the eighth capacitor; a third diode, the anode of the third diode is electrically connected to the output stage power amplifier circuit, and the cathode is electrically connected to the second end of the eighth capacitor; a fifth MOS tube, the fifth MO The gate of the S tube is electrically connected to the output side logic control module, and the source terminal is connected to the output side ground; a second voltage stabilizing diode, the anode of the second voltage stabilizing diode is electrically connected to the drain of the fifth MOS tube, and the cathode is electrically connected to the output stage power amplifier circuit; wherein, in the first stage, the output side logic control module sends a turn-on signal to the fifth MOS tube, and the fifth MOS tube is turned on; in the second stage, the output side logic control module sends a turn-on signal to the fourth MOS tube, and the fourth MOS tube is turned on; in the third stage, the output side logic control module sends a turn-off signal to the fourth MOS tube and the fifth MOS tube, and the fourth MOS tube and the fifth MOS tube are turned off.

[0009] In some embodiments of the present application, the short circuit detection module includes: the output stage power amplifier circuit includes a push-pull drive circuit composed of a PMOS tube and an NMOS tube, or includes a push-pull drive circuit composed of an NPN and a PNP transistor.

[0010] In some embodiments of the present application, the output-stage power amplifier circuit includes: an amplifier, the input end of the amplifier is electrically connected to the output-side logic control module, and the amplifier is also electrically connected to a DC positive voltage, a DC negative voltage and an output-side ground; a PMOS tube, the source of the PMOS tube is electrically connected to the DC positive voltage, the gate is electrically connected to the output end of the amplifier, and the drain is electrically connected to the gate of the SiC MOSFET through a third resistor; an NMOS tube, the source of the NMOS tube is electrically connected to the DC negative voltage, the gate is electrically connected to the output end of the amplifier, and the drain is electrically connected to the gate of the SiC MOSFET through a first resistor.

[0011] In some embodiments of the present application, the soft-off module is electrically connected to the drain of the NMOS tube.

[0012] In some embodiments of the present application, the soft shutdown circuit also includes a short-circuit detection module, which is electrically connected to the output-side logic control module and the drain of the SiC MOSFET, and is used to detect whether the circuit where the SiC MOSFET is located is short-circuited, and feed back the short-circuit detection result to the output-side logic control module.

[0013] In some embodiments of the present application, the soft shutdown circuit also includes an input side logic control module, which is used to receive the drive pulse signal of the SiC MOSFET and output it to the output side logic control module, and is also used to receive the short circuit detection result fed back by the output side logic control module.

[0014] In some embodiments of the present application, a first encoding and decoding module is also electrically connected between the input side logic control module and the output side logic control module, and the first encoding and decoding module includes: a driving encoding module, which is electrically connected to the input side logic control module; and a driving decoding module, which is signal-isolated from the driving encoding module and electrically connected to the output side logic control module.

[0015] In some embodiments of the present application, a second encoding and decoding module is also electrically connected between the input side logic control module and the output side logic control module, and the second encoding and decoding module includes: a feedback encoding module, which is electrically connected to the output side logic control module; a feedback decoding module, which is signal-isolated from the feedback encoding module and electrically connected to the input side logic control module.

[0016] In some embodiments of the present application, the soft shutdown circuit further includes: an auxiliary detection module, located between the Kelvin pin and the source pin of the SiCMOSFET and used for detecting the current change rate of the SiCMOSFET.

[0017] In some embodiments of the present application, the auxiliary detection module includes: a second diode, the anode of the second diode is connected to the output side ground; an eleventh resistor, the first end of the eleventh resistor is electrically connected to the cathode of the second diode, and the second end is electrically connected to the source of the SiC MOSFET; a twelfth resistor, the first end of the twelfth resistor is electrically connected to the cathode of the second diode; a seventh capacitor, the first end of the seventh capacitor is electrically connected to the second end of the twelfth resistor, and the second end is electrically connected to the source of the SiC MOSFET; a transformer, the primary side of the transformer is electrically connected to the two ends of the seventh capacitor, one end of the secondary side is electrically connected to the output side logic control module, and the other end is connected to the output side ground.

[0018] The present application also provides a soft shutdown method for SiC MOSFET, which adopts the soft shutdown circuit described in any of the above items. The soft shutdown method includes: determining that a short circuit or overcurrent fault occurs in the SiC MOSFET; the soft shutdown module gradually reduces the drive pulse voltage to achieve delayed shutdown of the drive pulse signal.

[0019] In some embodiments of the present application, the soft shutdown module gradually reduces the drive pulse voltage to achieve delayed shutdown of the drive pulse signal, including: in a first stage, reducing the drive pulse voltage from a first positive voltage to a second positive voltage; in a second stage, reducing the drive pulse voltage from the second positive voltage to a third positive voltage; when the drive pulse signal is a shutdown signal, performing a third stage to reduce the drive pulse voltage from the third positive voltage to a negative voltage.

[0020] The soft-shutdown circuit of the technical solution of the present application is provided with a soft-shutdown module, which can gradually reduce the driving pulse voltage after a short circuit or overcurrent fault occurs, so that the driving pulse signal is delayed to be turned off, effectively reducing the drain-source spike voltage of the SiC MOSFET, avoiding the problem of excessive drain-source spike voltage when the gate driving voltage is turned off by the current hard-shutdown method, thereby damaging the SiC MOSFET, and having a good protection effect on the SiC MOSFET. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals represent similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting, exemplary embodiments, and the drawings are only used for the purpose of illustration and description, and are not intended to limit the scope of this application. Other embodiments may also accomplish the inventive intent in this application. It should be understood that the drawings are not drawn to scale. Among them:

[0022] Figure 1 A schematic structural diagram of a soft turn-off circuit of a SiC MOSFET according to an embodiment of the present application;

[0023] Figure 2 This is a state diagram of the driving pulse voltage change of the soft shutdown module of the embodiment of the present application after a short circuit or overcurrent fault occurs in the SiC MOSFET;

[0024] Figure 3 A schematic structural diagram of another soft-turn-off circuit of SiC MOSFET according to an embodiment of the present application;

[0025] Figure 4 Schematic diagram of the structure of a soft-turn-off circuit of another SiC MOSFET according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0027] It should be understood that the "module" and "circuit" used herein are a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

[0028] The terms used in this application are only used for the purpose of describing specific example embodiments and are not restrictive. For example, unless the context clearly indicates otherwise, the singular forms "one", "an" and "the" used here may also include plural forms. When used in this specification, the terms "include", "comprise" and / or "contain" mean that the associated integers, steps, operations, elements and / or components exist, but do not exclude the existence of one or more other features, integers, steps, operations, elements, components and / or groups or other features, integers, steps, operations, elements, components and / or groups can be added in the system / method. When describing the association of different components in this specification, it can be a direct relationship or an indirect relationship. For example, "A and B are connected" can be A and B directly connected, or A and B can be indirectly connected through other components.

[0029] In view of the following description, the operation and function of the related elements of the structure, the combination of parts and the economy of manufacturing can be significantly improved. With reference to the accompanying drawings, all of which form a part of the disclosure of this specification. However, it should be clearly understood that the drawings are only for the purpose of illustration and description and are not intended to limit the scope of the disclosure of this specification. Flowcharts are used in this application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the previous or following operations are not necessarily performed accurately in order. On the contrary, each step can be processed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or a certain step or several steps can be removed from these processes.

[0030] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content in the present application. It will be apparent to those skilled in the art that various local modifications to the disclosed embodiments are apparent, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments shown, but to the widest scope consistent with the claims.

[0031] At present, when a short circuit or overcurrent fault occurs in SiC MOSFET, the gate drive voltage of SiC MOSFET is turned off by hard shutdown, so as to quickly turn off the fault current. However, hard shutdown will cause an excessively high current change rate (di / dt). Under the influence of stray inductance, the excessively high di / dt will produce an excessively high V Ds The spike voltage may cause the SiC MOSFET to fail due to overvoltage.

[0032] Based on this, the present application provides a soft shutdown circuit and method for SiC MOSFET, which can gradually reduce the driving pulse voltage, thereby realizing delayed shutdown of the driving pulse signal, and can effectively reduce the drain-source peak voltage of SiC MOSFET, thereby protecting SiC MOSFET.

[0033] refer to Figure 1 , an embodiment of the present application provides a soft-shutdown circuit for SiC MOSFET, comprising: an output-side logic control module, an output-stage power amplifier circuit and a soft-shutdown module. The output-side logic control module is used to receive and output the drive pulse signal of the SiCMOSFET, and is also used to output a control signal synchronized with the drive pulse signal. The output-stage power amplifier circuit is electrically connected to the output-side logic control module, and is configured to amplify the drive pulse signal and output it to the SiC MOSFET. The soft-shutdown module is electrically connected to the output-side logic control module and the output-stage power amplifier circuit, and is configured to gradually reduce the drive pulse voltage after a short circuit or overcurrent fault occurs in the SiC MOSFET, so as to achieve delayed shutdown of the drive pulse signal. The drive pulse voltage can be regarded as the gate-source voltage V of the SiCMOSFET. Gs .

[0034] refer to Figure 2 The soft shutdown module is configured to perform the following operations after a short circuit or overcurrent fault occurs in the SiC MOSFET: in the first stage, the drive pulse voltage is reduced from a first positive voltage V1 to a second positive voltage V2, the first positive voltage V1 can be a DC positive voltage VCC, and the second positive voltage V2 is determined according to the specific structure of the specific soft shutdown module; in the second stage, the drive pulse voltage is reduced from the second positive voltage V2 to a third positive voltage V3, and the third positive voltage V3 is determined according to the specific structure of the specific soft shutdown module; when the drive pulse signal output by the output stage power amplifier circuit is a shutdown signal, the third stage is performed to reduce the drive pulse voltage from the third positive voltage V3 to a negative voltage V4, and the negative voltage V4 can be a DC negative voltage VEE.

[0035] refer to Figure 3, the soft shutdown module 400 may include: a fourth MOS tube M4, an eighth capacitor C8, a thirteenth resistor R13, a fourteenth resistor R14, a third diode, a fifth MOS tube M5 and a second voltage stabilizing diode T2. The gate of the fourth MOS tube M4 is electrically connected to the output side logic control module, the source end of the fourth MOS tube M4 is electrically connected to the output side ground GND, the drain end of the fourth MOS tube M4 is electrically connected to the first end of the thirteenth resistor R13, the second end of the thirteenth resistor R13 is electrically connected to the second end of the eighth capacitor C8, and the first end of the eighth capacitor C8 is electrically connected to the output side ground GND. The first end of the fourteenth resistor R14 is electrically connected to the DC positive voltage VCC, and the second end of the fourteenth resistor R14 is electrically connected to the second end of the eighth capacitor C8. The anode of the third diode Z3 is electrically connected to the output stage power amplifier circuit 300, and the cathode of the third diode Z3 is electrically connected to the second end of the eighth capacitor C8. The gate of the fifth MOS tube M5 is electrically connected to the output side logic control module, the source terminal of the fifth MOS tube M5 is connected to the output side ground GND, the drain terminal of the fifth MOS tube M5 is electrically connected to the anode of the second voltage regulator diode T2, and the cathode of the second voltage regulator diode T2 is electrically connected to the output stage power amplifier circuit 300.

[0036] In the first stage of shutdown, the output side logic control module sends a conduction signal to the fifth MOS tube M5, the fifth MOS tube M5 is turned on, and the driving pulse voltage is reduced from the DC positive voltage VCC to the voltage drop V on the second voltage regulator diode. T2 In the second stage, the output side logic control module sends a conduction signal to the fourth MOS tube M4, the fourth MOS tube M4 is turned on, and the driving pulse voltage is V T2 Reduced to the voltage drop V on the thirteenth resistor R13 R13 In the third stage, the output side logic control module sends a shutdown signal to the fourth MOS tube M4 and the fifth MOS tube M5, and the fourth MOS tube M4 and the fifth MOS tube M5 are both turned off, so that the drive pulse signal is turned off, and the drive pulse voltage is V R13 Reduce to DC negative pressure VEE.

[0037] The embodiment of the present application adopts a soft shutdown module to gradually reduce the drive pulse voltage when a short circuit or overcurrent fault occurs in the circuit where the SiC MOSFET is located, so as to achieve delayed shutdown of the drive pulse signal, reduce the drain-source spike voltage of the SiC MOSFET, and avoid the current hard shutdown method that immediately shuts off the gate drive voltage, thereby quickly shutting off the fault current and causing excessive drain-source spike voltage to damage the SiC MOSFET.

[0038] The output stage power amplifier circuit can be a totem pole structure constructed by a power operational amplifier or discrete components, and is used to amplify the driving signal power. As an example, the output stage power amplifier circuit can be a push-pull driving circuit composed of a PMOS tube and an NMOS tube, or a push-pull driving circuit composed of an NPN and a PNP transistor.

[0039] Continue to refer Figure 3 , the output stage power amplifier circuit 300 of the embodiment of the present application is, for example, a push-pull drive circuit composed of a PMOS tube and an NMOS tube. Specifically, the output stage power amplifier circuit 300 may include an amplifier, a PMOS tube P, an NMOS tube N, and a third resistor R3 as an output resistor, and may also include a first resistor R1 as a turn-off resistor. The input end of the amplifier is electrically connected to the output side logic control module, and the amplifier is also electrically connected to a DC positive voltage VCC, a DC negative voltage VEE, and an output side ground GND. The source of the PMOS tube P is electrically connected to the DC positive voltage VCC, the gate of the PMOS tube P is electrically connected to the output end of the amplifier, and the drain of the PMOS tube P is electrically connected to the gate of the SiC MOSFET through the third resistor R3. The source of the NMOS tube N is electrically connected to the DC negative voltage VEE, the gate of the NMOS tube N is electrically connected to the output end of the amplifier, and the drain of the NMOS tube N is electrically connected to the gate of the SiC MOSFET through the first resistor R1.

[0040] It should be noted that the soft-off module 400 of the embodiment of the present application needs to be electrically connected to the negative voltage output terminal of the output stage power amplifier circuit 300. As an example, the soft-off module 400 can be electrically connected to the drain of the NMOS tube N.

[0041] The circuit structure of the output side logic control module only needs to be able to receive the drive pulse signal of the SiCMOSFET and output it to the output stage power amplifier circuit, and can output a control signal synchronized with the drive pulse signal to the soft shutdown module. Therefore, the embodiment of the present application does not limit the specific circuit structure of the output side logic control module, and any circuit structure that can achieve the above functions can be used for the output side logic control module of the embodiment of the present application.

[0042] The soft shutdown circuit may further include a short circuit detection module, which is electrically connected to the output side logic control module and the drain of the SiC MOSFET, and is used to detect whether the circuit where the SiC MOSFET is located is short-circuited, and feed back the short circuit detection result to the output side logic control module.

[0043] The soft shutdown circuit may further include an input side logic control module, which is used to receive the driving pulse signal of the SiC MOSFET and output it to the output side logic control module, and the input side logic control module is also used to receive the short circuit detection result fed back by the output side logic control module. The specific structure of the input side logic control module is not limited, and any circuit structure that can achieve the above functions is acceptable.

[0044] refer to Figure 4 A first encoding and decoding module is also electrically connected between the input side logic control module and the output side logic control module. The first encoding and decoding module includes: a driving encoding module, which is electrically connected to the input side logic control module; a driving decoding module, which is signal-isolated from the driving encoding module and electrically connected to the output side logic control module.

[0045] A second encoding and decoding module may also be electrically connected between the input side logic control module and the output side logic control module. The second encoding and decoding module includes: a feedback encoding module electrically connected to the output side logic control module; a feedback decoding module, which is signal-isolated from the feedback encoding module and electrically connected to the input side logic control module.

[0046] The soft shutdown circuit may also include: an auxiliary detection module, located between the Kelvin pin K and the source pin of the SiC MOSFET, for detecting the current change rate (di / dt) of the SiC MOSFET. Existing drive circuits do not detect the current change rate of the SiC MOSFET, and the SiC MOSFET has a large di / dt in normal operation, short circuit fault, overcurrent fault, etc. Therefore, the embodiment of the present application uses a device in the form of a Kelvin pin package, and the di / dt parameter is measured from the parasitic reactance between the Kelvin pin and the source pin, which can be used as an auxiliary criterion for short circuit or overcurrent faults.

[0047] In some embodiments, the auxiliary detection module 200 includes a second diode Z2, an eleventh resistor R11, a twelfth resistor R12, a seventh capacitor C7 and a transformer, wherein the anode of the second diode Z2 and the Kelvin pin are both connected to the output side ground GND, the cathode of the second diode Z2 is electrically connected to the first end of the eleventh resistor R11, and the second end of the eleventh resistor R11 is electrically connected to the source S of the SiC MOSFET. The first end of the twelfth resistor R12 is electrically connected to the cathode of the second diode Z2, the second end of the twelfth resistor R12 is electrically connected to the first end of the seventh capacitor C7, and the second end of the seventh capacitor C7 is electrically connected to the source S of the SiC MOSFET. The primary side of the transformer is electrically connected to the two ends of the seventh capacitor C7, one end of the secondary side of the transformer is electrically connected to the output side logic control module, and the other end is connected to the output side ground GND.

[0048] An embodiment of the present application also provides a soft shutdown method for SiC MOSFET, using the soft shutdown circuit described in any of the above items, the soft shutdown method comprising: determining that a short circuit or overcurrent fault occurs in the SiC MOSFET; the soft shutdown module gradually reduces the drive pulse voltage to achieve delayed shutdown of the drive pulse signal.

[0049] In some embodiments, the soft shutdown module gradually reduces the drive pulse voltage to achieve delayed shutdown of the drive pulse signal, which may include: in a first stage, reducing the drive pulse voltage from a first positive voltage to a second positive voltage; in a second stage, reducing the drive pulse voltage from the second positive voltage to a third positive voltage; when the drive pulse signal is a shutdown signal, performing a third stage to reduce the drive pulse voltage from the third positive voltage to a negative voltage.

[0050] In summary, after reading the contents of this application, those skilled in the art will appreciate that the aforementioned application contents may be presented only in an exemplary manner and may not be restrictive. Although not explicitly stated herein, those skilled in the art will appreciate that this application is intended to encompass various reasonable changes, improvements and modifications to the embodiments. These changes, improvements and modifications are within the spirit and scope of the exemplary embodiments of this application.

[0051] It should also be understood that although the terms first, second, third, etc. can be used to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teachings of the present application, the first element in some embodiments can be referred to as the second element in other embodiments. The same reference numerals or the same reference signs represent the same elements throughout the specification.

Claims

1. A soft shutdown circuit for SiC MOSFET, characterized in that: include: An output-side logic control module, used to receive and output the driving pulse signal of the SiC MOSFET, and also used to output a control signal synchronized with the driving pulse signal; An output-stage power amplifier circuit is electrically connected to the output-side logic control module and is configured to amplify the drive pulse signal and output it to the SiC MOSFET; A soft shutdown module is electrically connected to the output-side logic control module and the output-stage power amplifier circuit, and is configured to perform the following operations after a short circuit or overcurrent fault occurs in the SiC MOSFET: in a first stage, the driving pulse voltage is reduced from a first positive voltage to a second positive voltage; In the second stage, the driving pulse voltage is reduced from the second positive voltage to a third positive voltage; When the driving pulse signal output by the output stage power amplifier circuit is a shutdown signal, the third stage is performed, so that the driving pulse voltage is reduced from the third positive voltage to the negative voltage, so that the driving pulse voltage is gradually reduced to achieve delayed shutdown of the driving pulse signal, and the soft shutdown module includes: a fourth MOS transistor, wherein a gate of the fourth MOS transistor is electrically connected to the output-side logic control module, and a source end of the fourth MOS transistor is electrically connected to an output-side ground; an eighth capacitor, a first end of the eighth capacitor being electrically connected to the output side ground; a thirteenth resistor, a first end of the thirteenth resistor being electrically connected to the drain end of the fourth MOS tube, and a second end of the thirteenth resistor being electrically connected to the second end of the eighth capacitor; a fourteenth resistor, a first end of the fourteenth resistor being electrically connected to a DC positive voltage, and a second end of the fourteenth resistor being electrically connected to the second end of the eighth capacitor; a third diode, wherein an anode of the third diode is electrically connected to the output-stage power amplifier circuit, and a cathode of the third diode is electrically connected to the second end of the eighth capacitor; a fifth MOS transistor, wherein a gate of the fifth MOS transistor is electrically connected to the output-side logic control module, and a source terminal of the fifth MOS transistor is connected to the output-side ground; a second voltage stabilizing diode, wherein an anode of the second voltage stabilizing diode is electrically connected to the drain of the fifth MOS tube, and a cathode of the second voltage stabilizing diode is electrically connected to the output-stage power amplifier circuit; Among them, in the first stage, the output side logic control module sends a turn-on signal to the fifth MOS tube, and the fifth MOS tube is turned on; in the second stage, the output side logic control module sends a turn-on signal to the fourth MOS tube, and the fourth MOS tube is turned on; in the third stage, the output side logic control module sends a turn-off signal to the fourth MOS tube and the fifth MOS tube, and the fourth MOS tube and the fifth MOS tube are turned off.

2. The soft turn-off circuit of SiC MOSFET according to claim 1, characterized in that: The output stage power amplifier circuit includes a push-pull drive circuit composed of a PMOS tube and an NMOS tube, or includes a push-pull drive circuit composed of an NPN and a PNP transistor.

3. The soft turn-off circuit of SiC MOSFET according to claim 2, characterized in that: The output stage power amplifier circuit comprises: An amplifier, wherein the input end of the amplifier is electrically connected to the output side logic control module, and the amplifier is also electrically connected to a DC positive voltage, a DC negative voltage and an output side ground; A PMOS tube, wherein the source of the PMOS tube is electrically connected to the DC positive voltage, the gate is electrically connected to the output end of the amplifier, and the drain is electrically connected to the gate of the SiC MOSFET through a third resistor; An NMOS tube, wherein the source of the NMOS tube is electrically connected to the DC negative voltage, the gate is electrically connected to the output end of the amplifier, and the drain is electrically connected to the gate of the SiC MOSFET through a first resistor.

4. The soft turn-off circuit of SiC MOSFET according to claim 3, characterized in that: The soft-off module is electrically connected to the drain of the NMOS tube.

5. The soft turn-off circuit of SiC MOSFET according to claim 1, characterized in that: The soft shutdown circuit also includes a short circuit detection module, which is electrically connected to the output side logic control module and the drain of the SiC MOSFET, and is used to detect whether the circuit where the SiC MOSFET is located is short-circuited, and feed back the short circuit detection result to the output side logic control module.

6. The soft turn-off circuit of SiC MOSFET according to claim 5, characterized in that: The soft shutdown circuit also includes an input side logic control module, which is used to receive the driving pulse signal of the SiC MOSFET and output it to the output side logic control module, and is also used to receive the short circuit detection result fed back by the output side logic control module.

7. The soft turn-off circuit of SiC MOSFET according to claim 6, characterized in that: A first encoding and decoding module is also electrically connected between the input side logic control module and the output side logic control module, and the first encoding and decoding module includes: A driving encoding module, electrically connected to the input-side logic control module; The driving decoding module is signal-isolated from the driving encoding module and is electrically connected to the output-side logic control module.

8. The soft turn-off circuit of SiC MOSFET according to claim 6, characterized in that: A second encoding and decoding module is also electrically connected between the input side logic control module and the output side logic control module, and the second encoding and decoding module includes: A feedback encoding module, electrically connected to the output side logic control module; The feedback decoding module is signal-isolated from the feedback encoding module and is electrically connected to the input-side logic control module.

9. The soft turn-off circuit of SiC MOSFET according to claim 1, characterized in that: The soft shutdown circuit further includes: an auxiliary detection module, located between the Kelvin pin and the source pin of the SiC MOSFET, and used to detect the current change rate of the SiC MOSFET.

10. The soft turn-off circuit of SiC MOSFET according to claim 9, characterized in that: The auxiliary detection module comprises: a second diode, wherein an anode of the second diode is connected to an output side ground; an eleventh resistor, a first end of the eleventh resistor being electrically connected to the cathode of the second diode, and a second end of the eleventh resistor being electrically connected to the source of the SiC MOSFET; a twelfth resistor, a first end of the twelfth resistor being electrically connected to a cathode of the second diode; a seventh capacitor, wherein a first end of the seventh capacitor is electrically connected to the second end of the twelfth resistor, and a second end of the seventh capacitor is electrically connected to the source of the SiC MOSFET; A transformer, wherein a primary side of the transformer is electrically connected to both ends of the seventh capacitor, one end of a secondary side is electrically connected to the output side logic control module, and the other end is connected to the output side ground.

11. A soft shutdown method for SiC MOSFET, characterized in that: Using the soft shutdown circuit according to any one of claims 1 to 10, the soft shutdown method comprises: Determine if the SiC MOSFET has a short circuit or overcurrent fault; The soft shutdown module gradually reduces the driving pulse voltage to achieve delayed shutdown of the driving pulse signal.

12. The soft shut-off method of SiC MOSFET according to claim 11, characterized in that: The method in which the soft shutdown module gradually reduces the driving pulse voltage to achieve delayed shutdown of the driving pulse signal includes: In the first stage, the driving pulse voltage is reduced from a first positive voltage to a second positive voltage; In the second stage, the driving pulse voltage is reduced from the second positive voltage to a third positive voltage; When the driving pulse signal is a shut-off signal, the third stage is performed to reduce the driving pulse voltage from the third positive voltage to a negative voltage.

Images