A silicon carbide mosfet short circuit and overcurrent combined detection method and system

Abstract

This invention belongs to the field of electronic circuit technology and relates to a combined detection method and system for short-circuit overcurrent of silicon carbide MOSFETs. The method includes: determining whether the on-state voltage of the SiC MOSFET is greater than a first voltage threshold based on the output characteristic curve of the SiC MOSFET; if so, triggering a protection action; setting a parasitic inductance between the Kelvin and source terminals of the SiC MOSFET, detecting the induced voltage generated by the parasitic inductance, inputting the induced voltage into an integrator to obtain an integrated voltage, determining whether the integrated voltage is less than a second voltage threshold; if so, triggering a protection action; performing an OR operation on the desaturation protection detection signal and the Kelvin protection detection signal, and then outputting a total protection signal to uniformly trigger subsequent protection actions. It can detect the on-state voltage V of the SiC MOSFET. DK‑on On-current I DK‑on Joint testing facilitates the integration and implementation of multiple functions.

Description

Technical Field

[0001] This invention relates to a combined detection method and system for short-circuit overcurrent of silicon carbide MOSFETs, belonging to the field of electronic circuit technology, and particularly to the field of short-circuit overcurrent detection technology in electronic circuits. Background Technology

[0002] In power electronics applications, silicon carbide MOSFETs, as wide-bandgap devices, possess superior performance characteristics such as high breakdown electric field, low on-resistance, fast switching speed, and high operating temperature. These advantages enable power electronic converters to operate at high switching frequencies, high efficiency, and high power density. Furthermore, with the gradual reduction in cost and advancements in packaging technology, SiC MOSFETs are becoming a viable alternative to traditional IGBTs in high-power applications.

[0003] The introduction of protection functions is an important guarantee for the safe and reliable operation of SiC MOSFETs. Among the various factors that lead to SiC MOSFET failure, approximately 55% of failures originate from overheating events, with short-circuit and overcurrent faults being the main causes of SiC MOSFET overheating.

[0004] Existing IGBT gate drivers already possess some short-circuit and overcurrent protection capabilities, primarily through desaturation protection, which is relatively simple to implement and easy to integrate. This method detects the magnitude of the on-current by measuring the on-voltage of the switching transistor. However, protection methods for SiC MOSFETs are still immature. Currently, the most widely used approach is to apply the IGBT desaturation protection circuit topology to SiC MOSFETs by adjusting appropriate parameters. However, the IGBT desaturation method may not meet the characteristic requirements of SiC MOSFETs. The setting of its blanking time is contradictory due to the dual limitations of high switching frequency and short withstand time. Besides desaturation protection, existing research has proposed other protection methods, such as resistance sampling, parasitic inductance, and gate charging. Each has its own advantages and disadvantages and has not been widely adopted. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a combined method and system for detecting short-circuit overcurrent in silicon carbide MOSFETs, which can detect the on-state voltage V of SiC MOSFETs. DK-on On-current I DK-on The joint detection of these two important electrical parameters lays an important foundation for the detection of other functions of the SiC MOSFET drive circuit, which is conducive to the integrated realization of multiple functions.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: a combined detection method for short-circuit overcurrent of a silicon carbide MOSFET, comprising: desaturation protection detection: based on the output characteristic curve of the SiC MOSFET, determining whether the on-state voltage of the SiC MOSFET is greater than a first voltage threshold; if so, triggering protection action; Kelvin protection detection: setting a parasitic inductance between the Kelvin terminal and the source terminal of the SiC MOSFET, detecting the induced voltage generated by the parasitic inductance, inputting the induced voltage into an integrator to obtain an integrated voltage, determining whether the integrated voltage is less than a second voltage threshold; if so, triggering protection action; performing an OR operation on the desaturation protection detection signal and the Kelvin protection detection signal, and then outputting a total protection signal to uniformly trigger subsequent protection actions.

[0007] Furthermore, the desaturation protection detection circuit includes: a first resistor, a second resistor, a first capacitor, and a first comparator; the drain and gate of the SiC MOSFET are both connected to the first resistor; the Kelvin terminal of the SiC MOSFET is connected to the second resistor; the second resistor is connected in series with the first resistor and in parallel with the first capacitor; the first capacitor is connected to the first comparator; the detection voltage of the first capacitor is proportional to the conduction voltage, and the detection voltage of the first capacitor is compared with a first voltage threshold in the first comparator. If the detection voltage is greater than the first voltage threshold, the first comparator outputs a high-level signal.

[0008] Furthermore, the charging time of the first capacitor is the blanking time, and its calculation formula is as follows:

[0009]

[0010] Among them, t blk This refers to the blanking time. R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, and C1 is the first capacitor. It is the detection voltage of the first capacitor; V G It is the gate voltage.

[0011] Furthermore, a third resistor is disposed between the gate and the first resistor; and the third resistor is connected in parallel with the first diode; the first capacitor discharges rapidly through the first resistor and the first diode.

[0012] Furthermore, a second diode and a fourth resistor are connected in series between the drain of the SiC MOSFET and the first resistor, and a third diode is connected in parallel with the first and second resistors between the gate and the Kelvin terminal. The desaturation protection detection circuit also includes a fourth diode, which is connected in parallel with the first capacitor. The third diode and the fourth diode are used to limit the maximum and minimum values ​​of the first capacitor, respectively.

[0013] Furthermore, the on-state voltage V DK-on The calculation formula is:

[0014]

[0015] Where R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, and C1 is the first capacitor. VD2 is the detection voltage of the first capacitor; VD2 is the second diode. It is the detection voltage of the second diode.

[0016] Furthermore, the Kelvin protection detection circuit includes: a parasitic inductor, a passive integrator, and a second comparator. The parasitic inductor is located between the source and the Kelvin terminal of the SiC MOSFET. The passive integrator is connected in parallel with the parasitic inductor and is used to input the induced voltage generated by the parasitic inductor into the passive integrator to generate an integrated voltage. The passive integrator is connected to the second comparator, which compares the integrated voltage with a second voltage threshold. If the integrated voltage is less than the second voltage threshold, the second comparator outputs a high-level signal.

[0017] Furthermore, the passive integrator includes a second capacitor and a fifth resistor, which are connected in series. A fifth diode and a sixth diode are connected in series between the Kelvin terminal and the negative power supply terminal, and are used to limit the maximum and minimum values ​​of the induced voltage of the second capacitor, respectively.

[0018] Furthermore, the integral voltage V CK The calculation formula is:

[0019]

[0020] Among them, L S For parasitic inductance, R5 is the fifth resistor, C2 is the second capacitor, and I... KS-on It is the source conduction current.

[0021] Based on the same inventive concept, this invention also discloses a silicon carbide MOSFET short-circuit overcurrent combined detection system, including: a desaturation protection detection circuit, a Kelvin protection detection circuit, and a protection signal combination circuit; the desaturation protection detection circuit includes: a first resistor, a second resistor, a first capacitor, and a first comparator; the drain and gate of the SiC MOSFET are both connected to the first resistor; the Kelvin terminal of the SiC MOSFET is connected to the second resistor; the second resistor is connected in series with the first resistor, and the second resistor is connected in parallel with the first capacitor; the first capacitor is connected to the first comparator; the detection voltage of the first capacitor is proportional to the conduction voltage, and the detection voltage of the first capacitor is compared with a first voltage threshold in the first comparator. If the detection voltage is greater than the first voltage threshold, the first comparator outputs a high-level signal; the Kelvin protection detection circuit includes: a parasitic inductor, a passive integrator, and a second comparator, the parasitic inductor being disposed on the SiC MOSFET. Between the source and Kelvin terminals of the MOSFET, a passive integrator is connected in parallel with a parasitic inductor. The induced voltage generated by the parasitic inductor is input to the passive integrator to generate an integrated voltage. The passive integrator is connected to a second comparator, which compares the integrated voltage with a second voltage threshold. If the integrated voltage is less than the second voltage threshold, the second comparator outputs a high-level signal. The protection signal combination circuit receives signals from the desaturation protection detection circuit and the Kelvin protection detection circuit, respectively. The signals from the two circuits are combined and processed through a first-level buffer input or logic gate to output a total protection signal, which triggers subsequent protection actions in a unified manner.

[0022] The present invention has the following advantages due to the adoption of the above technical solutions:

[0023] 1. The solution in this invention solves the problem that the blanking time in the desaturation protection method restricts the improvement of response speed, and the problems in the Kelvin protection method that the detection effect is reduced when the current increases slowly and the current change rate is low, and the inability to detect static DC state. It improves the response speed for short circuit or overcurrent faults and can more reliably protect the operation of SiC MOSFET devices.

[0024] 2. The solution in this invention achieves the turn-on voltage V of the SiC MOSFET. DK-on On-current I DK-on The joint detection of these two important electrical parameters lays an important foundation for the detection of other functions of SiC MOSFET drive circuits, such as overheat protection, condition monitoring, and aging assessment, and is conducive to the integrated realization of multiple functions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a SiC MOSFET device in one embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a desaturation protection detection circuit in one embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of a Kelvin protection detection circuit in one embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of a silicon carbide MOSFET short-circuit overcurrent combined detection system in one embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of a protection signal combination circuit in one embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] To address the problems existing in the desaturation method for detecting short-circuit and overcurrent faults in SiC MOSFETs, this invention provides a combined detection method and system for silicon carbide MOSFET short-circuit and overcurrent faults. It consists of three parts: desaturation protection, Kelvin protection, and signal combination. These components monitor the drain on-state voltage and source on-state current of the SiC MOSFET device, respectively, and determine whether a short-circuit or overcurrent fault has occurred by comparing these values ​​with threshold values. A protection signal is then output to trigger the protection action. This invention achieves a functional combination of short-circuit and overcurrent protection methods for SiC MOSFETs, overcoming the inherent defects of existing protection methods, improving the response speed to short-circuit or overcurrent faults, and providing more reliable protection for SiC MOSFET device operation. Furthermore, it enables the joint detection of two important electrical parameters of the SiC MOSFET: on-state voltage and on-state current. This lays an important foundation for the detection of other functions in the SiC MOSFET drive circuit, such as overheat protection, condition monitoring, and aging assessment, and facilitates the integrated implementation of multiple functions on the SiC MOSFET drive side. The following detailed description, in conjunction with the accompanying drawings and embodiments, illustrates the invention.

[0032] Example 1

[0033] Figure 1 This is a schematic diagram of the SiC MOSFET device in this embodiment, as shown below. Figure 1As shown, a SiC MOSFET device includes a drain (D), a gate (G), a source (S), and a Kelvin terminal (K). The Kelvin terminal is a major limitation of SiC MOSFET types; only some SiC MOSFET devices have a Kelvin terminal. Without a Kelvin terminal, the Kelvin protection detection circuit cannot be effectively used, meaning the parasitic source inductance of the SiC MOSFET device itself cannot be utilized. The driver board in this embodiment needs to be able to connect to the drain (D), gate (G), source (S), and Kelvin terminal (K) of the SiC MOSFET device. The driver board can detect a single SiC MOSFET device or an integrated module of multiple SiC MOSFET devices.

[0034] based on Figure 1 This embodiment discloses a combined short-circuit overcurrent detection method for silicon carbide MOSFET devices, including:

[0035] S1 Desaturation Protection Detection: Based on the output characteristic curve of the SiC MOSFET, determine the on-state voltage V of the SiC MOSFET. DK-on Is it greater than the first voltage threshold V? th1 If so, a protection action will be triggered.

[0036] The circuit for desaturation protection detection in this embodiment is as follows: Figure 2 As shown, it includes: a first resistor R1, a second resistor R2, a first capacitor C1, and a first comparator;

[0037] The drain and gate of the SiC MOSFET are both connected to the first resistor R1; the Kelvin terminal of the SiC MOSFET is connected to the second resistor R2; the second resistor R2 is connected in series with the first resistor R1, and in parallel with the first capacitor C1; the first capacitor C1 is connected to the first comparator; the detection voltage of the first capacitor C1 is equal to the conduction voltage V. DK-on Proportional to the first voltage threshold V, the detected voltage of the first capacitor C1 is compared with the first voltage threshold V in the first comparator. th1 If the detected voltage is greater than the first voltage threshold V, then... th1The first comparator outputs a high-level signal. A third resistor R3 is positioned between the gate and the first resistor R1; and the third resistor R3 is connected in parallel with the first diode VD1. When the SiC MOSFET is turned off, the first capacitor C1 discharges rapidly through the first resistor R1 and the first diode VD1. A second diode VD2 and a fourth resistor R4 are connected in series between the drain of the SiC MOSFET and the first resistor R1. The second diode VD2 is used to block the high bus voltage on the power side of the SiC MOSFET. A third diode VD3 is connected in parallel with the first resistor R1 and the second resistor R2 between the gate and the Kelvin terminal. The desaturation protection detection circuit also includes a fourth diode VD4, which is connected in parallel with the first capacitor C1. The third diode VD3 and the fourth diode VD4 are used to limit the maximum and minimum values ​​of the first capacitor C1, respectively. Figure 2 In the circuit, the D, G, and GND terminals are connected to the drain, gate, and Kelvin terminals of the SiC MOSFET, respectively; the DESAT terminal outputs a protection signal to trigger the protection action.

[0038] When the SiC MOSFET is turned on, capacitor C1 is supplied by the gate voltage V. G After charging through resistors R1 and R3, its detection voltage rises until it reaches the turn-on voltage V of the SiC MOSFET. DK-on Clamping. After charging is complete and the system enters a steady state, the following formula applies:

[0039]

[0040] Since the third resistor R3 in the circuit is much larger than the fourth resistor R4, the voltage drop across the third resistor R3 is also much greater than the voltage drop across the fourth resistor R4. This can be ignored, thus simplifying the above formula to:

[0041]

[0042] This establishes the on-state voltage V. DK-on With detection voltage The connection is established. By adjusting the resistance values ​​of R1, R2, and R3, V can be flexibly changed. DK-on and The relationship between them is thus adapted to different protection needs.

[0043] Based on the output characteristic curve of SiC MOSFET, the on-state voltage V of SiC MOSFET is... DK-on With its conduction current I DK-on It increases with the increase, and at the same time It also increases accordingly. When Exceeding the set threshold V th1 At that time, the first comparator outputs a high-level protection signal.

[0044] The charging time of the first capacitor C1 is the blanking time, and its calculation formula is as follows:

[0045]

[0046] The existence of blanking time can temporarily shield the protection function and avoid false triggering during normal conduction, but it also restricts the response speed of the desaturation protection detection circuit when a short circuit fault occurs at the moment of conduction.

[0047] S2 Kelvin Protection Detection: A parasitic inductance L is set between the Kelvin terminal and the source of the SiC MOSFET. S Detecting parasitic inductance L S The generated induced voltage V L , induced voltage V L The input is fed into the integrator to obtain the integrated voltage V. CK Determine the integral voltage V CK Is it less than the second voltage threshold V? th2 If so, a protection action will be triggered.

[0048] Figure 3 This is a schematic diagram of the Kelvin protection detection circuit in this embodiment. Figure 3 The S and GND terminals are connected to the source and Kelvin terminals of the SiC MOSFET, respectively; the VEE terminal is connected to the negative power supply output on the secondary side of the driver board; the KEL terminal outputs a protection signal to trigger the protection action. Figure 3 As shown, the Kelvin protection detection circuit includes: parasitic inductance L S Passive integrator and second comparator, parasitic inductance L S The passive integrator is positioned between the source and Kelvin terminals of the SiC MOSFET and the parasitic inductor L. S Parallel connection, used to control parasitic inductance L S The generated induced voltage V L The input is a passive integrator, which generates an integrating voltage V. CK The passive integrator is connected to the second comparator, which compares the integrated voltage with the second voltage threshold V. th2 If the integral voltage is less than the second voltage threshold V, then... th2 If the voltage is high, the second comparator outputs a high-level signal. The passive integrator includes a second capacitor C2 and a fifth resistor R5, connected in series. A fifth diode VD5 and a sixth diode VD6 are connected in series between the Kelvin terminal and the negative power supply terminal. These diodes limit the maximum and minimum values ​​of the induced voltage of the second capacitor C2, respectively, keeping the detected voltage within a safe range.

[0049] Parasitic inductance LS Induced voltage V L The integral reflects the magnitude I of the conduction current flowing through the source. KS-on More precisely, it refers to the magnitude of the change in conduction current. Integral voltage V CK The calculation formula is:

[0050]

[0051] In an ideal situation, 1 / s can be ignored, and the above equation can be simplified to:

[0052]

[0053] That is, in the high-frequency band, the integrated voltage V CK With source conduction current I KS-on A negative correlation exists. KS-on Increasing makes V CK Decrease, when V CK Less than the set threshold V th2 At this time, the second comparator outputs a high-level protection signal.

[0054] S3 performs an OR operation on the desaturation protection detection signal and the Kelvin protection detection signal, and then outputs the total protection signal to trigger subsequent protection actions in a unified manner.

[0055] Example 2

[0056] Based on the same inventive concept, this embodiment discloses a silicon carbide MOSFET short-circuit overcurrent combined detection system, such as... Figure 4 As shown, it includes: a desaturation protection detection circuit, a Kelvin protection detection circuit, and a protection signal combination circuit; these three circuits are all located on the gate driver board of the SiC MOSFET, and have a high degree of integration; in addition, the components involved in the circuit are all basic circuit elements and simple logic operation elements, which are easy to implement.

[0057] In this embodiment, the saturation protection detection circuit includes: a first resistor R1, a second resistor R2, a first capacitor C1, and a first comparator;

[0058] The drain and gate of the SiC MOSFET are both connected to the first resistor R1; the Kelvin terminal of the SiC MOSFET is connected to the second resistor R2; the second resistor R2 is connected in series with the first resistor R1, and in parallel with the first capacitor C1; the first capacitor C1 is connected to the first comparator; the detection voltage of the first capacitor C1 is equal to the conduction voltage V. DK-on Proportional to the first voltage threshold V, the detected voltage of the first capacitor C1 is compared with the first voltage threshold V in the first comparator. th1 If the detected voltage is greater than the first voltage threshold V, then... th1The first comparator outputs a high-level signal. A third resistor R3 is positioned between the gate and the first resistor R1; and the third resistor R3 is connected in parallel with the first diode VD1. When the SiC MOSFET is turned off, the first capacitor C1 discharges rapidly through the first resistor R1 and the first diode VD1. A second diode VD2 and a fourth resistor R4 are connected in series between the drain of the SiC MOSFET and the first resistor R1. The second diode VD2 is used to block the high bus voltage on the power side of the SiC MOSFET. A third diode VD3 is connected in parallel with the first resistor R1 and the second resistor R2 between the gate and the Kelvin terminal. The desaturation protection detection circuit also includes a fourth diode VD4, which is connected in parallel with the first capacitor C1. The third diode VD3 and the fourth diode VD4 are used to limit the maximum and minimum values ​​of the first capacitor C1, respectively. Figure 2 In the circuit, the D, G, and GND terminals are connected to the drain, gate, and Kelvin terminals of the SiC MOSFET, respectively; the DESAT terminal outputs a protection signal to trigger the protection action.

[0059] Kelvin protection detection circuit includes: parasitic inductance L S Passive integrator and second comparator, parasitic inductance L S The passive integrator is positioned between the source and Kelvin terminals of the SiC MOSFET and the parasitic inductor L. S Parallel connection, used to control parasitic inductance L S The generated induced voltage V L The input is a passive integrator, which generates an integrating voltage V. CK The passive integrator is connected to the second comparator, which compares the integrated voltage with the second voltage threshold V. th2 If the integral voltage is less than the second voltage threshold V, then... th2 If the voltage is high, the second comparator outputs a high-level signal. The passive integrator includes a second capacitor C2 and a fifth resistor R5, connected in series. A fifth diode VD5 and a sixth diode VD6 are connected in series between the Kelvin terminal and the negative power supply terminal. These diodes limit the maximum and minimum values ​​of the induced voltage of the second capacitor VD5, respectively, keeping the detected voltage within a safe range.

[0060] Figure 5This is a schematic diagram of the protection signal combination circuit in this embodiment. The protection signal combination circuit receives signals from the desaturation protection detection circuit and the Kelvin protection detection circuit, respectively. The DESAT and KEL terminals receive the output signals from the desaturation protection detection circuit and the Kelvin protection detection circuit, respectively. The signals from the two circuits are combined and processed through a first-stage buffer or logic gate to output a total protection signal OC, which triggers subsequent protection actions in a unified manner. The first-stage buffer is used to suppress signal interference.

[0061] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0062] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0063] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0064] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method of detecting short-circuit and over-current combination in a silicon carbide MOSFET, characterized by, The application relates to a silicon carbide MOSFET protection device and a protection method thereof. The application comprises: Desaturation protection detection: according to the output characteristic curve of the silicon carbide MOSFET, it is judged whether the conduction voltage of the silicon carbide MOSFET is greater than a first voltage threshold value, if yes, a protection action is triggered, and a desaturation protection detection signal is generated; Kelvin protection detection: a parasitic inductor is arranged between the Kelvin pole and the source pole of the silicon carbide MOSFET, an induced voltage generated by the parasitic inductor is detected, the induced voltage is input into an integrator, an integrated voltage is obtained, it is judged whether the integrated voltage is less than a second voltage threshold value, if yes, a protection action is triggered, and a Kelvin protection detection signal is generated; The desaturation protection detection signal and the Kelvin protection detection signal are subjected to OR operation, and then a total protection signal is output, and a subsequent protection action is triggered uniformly; The Kelvin protection detection circuit for the Kelvin protection detection comprises a parasitic inductor, a passive integrator and a second comparator, the parasitic inductor is arranged between the source pole and the Kelvin pole of the silicon carbide MOSFET, the passive integrator is connected in parallel with the parasitic inductor, the induced voltage generated by the parasitic inductor is input into the passive integrator, so as to generate the integrated voltage, the passive integrator is connected with the second comparator, the second comparator compares the integrated voltage with the second voltage threshold value, if the integrated voltage is less than the second voltage threshold value, the second comparator outputs a high-level signal; 2. The method of claim 1, wherein the short-circuit overcurrent combined detection method of the silicon carbide MOSFET is characterized by, The passive integrator comprises a second capacitor and a fifth resistor, the second capacitor is connected in series with the fifth resistor, a fifth diode and a sixth diode are arranged between the Kelvin pole and the power supply negative pole, the fifth diode and the sixth diode are connected in series, and are respectively used for limiting the maximum value and the minimum value of the induced voltage of the second capacitor. The circuit of the desaturation protection detection comprises a first resistor, a second resistor, a first capacitor and a first comparator; The drain pole and the gate pole of the silicon carbide MOSFET are connected with the first resistor; The Kelvin pole of the silicon carbide MOSFET is connected with the second resistor; The second resistor is connected in series with the first resistor, and the second resistor is connected in parallel with the first capacitor; The first capacitor is connected with the first comparator; 3. The method of claim 2, wherein the short-circuit overcurrent combined detection method of the silicon carbide MOSFET is characterized by, The detection voltage of the first capacitor is proportional to the conduction voltage, the detection voltage of the first capacitor is compared with the first voltage threshold value in the first comparator, if the detection voltage is greater than the first voltage threshold value, the first comparator outputs a high-level signal. wherein, is a blanking time, is a first resistance, is a second resistance, is a third resistance, is a first capacitance, is a detection voltage of the first capacitance; is a gate voltage.

4. The method of claim 3, wherein the short-circuit overcurrent combined detection method of the silicon carbide MOSFET is characterized by, The charging time of the first capacitor is the blanking time, and the calculation formula is:

5. The method of claim 2, wherein the short-circuit overcurrent combined detection method of the silicon carbide MOSFET is characterized by, The third resistor is arranged between the gate pole and the first resistor, and the third resistor is connected in parallel with a first diode; the first capacitor is subjected to rapid discharge through the first resistor and the first diode.

6. The method of claim 1, wherein the short-circuit overcurrent combined detection method of the silicon carbide MOSFET is characterized by, The on voltage The calculation formula is: wherein, is a first resistance, is a second resistance, is a third resistance, is a first capacitance, is a detection voltage of the first capacitance; is a second diode, is a detection voltage of the second diode.

7. A silicon carbide MOSFET short-circuit overcurrent combined detection system, characterized by, The drain pole of the silicon carbide MOSFET is connected with the first resistor in series, a second diode and a fourth resistor are arranged between the drain pole and the first resistor, a third diode is arranged in parallel with the first resistor and the second resistor between the gate pole and the Kelvin pole, the circuit of the desaturation protection detection further comprises a fourth diode, the fourth diode is connected in parallel with the first capacitor, and the third diode and the fourth diode are respectively used for limiting the maximum value and the minimum value of the first capacitor. The application relates to a silicon carbide MOSFET protection device and a protection method thereof. The desaturation protection detection circuit, the Kelvin protection detection circuit and the protection signal combination circuit; The desaturation protection detection circuit comprises a first resistor, a second resistor, a first capacitor and a first comparator; The drain and the gate of the silicon carbide MOSFET are connected with the first resistor; The Kelvin electrode of the silicon carbide MOSFET is connected with the second resistor; The second resistor is connected with the first resistor in series, and the second resistor is connected with the first capacitor in parallel; The first capacitor is connected with the first comparator; The detection voltage of the first capacitor is proportional to the on-voltage, the detection voltage of the first capacitor is compared with a first voltage threshold in the first comparator, if the detection voltage is greater than the first voltage threshold, the first comparator outputs a high level signal; The Kelvin protection detection circuit comprises a parasitic inductor, a passive integrator and a second comparator, the parasitic inductor is arranged between the source and the Kelvin electrode of the silicon carbide MOSFET, the passive integrator is connected with the parasitic inductor in parallel, the passive integrator is used for inputting the induced voltage generated by the parasitic inductor into the passive integrator to generate an integrated voltage, the passive integrator is connected with the second comparator, the second comparator compares the integrated voltage with a second voltage threshold, if the integrated voltage is less than the second voltage threshold, the second comparator outputs a high level signal; The protection signal combination circuit receives the signals of the desaturation protection detection circuit and the Kelvin protection detection circuit respectively, makes the signals of the two circuits input through a one-stage buffer or a logic gate respectively, carries out combination processing, outputs a total protection signal, and uniformly triggers a subsequent protection action.

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