SiC MOSFET short circuit turn-off protection circuit based on short circuit type judgment

Abstract

The invention discloses a SiC MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) short-circuit turn-off protection circuit based on short-circuit type judgment, which is used for carrying out short-circuit detection and judging the short-circuit type by detecting the charge quantity of a SiC MOSFET driving resistor and the change of gate-source voltage, and adopts different short-circuit turn-off methods aiming at different short-circuit faults. According to the invention, the types of short-circuit faults can be distinguished, and different turn-off methods are adopted according to different fault types. Compared with a traditional short-circuit soft turn-off method, the short-circuit soft turn-off method has the advantages that the relation between turn-off overvoltage and turn-off loss can be better balanced, and the probability of degradation and even damage after the SiC MOSFET is short-circuited is reduced.

Description

Technical Field

[0001] The present invention relates to a short-circuit shutdown protection circuit, and in particular to a short-circuit type judgment and short-circuit shutdown protection circuit for a SiC MOSFET. Background Art

[0002] Wide-bandgap SiC MOSFETs (Silicon Carbide MOSFETs) offer promising application prospects due to their low switching losses, high switching frequency, high voltage resistance, and excellent temperature characteristics. However, short-circuit failure is a major cause of SiC MOSFET failure, severely hindering their application. When a short-circuit fault is detected, the detection circuit should quickly shut down the SiC MOSFET. However, excessively fast shutdown speeds result in high turn-off overvoltages, which can damage the SiC MOSFET. Therefore, soft shutdown techniques are needed to slow the decline in short-circuit current.

[0003] Based on the switching state of the SiC MOSFET when it is in the short-circuit loop, short-circuit types can be divided into hard switching fault (HSF) and load short-circuit fault (FUL). If the SiC MOSFET is in the off state when in the short-circuit loop, it will short-circuit once it is turned on, which is called HSF. If the SiC MOSFET is in the on state when it is in the short-circuit loop, the SiC MOSFET has already been shorted, which is called FUL.

[0004] Conventional short-circuit soft-turn-off technology suppresses turn-off overvoltage by reducing the turn-off speed of the SiC MOSFET, regardless of whether HSF or FUL occurs. However, this increases the turn-off loss of the SiC MOSFET and causes SiC MOSFET degradation. Summary of the Invention

[0005] Purpose of the invention: In view of the above-mentioned prior art, a method for determining the type of short circuit and adopting different short circuit shutdown methods for different short circuit fault types is proposed.

[0006] Technical solution: A short-circuit shutdown protection circuit for SiC MOSFET based on short-circuit type judgment, including a tested SiC MOSFET M1, a current sampling circuit, an inverting integration circuit, a short-circuit detection logic circuit, a short-circuit type judgment logic circuit, and a soft shutdown circuit;

[0007] The current sampling circuit uses a differential amplifier circuit to sample the driving resistance R of the SiC MOSFET M1. g1 The voltage across the two terminals is used to indirectly measure the driving resistance R g1 The current on

[0008] The inverting integration circuit is connected to the driving resistor R g1 The current flowing through the driving resistor R is integrated and measured. g1 The amount of charge on

[0009] The short-circuit detection logic circuit uses two comparators to compare the gate-source voltage of SiC MOSFET M1 with the reference voltage V ref After comparison, the comparison signal U1 is output to drive the resistor R g1 The charge on the reference charge Q ref After comparison, the comparison signal U2 is output. After U1 and U2 are multiplied by the AND gate, the short-circuit signal U3 is output. If U3 is high, it indicates a short-circuit fault.

[0010] The short-circuit type judgment logic circuit uses a comparator to compare the gate-source voltage of SiC MOSFET M1 with the reference voltage V ref After comparison, a comparison signal U4 is output. U4 and the short-circuit signal U3 are multiplied by an AND gate to output a short-circuit type judgment signal U5. If U5 is low, it indicates a hard switch short-circuit fault. If U5 is high, it indicates a load short-circuit fault.

[0011] The soft-off circuit includes a soft-off resistor R soft When the MOSFET M2 is working normally, the controller output drive signal PWM2 is kept high, and the soft turn-off resistor R soft When the short-circuit detection logic circuit outputs a short-circuit signal and the short-circuit type judgment logic circuit detects that a load short-circuit fault occurs, the controller outputs a drive signal PWM2 to a low level to turn off the MOSFET M2, thereby soft-turning off the resistor R soft It is connected in series to the driving loop of the SiC MOSFET M1 to slow down the turn-off speed of the SiC MOSFET M1. When the short-circuit detection logic circuit outputs a short-circuit signal and the short-circuit type judgment logic circuit detects that a hard switch short-circuit fault has occurred, the controller outputs the drive signal PWM2 to maintain a high level and outputs PWM1 to a low level to directly turn off the SiC MOSFET M1.

[0012] Furthermore, a two-dimensional coordinate system is established with the charge as the horizontal coordinate and the voltage as the vertical coordinate. The reference voltage V ref With the reference charge Q ref Set the following range in the two-dimensional coordinate system: from point (Q1, V miller1 )、(Q4,V miller2 )、(Q5,V D )、(Q3,V D), where Q1 is the gate charge required to reach the Miller platform, Q2 is the gate charge when FUL occurs, Q3 is the gate charge when HSF occurs, Q4 is the gate charge at the end of the Miller platform, and Q5 is the gate charge required for normal turn-on. D For driving positive voltage, V miller1 is the Miller voltage at the beginning of the Miller voltage platform, V miller2 is the Miller voltage at the end of the Miller voltage platform; the reference voltage V ref 'Satisfy V ref <V ref ' <V D .

[0013] Furthermore, the current sampling circuit includes an operational amplifier A1 and resistors R1 to R4; the driving resistor R g1 One end is connected to the gate of SiC MOSFET M1, and the other end is connected to the soft turn-off resistor R soft One end of the soft turn-off resistor R soft The other end is connected to the driving signal PWM1 output by the controller; the positive input terminal of the operational amplifier A1 is connected to one end of the resistors R1 and R3, and the other end of the resistor R1 is connected to the driving resistor R g1 The other end of the resistor R3 is grounded; the negative input terminal of the operational amplifier A1 is connected to one end of the resistors R2 and R4, the other end of the resistor R2 is connected to the gate of the SiC MOSFET M1, and the other end of the resistor R4 is connected to the output terminal of the operational amplifier A1 and one end of the resistor R5.

[0014] Furthermore, the inverting integration circuit includes an operational amplifier A2, resistors R5 to R7, and a capacitor C1; the positive input terminal of the operational amplifier A2 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the reference ground; the negative input terminal of the operational amplifier A2 is connected to the other end of the resistor R5, and the resistor R7 and the capacitor C1 are respectively connected in parallel between the output terminal and the negative input terminal of the operational amplifier A2, and the output terminal of the operational amplifier A2.

[0015] Furthermore, the short-circuit detection logic circuit includes comparator A3, comparator A4, and AND gate AND1; the positive input terminal of comparator A3 is connected to the gate of SiC MOSFET M1, and the negative input terminal of comparator A3 is connected to the reference voltage V ref The comparator A3 outputs the comparison signal U1, which is connected to one input terminal of the AND gate AND1; the positive input terminal of the comparator A4 is connected to the output terminal of the operational amplifier A2, and the negative input terminal of the comparator A4 is connected to the reference charge -Q ref The comparator A4 outputs the comparison signal U2, which is connected to the other input terminal of the AND gate AND1; the AND gate AND1 outputs a short-circuit judgment signal U3.

[0016] Furthermore, the short-circuit type judgment logic circuit includes a comparator A5 and an AND gate AND2; the positive input terminal of the comparator A5 is connected to the gate of the SiC MOSFET M1, and the negative input terminal of the comparator A5 is connected to the reference voltage V. ref The output end of the comparator A5 and the short-circuit judgment signal U3 are respectively connected to an input end of the AND gate AND2, and the AND gate AND2 outputs the short-circuit type judgment signal U5, and the short-circuit type judgment signal U5 is input to the controller.

[0017] Furthermore, the soft shutdown circuit further includes a driving resistor R g2 MOSFET M2 is connected in parallel with the soft turn-off resistor R through the drain and source soft At both ends, the gate of MOSFET M2 is connected to the driving resistor R g2 One end of the drive resistor R g2 The other end is connected to the driving signal PWM2.

[0018] Beneficial Effects: In existing technologies, when a short-circuit detection circuit detects a short-circuit fault in a SiC MOSFET, the short-circuit current is typically much greater than the rated operating current of the SiC MOSFET. If the SiC MOSFET is directly turned off, the excessive di / dt will cause a large turn-off overvoltage, which may damage the SiC MOSFET. Therefore, to solve this problem, a soft turn-off of the SiC MOSFET is required. Traditional soft turn-off methods extend the turn-off time to suppress the turn-off overvoltage, which will increase the turn-off loss of the SiC MOSFET.

[0019] The present invention provides a SiC MOSFET short-circuit shutdown protection circuit based on short-circuit type judgment, Figure 1 In the red box, the amount of charge flowing through the SiC MOSFET drive resistor in the drive loop is sampled through a differential amplifier circuit and an inverting integration circuit. Figure 1 The blue box is the short-circuit detection logic processing circuit, which compares the gate-source voltage with the reference voltage V through comparator A3. ref , output comparison signal U1; compare the driving resistor charge with the reference charge Q through comparator A4 ref , output comparison signal U2; multiply U1 and U2 through AND gate AND1 to output short-circuit detection signal U3. If U3 is high, it means a short-circuit fault has occurred. Figure 1 The green box is the short-circuit type judgment logic processing circuit, which compares the gate-source voltage with the reference voltage V through comparator A5. ref', output comparison signal U4; multiply U3 and U4 through AND gate AND2 to output short circuit type judgment signal U5. If U5 is low, it means a hard switch short circuit fault (HSF) has occurred. If U5 is high, it means a load short circuit fault (FUL) has occurred. When a hard switch short circuit (HSF) is detected, the SiC MOSFET is directly turned off; when a load short circuit (FUL) is detected, the Figure 1 The large resistance turn-off method in the orange box prolongs the turn-off time of the SiC MOSFET, thereby suppressing the turn-off overvoltage.

[0020] This method detects short circuits by measuring the charge on the SiC MOSFET drive resistor and the change in gate-source voltage, determining the type of short circuit. Different short-circuit shutdown methods are then employed for different short-circuit faults. This method can distinguish the type of short-circuit fault and employ different shutdown methods based on the fault type. Compared to traditional short-circuit soft shutdown methods, this method can better balance the relationship between turn-off overvoltage and turn-off losses, reducing the probability of SiC MOSFET degradation or even damage after a short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of short circuit detection, short circuit type judgment and classification, and short circuit shutdown protection circuit;

[0022] Figure 2 (a), (b), and (c) are the working timing diagrams of normal operation, HSF occurrence, and FUL occurrence respectively;

[0023] Figure 3 The relationship between the charge flowing through the driving resistor and the gate voltage under normal operation (blue), HSF (red), and FUL (green);

[0024] Figure 4 (a) and (b) are the waveforms of short circuit detection and short circuit type judgment when HSF and FUL occur, respectively;

[0025] Figure 5 Figure 3 is a short-circuit shutdown waveform diagram, where (a) is the drain-source voltage and drain current waveform diagram of direct shutdown when HSF occurs, (b) is the power loss waveform diagram of direct shutdown when HSF occurs, (c) is the drain-source voltage and drain current waveform diagram of large resistance shutdown when HSF occurs, (d) is the power loss waveform diagram of large resistance shutdown when HSF occurs, and (e) is the drain-source voltage and drain current waveform diagram when FUL occurs. DETAILED DESCRIPTION

[0026] The present invention will be further explained below with reference to the accompanying drawings.

[0027] Figure 1Where M1 is the SiC MOSFET under test, R g1 The current sampling circuit uses a differential amplifier circuit, taking R1 = R2 = R3 = R4, then the output voltage signal V at point A is A for:

[0028]

[0029] Where V Rg1 is the driving resistor R g1 Voltage across the resistor. Current flowing through the resistor for:

[0030]

[0031] In the inverting integration circuit, R5=R6, R7>10R5, then the output voltage signal V at point B is B for:

[0032]

[0033] Where, t a is the time when SiC MOSFET starts working, t b Time for the SiC MOSFET to end its operation.

[0034] From equations (1), (2), and (3), we can get that the current flowing through the driving resistor R g1 The amount of charge for:

[0035]

[0036] Order-R5C1 / R g1 =k, k is a constant, -V B =Q Rg1 , then Q * Rg1 =-k·Q Rg1 , so the output voltage V at point B B The opposite of is regarded as the equivalent charge flowing through the driving resistor.

[0037] The gate voltage of M1 is V GS With the set reference voltage V ref Comparator A3 is used to compare the size and output comparison signal U1; point B outputs voltage signal V B =-Q Rg1 With the set reference charge -Q ref Comparator A4 compares the magnitudes and outputs comparison signal U2. Signals U1 and U2 are input and multiplied by the gate to obtain the final short circuit detection signal U3. If the output of U3 is high, it means a short circuit has occurred. Figure 2It can be seen that the reference voltage V ref With reference charge Q ref Set in Figure 3 In the middle purple area, (Q1, V miller1 )、(Q4,V miller2 )、(Q5,V D )、(Q3,V D ) The quadrilateral enclosed by Q2 is the part on the right side. Q1 is the gate charge required to reach the Miller platform, Q2 is the gate charge when FUL occurs, Q3 is the gate charge when HSF occurs, Q4 is the gate charge at the end of the Miller platform, Q5 is the gate charge required for normal turn-on, V D For driving positive voltage, V miller1 is the Miller voltage at the beginning of the Miller voltage platform, V miller2 is the Miller voltage at the end of the Miller voltage plateau.

[0038] according to Figure 2 It can be seen that the reference voltage V ref 'Set in V ref <V ref ' <V D The short circuit type can be distinguished within the range. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 A detailed description of the short circuit detection and short circuit type judgment process:

[0039] During normal operation, the PWM2 output remains high and the soft shutdown resistor R soft Short-circuited. Figure 2 (b) HSF occurs. Before t'1, the drive signal PWM1 is at a low level, and the SiC MOSFET is already in a short-circuit loop. At t'1, the drive signal PWM1 becomes high, the SiC MOSFET is short-circuited, and the drive power is connected to the drive resistor R g1 The gate source of M1 is charged, and the gate voltage of M1 is V GS With Q * Rg1 Starts to rise. t'1~t'2:V GS <V ref , U1 outputs low level; Q * Rg1 ref , U2 outputs high level; U3 outputs low level. t'2~t'4: V GS >V ref , U1 outputs high level; Q * Rg1 ref ​​, U2 outputs high level; U3 outputs high level and outputs short circuit signal. When outputting short circuit signal at time t'2, V GS <V ref ', U5 outputs a low level, indicating that an HSF has occurred. At this point, the SiC MOSFET has not yet fully turned on, and the short-circuit current is still rising, resulting in a small short-circuit current. PWM2 output remains high, while PWM1 outputs a low level, directly turning off the SiC MOSFET.

[0040] Figure 2 (c) FUL occurs. At t”1, SiC MOSFET M1 is fully turned on. FUL occurs at t”1, Q * Rg1 Starts to decrease. t”1~t”2:V GS >V ref , U1 outputs high level; Q * Rg1 >Q ref , U2 outputs low level; U3 outputs low level. t"2~t"4: V GS >V ref , U1 outputs high level; Q * Rg1 ref , U2 outputs high level; U3 outputs high level and outputs short circuit signal. When outputting short circuit signal at time t"2, V GS >V ref ', U5 outputs a high level, and it is recognized that a FUL occurs at this time. At this time, the SiC MOSFET is fully turned on, the short-circuit current is large, and has reached the short-circuit peak current. PWM2 outputs a low level, and the soft turn-off resistor R soft It is connected in series to the drive circuit to slow down the turn-off speed of the SiC MOSFET. PWM1 outputs a low level to slowly turn off the SiC MOSFET.

[0041] Figure 4 、 Figure 5 The working waveform of the short circuit detection and shutdown protection of this circuit is shown in Figure 2. Taking SiC MOSFET with a withstand voltage of 1200V and a current of 40A as an example, V DS is the SiC MOSFET drain-source voltage, I D is the SiC MOSFET drain current, and the operating bus voltage is set to 1000V.

[0042] Figure 4 (a) and Figure 5 (a) and (b) are the waveforms of the short-circuit type judgment and classification short-circuit shutdown protection circuit of SiC MOSFET in this embodiment when HSF occurs in SiC MOSFET. HSF occurs at 1μs, Figure 5 ​In (a), the short-circuit drain current (blue) begins to rise, and the short-circuit detection circuit detects a short-circuit fault at 1.045 μs. Figure 4 In (a), U3 outputs a high level and U5 outputs a low level, indicating that the short-circuit fault is HSF. At this time, the short-circuit drain current is still in the rising stage, about 43A, and the SiCMOSFET can be directly turned off. Figure 5 The drain-source voltage (red) in (a) is about 1039V when it turns off. Figure 5 In (b), the turn-off loss at this time is 0.466mJ, and the total loss of the entire detection and turn-off protection is 1.483mJ, which is within the safe operating range.

[0043] Figure 5 Figures (c) and (d) show the waveforms of the SiC MOSFET short-circuit type determination and classification short-circuit shutdown protection circuit of this embodiment performing high-resistance shutdown when an HSF occurs. High-resistance shutdown suppresses the drain-source voltage (red) shutdown spike to approximately 1020V. While this slightly reduces the voltage spike compared to directly shutting off the SiC MOSFET, the shutdown loss is 1.118mJ, an increase of 58.32%. The total loss for the entire detection and shutdown protection process is 1.679mJ, an increase of 11.67% in total short-circuit losses. Comparison shows that the proposed SiC MOSFET short-circuit type determination and classification short-circuit shutdown protection circuit not only reduces the drain-source voltage shutdown spike when an HSF occurs in the SiC MOSFET, but also significantly reduces the shutdown loss of the SiC MOSFET when an HSF occurs.

[0044] Figure 4 (b) and Figure 5 (e) is the waveform of the proposed SiC MOSFET short-circuit type judgment and classification short-circuit shutdown protection circuit when the SiC MOSFET fails. FUL occurs at 3μs, Figure 5 In (e), the short-circuit drain current (blue) begins to rise, and the short-circuit detection circuit detects a short-circuit fault at 3.4us. Figure 4 In (b), U3 outputs a high level and U5 outputs a high level, indicating that the short-circuit fault is FUL. At this time, the short-circuit drain current is about 140A and cannot be directly shut down. Figure 5 The orange waveform in (e) is the drain-source voltage of the SiC MOSFET when it is directly turned off. The peak value of the voltage spike is about 1177V. The voltage spike is large, so soft shutdown is required. Figure 5 The red waveform (e) shows the drain-source voltage of the SiC MOSFET using soft shutdown. The voltage spike peak is approximately 1072V, which is within the safe operating range and effectively suppresses the voltage spike during short-circuit shutdown of the SiC MOSFET. The above waveform results demonstrate the effectiveness of this invention.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A short-circuit shutdown protection circuit for SiC MOSFET based on short-circuit type judgment, characterized in that: It includes the tested SiC MOSFET M1, current sampling circuit, inverting integration circuit, short-circuit detection logic circuit, short-circuit type judgment logic circuit, and soft shutdown circuit; The current sampling circuit uses a differential amplifier circuit to sample the driving resistance of SiC MOSFET M1 R g1 Voltage across both ends, indirectly measuring the driving resistance R g1 The current on The inverting integration circuit is connected to the driving resistor R g1 The current flowing through the driving resistor is integrated to measure the R g1 The amount of charge on The short-circuit detection logic circuit uses two comparators to compare the gate-source voltage of SiC MOSFET M1 with the reference voltage. V ref Output comparison signal after comparison U 1. Drive the resistor R g1 The charge on the reference charge Q ref Output comparison signal after comparison U 2, U 1 and U 2 outputs short-circuit signal after multiplication by AND gate U 3. If U 3 is high level, indicating a short circuit fault; The short-circuit type judgment logic circuit uses a comparator to compare the gate-source voltage of SiC MOSFET M1 with the reference voltage. V ref 'Output comparison signal after comparison U 4. U 4 with the short circuit signal U 3 After multiplication by the AND gate, the short circuit type judgment signal is output U 5. If U 5 is low, it means a hard switch short circuit fault occurs. U 5 is high level, indicating that a load short circuit fault has occurred; The soft-off circuit includes a soft-off resistor R soft When the MOSFET M2 is working normally, the controller output drive signal PWM2 remains high, and the soft turn-off resistor R soft When the short-circuit detection logic circuit outputs a short-circuit signal and the short-circuit type judgment logic circuit detects that a load short-circuit fault occurs, the controller outputs a drive signal PWM2 to a low level to turn off the MOSFET M2, thereby soft-turning off the resistor R soft It is connected in series to the drive circuit of SiC MOSFET M1 to slow down the shutdown speed of SiC MOSFET M1; when the short-circuit detection logic circuit outputs a short-circuit signal and the short-circuit type judgment logic circuit detects that a hard switch short-circuit fault has occurred, the controller outputs the drive signal PWM2 to maintain a high level and outputs PWM1 to a low level to directly turn off SiC MOSFET M1.

2. The SiC MOSFET short-circuit shutdown protection circuit according to claim 1, wherein: Establish a two-dimensional coordinate system with charge as the horizontal coordinate and voltage as the vertical coordinate. V ref With the reference charge Q ref Set within the following range of the two-dimensional coordinate system: from point ( Q 1, V miller1 )、( Q 4, V miller2 )、( Q 5, V D )、( Q 3, V D ) The horizontal coordinate of the quadrilateral is located at Q 2 The right side part, where Q 1 is the gate charge required to reach the Miller plateau, Q 2 is the gate charge when FUL occurs, Q 3 is the gate charge when HSF occurs, Q 4 is the gate charge at the end of the Miller platform, Q 5 is the gate charge required for normal turn-on, V D To drive positive voltage, V miller1 is the Miller voltage at the beginning of the Miller voltage platform, V miller2 is the Miller voltage at the end of the Miller voltage platform; the reference voltage V ref 'satisfy V ref < V ref '< V D .

3. The SiC MOSFET short-circuit shutdown protection circuit according to claim 1 or 2, characterized in that: The current sampling circuit includes an operational amplifier A1, a resistor R 1~ R 4; the driving resistor R g1 One end is connected to the gate of SiC MOSFET M1, and the other end is connected to the soft turn-off resistor. R soft One end of the soft turn-off resistor R soft The other end is connected to the drive signal PWM1 output by the controller; the positive input terminal of the operational amplifier A1 is connected to the resistor R 1 and R One end of 3, resistor R The other end of 1 is connected to the driving resistor R g1 The other end of the resistor R The other end of 3 is grounded; the negative input terminal of operational amplifier A1 is connected to a resistor R 2 、R One end of 4, resistor R The other end of 2 is connected to the gate of SiC MOSFET M1, and the resistor R The other end of 4 is connected to the output of operational amplifier A1 and resistor R One end of 5.

4. The SiC MOSFET short-circuit shutdown protection circuit according to claim 3, wherein: The inverting integration circuit includes an operational amplifier A2, a resistor R 5~ R 7. Capacitor C 1. Connect a resistor to the positive input of operational amplifier A2 R One end of 6, resistor R The other end of 6 is connected to the reference ground; the negative input end of the operational amplifier A2 is connected to the resistor R The other end of the resistor R 7 and capacitor C 1 are respectively connected in parallel between the output terminal and the negative input terminal of the operational amplifier A2, and the output terminal of the operational amplifier A2.

5. The SiC MOSFET short-circuit shutdown protection circuit according to claim 4, wherein: The short circuit detection logic circuit includes comparator A3, comparator A4, and AND gate AND1; the positive input terminal of comparator A3 is connected to the gate of SiC MOSFET M1, and the negative input terminal of comparator A3 is connected to the reference voltage V ref , comparator A3 outputs the comparison signal U 1, connected to one input terminal of AND gate AND1; the positive input terminal of comparator A4 is connected to the output terminal of operational amplifier A2, and the negative input terminal of comparator A4 is connected to the reference charge - Q ref , comparator A4 outputs the comparison signal U 2. Connect to the other input terminal of the AND gate AND1; the AND gate AND1 outputs a short circuit judgment signal U 3.

6. The SiC MOSFET short-circuit shutdown protection circuit according to claim 1, 2 or 5, characterized in that: The short-circuit type judgment logic circuit includes a comparator A5 and an AND gate AND2; the positive input terminal of the comparator A5 is connected to the gate of the SiC MOSFET M1, and the negative input terminal of the comparator A5 is connected to the reference voltage V , ref , the output terminal of the comparator A5 and the short circuit judgment signal U 3 are connected to an input terminal of AND gate AND2, and gate AND2 outputs the short circuit type judgment signal U 5. The short circuit type judgment signal U 5-input controller.

7. The SiC MOSFET short-circuit shutdown protection circuit according to claim 3, wherein: The soft shutdown circuit further includes a driving resistor R g2 MOSFET M2 is connected in parallel to the soft turn-off resistor through the drain and source R soft At both ends, the gate of MOSFETM2 is connected to the driving resistor R g2 One end of the drive resistor R g2 The other end is connected to the driving signal PWM2.

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