A protection circuit, device and method for a high-voltage silicon carbide MOSFET

Abstract

The application discloses a kind of protection circuit, device and method of high-voltage silicon carbide MOSFET, belong to protection circuit technical field.The protection circuit provided by the present application can identify and handle short-circuit fault in time, provide comprehensive circuit protection for high-voltage silicon carbide MOSFET, realize the identification of hard switching short-circuit fault through the cooperative work of full-on detection circuit and gate voltage detection circuit, realize the identification of load short-circuit fault through the setting of full-on detection circuit and drain-source voltage detection circuit;When identifying that the high-voltage silicon carbide MOSFET to be protected exists hard switching short-circuit fault or load short-circuit fault, logic processing circuit can quickly receive relevant signals and make accurate judgment, lock external PWM control signal, output corresponding level signal, level signal passes through first drive circuit and second drive circuit, realize the fast turn-off of MOSFET, effectively protect device.

Description

Technical Field

[0001] This invention relates to the field of protection circuit technology, and more specifically to a protection circuit for a high-voltage silicon carbide MOSFET. Background Technology

[0002] In the field of power electronics, SiC (silicon carbide) power devices possess excellent properties such as high blocking voltage capability, high switching frequency, and low switching losses, offering significant advantages for simplifying circuit topologies, reducing the number of power devices, and increasing power density. However, high-voltage silicon carbide MOSFET chips have a small area, which poses a significant challenge to electrical stress under short-circuit conditions. Typically, the short-circuit withstand time of these devices is limited to the range of 2 to 7 microseconds, and this withstand time decreases further as the voltage increases.

[0003] Common short-circuit faults in high-voltage silicon carbide MOSFETs include hard-switching faults (HSF) and load short-circuit faults (FUL). Although various short-circuit fault protection strategies for silicon carbide MOSFETs have emerged, they still have certain limitations. For example, using gate charge characteristics to assess the presence of a Miller plateau as a basis for judging short-circuit faults can effectively identify hard-switching faults, but its detection circuit is relatively complex, data processing is difficult, and it cannot be applied to detect load short-circuit faults. Traditional desaturation schemes determine whether a fault has occurred by detecting the drain-source voltage of the device. This method has a simple circuit, but it requires adding a blanking time when the device is turned on to shield the short-circuit detection, so this method cannot identify hard-switching faults in a timely manner.

[0004] Therefore, how to design a protection circuit that can accurately identify hard switch faults and effectively deal with load short-circuit faults has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a protection circuit, device and method for high-voltage silicon carbide MOSFETs, so as to overcome the problem that the prior art cannot simultaneously and effectively detect hard switching faults and load short circuit faults of high-voltage silicon carbide MOSFETs.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] A protection circuit for a high-voltage silicon carbide MOSFET includes a drain-source voltage detection circuit, a full-turn-on detection circuit, a gate voltage detection circuit, a logic processing circuit, a first driving circuit, and a second driving circuit.

[0008] The input terminal of the drain-source voltage detection circuit is connected to the drain of the high-voltage silicon carbide MOSFET to be protected. The input terminal of the fully turn-on detection circuit is connected to the drain of the high-voltage silicon carbide MOSFET to be protected. The input terminal of the gate voltage detection circuit is connected to the gate of the high-voltage silicon carbide MOSFET to be protected. The drain-source voltage detection circuit, the fully turn-on detection circuit and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together.

[0009] The output of the logic processing circuit is connected to the gate of the high-voltage silicon carbide MOSFET to be protected via the first driving circuit. The input of the logic processing circuit is connected to the output of the drain-source voltage detection circuit, the fully turn-on detection circuit, and the gate voltage detection circuit, respectively. The output of the logic processing circuit is also connected to the input of the second driving circuit, and the output of the second driving circuit is connected to the input of the drain-source voltage detection circuit and the fully turn-on detection circuit, respectively.

[0010] It also includes an external PWM control signal, which is connected to the input of the logic processing circuit.

[0011] A further improvement of the present invention is that the drain-source voltage detection circuit includes a first diode D1, a TVS diode, a first capacitor C1, a first resistor R1, a second resistor R2, a third diode D3, a second MOSFET M2, and a first comparator COM1;

[0012] The anode of the first diode D1 is connected to the cathode of the TVS diode, the first terminal of the first capacitor C1, the first terminal of the first resistor R1, and the first terminal of the second resistor R2. The anode of the TVS diode is connected to the negative power supply V. EE The second terminal of the first resistor R1 is connected to the positive power supply V. cc The anode of the third diode D3 and the second terminal of the second resistor R2 are both connected to the positive input terminal of the first comparator COM1, and the inverting input terminal of the first comparator COM1 is connected to the first preset reference voltage V. th1 The cathode of the third diode D3 is connected to the drain of the second MOSFET M2. The second terminal of the first capacitor C1 is grounded. The source of the second MOSFET M2 and the source of the high-voltage silicon carbide MOSFET to be protected are both grounded. The cathode of the first diode D1 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected. The output of the first comparator COM1 is connected to the input of the logic processing circuit. The output of the second drive circuit is connected to the gate of the second MOSFET M2.

[0013] A further improvement of the present invention is that the fully turn-on detection circuit includes a second diode D2, a second capacitor C2, a first MOSFET M1, and a second comparator COM2;

[0014] The cathode of the second diode D2 is connected to the first terminal of the second resistor R2. The anode of the second diode D2 is connected to the first terminal of the second capacitor C2 and the drain of the first MOSFET M1. The second terminal of the second capacitor C2, the source of the first MOSFET M1, and the source of the high-voltage silicon carbide MOSFET to be protected are all grounded. The inverting input of the second comparator COM2 is connected to the anode of the second diode D2 and the drain of the first MOSFET M1. The non-inverting input of the second comparator COM2 is connected to the second preset reference voltage V. th2 The output of the second comparator COM2 is connected to the input of the logic processing circuit, and the output of the second drive circuit is connected to the gate of the first MOS transistor M1.

[0015] A further improvement of the present invention is that the gate voltage detection circuit includes a third resistor R3, a fourth resistor R4, and a third comparator COM3;

[0016] The first terminal of the third resistor R3 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected. The second terminal of the third resistor R3 is connected to the first terminal of the fourth resistor R4 and the positive input terminal of the third comparator COM3. The inverting input terminal of the third comparator COM3 is connected to the third preset reference voltage V. th3 The output of the third comparator COM3 is connected to the input of the logic processing circuit.

[0017] A further improvement of the present invention is that the logic processing circuit includes a first flip-flop U1, a second flip-flop U2, an inverter U3, and a logic OR gate U4;

[0018] The first input of the NOR gate U4 is connected to an external PWM control signal. The clock input of the first flip-flop U1 is connected to the output of the first comparator COM1. The data input of the first flip-flop U1 is connected to the output of the second comparator COM2. The output of the first flip-flop U1 is connected to the second input of the NOR gate U4. The third input of the NOR gate U4 is connected to the output of the second flip-flop U2. The output of the NOR gate U4 is connected to the input of the first driving circuit and the input of the second driving circuit, respectively.

[0019] The clock input of the second flip-flop U2 is connected to the output of the third comparator COM3, the data input of the second flip-flop U2 is connected to the output of the inverter U3, and the input of the inverter U3 is connected to the output of the second comparator COM2.

[0020] A further improvement of the present invention is that the first flip-flop U1 and the second flip-flop U2 are D flip-flops, RS flip-flops, or chips containing RS trigger circuit functions.

[0021] A further improvement of the present invention is that the first driving circuit adopts a push-pull driving circuit for current amplification.

[0022] A further improvement of the present invention is that the second driving circuit uses a driving chip to drive the first MOS transistor M1 and the second MOS transistor M2.

[0023] A protection device for a high-voltage silicon carbide MOSFET, the device comprising the protection circuit for the high-voltage silicon carbide MOSFET as described above.

[0024] A protection method for a high-voltage silicon carbide MOSFET, employing the protection device for the high-voltage silicon carbide MOSFET as described above, includes the following steps:

[0025] When the fully turned-on detection circuit detects that the high-voltage silicon carbide MOSFET to be protected is not fully turned on, and the gate voltage detection circuit detects that the gate voltage is significantly higher than the Miller plateau voltage, it is determined that the high-voltage silicon carbide MOSFET to be protected has a hard-switching short-circuit fault.

[0026] When the fully turned-on detection circuit detects that the high-voltage silicon carbide MOSFET to be protected is fully turned on, and the drain-source voltage detection circuit detects that the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected is significantly outside the normal range, it is determined that the high-voltage silicon carbide MOSFET to be protected has a load short circuit fault.

[0027] When the high-voltage silicon carbide MOSFET to be protected does not experience a load short circuit fault or a hard switch short circuit fault, the external PWM control signal inputs the first level signal A to the logic processing circuit. The logic processing circuit outputs the inverted signal B of the first level signal to the first drive circuit and the second drive circuit respectively. The first drive circuit provides the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn on or off. The second drive circuit provides the turn-off or turn-on signal to the fully turned-on detection circuit and the drain-source voltage detection circuit.

[0028] When a load short circuit fault or hard switch short circuit fault is detected in the high-voltage silicon carbide MOSFET to be protected, the external PWM control signal is blocked. The logic processing circuit outputs the first level signal A to the first drive circuit and the second drive circuit respectively. The first drive circuit provides the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn off, and the second drive circuit provides the turn-on signal to the fully turn-on detection circuit and the drain-source voltage detection circuit.

[0029] Compared with the prior art, the positive and progressive effects of the present invention are as follows:

[0030] The protection circuit for high-voltage silicon carbide MOSFETs provided by this invention has the function of real-time monitoring of the high-voltage silicon carbide MOSFET to be protected, and can promptly identify and handle short-circuit faults, thereby providing comprehensive circuit protection for the high-voltage silicon carbide MOSFET. Once a MOSFET fault occurs, the circuit can respond immediately. Through the coordinated operation of the full-on detection circuit and the gate voltage detection circuit, the identification of hard-switching short-circuit faults is realized. Through the setting of the full-on detection circuit and the drain-source voltage detection circuit, the identification of load short-circuit faults is realized. When a hard-switching short-circuit fault or a load short-circuit fault is detected in the high-voltage silicon carbide MOSFET to be protected, the logic processing circuit can quickly receive relevant signals and make accurate judgments, block the external PWM control signal, and output a corresponding level signal. The level signal passes through the first drive circuit and the second drive circuit to realize the rapid turn-off of the MOSFET, effectively protecting the device.

[0031] Furthermore, high-voltage silicon carbide MOSFETs are prone to flashover faults under high-voltage conditions. Flashover faults require short-circuit protection with a shorter response time. In the protection circuit provided by this invention, the first capacitor C1 and the first resistor R1 in the drain-source voltage detection circuit are used to make the connection point potential follow the drain-source voltage of the high-voltage silicon carbide MOSFET after it is normally turned on. Moreover, the time constant of the RC circuit composed of the first resistor R1 and the first capacitor C1 is no longer limited by the blanking time, which can effectively improve the response speed of the protection circuit.

[0032] Furthermore, the second diode D2 has a certain reverse recovery time. After the high-voltage silicon carbide MOSFET to be protected is fully turned on, it can maintain a negative voltage at the positive input terminal of the first comparator COM1 for a period of time, thereby avoiding the influence of drain-source voltage oscillation on the potential of the positive input terminal of the first comparator COM1 after the MOSFET is fully turned on, thus improving the noise immunity of the protection circuit. Attached Figure Description

[0033] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a circuit structure block diagram of the present invention;

[0035] Figure 2 This is a waveform diagram of the present invention during normal activation;

[0036] Figure 3 This is a waveform diagram of a hard switch failure according to the present invention;

[0037] Figure 4 This is a waveform diagram of the load short-circuit fault according to the present invention;

[0038] Figure 5 This is a schematic diagram of the circuit principle of the present invention;

[0039] Among them, there are a fully open detection circuit-10, a drain-source voltage detection circuit-20, a gate voltage detection circuit-30, a first driving circuit-40, a logic processing circuit-50, and a second driving circuit-60. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0043] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0044] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This is an explanation of the present invention and not a limitation thereof.

[0046] See Figure 1 A protection circuit for a high-voltage silicon carbide MOSFET includes a drain-source voltage detection circuit 20, a full-on detection circuit 10, a gate voltage detection circuit 30, a logic processing circuit 50, a first driving circuit 40, and a second driving circuit 60.

[0047] The input terminal of the drain-source voltage detection circuit 20 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, the input terminal of the fully turn-on detection circuit 10 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, and the input terminal of the gate voltage detection circuit 30 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected. The drain-source voltage detection circuit 20, the fully turn-on detection circuit 10 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together.

[0048] The output of the logic processing circuit 50 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected via the first driving circuit 40. The input of the logic processing circuit 50 is connected to the output of the drain-source voltage detection circuit 20, the fully turn-on detection circuit 10, and the gate voltage detection circuit 30, respectively. The output of the logic processing circuit 50 is also connected to the input of the second driving circuit 60. The output of the second driving circuit 60 is connected to the input of the drain-source voltage detection circuit 20 and the fully turn-on detection circuit 10, respectively.

[0049] It also includes an external PWM control signal, which is connected to the input of the logic processing circuit 50.

[0050] In this embodiment, the drain-source voltage detection circuit 20 is used to detect the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected after normal turn-on and output it to the logic processing circuit 50; the full turn-on detection circuit 10 is used to detect whether there is a significant voltage drop in the high-voltage silicon carbide MOSFET to be protected during the turn-on transient process and output it to the logic processing circuit 50; the gate voltage detection circuit 30 is used to detect the gate voltage of the high-voltage silicon carbide MOSFET to be protected and output it to the logic processing circuit 50; the logic processing circuit 50 is used to determine the gate voltage based on the full turn-on detection circuit 10, the drain-source voltage detection circuit 20, and the gate voltage. The output signal of the voltage detection circuit 30 determines whether the high-voltage silicon carbide MOSFET to be protected has a hard-switching short-circuit fault or a load short-circuit fault. Then, based on the judgment result of the logic processing circuit 50, it outputs a first-level signal to the first drive circuit 40 and the second drive circuit 60 in combination with the external PWM control signal. The first drive circuit 40 is used to provide the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn on or off according to the first-level signal. The second drive circuit 60 is used to provide the turn-on or turn-off signal to the fully turn-on detection circuit 10 and the drain-source voltage detection circuit 20 according to the first-level signal.

[0051] The protection circuit for high-voltage silicon carbide MOSFETs provided by this invention has the function of real-time monitoring of the high-voltage silicon carbide MOSFET to be protected, and can promptly identify and handle short-circuit faults, thereby providing comprehensive circuit protection for the high-voltage silicon carbide MOSFET. Once a MOSFET fault occurs, the circuit can respond immediately. Through the coordinated operation of the full-on detection circuit and the gate voltage detection circuit, the identification of hard-switching short-circuit faults is realized. Through the setting of the full-on detection circuit and the drain-source voltage detection circuit, the identification of load short-circuit faults is realized. When a hard-switching short-circuit fault or a load short-circuit fault is detected in the high-voltage silicon carbide MOSFET to be protected, the logic processing circuit can quickly receive relevant signals and make accurate judgments, block the external PWM control signal, and output a corresponding level signal. The level signal passes through the first drive circuit and the second drive circuit to realize the rapid turn-off of the MOSFET, effectively protecting the device.

[0052] For details, see Figure 5 The drain-source voltage detection circuit 20 includes a first diode D1, a TVS diode, a first capacitor C1, a first resistor R1, a second resistor R2, a third diode D3, a second MOSFET M2, and a first comparator COM1.

[0053] The anode of the first diode D1 is connected to the cathode of the TVS diode, the first terminal of the first capacitor C1, the first terminal of the first resistor R1, and the first terminal of the second resistor R2. The anode of the TVS diode is connected to the negative power supply V. EE The second terminal of the first resistor R1 is connected to the positive power supply V. ccThe anode of the third diode D3 and the second terminal of the second resistor R2 are both connected to the positive input terminal of the first comparator COM1. The inverting input terminal of the first comparator COM1 is connected to the first preset reference voltage. The cathode of the third diode D3 is connected to the drain of the second MOSFET M2. The second terminal of the first capacitor C1 is grounded. The source of the second MOSFET M2 and the source of the high-voltage silicon carbide MOSFET to be protected are both grounded. The cathode of the first diode D1 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected. The output terminal of the first comparator COM1 is connected to the input terminal of the logic processing circuit 50. The output terminal of the second drive circuit is connected to the gate of the second MOSFET M2.

[0054] High-voltage silicon carbide MOSFETs are prone to flashover faults under high-voltage conditions. Flashover faults require short-circuit protection with a shorter response time. In the protection circuit provided by this invention, the drain-source voltage detection circuit uses a first capacitor C1 and a first resistor R1 to make the connection point potential follow the drain-source voltage of the high-voltage silicon carbide MOSFET after it is normally turned on. Furthermore, the time constant of the RC circuit composed of the first resistor R1 and the first capacitor C1 is no longer limited by the blanking time, which can effectively improve the response speed of the protection circuit.

[0055] The capacitance value of the first capacitor C1 and the resistance value of the first resistor R1 can be set according to the actual situation, and are not specifically limited here; the first comparator COM1 is used to compare the voltage signal with the reference voltage to generate a digital signal and output it to the logic processing circuit 50.

[0056] Specifically, the fully turned-on detection circuit 10 includes a second diode D2, a second capacitor C2, a first MOSFET M1, and a second comparator COM2;

[0057] The cathode of the second diode D2 is connected to the first terminal of the second resistor R2. The anode of the second diode D2 is connected to the first terminal of the second capacitor C2 and the drain of the first MOSFET M1. The second terminal of the second capacitor C2, the source of the first MOSFET M1, and the source of the high-voltage silicon carbide MOSFET to be protected are all grounded. The inverting input terminal of the second comparator COM2 is connected to the anode of the second diode D2 and the drain of the first MOSFET M1. The non-inverting input terminal of the second comparator COM2 is connected to the second preset reference voltage. The output terminal of the second comparator COM2 is connected to the input terminal of the logic processing circuit 50. The output terminal of the second driving circuit is connected to the gate of the first MOSFET M1.

[0058] The second diode D2 has a certain reverse recovery time. After the high-voltage silicon carbide MOSFET to be protected is fully turned on, it can maintain a negative voltage at the positive input terminal of the first comparator COM1 for a period of time, avoiding the influence of drain-source voltage oscillation on the potential of the positive input terminal of the first comparator COM1 after the MOSFET is fully turned on, thereby improving the noise immunity of the protection circuit. The second capacitor C2 is used to store the charge transferred during the drain-source voltage drop of the high-voltage silicon carbide MOSFET to be protected. The capacitance value of the second capacitor C2 can be set according to the actual situation and is not specifically limited here. The second comparator COM2 is used to compare the voltage signal with the reference voltage to generate a digital signal output to the logic processing circuit 50.

[0059] Specifically, the gate voltage detection circuit 30 includes a third resistor R3, a fourth resistor R4, and a third comparator COM3;

[0060] The first end of the third resistor R3 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected. The second end of the third resistor R3 is connected to the first end of the fourth resistor R4 and the positive input of the third comparator COM3. The inverting input of the third comparator COM3 is connected to the third preset reference voltage. The output of the third comparator COM3 is connected to the input of the logic processing circuit 50.

[0061] The third comparator COM2 is used to compare the gate voltage signal with the reference voltage to generate a digital signal that is output to the logic processing circuit 50.

[0062] Specifically, the logic processing circuit 50 includes a first flip-flop U1, a second flip-flop U2, an inverter U3, and a logic OR gate U4;

[0063] The first input of the NOR gate U4 is connected to an external PWM control signal. The clock input of the first flip-flop U1 is connected to the output of the first comparator COM1. The data input of the first flip-flop U1 is connected to the output of the second comparator COM2. The output of the first flip-flop U1 is connected to the second input of the NOR gate U4. The third input of the NOR gate U4 is connected to the output of the second flip-flop U2. The output of the NOR gate U4 is connected to the inputs of the first drive circuit 40 and the second drive circuit 60, respectively.

[0064] The clock input of the second flip-flop U2 is connected to the output of the third comparator COM3, the data input of the second flip-flop U2 is connected to the output of the inverter U3, and the input of the inverter U3 is connected to the output of the second comparator COM2.

[0065] Specifically, the use of D flip-flops, RS flip-flops, or chips containing RS trigger circuitry as the first flip-flop U1 and the second flip-flop U2 helps improve the response speed of the protection circuit.

[0066] Specifically, the first driving circuit 40 adopts a push-pull driving circuit for current amplification.

[0067] Specifically, the second driving circuit 60 uses a driving chip to drive the first MOS transistor M1 and the second MOS transistor M2. The driving chip can realize a single signal input and simultaneously drive the first MOS transistor PMOS transistor M1 and the second MOS transistor NMOS transistor M2 to turn on or off. Simultaneous turn-on can realize the internal signal reset of the drain-source voltage detection circuit 20 and the fully turn-on detection circuit 10.

[0068] See Figure 2 , Figure 3 and Figure 4 During normal turn-on, the gate voltage of the protected high-voltage silicon carbide MOSFET gradually increases. After the gate voltage reaches the threshold voltage, the current flowing through the protected high-voltage silicon carbide MOSFET gradually increases. After the gate voltage reaches the Miller voltage, the current reaches its peak value. The drain-source voltage of the protected high-voltage silicon carbide MOSFET gradually decreases, and the gate voltage will maintain the Miller voltage for a period of time. Afterward, the gate voltage gradually increases. During the hard turn-on short-circuit fault process, the gate voltage of the protected high-voltage silicon carbide MOSFET gradually increases. After the gate voltage reaches the threshold voltage, the current flowing through the protected high-voltage silicon carbide MOSFET increases sharply. The drain-source voltage of the protected high-voltage silicon carbide MOSFET decreases slightly and then rises to the bus voltage, and there is no Miller plateau in the gate voltage. During the load short-circuit fault process, this fault occurs after normal conduction. After this fault occurs, the current flowing through the protected high-voltage silicon carbide MOSFET increases sharply. The drain-source voltage of the protected high-voltage silicon carbide MOSFET gradually increases with the increase of current and eventually rises to the bus voltage.

[0069] In a specific embodiment of the present invention, when the high-voltage silicon carbide MOSFET to be protected is in the off state, the first MOSFET M1 and the second MOSFET M2 are both in the on state. The outputs of the fully turned-on detection circuit 10, the drain-source voltage detection circuit 20, and the gate voltage detection circuit 30 are all low level, and an external PWM control signal (low level signal) is input to the logic processing circuit 50. The logic processing circuit 50 outputs a high level to the first driving circuit 40 and the second driving circuit 60. The first driving circuit 40 provides the driving signal required for turning on the high-voltage silicon carbide MOSFET to be protected, and the second driving circuit 60 provides the driving signal required for turning off the first MOSFET M1 and the second MOSFET M2.

[0070] Under normal circumstances, that is, when the high-voltage silicon carbide MOSFET to be protected does not experience a hard switching short circuit fault or a load short circuit fault, the gate voltage of the high-voltage silicon carbide MOSFET to be protected gradually increases. When the gate voltage reaches the threshold voltage, the current flowing through the high-voltage silicon carbide MOSFET to be protected gradually increases. After the gate voltage of the high-voltage silicon carbide MOSFET to be protected reaches the Miller voltage, the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected gradually decreases.

[0071] Under high-voltage conditions, the drain-source voltage drop rate of the protected high-voltage silicon carbide MOSFET can reach tens or even hundreds of volts per nanosecond. Due to the junction capacitance of the first diode D1, a current of tens or even hundreds of milliamperes will be generated during the drain-source voltage drop of the protected high-voltage silicon carbide MOSFET, causing the voltage at the first terminal of the second capacitor C2 to drop. After the drain-source voltage of the protected high-voltage silicon carbide MOSFET drops significantly, the voltage at the first terminal of the second capacitor C2 will be lower than the preset reference voltage V. th2 The fully turned-on detection circuit 10 outputs a high level to the logic processing circuit 50. The gate voltage detection circuit 30 detects that the gate voltage is significantly higher than the Miller plateau voltage and outputs a high level to the logic processing circuit 50. The logic processing circuit 50 determines, based on the signals from the fully turned-on detection circuit 10 and the gate voltage detection circuit 30, that the high-voltage silicon carbide MOSFET to be protected has not experienced a hard-switching short-circuit fault.

[0072] After normal power-on, the drain-source voltage detection circuit 20 detects that the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected is within the normal range. Then, it outputs a low level to the logic processing circuit 50. The logic processing circuit 50 determines, based on the signals from the full power-on detection circuit 10 and the drain-source voltage detection circuit 20, that the high-voltage silicon carbide MOSFET to be protected has not experienced a hard-switching short-circuit fault or a load short-circuit fault. Combined with the external PWM control signal (low-level signal) input to its first input terminal, it ensures that the drive signals input to the first drive circuit 40 and the second drive circuit 60 are always kept at a high level. This provides the drive signal required to turn on the high-voltage silicon carbide MOSFET to be protected, thereby enabling the normal operation of the high-voltage silicon carbide MOSFET to be protected.

[0073] When a hard-switching short-circuit fault occurs, the gate voltage of the protected high-voltage silicon carbide MOSFET gradually rises until it reaches the threshold voltage. The current flowing through the protected high-voltage silicon carbide MOSFET then increases sharply. After the gate voltage of the protected high-voltage silicon carbide MOSFET reaches the Miller voltage, there is no Miller plateau. The drain-source voltage of the protected high-voltage silicon carbide MOSFET then decreases slightly before rising to the bus voltage. The voltage at the first terminal of the second capacitor decreases slightly but remains above the preset reference voltage V. th2The fully turned-on detection circuit 10 outputs a low level to the logic processing circuit 50. The low level output by the fully turned-on detection circuit 10 is then input as a high level to the data input terminal of the second flip-flop U2 after passing through the inverter U3. The gate voltage detection circuit 30 detects that the gate voltage is significantly higher than the Miller plateau voltage and outputs a high level to the data input terminal of the second flip-flop U2 in the logic processing circuit 50 to latch the data. The second flip-flop U2 outputs a high level to the logic NOR gate U3. The logic processing circuit 50 outputs a low level to the first drive circuit 40 and the second drive circuit 60. The first drive circuit 40 provides the drive signal required to turn off the high-voltage silicon carbide MOSFET to be protected. The second drive circuit provides the drive signal required to turn on the first MOSFET M1 and the second MOSFET M2.

[0074] When a load short-circuit fault occurs, the protected high-voltage silicon carbide MOSFET is normally turned on. The fully turned-on detection circuit 10 outputs a high level to the logic processing circuit 50, and the gate voltage detection circuit 30 outputs a high level to the logic processing circuit 50. After the load short-circuit fault occurs, the current flowing through the protected high-voltage silicon carbide MOSFET rises sharply, and the drain-source voltage of the protected high-voltage silicon carbide MOSFET rises accordingly. The current exceeds the normal range, and the voltage detected by the drain-source voltage detection circuit 20 is higher than the preset reference voltage V. th1 The drain-source voltage detection circuit outputs a high level to the clock input of the first flip-flop U1 in the logic processing circuit 50, latching the high-level signal. The first flip-flop U1 outputs a high level to the logic NOR gate U3. The logic processing circuit 50 outputs a low level to the first drive circuit 40 and the second drive circuit 60. The first drive circuit 40 provides the drive signal required to turn off the high-voltage silicon carbide MOSFET to be protected. The second drive circuit 60 provides the drive signal required to turn on the first MOSFET M1 and the second MOSFET M2.

[0075] Therefore, short-circuit / overcurrent faults in high-voltage silicon carbide MOSFETs can be quickly detected, and the protected high-voltage silicon carbide MOSFETs can be shut down in a timely manner to protect the device. Compared with existing short-circuit / protection circuits, it has a shorter detection time and can simultaneously achieve strong noise immunity, simplicity, low cost, and fast response. It can quickly and accurately detect short-circuit conditions in high-voltage silicon carbide devices and shut them down in a timely manner, thereby protecting the safe operation of high-voltage silicon carbide MOSFET devices.

[0076] Based on the same inventive concept, the present invention also provides a protection device for a high-voltage silicon carbide MOSFET, the device comprising the above-mentioned protection circuit for the high-voltage silicon carbide MOSFET.

[0077] Based on the same inventive concept, the present invention also provides a protection method for a high-voltage silicon carbide MOSFET, employing the protection device for the high-voltage silicon carbide MOSFET as described above, comprising the following steps:

[0078] When the fully turned-on detection circuit 10 detects that the high-voltage silicon carbide MOSFET to be protected is not fully turned on, and the gate voltage detection circuit 30 detects that the gate voltage is significantly higher than the Miller plateau voltage, it is determined that the high-voltage silicon carbide MOSFET to be protected has a hard switch short circuit fault.

[0079] When the fully turned-on detection circuit 10 detects that the high-voltage silicon carbide MOSFET to be protected has been fully turned on, the drain-source voltage detection circuit 20 detects that the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected is significantly beyond the normal range, and it is determined that the high-voltage silicon carbide MOSFET to be protected has a load short circuit fault.

[0080] When the high-voltage silicon carbide MOSFET to be protected does not experience a load short circuit fault or a hard switch short circuit fault, the external PWM control signal inputs the first level signal A to the logic processing circuit 50. The logic processing circuit 50 outputs the inverted signal B of the first level signal to the first drive circuit 40 and the second drive circuit 60 respectively. The first drive circuit 40 provides the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn on or off. The second drive circuit 60 provides the turn-off or turn-on signal to the fully turned-on detection circuit 10 and the drain-source voltage detection circuit 20.

[0081] When a load short circuit fault or hard switch short circuit fault is detected in the high-voltage silicon carbide MOSFET to be protected, the external PWM control signal is blocked. The logic processing circuit 50 outputs a first level signal A to the first drive circuit 40 and the second drive circuit 60 respectively. The first drive circuit 40 provides the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn off, and the second drive circuit 60 provides the turn-on signal to the fully turn-on detection circuit 10 and the drain-source voltage detection circuit 20.

[0082] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of this invention. Their purpose is to clearly illustrate the concept, principle, and application of this invention through specific examples, and is by no means intended to limit the scope of protection of this invention to these specific embodiments. In fact, the true value of this invention lies in its proposed technical ideas and innovations, rather than its manifestations or implementation methods.

[0083] For those skilled in the art, after thoroughly reading and understanding the technical solution of this invention, they are fully capable of making various changes, modifications, or equivalent substitutions to the specific implementation of the invention based on their own professional knowledge and skills. These changes may include, but are not limited to: adjusting the range of technical parameters, optimizing the algorithm flow to improve efficiency, and replacing some technical components to achieve better compatibility or reduce costs. As long as these modified technical solutions substantially retain the technical features claimed by the original invention, that is, they can still achieve the core functions and effects of this invention, then these changes should be considered to fall within the scope of protection of the pending claims of this invention.

[0084] Furthermore, with the continuous progress and development of technology, new technical means and methods are constantly emerging, which provides ample space for further improvement and perfection of this invention. Therefore, the scope of protection of this invention should also include reasonable and foresightful improvements and extensions based on existing technology. As long as these improvements and extensions do not depart from the basic principles and core concepts of this invention, they should be considered equivalents of this invention and are equally protected by patent rights.

Claims

1. A protection circuit for a high-voltage silicon carbide MOSFET, characterized by, The protection circuit comprises a drain-source voltage detection circuit (20), a full-on detection circuit (10), a gate voltage detection circuit (30), a logic processing circuit (50), a first driving circuit (40) and a second driving circuit (60). The input end of the drain-source voltage detection circuit (20) is connected to the drain electrode of the high-voltage silicon carbide MOSFET to be protected, the input end of the full-on detection circuit (10) is connected to the drain electrode of the high-voltage silicon carbide MOSFET to be protected, and the input end of the gate voltage detection circuit (30) is connected to the gate electrode of the high-voltage silicon carbide MOSFET to be protected. The output end of the logic processing circuit (50) is connected to the gate electrode of the high-voltage silicon carbide MOSFET to be protected through the first driving circuit (40), the input end of the logic processing circuit (50) is connected to the output end of the drain-source voltage detection circuit (20), the full-on detection circuit (10) and the gate voltage detection circuit (30) respectively, and the output end of the logic processing circuit (50) is also connected to the input end of the second driving circuit (60). The protection circuit further comprises an external PWM control signal connected to the input end of the logic processing circuit (50). The anode of the first diode D1 is connected to the cathode of the TVS diode, the first end of the first capacitor C1, the first end of the first resistor R1, and the first end of the second resistor R2, respectively; the anode of the TVS diode is connected to the negative power supply V EE ; the second end of the first resistor R1 is connected to the positive power supply V cc ; the anode of the third diode D3 and the second end of the second resistor R2 are both connected to the positive input end of the first comparator COM1; the reverse input end of the first comparator COM1 is connected to the first preset reference voltage V th1 ; the cathode of the third diode D3 is connected to the drain of the second MOS tube M2; the second end of the first capacitor C1, the source of the second MOS tube M2, and the source of the high-voltage silicon carbide MOSFET to be protected are all grounded; the cathode of the first diode D1 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected; the output end of the first comparator COM1 is connected to the input end of the logic processing circuit (50); and the output end of the second driving circuit is connected to the gate of the second MOS tube M2. The full-on detection circuit (10) comprises a second diode D2, a second capacitor C2, a first MOS tube M1, and a second comparator COM2. The cathode of the second diode D2 is connected to the first end of the second resistor R2, the anode of the second diode D2 is connected to the first end of the second capacitor C2 and the drain of the first MOS transistor M1 respectively, the second end of the second capacitor C2, the source of the first MOS transistor M1 and the source of the high-voltage silicon carbide MOSFET to be protected are commonly grounded, the reverse input end of the second comparator COM2 is connected to the anode of the second diode D2 and the drain of the first MOS transistor M1 respectively, the forward input end of the second comparator COM2 is connected to the second preset reference voltage V th2 , the output end of the second comparator COM2 is connected to the input end of the logic processing circuit (50), and the output end of the second drive circuit is connected to the gate of the first MOS transistor M1; the gate voltage detection circuit (30) comprises a third resistor R3, a fourth resistor R4 and a third comparator COM3. The first end of the third resistor R3 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected, the second end of the third resistor R3 is respectively connected to the first end of the fourth resistor R4 and the positive input end of the third comparator COM3, the reverse input end of the third comparator COM3 is connected to the third preset reference voltage V th3 , and the output end of the third comparator COM3 is connected to the input end of the logic processing circuit (50); the logic processing circuit (50) comprises a first flip-flop U1, a second flip-flop U2, an inverter U3 and a logic NOR gate U4. The drain-source voltage detection circuit (20) comprises a first diode D1, a TVS diode, a first capacitor C1, a first resistor R1, a second resistor R2, a third diode D3, a second MOS transistor M2 and a first comparator COM1. The first input end of the logic NOR gate U4 is connected to the external PWM control signal, the clock input end of the first flip-flop U1 is connected to the output end of the first comparator COM1, the data input end of the first flip-flop U1 is connected to the output end of the second comparator COM2, the output end of the first flip-flop U1 is connected to the second input end of the logic NOR gate U4, the third input end of the logic NOR gate U4 is connected to the output end of the second flip-flop U2, and the output end of the logic NOR gate U4 is connected to the input end of the first driving circuit (40) and the input end of the second driving circuit (60) respectively. The clock input end of the second flip-flop U2 is connected to the output end of the third comparator COM3, and the data input end of the second flip-flop U2 is connected to the output end of the inverter U3. The first driving circuit (40) adopts a push-pull driving circuit for current expansion.

2. The protection circuit for a high-voltage silicon carbide MOSFET according to claim 1, wherein The second driving circuit (60) adopts a driving chip for driving the first MOS transistor M1 and the second MOS transistor M2.

3. A protection device for a high-voltage silicon carbide MOSFET, characterized by The first flip-flop U1 and the second flip-flop U2 are D flip-flops, RS flip-flops or chips containing RS flip-flop functions.

4. A method of protecting a high-voltage silicon carbide MOSFET, characterized by, The device comprises the protection circuit of the high-voltage silicon carbide MOSFET according to claim 1 or 2. The protection device of the high-voltage silicon carbide MOSFET according to claim 3 comprises the following steps: When the full-on detection circuit (10) detects that the high-voltage silicon carbide MOSFET to be protected is not fully turned on, and the gate voltage detection circuit (30) detects that the gate voltage is significantly higher than the Miller platform voltage, it is judged that the high-voltage silicon carbide MOSFET to be protected is a hard switching short circuit fault; When the full-on detection circuit (10) detects that the high-voltage silicon carbide MOSFET to be protected has been fully turned on, and the drain-source voltage detection circuit (20) detects that the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected is significantly out of the normal range, it is judged that the high-voltage silicon carbide MOSFET to be protected is a load short circuit fault; When the high-voltage silicon carbide MOSFET to be protected does not have a load short circuit fault or a hard switching short circuit fault, the external PWM control signal inputs the first level signal A to the logic processing circuit (50), the logic processing circuit (50) outputs the inverse signal B of the first level signal to the first drive circuit (40) and the second drive circuit (60) respectively, the first drive circuit (40) provides the high-voltage silicon carbide MOSFET to be protected with the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn on or turn off, and the second drive circuit (60) provides the full-on detection circuit (10) and the drain-source voltage detection circuit (20) with the turn-off or turn-on signal; When the high-voltage silicon carbide MOSFET to be protected is identified to have a load short circuit fault or a hard switching short circuit fault, the external PWM control signal is locked out, the logic processing circuit (50) outputs the first level signal A to the first drive circuit (40) and the second drive circuit (60) respectively, the first drive circuit (40) provides the high-voltage silicon carbide MOSFET to be protected with the drive signal required for the high-voltage silicon carbide MOSFET to be protected to turn off, and the second drive circuit (60) provides the full-on detection circuit (10) and the drain-source voltage detection circuit (20) with the turn-on signal.

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