Protection circuit, device and method for high-voltage silicon carbide MOSFET

Abstract

The invention discloses a protection circuit, device and method for a high-voltage silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and belongs to the technical field of protection circuits. The protection circuit provided by the invention can identify and process a short circuit fault in time, provides comprehensive circuit protection for the high-voltage silicon carbide MOSFET, realizes identification of a hard switch short circuit fault through cooperative work of the complete opening detection circuit and the grid voltage detection circuit, and realizes fault detection of the high-voltage silicon carbide MOSFET through arrangement of the complete opening detection circuit and the drain-source voltage detection circuit. Identification of a load short-circuit fault is realized; when it is recognized that a hard switch short circuit fault or a load short circuit fault exists in the high-voltage silicon carbide MOSFET to be protected, the logic processing circuit can rapidly receive related signals, make accurate judgment, lock external PWM control signals and output corresponding level signals, and the level signals pass through the first drive circuit and the second drive circuit to be output to the high-voltage silicon carbide MOSFET to be protected. The quick turn-off of the MOSFET is realized, and the device is effectively protected.

Description

Technical Field

[0001] The present invention relates to the technical field of protection circuits, and in particular to a protection circuit for a high-voltage silicon carbide MOSFET. Background Art

[0002] In the field of power electronics, SiC (silicon carbide) power devices have excellent performance such as high blocking voltage capability, high switching frequency and low switching loss, which provides significant advantages for simplifying circuit topology, reducing the number of power devices and improving power density. However, high-voltage silicon carbide MOSFET chips are small in area and will suffer huge electrical stress challenges when facing short-circuit situations. Generally, the short-circuit withstand time of such devices is limited to 2 to 7 microseconds, and as the voltage increases, its short-circuit withstand time is further shortened.

[0003] Conventional short-circuit faults of high-voltage SiC MOSFETs include hard switch faults (HSF) and load short-circuit faults (FUL). Although a variety of short-circuit fault protection strategies for SiC MOSFETs have emerged, they still have certain limitations. For example, the gate charge characteristics are used to evaluate whether the Miller platform exists as a basis for judging short-circuit faults. Although this method can effectively identify hard switch faults, its detection circuit is relatively complex, data processing is difficult, and it cannot be applied to detect load short-circuit faults. The traditional desaturation scheme determines whether a fault occurs by detecting the drain-source voltage of the device. This method has a simple circuit, but it needs to add a blanking time to shield the short-circuit detection when the device is turned on, so this method cannot identify hard switch faults in time.

[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 technical personnel in this field urgently need to overcome. Summary of the invention

[0005] The purpose of the present invention is to provide a protection circuit, device and method for a high-voltage silicon carbide MOSFET to overcome the problem in the prior art that it is impossible to effectively detect hard switching faults and load short circuit faults of the high-voltage silicon carbide MOSFET at the same time.

[0006] The present invention solves the above technical problems through the following technical solutions: A protection circuit for a high-voltage silicon carbide MOSFET, comprising a drain-source voltage detection circuit, a fully turned-on detection circuit, a gate voltage detection circuit, a logic processing circuit, a first drive circuit, and a second drive circuit; The input end of the drain-source voltage detection circuit is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, the input end of the fully-opened detection circuit is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, the input end of the gate voltage detection circuit is connected to the gate of the high-voltage silicon carbide MOSFET to be protected, and the drain-source voltage detection circuit, the fully-opened detection circuit and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together; The output end of the logic processing circuit is connected to the gate of the high-voltage silicon carbide MOSFET to be protected via the first drive circuit, the input end of the logic processing circuit is respectively connected to the output ends of the drain-source voltage detection circuit, the full-open detection circuit and the gate voltage detection circuit, the output end of the logic processing circuit is also connected to the input end of the second drive circuit, and the output end of the second drive circuit is respectively connected to the input ends of the drain-source voltage detection circuit and the full-open detection circuit; It also includes an external PWM control signal connected to the input end of the logic processing circuit.

[0007] 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 MOS tube M2 and a first comparator COM1; 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, and the negative 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 is grounded, the source of the second MOS tube M2 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, 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, and the output end of the second drive circuit is connected to the gate of the second MOS tube M2.

[0008] A further improvement of the present invention is that: the fully open detection circuit includes 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 tube M1 respectively, the second end of the second capacitor C2, the source of the first MOS tube M1 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, 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 tube M1 respectively, and 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, and the output end of the second driving circuit is connected to the gate of the first MOS tube M1.

[0009] 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; 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, and the reverse input end of the third comparator COM3 is connected to the third preset reference voltage V th3 , the output end of the third comparator COM3 is connected to the input end of the logic processing circuit.

[0010] A further improvement of the present invention is that: the logic processing circuit includes a first trigger U1, a second trigger U2, an inverter U3 and a logic NOR gate U4; A first input terminal of the logic NOR gate U4 is connected to an external PWM control signal, a clock input terminal of the first trigger U1 is connected to an output terminal of the first comparator COM1, a data input terminal of the first trigger U1 is connected to an output terminal of the second comparator COM2, an output terminal of the first trigger U1 is connected to a second input terminal of the logic NOR gate U4, a third input terminal of the logic NOR gate U4 is connected to an output terminal of the second trigger U2, and an output terminal of the logic NOR gate U4 is respectively connected to an input terminal of the first drive circuit and an input terminal of the second drive circuit; The clock input terminal of the second trigger U2 is connected to the output terminal of the third comparator COM3, the data input terminal of the second trigger U2 is connected to the output terminal of the inverter U3, and the input terminal of the inverter U3 is connected to the output terminal of the second comparator COM2.

[0011] A further improvement of the present invention is that the first trigger U1 and the second trigger U2 are D triggers, RS triggers or chips containing RS trigger circuit functions.

[0012] A further improvement of the present invention is that the first driving circuit adopts a push-pull driving circuit for current expansion.

[0013] A further improvement of the present invention is that the second driving circuit uses a driving chip for driving the first MOS transistor M1 and the second MOS transistor M2.

[0014] A protection device for a high-voltage silicon carbide MOSFET comprises the protection circuit for the high-voltage silicon carbide MOSFET as described above.

[0015] A method for protecting a high-voltage silicon carbide MOSFET, using the above-mentioned high-voltage silicon carbide MOSFET protection device, comprises the following steps: 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 platform voltage, it is determined that the high-voltage silicon carbide MOSFET to be protected is a hard switch short circuit fault; When the fully turned-on detection circuit detects that the high-voltage silicon carbide MOSFET to be protected has been 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 obviously beyond the normal range, it is determined 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 switch short-circuit fault, the external PWM control signal inputs a first level signal A to the logic processing circuit, and the logic processing circuit outputs an inverted signal B of the first level signal to the first drive circuit and the second drive circuit respectively, and the first drive circuit provides the high-voltage silicon carbide MOSFET to be protected with a drive signal required for turning on or off the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit provides a turn-off or turn-on signal to the full turn-on detection circuit and the drain-source voltage detection circuit; When a load short-circuit fault or a hard switch short-circuit fault is identified in the high-voltage silicon carbide MOSFET to be protected, the external PWM control signal is locked, and the logic processing circuit outputs a first level signal A to the first drive circuit and the second drive circuit respectively, and the first drive circuit provides the high-voltage silicon carbide MOSFET to be protected with the drive signal required to shut down the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit provides an opening signal to the full opening detection circuit and the drain-source voltage detection circuit.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are: The protection circuit of the high-voltage silicon carbide MOSFET provided by the present invention has the function of real-time monitoring of the high-voltage silicon carbide MOSFET to be protected, and can timely identify and handle short-circuit faults, thereby providing comprehensive circuit protection for the high-voltage silicon carbide MOSFET. Once the MOSFET fails, the circuit can respond immediately, and the identification of the hard switch short-circuit fault is realized by the coordinated work of the fully open detection circuit and the gate voltage detection circuit, and the identification of the load short-circuit fault is realized by the setting of the fully open detection circuit and the drain-source voltage detection circuit; when it is identified that the high-voltage silicon carbide MOSFET to be protected has a hard switch short-circuit fault and a load short-circuit fault, the logic processing circuit can quickly receive the relevant signal and make an accurate judgment, lock the external PWM control signal, and output the corresponding level signal, and the level signal passes through the first drive circuit and the second drive circuit to realize the rapid shutdown of the MOSFET, effectively protecting the device.

[0017] Furthermore, high-voltage silicon carbide MOSFETs are prone to flashover failures under high-voltage conditions. Flashover failures require short-circuit protection to have a shorter response time. In the protection circuit provided by the present invention, the first capacitor C1 and the first resistor R1 in the drain-source voltage detection circuit are used to make the potential of their connection points follow the drain-source voltage after the high-voltage silicon carbide MOSFET to be protected is normally turned on, and 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.

[0018] 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 the 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 resistance of the protection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 is a circuit structure block diagram of the present invention; Figure 2 This is a waveform diagram of the present invention when it is normally turned on; Figure 3 This is a waveform diagram of a hard switch failure of the present invention; Figure 4 This is a waveform diagram of a load short-circuit fault in the present invention; Figure 5 It is a schematic diagram of the circuit principle of the present invention; Among them, the fully turned-on detection circuit-10, the drain-source voltage detection circuit-20, the gate voltage detection circuit-30, the first driving circuit-40, the logic processing circuit-50, and the second driving circuit-60. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0025] In addition, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0027] See also Figure 1 , a protection circuit for a high-voltage silicon carbide MOSFET, comprising a drain-source voltage detection circuit 20, a fully turned-on detection circuit 10, a gate voltage detection circuit 30, a logic processing circuit 50, a first drive circuit 40 and a second drive circuit 60; The input end 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 end of the fully-opened detection circuit 10 is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, the input end of the gate voltage detection circuit 30 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected, and the drain-source voltage detection circuit 20, the fully-opened detection circuit 10 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together; The output end of the logic processing circuit 50 is connected to the gate of the high-voltage silicon carbide MOSFET to be protected via the first drive circuit 40, and the input end of the logic processing circuit 50 is respectively connected to the output ends of the drain-source voltage detection circuit 20, the fully-opened detection circuit 10 and the gate voltage detection circuit 30, and the output end of the logic processing circuit 50 is also connected to the input end of the second drive circuit 60, and the output end of the second drive circuit 60 is respectively connected to the input ends of the drain-source voltage detection circuit 20 and the fully-opened detection circuit 10; It also includes an external PWM control signal connected to the input end of the logic processing circuit 50 .

[0028] 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 opening and output it to the logic processing circuit 50; the fully turned-on detection circuit 10 is used to detect whether there is a large 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 detect the gate voltage of the high-voltage silicon carbide MOSFET to be protected according to the fully turned-on detection circuit 10, the drain-source voltage detection circuit 20, and the gate voltage detection circuit 30. The output signal of the voltage detection circuit 30 determines whether the high-voltage silicon carbide MOSFET to be protected has a hard switch short circuit fault or a load short circuit fault, and then 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 according to the judgment result of the logic processing circuit 50; the first drive circuit 40 is used to provide the high-voltage silicon carbide MOSFET to be protected with the drive signal required for turning it on or off according to the first level signal; the second drive circuit 60 is used to provide an on or off signal to the full turn-on detection circuit 10 and the drain-source voltage detection circuit 20 according to the first level signal.

[0029] The protection circuit of the high-voltage silicon carbide MOSFET provided by the present invention has the function of real-time monitoring of the high-voltage silicon carbide MOSFET to be protected, and can timely identify and handle short-circuit faults, thereby providing comprehensive circuit protection for the high-voltage silicon carbide MOSFET. Once the MOSFET fails, the circuit can respond immediately, and the identification of the hard switch short-circuit fault is realized by the coordinated work of the fully open detection circuit and the gate voltage detection circuit, and the identification of the load short-circuit fault is realized by the setting of the fully open detection circuit and the drain-source voltage detection circuit; when it is identified that the high-voltage silicon carbide MOSFET to be protected has a hard switch short-circuit fault and a load short-circuit fault, the logic processing circuit can quickly receive the relevant signal and make an accurate judgment, lock the external PWM control signal, and output the corresponding level signal, and the level signal passes through the first drive circuit and the second drive circuit to realize the rapid shutdown of the MOSFET, effectively protecting the device.

[0030] 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 MOS tube M2 and a first comparator COM1; 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, 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 is grounded, the source of the second MOS tube M2 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, 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 drive circuit is connected to the gate of the second MOS tube M2.

[0031] High-voltage silicon carbide MOSFET is prone to flashover failure under high-voltage conditions. Flashover failure requires short-circuit protection to have a shorter response time. In the protection circuit provided by the present invention, in the drain-source voltage detection circuit, the first capacitor C1 and the first resistor R1 are used to make the potential of their connection point follow the drain-source voltage after the high-voltage silicon carbide MOSFET to be protected is normally turned on, and 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] The capacitance of the first capacitor C1 and the resistance of the first resistor R1 can be set according to actual conditions 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.

[0033] Specifically, the fully turned-on detection circuit 10 includes a second diode D2, a second capacitor C2, a first MOS transistor 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 respectively connected to the first end of the second capacitor C2 and the drain of the first MOS tube M1, the second end of the second capacitor C2, the source of the first MOS tube M1 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, the reverse input end of the second comparator COM2 is respectively connected to the anode of the second diode D2 and the drain of the first MOS tube M1, the forward input end of the second comparator COM2 is connected to the second preset reference voltage, 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 tube M1.

[0034] 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 the 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 resistance of the protection circuit. Among them, the second capacitor C2 is used to store the charge transferred during the drain-source voltage drop process of the high-voltage silicon carbide MOSFET to be protected. The capacitance value of the second capacitor C2 can be set according to actual conditions 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 and output it to the logic processing circuit 50.

[0035] Specifically, the gate voltage detection circuit 30 includes 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, and the output end of the third comparator COM3 is connected to the input end of the logic processing circuit 50.

[0036] The third comparator COM2 is used for comparing the gate voltage signal with the reference voltage to generate a digital signal and output it to the logic processing circuit 50 .

[0037] Specifically, the logic processing circuit 50 includes a first trigger U1, a second trigger U2, an inverter U3 and a logic NOR gate U4; The first input terminal of the logic NOR gate U4 is connected to the external PWM control signal, the clock input terminal of the first trigger U1 is connected to the output terminal of the first comparator COM1, the data input terminal of the first trigger U1 is connected to the output terminal of the second comparator COM2, the output terminal of the first trigger U1 is connected to the second input terminal of the logic NOR gate U4, the third input terminal of the logic NOR gate U4 is connected to the output terminal of the second trigger U2, and the output terminal of the logic NOR gate U4 is respectively connected to the input terminal of the first driving circuit 40 and the input terminal of the second driving circuit 60. The clock input terminal of the second trigger U2 is connected to the output terminal of the third comparator COM3, the data input terminal of the second trigger U2 is connected to the output terminal of the inverter U3, and the input terminal of the inverter U3 is connected to the output terminal of the second comparator COM2.

[0038] Specifically, the first trigger U1 and the second trigger U2 are D triggers, RS triggers, or chips including RS trigger circuit functions, which helps to improve the response speed of the protection circuit.

[0039] Specifically, the first driving circuit 40 adopts a push-pull driving circuit for current expansion.

[0040] Specifically, the second driving circuit 60 uses a driving chip to drive the first MOS tube M1 and the second MOS tube M2; the driving chip can realize a single signal input, and simultaneously drive the first MOS tube PMOS tube M1 and the second MOS tube NMOS tube M2 to turn on or off, and simultaneous opening can realize internal signal reset of the drain-source voltage detection circuit 20 and the full opening detection circuit 10.

[0041] See also Figure 2 , Figure 3 and Figure 4, in the normal turn-on process, the gate voltage of the high-voltage silicon carbide MOSFET to be protected gradually rises. After the gate voltage reaches the threshold voltage, the current flowing through the high-voltage silicon carbide MOSFET to be protected gradually rises. After the gate voltage reaches the Miller voltage, the current reaches the peak value, and the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected gradually decreases and the gate voltage will maintain the Miller voltage for a period of time; after that, the gate voltage gradually rises; in the hard turn-on short-circuit fault process, the gate voltage of the high-voltage silicon carbide MOSFET to be protected gradually rises. After the gate voltage reaches the threshold voltage, the current flowing through the high-voltage silicon carbide MOSFET to be protected rises sharply, and the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected drops slightly and then rises to the bus voltage, and there is no Miller platform for the gate voltage; in the load short-circuit fault process, this fault occurs after normal conduction. After the fault occurs, the current flowing through the high-voltage silicon carbide MOSFET to be protected rises sharply, and the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected gradually increases with the increase of current, and finally rises to the bus voltage.

[0042] 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 MOS tube M1 and the second MOS tube M2 are both in the on state, the outputs of the full-on detection circuit 10, the drain-source voltage detection circuit 20, and the gate voltage detection circuit 30 are all low level, and the external PWM control signal (low level signal) is input to the logic processing circuit 50, and the logic processing circuit 50 outputs a high level to the first drive circuit 40 and the second drive circuit 60. The first drive circuit 40 provides the drive signal required for turning on the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit 60 provides the drive signal required for turning off to the first MOS tube M1 and the second MOS tube M2.

[0043] Under normal circumstances, that is, when the high-voltage silicon carbide MOSFET to be protected does not have a hard switch short circuit fault or a load short circuit fault, the gate voltage of the high-voltage silicon carbide MOSFET to be protected gradually increases, the gate voltage reaches the threshold voltage, and 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.

[0044] Under high-voltage conditions, the drain-source voltage drop rate of the high-voltage silicon carbide MOSFET to be protected can reach tens or even hundreds of volts per nanosecond. Due to the junction capacitance of the first diode D1 itself, tens or even hundreds of milliamperes of current will be generated during the process of the drain-source voltage drop of the high-voltage silicon carbide MOSFET to be protected, causing the voltage at the first end of the second capacitor C2 to drop. After the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected drops significantly, the voltage at the first end of the second capacitor C2 is 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 platform voltage, and outputs a high level to the logic processing circuit 50. The logic processing circuit 50 determines that the high-voltage silicon carbide MOSFET to be protected has not suffered a hard switching short circuit fault based on the signals of the fully turned-on detection circuit 10 and the gate voltage detection circuit 30.

[0045] After normal opening, 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, and outputs a low level to the logic processing circuit 50. The logic processing circuit 50 determines that the high-voltage silicon carbide MOSFET to be protected has not suffered a hard switch short circuit fault or a load short circuit fault based on the signals of the full opening detection circuit 10 and the drain-source voltage detection circuit 20, and combines the external PWM control signal (low level signal) input to its first input terminal, so that the drive signal input to the first drive circuit 40 and the second drive circuit 60 is always maintained as a high level signal, so that the drive signal required to turn on the high-voltage silicon carbide MOSFET to be protected can be provided to the high-voltage silicon carbide MOSFET to be protected, thereby realizing the normal operation of the high-voltage silicon carbide MOSFET to be protected.

[0046] When a hard switch short circuit fault occurs, the gate voltage of the high-voltage silicon carbide MOSFET to be protected gradually increases, and the gate voltage reaches the threshold voltage. The current flowing through the high-voltage silicon carbide MOSFET to be protected rises sharply. After the gate voltage of the high-voltage silicon carbide MOSFET to be protected reaches the Miller voltage, there is no Miller platform. The drain-source voltage of the high-voltage silicon carbide MOSFET to be protected drops slightly and then rises to the bus voltage; the voltage at the first end of the second capacitor drops slightly, but is higher than the preset reference voltage V th2 , the 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 input into a high level to the data input terminal of the second trigger U2 after passing through the inverter U3, the gate voltage detection circuit 30 detects that the gate voltage is significantly higher than the Miller platform voltage, and outputs a high level to the data input terminal of the second trigger U2 in the logic processing circuit 50 to latch the data, the second trigger 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 driving signal required to turn off the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit provides the driving signal required to turn on the first MOS tube M1 and the second MOS tube M2.

[0047] When a load short circuit fault occurs, the high-voltage silicon carbide MOSFET to be protected 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 high-voltage silicon carbide MOSFET to be protected rises sharply, and the drain-source voltage of the high-voltage silicon carbide MOSFET to be protected rises with the current. 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 terminal of the first trigger U1 in the logic processing circuit 50, latches the high level signal, the first trigger 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, and the second drive circuit 60 provides the drive signal required to turn on the first MOS tube M1 and the second MOS tube M2.

[0048] Thus, the short circuit / overcurrent fault of the high-voltage silicon carbide MOSFET to be protected can be quickly detected and the high-voltage silicon carbide MOSFET to be protected can be quickly and timely shut down to protect the device safety. Compared with the existing short circuit / protection circuit, it has a shorter detection time, can take into account strong noise resistance, simple low cost and fast response at the same time, can quickly and accurately detect the short circuit of the high-voltage silicon carbide device and shut it down in time, thereby protecting the safe operation of the high-voltage silicon carbide MOSFET device.

[0049] Based on the same inventive concept, the present invention also provides a protection device for a high-voltage silicon carbide MOSFET, and the device includes the above-mentioned protection circuit for the high-voltage silicon carbide MOSFET.

[0050] Based on the same inventive concept, the present invention also provides a method for protecting a high-voltage silicon carbide MOSFET, using the protection device for the high-voltage silicon carbide MOSFET as described above, comprising the following steps: 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 platform voltage, it is determined that the high-voltage silicon carbide MOSFET to be protected is a hard switch short circuit fault; When the fully turned-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 obviously beyond the normal range, it is determined 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 switch short-circuit fault, the external PWM control signal inputs the first level signal A to the logic processing circuit 50, and 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, and the first drive circuit 40 provides the high-voltage silicon carbide MOSFET to be protected with the drive signal required for turning on or off the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit 60 provides a turn-off or turn-on signal to the full turn-on detection circuit 10 and the drain-source voltage detection circuit 20; When a load short circuit fault or a hard switch short circuit fault is identified in the high-voltage silicon carbide MOSFET to be protected, the external PWM control signal is locked, and the logic processing circuit 50 outputs a first level signal A to the first drive circuit 40 and the second drive circuit 60 respectively, and the first drive circuit 40 provides the high-voltage silicon carbide MOSFET to be protected with the drive signal required to shut down the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit 60 provides an opening signal to the full opening detection circuit 10 and the drain-source voltage detection circuit 20.

[0051] Finally, it should be noted that the above-listed embodiments exist only as one or more specific forms of expression of the technical solution of the present invention. Their purpose is to clearly explain the concept, principle and application of the present invention through specific examples, and it is by no means intended to limit the protection scope of the present invention to these specific embodiments. In fact, the real value of the present invention lies in the technical ideas and innovations it proposes, rather than its form of expression or means of implementation.

[0052] For ordinary technicians in the relevant technical field, after in-depth reading and understanding of the technical solution of the present invention, they are fully capable of making various forms of changes, modifications or equivalent substitutions to the specific implementation methods of the invention based on their own professional knowledge and skills. These changes may include but are not limited to: adjusting the value range of technical parameters, optimizing algorithm processes to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as these changed technical solutions still substantially maintain the technical features claimed for protection by the original invention, that is, they can still achieve the core functions and effects of the present invention, then these changes should be deemed to fall within the scope of protection of the pending claims of the present invention.

[0053] In addition, with the continuous progress and development of technology, new technical means and methods continue to emerge, which also provides broad space for further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and extensions based on the existing technology. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are also protected by patent rights.

Claims

1. A protection circuit for a high voltage silicon carbide MOSFET, characterized in that: It comprises a drain-source voltage detection circuit (20), a fully turned-on detection circuit (10), a gate voltage detection circuit (30), a logic processing circuit (50), a first drive circuit (40) and a second drive circuit (60); The input end 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 end of the fully-opened detection circuit (10) is connected to the drain of the high-voltage silicon carbide MOSFET to be protected, the input end of the gate voltage detection circuit (30) is connected to the gate of the high-voltage silicon carbide MOSFET to be protected, and the drain-source voltage detection circuit (20), the fully-opened detection circuit (10) and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together; The output end of the logic processing circuit (50) is connected to the gate of the high-voltage silicon carbide MOSFET to be protected via the first drive circuit (40); the input end of the logic processing circuit (50) is respectively connected to the output ends of the drain-source voltage detection circuit (20), the full-on detection circuit (10) and the gate voltage detection circuit (30); the output end of the logic processing circuit (50) is also connected to the input end of the second drive circuit (60); the output end of the second drive circuit (60) is respectively connected to the input ends of the drain-source voltage detection circuit (20) and the full-on detection circuit (10); It also includes an external PWM control signal connected to the input end of the logic processing circuit (50).

2. A protection circuit for a high voltage silicon carbide MOSFET according to claim 1, characterized in that: 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 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, and the negative 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 is grounded, the source of the second MOS tube M2 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, 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 drive circuit is connected to the gate of the second MOS tube M2.

3. A protection circuit for a high voltage silicon carbide MOSFET according to claim 2, characterized in that: The fully-open detection circuit (10) comprises a second diode D2, a second capacitor C2, a first MOS transistor 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 tube M1 respectively, the second end of the second capacitor C2, the source of the first MOS tube M1 and the source of the high-voltage silicon carbide MOSFET to be protected are grounded together, 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 tube M1 respectively, and 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 driving circuit is connected to the gate of the first MOS tube M1.

4. A protection circuit for a high voltage silicon carbide MOSFET according to claim 3, characterized in that: 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, and the reverse input end of the third comparator COM3 is connected to the third preset reference voltage V th3 The output end of the third comparator COM3 is connected to the input end of the logic processing circuit (50).

5. A protection circuit for a high voltage silicon carbide MOSFET according to claim 4, characterized in that: The logic processing circuit (50) comprises a first trigger U1, a second trigger U2, an inverter U3 and a logic NOR gate U4; The first input terminal of the logic NOR gate U4 is connected to the external PWM control signal, the clock input terminal of the first trigger U1 is connected to the output terminal of the first comparator COM1, the data input terminal of the first trigger U1 is connected to the output terminal of the second comparator COM2, the output terminal of the first trigger U1 is connected to the second input terminal of the logic NOR gate U4, the third input terminal of the logic NOR gate U4 is connected to the output terminal of the second trigger U2, and the output terminal of the logic NOR gate U4 is respectively connected to the input terminal of the first drive circuit (40) and the input terminal of the second drive circuit (60); The clock input terminal of the second trigger U2 is connected to the output terminal of the third comparator COM3, the data input terminal of the second trigger U2 is connected to the output terminal of the inverter U3, and the input terminal of the inverter U3 is connected to the output terminal of the second comparator COM2.

6. A protection circuit for a high voltage silicon carbide MOSFET according to claim 5, characterized in that: The first trigger U1 and the second trigger U2 are D triggers, RS triggers or chips including RS trigger circuit functions.

7. A protection circuit for a high voltage silicon carbide MOSFET according to claim 1, characterized in that: The first drive circuit (40) adopts a push-pull drive circuit for current expansion.

8. A protection circuit for a high voltage silicon carbide MOSFET according to claim 1, characterized in that: The second driving circuit (60) uses a driving chip, and is used to drive the first MOS transistor M1 and the second MOS transistor M2.

9. A protection device for a high voltage silicon carbide MOSFET, characterized in that: The device comprises a protection circuit for a high-voltage silicon carbide MOSFET as described in any one of claims 1 to 8.

10. A method for protecting a high voltage silicon carbide MOSFET, characterized in that: The protection device for high-voltage silicon carbide MOSFET as claimed in claim 9 comprises the following steps: 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 platform voltage, it is determined that the high-voltage silicon carbide MOSFET to be protected is a hard switch short circuit fault; When the fully turned-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 obviously beyond a normal range, it is determined that the high-voltage silicon carbide MOSFET to be protected is at 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 switch short-circuit fault, the external PWM control signal inputs a first level signal A to the logic processing circuit (50), the logic processing circuit (50) outputs an 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 high-voltage silicon carbide MOSFET to be protected with a drive signal required for turning on or off the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit (60) provides a turn-off or turn-on signal to the full turn-on detection circuit (10) and the drain-source voltage detection circuit (20); When a load short circuit fault or a hard switch short circuit fault is identified in the high-voltage silicon carbide MOSFET to be protected, the external PWM control signal is locked, and 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 high-voltage silicon carbide MOSFET to be protected with a drive signal required for shutting down the high-voltage silicon carbide MOSFET to be protected, and the second drive circuit (60) provides an on signal to the full on detection circuit (10) and the drain-source voltage detection circuit (20).

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