Short circuit protection circuit for SiC power devices

Abstract

The application relates to the field of power electronics, in particular to a short-circuit protection circuit of a SiC power device, which comprises a driving unit, a short-circuit voltage adaptation unit and a short-circuit protection action unit; the driving unit is used for driving the SiC power device according to a driving signal when the driving signal is received; the SiC power device is turned off when a turn-off signal is received; the short-circuit voltage adaptation unit is used for monitoring the on-voltage of the SiC power device in real time; a short-circuit trigger signal is generated and transmitted to the short-circuit protection action unit when the on-voltage is greater than the short-circuit threshold voltage for a duration greater than the blanking time; the size of the on-voltage and the size of the blanking time are in a linear inverse relationship; the short-circuit protection action unit is used for receiving the driving signal and transmitting the driving signal to the driving unit; a turn-off signal is generated and transmitted to the driving unit when the short-circuit trigger signal is received, so that the blanking time is more adaptive to different bus voltages, the short-circuit protection is more accurate, and the performance requirement of the SiC power device is met.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a short-circuit protection circuit for a SiC power device. Background Art

[0002] Compared to silicon devices, SiC (silicon carbide) power devices offer performance advantages such as low on-state resistance, fast switching speed, and high thermal conductivity. These advantages help improve converter efficiency and power density, and they are widely used in integrated circuits to enhance overall performance. However, in practical applications, SiC power devices inevitably operate in conditions such as overload and desaturation, which can cause short circuits in the SiC power devices. Furthermore, due to their characteristics and application environment, SiC power devices are more sensitive to various types of short-circuit faults and are prone to false triggering. This requires them to have short-circuit fault protection capabilities to protect themselves and the integrated circuits they are used in, and to be able to implement protective measures in the event of short-circuit faults such as overload and desaturation. Therefore, the performance of the short-circuit protection circuit of SiC power devices is key to whether short-circuit protection can be implemented quickly and accurately.

[0003] Existing short-circuit protection circuits typically determine whether a short-circuit fault has occurred by detecting the on-state voltage (e.g., drain-source voltage) of SiC power devices (e.g., SiC-MOSFETs). An RC charge-discharge circuit is then configured to adapt to different short-circuit voltages. The time it takes for the RC charge-discharge circuit to charge to the short-circuit threshold voltage is the adapted reserved blanking time, which is used to prevent the SiC power device from falsely triggering short-circuit protection due to disturbances.

[0004] When a SiC power device experiences a short-circuit fault, the short-circuit voltage will vary depending on the bus voltage to which it is connected. Therefore, the short-circuit protection response time of the SiC power device should also vary to avoid false triggering. However, if the resistance and capacitance specifications of the RC charge-discharge circuit are fixed, different short-circuit voltages have little effect on the time it takes for the RC charge-discharge circuit to charge to the short-circuit threshold voltage. In other words, the reserved blanking time is essentially constant. This results in the reserved blanking time not being able to adapt to different bus voltages. When the bus voltage changes, the reserved blanking time does not match the actual short-circuit protection response time. If the reserved blanking time is too long, it will affect the performance of the SiC power device and is not suitable for applications involving high-frequency switching power devices. If the reserved blanking time is too short, the short-circuit protection may be falsely triggered. (For example, if the SiC power device is a SiC-MOSFET, a brief, narrow pulse during normal conduction can cause the SiC-MOSFET to temporarily desaturate. If the reserved blanking time is too short, it will be too sensitive and directly trigger the short-circuit protection.)

[0005] More importantly, the short-circuit withstand time of SiC power devices is usually short. For example, the short-circuit withstand time of SiC-MOSFET is only 2 to 7 seconds. Moreover, the higher the bus voltage connected to the SiC power device, the shorter the short-circuit withstand time. Therefore, this requires that the reserved blanking time and the short-circuit voltage must be highly matched. Obviously, the existing short-circuit protection circuit cannot meet this requirement. Summary of the Invention

[0006] In view of the above-mentioned defects, the purpose of the present invention is to propose a short-circuit protection circuit for SiC power devices, whose blanking time is more adaptable to different bus voltages, the short-circuit protection is more accurate, and it better meets the performance requirements of SiC power devices.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A short-circuit protection circuit for a SiC power device comprises a drive unit, a short-circuit voltage adaptation unit, and a short-circuit protection action unit; an input terminal of the short-circuit protection action unit is externally connected to a drive signal, an output terminal of the short-circuit protection action unit is electrically connected to the input terminal of the drive unit, a drive terminal of the SiC power device and a feedback terminal of the short-circuit voltage adaptation unit are both electrically connected to the output terminal of the drive unit, a conduction voltage terminal of the SiC power device is electrically connected to the input terminal of the short-circuit voltage adaptation unit, and an output terminal of the short-circuit voltage adaptation unit is electrically connected to a trigger terminal of the short-circuit protection action unit;

[0009] The driving unit is configured to drive the SiC power device according to the driving signal when receiving the driving signal; and shut down the SiC power device when receiving the shut-down signal;

[0010] The short-circuit voltage adaptation unit is used to monitor the on-state voltage of the SiC power device in real time; when the on-state voltage is greater than the short-circuit threshold voltage for a duration greater than the blanking time, a short-circuit trigger signal is generated and transmitted to the short-circuit protection action unit; the magnitude of the on-state voltage and the magnitude of the blanking time are in a linear inverse proportional relationship;

[0011] The short-circuit protection action unit is used to receive the driving signal and transmit it to the driving unit; when receiving the short-circuit trigger signal, it generates the shutdown signal and transmits it to the driving unit.

[0012] Furthermore, the short-circuit voltage adaptation unit includes a trigger-type acquisition circuit, an isolation circuit, and a trigger-type judgment circuit; the input end of the trigger-type acquisition circuit is used as the input end of the short-circuit voltage adaptation unit, the feedback end of the trigger-type judgment circuit is used as the feedback end of the short-circuit voltage adaptation unit, and the output end of the trigger-type judgment circuit is used as the output end of the short-circuit voltage adaptation unit;

[0013] The output end of the trigger acquisition circuit is electrically connected to the input end of the isolation circuit, and the output end of the isolation circuit is electrically connected to the input end of the trigger judgment circuit;

[0014] The short-circuit threshold voltage includes a first threshold voltage and a second threshold voltage;

[0015] The trigger acquisition circuit is used to monitor the conduction voltage in real time; when the conduction voltage is greater than the first threshold voltage, the conduction voltage is transmitted to the trigger judgment circuit via the isolation circuit;

[0016] The trigger judgment circuit is configured to, when receiving the conduction voltage, determine that a value decreases, and the magnitude of the conduction voltage is linearly proportional to the rate of decrease of the judgment value; if the judgment value decreases to less than the second threshold voltage, the short-circuit trigger signal is generated; and the time for the trigger judgment circuit to decrease to less than the second threshold voltage is the blanking time;

[0017] The isolation circuit is used to electrically isolate the trigger-type acquisition circuit and the trigger-type judgment circuit.

[0018] Furthermore, the trigger judgment circuit includes a NOT gate U1, a MOS tube M1, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a comparator A2 and a Schmitt trigger U5; the input end of the NOT gate U1 is used as the feedback end of the trigger judgment circuit, one end of the resistor R6 is used as the input end of the trigger judgment circuit, and the output end of the Schmitt trigger U5 is used as the output end of the trigger judgment circuit;

[0019] The other end of the resistor R6, one end of the capacitor C1, and the source of the MOS transistor M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS transistor M1 is electrically connected to the output end of the NOT gate U1, the drain of the MOS transistor M1 is electrically connected to one end of the resistor R8, the other end of the resistor R8, the other end of the capacitor C1, and the input end of the Schmitt trigger U5 are all electrically connected to the output end of the comparator A2, the positive input end of the comparator A2 is electrically connected to one end of the resistor R7, and the other end of the resistor R7 is grounded.

[0020] Furthermore, the short-circuit protection action unit includes an AND gate U2, an AND gate U4 and a rising edge trigger U3; the first input end of the AND gate U2 is used as the trigger end of the short-circuit protection action unit, the second input end of the AND gate U2 is used as the input end of the short-circuit protection action unit, and the output end of the AND gate U4 is used as the output end of the short-circuit protection action unit;

[0021] The first input terminal of the AND gate U2 is electrically connected to the input terminal of the rising edge trigger U3, the output terminal of the AND gate U2 is electrically connected to the clock terminal of the rising edge trigger U3, the input terminal of the AND gate U4 is electrically connected to the second input terminal of the AND gate U2, and the inverting input terminal of the AND gate U4 is electrically connected to the output terminal of the rising edge trigger U3.

[0022] Furthermore, the trigger acquisition circuit includes a diode D1, a resistor R2, and a resistor element R1; the cathode of the diode D1 serves as the positive electrode of the input end of the trigger acquisition circuit, one end of the resistor R2 serves as the negative electrode of the input end of the trigger acquisition circuit, and one end of the resistor element R1 serves as the output end of the trigger acquisition circuit;

[0023] An anode of the diode D1 is electrically connected to the other end of the resistor R1 , and one end of the resistor R1 is electrically connected to the other end of the resistor R2 .

[0024] Furthermore, the isolation circuit includes a resistor R4, a resistor R5 and a comparator A1; one end of the resistor R4 is used as an input end of the isolation circuit, and the output end of the comparator A1 is used as an output end of the isolation circuit;

[0025] The other end of the resistor R4 is electrically connected to the positive input end of the comparator A1, one end of the resistor R5 is electrically connected to the negative input end of the comparator A1, and the other end of the resistor R5 is electrically connected to the output end of the comparator A1.

[0026] Furthermore, the trigger judgment circuit is used to, when receiving the conduction voltage, the judgment value rises, and the magnitude of the conduction voltage is linearly proportional to the rising speed of the judgment value; if the judgment value rises to be greater than the second threshold voltage, the short-circuit trigger signal is generated; the time for the trigger judgment circuit to rise to be greater than the second threshold voltage is the blanking time.

[0027] Furthermore, the rising edge trigger U3 is a D trigger with a clear terminal; the D terminal of the D trigger is used as the input terminal of the rising edge trigger U3, the Q terminal of the D trigger is used as the output terminal of the rising edge trigger U3, and the CLK terminal of the D trigger is used as the clock terminal of the rising edge trigger U3.

[0028] Furthermore, the resistor R1 is a single large resistor whose resistance is much greater than that of the resistor R2, one end of the large resistor serves as one end of the resistor R1, and the other end of the large resistor serves as the other end of the resistor R1;

[0029] Or the resistor R1 is a series resistor circuit with a total resistance much larger than the resistance R2, and the series resistor circuit is composed of a plurality of small resistors, the other end of the first small resistor and the one end of the last small resistor are electrically connected, the one end of the first small resistor is used as one end of the resistor R1, and the other end of the last small resistor is used as the other end of the resistor R1.

[0030] The technical scheme provided by the application can have the following beneficial effects: taking SiC-MOSFET as an example of the SiC power device, the gate of the SiC-MOSFET is used as the driving end of the SiC power device, the drain of the SiC-MOSFET is used as the positive electrode of the conduction voltage end of the SiC power device, and the source of the SiC-MOSFET is used as the negative electrode of the conduction voltage end of the SiC power device, so that the SiC-MOSFET normally works under the driving of the driving unit; when the SiC-MOSFET has a short-circuit fault such as overload and desaturation, the voltage between the drain and the source of the SiC-MOSFET (i.e. the conduction voltage) will rise to the voltage of the bus to which the SiC-MOSFET is connected, and the higher the bus voltage, the shorter the tolerance time of the SiC-MOSFET; therefore, the short-circuit voltage adaptation unit monitors the conduction voltage of the SiC power device in real time, generates a short-circuit trigger signal when the conduction voltage is greater than the short-circuit threshold voltage for a duration greater than the blanking time, and transmits the short-circuit trigger signal to the short-circuit protection action unit, so that the short-circuit protection action unit enables the driving unit to turn off the SiC power device to achieve protection and prevent false triggering of the short-circuit protection; and since the size of the conduction voltage and the size of the blanking time are in a linear inverse relationship, compared with the RC charging and discharging circuit which makes the size of the conduction voltage (short-circuit voltage) and the size of the blanking time in a parabolic inverse relationship (i.e. facing different short-circuit voltages, the blanking time changes very little), facing different conduction voltages, the blanking time changes linearly, so that the blanking time is more adaptive to different bus voltages; and finally, the short-circuit protection is more accurate and more in line with the performance requirements of the SiC power device. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a circuit schematic diagram of a short-circuit protection circuit of a SiC power device according to one embodiment of the application.

[0032] Figure 2 is a Vc-t waveform diagram of the trigger type judgment circuit as Figure 1 indicated.

[0033] Among them: driving unit 1, short-circuit voltage adaptation unit 2, short-circuit protection action unit 3, SiC power device 4, trigger acquisition circuit 21, isolation circuit 22, trigger judgment circuit 23, NOT gate U1, MOS tube M1, resistor R6, resistor R7, resistor R8, capacitor C1, comparator A2, Schmitt trigger U5, AND gate U2, AND gate U4, rising edge trigger U3, diode D1, resistor R2, resistor element R1, resistor R4, resistor R5, comparator A1. DETAILED DESCRIPTION

[0034] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0035] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically specified.

[0036] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediate medium; they may refer to internal communication between two components or an interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0037] The following combination Figures 1 to 2 , describes a short-circuit protection circuit of a SiC power device according to an embodiment of the present invention.

[0038] A short-circuit protection circuit for a SiC power device includes a drive unit 1, a short-circuit voltage adaptation unit 2, and a short-circuit protection action unit 3; an input terminal of the short-circuit protection action unit 3 is externally connected to a drive signal, an output terminal of the short-circuit protection action unit 3 is electrically connected to the input terminal of the drive unit 1, a drive terminal of a SiC power device 4 and a feedback terminal of the short-circuit voltage adaptation unit 2 are both electrically connected to the output terminal of the drive unit 1, a conduction voltage terminal of the SiC power device 4 is electrically connected to the input terminal of the short-circuit voltage adaptation unit 2, and an output terminal of the short-circuit voltage adaptation unit 2 is electrically connected to a trigger terminal of the short-circuit protection action unit 3;

[0039] The driving unit 1 is configured to drive the SiC power device 4 according to the driving signal when receiving the driving signal; and to shut down the SiC power device 4 when receiving the shut-down signal;

[0040] The short-circuit voltage adaptation unit 2 is used to monitor the on-state voltage of the SiC power device 4 in real time; when the on-state voltage is greater than the short-circuit threshold voltage for a period longer than the blanking time, a short-circuit trigger signal is generated and transmitted to the short-circuit protection action unit 3; the magnitude of the on-state voltage and the magnitude of the blanking time are inversely proportional to each other;

[0041] The short-circuit protection action unit 3 is used to receive a driving signal and transmit it to the driving unit 1 ; when a short-circuit trigger signal is received, a shutdown signal is generated and transmitted to the driving unit 1 .

[0042] The present invention proposes a preferred embodiment of a short-circuit protection circuit for a SiC power device, as shown in FIG. Figure 1 As shown, the SiC power device 4 takes SiC-MOSFET as an example, the gate of the SiC-MOSFET is used as the driving end of the SiC power device 4, the drain of the SiC-MOSFET is used as the positive electrode of the on-voltage end of the SiC power device 4, and the source of the SiC-MOSFET is used as the negative electrode of the on-voltage end of the SiC power device 4. Then, the SiC-MOSFET works normally when driven by the driving unit 1; when the SiC-MOSFET has a short-circuit fault such as overload or desaturation, it will cause the voltage between the drain and source of the SiC-MOSFET (i.e., the on-voltage) to rise to the voltage of the bus to which it is connected. The higher the bus voltage is, the shorter the tolerance time of the SiC-MOSFET is; therefore, the short-circuit voltage adaptation unit 2 is used to monitor the voltage in real time. The on-state voltage of the SiC power device 4, when the on-state voltage is greater than the short-circuit threshold voltage for a duration greater than the blanking time, generates a short-circuit trigger signal and transmits it to the short-circuit protection action unit 3, which enables the driving unit 1 to shut down the SiC power device 4 to achieve protection and prevent false triggering of the short-circuit protection; and since the magnitude of the on-state voltage and the magnitude of the blanking time are in a linear inverse proportional relationship, compared to the RC charge and discharge circuit that makes the magnitude of the on-state voltage (short-circuit voltage) and the magnitude of the blanking time in a parabolic inverse proportional relationship (that is, the blanking time changes very little in the face of different short-circuit voltages), the blanking time changes linearly in the face of different on-state voltages, thereby making the blanking time more adaptable to different bus voltages; ultimately, the short-circuit protection is more accurate and more in line with the performance requirements of the SiC power device.

[0043] Furthermore, the short-circuit voltage adaptation unit 2 includes a trigger-type acquisition circuit 21, an isolation circuit 22, and a trigger-type judgment circuit 23; the input end of the trigger-type acquisition circuit 21 is used as the input end of the short-circuit voltage adaptation unit 2, the feedback end of the trigger-type judgment circuit 23 is used as the feedback end of the short-circuit voltage adaptation unit 2, and the output end of the trigger-type judgment circuit 23 is used as the output end of the short-circuit voltage adaptation unit 2;

[0044] The output end of the trigger acquisition circuit 21 is electrically connected to the input end of the isolation circuit 22, and the output end of the isolation circuit 22 is electrically connected to the input end of the trigger judgment circuit 23;

[0045] The short-circuit threshold voltage includes a first threshold voltage and a second threshold voltage;

[0046] The trigger acquisition circuit 21 is used to monitor the conduction voltage in real time; when the conduction voltage is greater than the first threshold voltage, the conduction voltage is transmitted to the trigger judgment circuit 23 via the isolation circuit 22;

[0047] The trigger judgment circuit 23 is configured to determine a decrease in the judgment value when receiving the conduction voltage, and the magnitude of the conduction voltage is linearly proportional to the rate of decrease of the judgment value; if the judgment value decreases to less than a second threshold voltage, a short-circuit trigger signal is generated; the time during which the trigger judgment circuit 23 decreases to less than the second threshold voltage is the blanking time;

[0048] The isolation circuit 22 is used to electrically isolate the trigger-type acquisition circuit 21 and the trigger-type judgment circuit 23 .

[0049] In this embodiment, in order to realize the generation of blanking time according to the linear inverse relationship between the magnitude of the conduction voltage, the short-circuit threshold voltage is set as two thresholds, the first threshold voltage and the second threshold voltage, to limit the blanking time; wherein the first threshold voltage is the trigger value used by the trigger acquisition circuit 21 to determine whether a short-circuit fault occurs. The trigger acquisition circuit 21 monitors the conduction voltage in real time. When the conduction voltage is greater than the first threshold voltage, it means that a short circuit occurs but it cannot be determined whether it is a permanent fault. Therefore, the conduction voltage is transmitted to the trigger judgment circuit 23 at this time; the second threshold voltage is the trigger judgment circuit 23 used to determine whether it is a short circuit. The trigger value of a permanent short-circuit fault is that after the trigger-type judgment circuit 23 receives the conduction voltage, the internal judgment value decreases accordingly. The decreasing speed of the judgment value is linearly proportional to the magnitude of the conduction voltage. If the judgment value decreases to less than the second threshold voltage, a short-circuit trigger signal is generated (indicating a permanent short-circuit fault). It can be seen that the time it takes for the trigger-type judgment circuit 23 to drop below the second threshold voltage is the blanking time. From this, the relationship can be derived: decreasing speed = second threshold voltage / blanking time. It can be deduced that the magnitude of the conduction voltage (short-circuit voltage) and the magnitude of the blanking time are linearly inversely proportional, which meets the requirements.

[0050] More importantly, the isolation circuit 22 is arranged between the trigger acquisition circuit 21 and the trigger judgment circuit 23 for electrical isolation, which can effectively isolate the drive unit 1 side and the short-circuit protection unit side, avoid mutual interference between the signals on both sides, and make the normal drive work and the short-circuit protection work run separately, thereby improving the stability of the short-circuit protection circuit and the integrated circuit.

[0051] Furthermore, the trigger judgment circuit 23 includes a NOT gate U1, a MOS transistor M1, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a comparator A2, and a Schmitt trigger U5; the input end of the NOT gate U1 serves as a feedback end of the trigger judgment circuit 23, one end of the resistor R6 serves as an input end of the trigger judgment circuit 23, and the output end of the Schmitt trigger U5 serves as an output end of the trigger judgment circuit 23;

[0052] The other end of the resistor R6, one end of the capacitor C1, and the source of the MOS transistor M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS transistor M1 is electrically connected to the output end of the NOT gate U1, the drain of the MOS transistor M1 is electrically connected to one end of the resistor R8, the other end of the resistor R8, the other end of the capacitor C1, and the input end of the Schmitt trigger U5 are all electrically connected to the output end of the comparator A2, the positive input end of the comparator A2 is electrically connected to one end of the resistor R7, and the other end of the resistor R7 is grounded.

[0053] In this embodiment, the second threshold voltage of the trigger judgment circuit 23 is the trigger value of the Schmitt trigger U5, and its function is realized in conjunction with the active integration circuit composed of the NOT gate U1, MOS transistor M1, resistor R6, resistor R7, resistor R8, capacitor C1 and comparator A2. Specifically, when a short circuit fault occurs, such as Figure 2 As shown, the active integration circuit will continue to receive the conduction voltage (the negative input terminal of the comparator A2 is at a high level), and the output voltage Vc (i.e., the judgment value) of the active integration circuit will continue to decrease as the duration of receiving the conduction voltage continues until it drops to the second threshold voltage to trigger the Schmitt trigger U5 to output a high level (short-circuit trigger signal). Due to the characteristics of the active integration circuit, the decreasing speed of the output voltage Vc will be linearly proportional to the magnitude of the conduction voltage, as shown in FIG. Figure 2 As can be seen from the multiple curves in Figure 1, each curve represents a bus voltage connected to SiC power device 4, with a blanking time of t1 and a slope representing the rate of decrease of output voltage Vc. After SiC power device 4 is turned off, MOS transistor M1 is used to provide feedback on the shutdown status of SiC power device 4, turning MOS transistor M1 on. Resistor R8 provides a discharge circuit for capacitor C1, preparing for the next short-circuit detection.

[0054] Furthermore, the short-circuit protection action unit 3 includes an AND gate U2, an AND gate U4, and a rising-edge trigger U3; the first input end of the AND gate U2 is used as a trigger end of the short-circuit protection action unit 3, the second input end of the AND gate U2 is used as an input end of the short-circuit protection action unit 3, and the output end of the AND gate U4 is used as an output end of the short-circuit protection action unit 3;

[0055] The first input terminal of the AND gate U2 is electrically connected to the input terminal of the rising edge trigger U3, the output terminal of the AND gate U2 is electrically connected to the clock terminal of the rising edge trigger U3, the input terminal of the AND gate U4 is electrically connected to the second input terminal of the AND gate U2, and the inverting input terminal of the AND gate U4 is electrically connected to the output terminal of the rising edge trigger U3.

[0056] In this embodiment, the short-circuit protection action unit 3 needs to cooperate with the circuit logic of the trigger judgment circuit 23 to realize the control of the SiC power device 4 to be turned on and off according to the driving signal during normal operation and to keep it turned off when a short-circuit fault occurs. Therefore, the logic circuit is composed of the AND gate U2, the AND gate U4 and the rising edge trigger U3; when a short-circuit fault occurs, the Schmitt trigger U5 outputs a high level (short-circuit trigger signal). At this time, regardless of the driving signal ( Figure 1 IN terminal) input high level or low level, AND gate U2 always outputs high level, rising edge trigger U3 always outputs high level and transmits it to AND gate U4 for inversion, so that AND gate U4 also always outputs low level, enabling driving unit 1 to turn off SiC power device 4; when working normally, Schmitt trigger U5 always outputs low level. Figure 1 The AND gate U2 outputs a low level regardless of whether the input is a high level or a low level. The rising edge trigger U3 outputs a low level and transmits it to the AND gate U4 for inversion, so that the AND gate U4 can enable the driving unit 1 to disconnect the SiC power device 4 according to the high and low level changes of the driving signal.

[0057] Furthermore, the trigger acquisition circuit 21 includes a diode D1, a resistor R2, and a resistor element R1; the cathode of the diode D1 serves as the positive electrode of the input end of the trigger acquisition circuit 21, one end of the resistor R2 serves as the negative electrode of the input end of the trigger acquisition circuit 21, and one end of the resistor element R1 serves as the output end of the trigger acquisition circuit 21;

[0058] An anode of the diode D1 is electrically connected to the other end of the resistor R1 , and one end of the resistor R1 is electrically connected to the other end of the resistor R2 .

[0059] In this embodiment, the first threshold voltage of the trigger acquisition circuit 21 is the reverse bias voltage threshold of the diode D1. Only when the short-circuit fault conduction voltage is too large can the diode D1 be reverse biased, and the conduction voltage is collected and transmitted to the isolation circuit 22 and the subsequent trigger judgment circuit 23 through the voltage divider circuit composed of the resistor R2 and the resistor element R1.

[0060] Furthermore, the isolation circuit 22 includes a resistor R4, a resistor R5 and a comparator A1; one end of the resistor R4 is used as an input end of the isolation circuit 22, and the output end of the comparator A1 is used as an output end of the isolation circuit 22;

[0061] The other end of the resistor R4 is electrically connected to the positive input terminal of the comparator A1 , one end of the resistor R5 is electrically connected to the negative input terminal of the comparator A1 , and the other end of the resistor R5 is electrically connected to the output terminal of the comparator A1 .

[0062] In this embodiment, the isolation circuit 22 is a voltage follower composed of resistors R4, R5 and comparator A1. Since the impedance of the voltage divider resistor of the trigger acquisition circuit 21 is much larger than the impedance of the active integration circuit of the trigger judgment circuit 23, the voltage follower can be used to operationally amplify the conduction voltage and transmit it to the active integration circuit for integration in the event of a short circuit. At the same time, the voltage follower can also play the role of isolation and buffering, thereby achieving the function of electrical isolation.

[0063] Furthermore, the trigger judgment circuit 23 is used to increase the judgment value when receiving the on-state voltage, and the magnitude of the on-state voltage is linearly proportional to the rising speed of the judgment value; if the judgment value rises to be greater than the second threshold voltage, a short-circuit trigger signal is generated; the time for the trigger judgment circuit 23 to rise to be greater than the second threshold voltage is the blanking time.

[0064] In this embodiment, since the triggering mode of the Schmitt trigger U5 can also be positive voltage triggering, the function of the trigger-type judgment circuit 23 can also be realized by utilizing the relationship of the rising judgment value.

[0065] Furthermore, the rising edge trigger U3 is a D trigger with a clear terminal; the D terminal of the D trigger is used as the input terminal of the rising edge trigger U3, the Q terminal of the D trigger is used as the output terminal of the rising edge trigger U3, and the CLK terminal of the D trigger is used as the clock terminal of the rising edge trigger U3.

[0066] In this embodiment, the rising edge trigger U3 is preferably a D trigger with a clear terminal. Its logic meets the requirements and the clear terminal is provided to ensure the reset of the trigger, avoiding short circuit protection reset delay or reset failure.

[0067] Furthermore, the resistor R1 is a single large resistor having a resistance much greater than that of the resistor R2, one end of the large resistor serves as one end of the resistor R1, and the other end of the large resistor serves as the other end of the resistor R1;

[0068] Alternatively, the resistor element R1 is a series resistor circuit with a total resistance much greater than that of the resistor R2. The series resistor circuit is composed of multiple small resistors connected in series. The other end of the previous small resistor is electrically connected to one end of the next small resistor. One end of the first small resistor is used as one end of the resistor element R1, and the other end of the last small resistor is used as the other end of the resistor element R1.

[0069] In this embodiment, the resistance of the resistor R1 is much greater than the resistance of the resistor R2 to form a voltage divider circuit, which can improve the acquisition accuracy.

[0070] Other structures and operations of a short-circuit protection circuit for a SiC power device according to an embodiment of the present invention are well known to those skilled in the art and will not be described in detail here.

[0071] Throughout this specification, reference to terms such as "embodiment" or "example" indicates that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0072] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A short-circuit protection circuit for a SiC power device, characterized in that: It includes a driving unit, a short-circuit voltage adaptation unit and a short-circuit protection action unit; the input end of the short-circuit protection action unit is externally connected to the driving signal, the output end of the short-circuit protection action unit is electrically connected to the input end of the driving unit, the driving end of the SiC power device and the feedback end of the short-circuit voltage adaptation unit are both electrically connected to the output end of the driving unit, the conduction voltage end of the SiC power device is electrically connected to the input end of the short-circuit voltage adaptation unit, and the output end of the short-circuit voltage adaptation unit is electrically connected to the trigger end of the short-circuit protection action unit; The driving unit is configured to drive the SiC power device according to the driving signal when receiving the driving signal; and shut down the SiC power device when receiving the shut-down signal; The short-circuit voltage adaptation unit is used to monitor the on-state voltage of the SiC power device in real time; when the on-state voltage is greater than the short-circuit threshold voltage for a duration greater than the blanking time, a short-circuit trigger signal is generated and transmitted to the short-circuit protection action unit; the magnitude of the on-state voltage and the magnitude of the blanking time are in a linear inverse proportional relationship; The short-circuit protection action unit is used to receive the driving signal and transmit it to the driving unit; when receiving the short-circuit trigger signal, it generates the shutdown signal and transmits it to the driving unit; The short-circuit voltage adaptation unit includes a trigger-type acquisition circuit, an isolation circuit, and a trigger-type judgment circuit; the input end of the trigger-type acquisition circuit is used as the input end of the short-circuit voltage adaptation unit, the feedback end of the trigger-type judgment circuit is used as the feedback end of the short-circuit voltage adaptation unit, and the output end of the trigger-type judgment circuit is used as the output end of the short-circuit voltage adaptation unit; The output end of the trigger acquisition circuit is electrically connected to the input end of the isolation circuit, and the output end of the isolation circuit is electrically connected to the input end of the trigger judgment circuit; The short-circuit threshold voltage includes a first threshold voltage and a second threshold voltage; The trigger acquisition circuit is used to monitor the conduction voltage in real time; when the conduction voltage is greater than the first threshold voltage, the conduction voltage is transmitted to the trigger judgment circuit via the isolation circuit; The trigger judgment circuit is configured to, when receiving the conduction voltage, determine that a value decreases, and the magnitude of the conduction voltage is linearly proportional to the rate of decrease of the judgment value; if the judgment value decreases to less than the second threshold voltage, the short-circuit trigger signal is generated; The time it takes for the trigger judgment circuit to drop below the second threshold voltage is the blanking time; The isolation circuit is used to electrically isolate the trigger-type acquisition circuit and the trigger-type judgment circuit.

2. The short-circuit protection circuit for a SiC power device according to claim 1, wherein: The trigger judgment circuit includes a NOT gate U1, a MOS tube M1, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a comparator A2 and a Schmitt trigger U5; the input end of the NOT gate U1 is used as the feedback end of the trigger judgment circuit, one end of the resistor R6 is used as the input end of the trigger judgment circuit, and the output end of the Schmitt trigger U5 is used as the output end of the trigger judgment circuit; The other end of the resistor R6, one end of the capacitor C1, and the source of the MOS transistor M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS transistor M1 is electrically connected to the output end of the NOT gate U1, the drain of the MOS transistor M1 is electrically connected to one end of the resistor R8, the other end of the resistor R8, the other end of the capacitor C1, and the input end of the Schmitt trigger U5 are all electrically connected to the output end of the comparator A2, the positive input end of the comparator A2 is electrically connected to one end of the resistor R7, and the other end of the resistor R7 is grounded.

3. The short-circuit protection circuit for a SiC power device according to claim 1, wherein: The short-circuit protection action unit includes an AND gate U2, an AND gate U4 and a rising edge trigger U3; the first input end of the AND gate U2 is used as the trigger end of the short-circuit protection action unit, the second input end of the AND gate U2 is used as the input end of the short-circuit protection action unit, and the output end of the AND gate U4 is used as the output end of the short-circuit protection action unit; The first input terminal of the AND gate U2 is electrically connected to the input terminal of the rising edge trigger U3, the output terminal of the AND gate U2 is electrically connected to the clock terminal of the rising edge trigger U3, the input terminal of the AND gate U4 is electrically connected to the second input terminal of the AND gate U2, and the inverting input terminal of the AND gate U4 is electrically connected to the output terminal of the rising edge trigger U3.

4. The short-circuit protection circuit for a SiC power device according to claim 1, wherein: The trigger acquisition circuit includes a diode D1, a resistor R2, and a resistor element R1; the cathode of the diode D1 serves as the positive electrode of the input end of the trigger acquisition circuit, one end of the resistor R2 serves as the negative electrode of the input end of the trigger acquisition circuit, and one end of the resistor element R1 serves as the output end of the trigger acquisition circuit; An anode of the diode D1 is electrically connected to the other end of the resistor R1 , and one end of the resistor R1 is electrically connected to the other end of the resistor R2 .

5. The short-circuit protection circuit for a SiC power device according to claim 1, wherein: The isolation circuit includes a resistor R4, a resistor R5 and a comparator A1; one end of the resistor R4 is used as an input end of the isolation circuit, and the output end of the comparator A1 is used as an output end of the isolation circuit; The other end of the resistor R4 is electrically connected to the positive input end of the comparator A1, one end of the resistor R5 is electrically connected to the negative input end of the comparator A1, and the other end of the resistor R5 is electrically connected to the output end of the comparator A1.

6. The short-circuit protection circuit for a SiC power device according to claim 1, characterized in that: Alternatively, the trigger judgment circuit is used to increase the judgment value when receiving the conduction voltage, and the magnitude of the conduction voltage is linearly proportional to the rising speed of the judgment value; if the judgment value rises to be greater than the second threshold voltage, the short-circuit trigger signal is generated; the time when the trigger judgment circuit rises to be greater than the second threshold voltage is the blanking time.

7. The short-circuit protection circuit for a SiC power device according to claim 3, wherein: The rising edge trigger U3 is a D trigger with a clear terminal; the D terminal of the D trigger is used as the input terminal of the rising edge trigger U3, the Q terminal of the D trigger is used as the output terminal of the rising edge trigger U3, and the CLK terminal of the D trigger is used as the clock terminal of the rising edge trigger U3.

8. The short-circuit protection circuit for a SiC power device according to claim 4, characterized in that: The resistor R1 is a single large resistor with a resistance much greater than that of the resistor R2. One end of the large resistor serves as one end of the resistor R1, and the other end of the large resistor serves as the other end of the resistor R1. Alternatively, the resistor element R1 is a series resistor circuit with a total resistance much greater than that of the resistor R2, and the series resistor circuit is composed of multiple small resistors in series, the other end of the previous small resistor and one end of the next small resistor are electrically connected, one end of the first small resistor is used as one end of the resistor element R1, and the other end of the last small resistor is used as the other end of the resistor element R1.

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