Short-circuit protection circuit of SiC power device

Abstract

The invention relates to the technical 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 the driving signal when the driving signal is received; when the turn-off signal is received, the SiC power device is turned off; the short-circuit voltage adaptation unit is used for monitoring the conduction voltage of the SiC power device in real time; when the duration of the break-over voltage greater than the short-circuit threshold voltage is 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 turn-on voltage and the magnitude of the blanking time are in a linear inverse relation; the short-circuit protection action unit is used for receiving driving signals and transmitting the driving signals to the driving unit; and when the short circuit trigger signal is received, a turn-off signal is generated and transmitted to the driving unit, so that the blanking time is more adaptive to different bus voltages, the short circuit protection is more accurate, and the performance requirements of the SiC power device are better met.

Description

Technical Field

[0001] The 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 with silicon devices, SiC (silicon carbide) power devices have performance advantages such as low on-resistance, fast switching speed, and high thermal conductivity, which are beneficial to improving the efficiency and power density of the converter and are widely used in integrated circuits to improve overall performance. However, in practical applications, SiC power devices inevitably have to work under overload, desaturation and other working conditions that cause short circuits in SiC power devices. Due to the characteristics and application environment of SiC power devices, they are more sensitive to various types of short-circuit faults and are very easy to be falsely triggered; this requires that they must have short-circuit fault protection capabilities to protect themselves and the integrated circuits used, and can implement protection measures when short-circuit faults such as overload and desaturation occur; therefore, the performance of the short-circuit protection circuit of SiC power devices is the key to determining whether short-circuit protection can be implemented quickly and accurately.

[0003] Existing short-circuit protection circuits usually determine whether a short-circuit fault occurs by detecting the on-voltage (such as drain-source voltage) of a SiC power device (such as SiC-MOSFET), and then set an RC charge and discharge circuit to adapt to different short-circuit voltages. The time it takes for the RC charge and 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 the short-circuit protection due to disturbances.

[0004] When a SiC power device has a short-circuit fault, the short-circuit voltage will be different due to the different bus voltages connected to the SiC power device. Therefore, the short-circuit protection response time of the SiC power device should also change accordingly to avoid false triggering. However, when the resistance and capacitance specifications of the RC charge and discharge circuit are determined, different short-circuit voltages have little effect on the time it takes for the RC charge and discharge circuit to charge to the short-circuit threshold voltage, that is, the reserved blanking time is basically constant, which leads to the inability of the reserved blanking time to adapt to different bus voltages. When the bus voltage changes, the reserved blanking time and the actual required short-circuit protection response time do not match. If the reserved blanking time is large, the performance of the SiC power device is affected and it is not suitable for the application environment of high-frequency switching power devices. If the reserved blanking time is small, the short-circuit protection will be triggered by mistake (for example, if the SiC power device is SiC-MOSFET, during the normal conduction process, a short narrow pulse will cause the SiC-MOSFET to have a short desaturation fault. The reserved blanking time is too small and too sensitive, directly triggering 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. 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 object of the present invention is to propose a short-circuit protection circuit for a SiC power device, whose blanking time is more adaptable to different bus voltages, and the short-circuit protection is more accurate and more in line with the performance requirements of the SiC power device.

[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 driving unit, a short-circuit voltage adaptation unit and a short-circuit protection action unit; an input end of the short-circuit protection action unit is externally connected to a driving signal, an output end of the short-circuit protection action unit is electrically connected to an input end of the driving unit, a driving end of the SiC power device and a feedback end of the short-circuit voltage adaptation unit are both electrically connected to the output end of the driving unit, a conduction voltage end of the SiC power device is electrically connected to an input end of the short-circuit voltage adaptation unit, and an output end of the short-circuit voltage adaptation unit is electrically connected to a trigger end of the short-circuit protection action unit;

[0009] The driving unit is used 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-voltage of the SiC power device in real time; when the on-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-voltage is inversely proportional to the magnitude of the blanking time;

[0011] The short-circuit protection action unit is used to receive the driving signal and transmit it to the driving unit; when the short-circuit trigger signal is received, the shutdown signal is generated and transmitted 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-type 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-type judgment circuit via the isolation circuit;

[0016] The trigger judgment circuit is used to judge that the value decreases when receiving the conduction voltage, and the magnitude of the conduction voltage and the decreasing speed of the judgment value are linearly proportional; if the judgment value decreases to less than the second threshold voltage, the short circuit trigger signal is generated; the time when the trigger judgment circuit decreases 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-type 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 a feedback end of the trigger-type judgment circuit, one end of the resistor R6 is used as an input end of the trigger-type judgment circuit, and the output end of the Schmitt trigger U5 is used as an output end of the trigger-type judgment circuit;

[0019] The other end of the resistor R6, one end of the capacitor C1, and the source of the MOS tube M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS tube M1 is electrically connected to the output end of the NOT gate U5, the drain of the MOS tube 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 a trigger end of the short-circuit protection action unit, the second input end of the AND gate U2 is used as an input end of the short-circuit protection action unit, and the output end of the AND gate U4 is used as an 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 is used as the positive electrode of the input end of the trigger acquisition circuit, one end of the resistor R2 is used as the negative electrode of the input end of the trigger acquisition circuit, and one end of the resistor element R1 is used 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 the on-voltage is received, the judgment value rises, and the magnitude of the on-voltage and the rising speed of the judgment value are linearly proportional; 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] Further, 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 is used as one end of the resistor R1, and the other end of the large resistor is used as the other end of the resistor R1;

[0029] Alternatively, the resistor element R1 is a series resistor circuit with a total resistance value 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 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.

[0030] The technical solution provided by the present invention may include the following beneficial effects: taking SiC-MOSFET as an example of a 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 on-voltage end of the SiC power device, and the source of the SiC-MOSFET is used as the negative electrode of the on-voltage end of the SiC power device, then the SiC-MOSFET works normally when driven by a driving unit; when a short-circuit fault such as overload or desaturation occurs in the SiC-MOSFET, the voltage between the drain and source of the SiC-MOSFET (i.e., the on-voltage) will increase to the voltage of the bus to which it is connected, and the higher the bus voltage, the shorter the tolerance time of the SiC-MOSFET; therefore, through the short-circuit voltage The adaptation unit monitors the on-voltage of the SiC power device in real time. When the on-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, and the short-circuit protection action unit enables the driving unit to shut down the SiC power device to achieve protection, thereby preventing false triggering of the short-circuit protection. Moreover, since the on-voltage and the blanking time are in a linear inverse proportional relationship, compared to the RC charge and discharge circuit that makes the on-voltage (short-circuit voltage) and the blanking time in a parabolic inverse proportional relationship (i.e., the blanking time changes very little in the face of different short-circuit voltages), in the face of different on-voltages, the blanking time changes linearly, 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 SiC power devices. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0032] Figure 2 Yes Figure 1 The Vc-t waveform diagram of the trigger judgment circuit is shown.

[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] Embodiments of the present invention are described in detail below, examples of which 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 only used to explain the present invention, and cannot be understood 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 are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0037] Combine the following Figure 1 to Figure 2 , describing a short-circuit protection circuit of a SiC power device in an embodiment of the present invention.

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

[0039] The driving unit 1 is used to drive the SiC power device 4 according to the driving signal when receiving the driving signal; and 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-voltage of the SiC power device 4 in real time; when the on-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 3; the magnitude of the on-voltage is inversely proportional to the magnitude of the blanking time;

[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 Figure 1 As shown, the SiC power device 4 takes SiC-MOSFET as an example, the gate of SiC-MOSFET is used as the driving end of SiC power device 4, the drain of SiC-MOSFET is used as the positive electrode of the on-voltage end of SiC power device 4, and the source of SiC-MOSFET is used as the negative electrode of the on-voltage end of SiC power device 4, then SiC-MOSFET works normally under the drive of driving unit 1; when SiC-MOSFET has a short-circuit fault such as overload or desaturation, it will cause the voltage between the drain and source of SiC-MOSFET (i.e., the on-voltage) to increase to the voltage of the bus to which it is connected, then the higher the bus voltage is, the shorter the tolerance time of SiC-MOSFET is; therefore, the short-circuit voltage adaptation unit 2 is used to monitor in real time The on-voltage of the SiC power device 4, when the on-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, and the short-circuit protection action unit 3 enables the driving unit 1 to shut down the SiC power device 4 to achieve protection, thereby preventing false triggering of the short-circuit protection; and since the magnitude of the on-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-voltage (short-circuit voltage) and the magnitude of the blanking time in a parabolic inverse proportional relationship (that is, in the face of different short-circuit voltages, the blanking time changes very little), in the face of different on-voltages, the blanking time changes linearly, thereby making the blanking time more adaptable to different bus voltages; ultimately making the short-circuit protection more accurate and more in line with the performance requirements of SiC power devices.

[0043] Further, 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 used to judge that the value decreases when receiving the conduction voltage, and the magnitude of the conduction voltage and the decreasing speed of the judgment value are linearly proportional; if the judgment value decreases to less than the second threshold voltage, a short circuit trigger signal is generated; the time when 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 blanking time generated according to the linear inverse relationship between the magnitude of the conduction voltage, the short-circuit threshold voltage is set to two thresholds, the first threshold voltage and the second threshold voltage, to limit the blanking time; wherein the first threshold voltage is a 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 a trigger value used by the trigger judgment circuit 23 to determine whether it is a permanent fault. The trigger value of a permanent short circuit fault, after the trigger judgment circuit 23 receives the on-voltage, the internal judgment value decreases accordingly, and the decreasing speed of the judgment value is linearly proportional to the size of the on-voltage. If the judgment value decreases to less than the second threshold voltage, a short circuit trigger signal is generated (representing a permanent short circuit fault); it can be seen that the time when the trigger judgment circuit 23 drops to less than the second threshold voltage is the blanking time, from which the relationship can be obtained: decreasing speed = second threshold voltage / blanking time, it can be deduced that the size of the on-voltage (short-circuit voltage) and the size 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 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 a feedback end of the trigger judgment circuit 23, one end of the resistor R6 is used as an input end of the trigger judgment circuit 23, and the output end of the Schmitt trigger U5 is used 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 tube M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS tube M1 is electrically connected to the output end of the NOT gate U5, the drain of the MOS tube 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 the active integration circuit composed of the NOT gate U1, MOS tube M1, resistor R6, resistor R7, resistor R8, capacitor C1 and comparator A2 realizes its function. 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 with the duration of receiving the conduction voltage until it drops to the second threshold voltage to trigger the Schmitt trigger U5 to output a high level (short-circuit trigger signal), and 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 It can be seen from the multiple curves in that each curve represents a bus voltage connected to the SiC power device 4, the blanking time is t1, and the slope is the falling speed of the output voltage Vc. At the same time, after the SiC power device 4 is turned off, the MOS tube M1 is used to feedback the turn-off status of the SiC power device 4, so that the MOS tube M1 is turned on, and the resistor R8 provides a discharge circuit for the capacitor C1 to prepare for the next short circuit judgment.

[0054] Further, 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 opening and closing of the SiC power device 4 according to the driving signal during normal operation and keep it off when a short-circuit fault occurs, so 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) inputs high level or low level, AND gate U2 outputs high level, rising edge trigger U3 outputs high level and transmits it to AND gate U4 for inversion, so that AND gate U4 also outputs low level constantly, enabling driving unit 1 to turn off SiC power device 4; when working normally, Schmitt trigger U5 outputs low level constantly. Figure 1 Whether the input is high level or low level, the AND gate U2 outputs low level, and the rising edge trigger U3 outputs 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 type acquisition circuit 21 includes a diode D1, a resistor R2 and a resistor element R1; the cathode of the diode D1 is used as the positive electrode of the input end of the trigger type acquisition circuit 21, one end of the resistor R2 is used as the negative electrode of the input end of the trigger type acquisition circuit 21, and one end of the resistor element R1 is used as the output end of the trigger type 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. When the short-circuit fault conduction voltage is too large, the diode D1 can 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 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.

[0062] In this embodiment, the isolation circuit 22 is a voltage follower composed of a resistor R4, a resistor R5 and a comparator A1; since the impedance of the voltage-dividing resistor of the trigger-type acquisition circuit 21 is much larger than the impedance of the active integration circuit of the trigger-type judgment circuit 23, the use of a voltage follower can transmit the conduction voltage operational amplification to the active integration circuit for integration when a short circuit occurs. At the same time, the voltage follower can also play the role of isolation and buffering, and play the function of electrical isolation.

[0063] Furthermore, the trigger judgment circuit 23 is used to, when receiving the on-voltage, the judgment value rises, and the magnitude of the on-voltage and the rising speed of the judgment value are linearly proportional; 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 reset terminal. Its logic meets the requirements and is provided with a reset terminal. The reset terminal can be used to ensure the reset of the trigger to avoid short-circuit protection reset delay or reset failure.

[0067] Further, 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 is used as one end of the resistor R1, and the other end of the large resistor is used as the other end of the resistor R1;

[0068] Alternatively, the resistor element R1 is a series resistor circuit whose total resistance is much greater than the resistance of the resistor R2. The series resistor circuit is composed of multiple small resistors 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 value of the resistor R1 is much greater than the resistance value 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 known to those skilled in the art and will not be described in detail here.

[0071] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0072] Although the 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 present invention, and that the scope of the present 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 a 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 used 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-voltage of the SiC power device in real time; when the on-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-voltage is inversely proportional to the magnitude of the blanking time; The short-circuit protection action unit is used to receive the driving signal and transmit it to the driving unit; when the short-circuit trigger signal is received, the shutdown signal is generated and transmitted to the driving unit.

2. A short-circuit protection circuit for a SiC power device according to claim 1, characterized in that: 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-type 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-type judgment circuit via the isolation circuit; The trigger judgment circuit is used for judging that the value decreases when the conduction voltage is received, and the magnitude of the conduction voltage and the decreasing speed of the judgment value are in linear proportional relationship; if the judgment value decreases to be less than the second threshold voltage, the short circuit trigger signal is generated; The time for the trigger judgment circuit to drop to a voltage lower than 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.

3. The short-circuit protection circuit of a SiC power device according to claim 2, characterized in that: 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 a feedback end of the trigger judgment circuit, one end of the resistor R6 is used as an input end of the trigger judgment circuit, and the output end of the Schmitt trigger U5 is used as an 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 tube M1 are all electrically connected to the negative input end of the comparator A2, the gate of the MOS tube M1 is electrically connected to the output end of the NOT gate U5, the drain of the MOS tube 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.

4. The short-circuit protection circuit of a SiC power device according to claim 1, characterized in that: 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 a trigger end of the short-circuit protection action unit, the second input end of the AND gate U2 is used as an input end of the short-circuit protection action unit, and the output end of the AND gate U4 is used as an 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.

5. The short-circuit protection circuit of a SiC power device according to claim 2, characterized in that: The trigger acquisition circuit includes a diode D1, a resistor R2 and a resistor element R1; the cathode of the diode D1 is used as the positive electrode of the input end of the trigger acquisition circuit, one end of the resistor R2 is used as the negative electrode of the input end of the trigger acquisition circuit, and one end of the resistor element R1 is used 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 .

6. A short-circuit protection circuit for a SiC power device according to claim 2, characterized in that: 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.

7. The short-circuit protection circuit of a SiC power device according to claim 2, characterized in that: The trigger judgment circuit is used to, when receiving the on-state voltage, increase the judgment value, and the magnitude of the on-state voltage and the rising speed of the judgment value are linearly proportional; 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.

8. The short-circuit protection circuit of a SiC power device according to claim 4, characterized in that: 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.

9. The short-circuit protection circuit of a SiC power device according to claim 5, characterized in that: The resistor R1 is a single large resistor with a resistance value much greater than that of the resistor R2, one end of the large resistor is used as one end of the resistor R1, and the other end of the large resistor is used as the other end of the resistor R1; Alternatively, the resistor element R1 is a series resistor circuit with a total resistance value 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 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.

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