A protection circuit for IGBT overcurrent and short circuit

Abstract

The application provides an IGBT overcurrent and short circuit protection circuit, which comprises an IGBT, a driving circuit, a comparator U1A, a comparator U1B and a silicon carbide MOS tube Q1; the gate of the IGBT is electrically connected with the driving voltage end of the driving circuit; the driving circuit comprises resistors R12 and R13; the resistor R12 is electrically connected between the driving voltage end and the gate of the IGBT; the resistor R13 is connected with electricity; the gate of the IGBT is electrically connected with the 7th pin of the comparator U1B; the 6th pin of the comparator U1B and the 4th pin of the comparator U1A are both electrically connected with the reference voltage end; the 5th pin of the comparator U1A and the 1st pin of the comparator U1B are both electrically connected with the collector of the IGBT; one end of the silicon carbide MOS tube Q1 is electrically connected between the 4th pin of the comparator U1A and the reference voltage end; the other end of the silicon carbide MOS tube Q1 is electrically connected with the control circuit end; the protection circuit can be started quickly and has a good protection effect.

Description

Technical Field

[0001] This invention relates to the field of electronic equipment technology, and in particular to a protection circuit for IGBT overcurrent and short circuit. Background Technology

[0002] With the development of the automotive manufacturing industry, especially the new energy vehicle industry, power devices are being used more and more widely in new energy vehicles. Among them, the high-voltage, high-power power control device IGBT (Insulated Gate Bipolar Transistor) has become crucial in the control field of new energy vehicles. Therefore, the protection of IGBT power control devices has become particularly important. In existing products, when a short circuit occurs in the high-voltage circuit controlled by the IGBT, the current Ic flowing through the collector (C) to emitter (E) of the IGBT increases dramatically, the power loss of the IGBT increases dramatically, and the heat generation is severe. If the IGBT is not quickly turned off at this time, it will undergo thermal breakdown due to overheating, leading to IGBT damage. Existing IGBT protection circuits typically use IGBTs and silicon carbide MOSFETs that detect desaturation voltage. These short-circuit protection circuits require an RC circuit to set a blanking time to prevent the protection circuit from malfunctioning and shutting off the drive signal during the transition of the gate voltage from low to high and the VCE or VDS of the IGBT or silicon carbide MOSFET from high to low when the IGBT or silicon carbide MOSFET is turned on. However, different models of IGBTs and silicon carbide MOSFETs have different parasitic parameters, resulting in varying turn-on speeds. The blanking time needs to be adjusted for each specific device; otherwise, the module may burn out due to delayed protection. Furthermore, the threshold voltage of IGBTs and silicon carbide MOSFETs varies with temperature, causing significant differences in turn-on speed under different temperature conditions. A fixed blanking time cannot adapt adaptively, and under certain operating conditions, the IGBT may burn out due to delayed protection activation. This problem is even more severe for silicon carbide MOSFETs, which have faster switching speeds. Therefore, designing a fast-responding and reliable turn-off protection circuit is crucial for protecting IGBTs. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a protection circuit for IGBT overcurrent and short circuit.

[0004] This invention is achieved through the following technical solution:

[0005] This invention proposes an IGBT overcurrent and short-circuit protection circuit, including an IGBT, a driving circuit, comparators U1A and U1B, and a silicon carbide MOSFET Q1. The gate of the IGBT is electrically connected to the driving voltage terminal of the driving circuit. The driving circuit includes resistors R12 and R13. Resistor R12 is electrically connected between the driving voltage terminal and the gate of the IGBT, and resistor R13 is energized. The gate of the IGBT is electrically connected to pin 7 of comparator U1B. Pin 6 of comparator U1B and pin 4 of comparator U1A are both electrically connected to a reference voltage terminal. Pin 5 of comparator U1A and pin 1 of comparator U1B are both electrically connected to the collector of the IGBT. One end of the silicon carbide MOSFET Q1 is electrically connected between pin 4 of comparator U1A and the reference voltage terminal, and the other end of the silicon carbide MOSFET Q1 is electrically connected to a control circuit terminal.

[0006] Furthermore, the IGBT overcurrent and short circuit protection circuit also includes resistors R8 and R9, and capacitor C2. Resistor R9 is electrically connected between the gate of the IGBT and pin 7 of the comparator U1B. Resistor R8 and capacitor C2 are connected in parallel at pin 7 of the comparator U1B and are both grounded.

[0007] Furthermore, the IGBT overcurrent and short-circuit protection circuit also includes resistors R1, R2, R3, and R4. Resistor R3 is electrically connected between pin 4 of the comparator U1A and the reference voltage terminal. Resistor R4 is electrically connected between the silicon carbide MOSFET Q1 and pin 4 of the comparator U1A. Resistor R1 and resistor R2 are electrically connected, and resistor R2 is electrically connected to the silicon carbide MOSFET Q1.

[0008] Furthermore, the IGBT overcurrent and short circuit protection circuit also includes resistors R5, R6, and R7, and transistor Q2. One end of resistor R7 is electrically connected to pin 6 of comparator U1B, and the other end of resistor R7 is electrically connected to the collector of transistor Q2. The emitter of transistor Q2 is grounded, and the base of transistor Q2 is electrically connected to resistor R5.

[0009] Furthermore, the IGBT overcurrent and short-circuit protection circuit also includes diode D1, diode D2, resistor R10, resistor R11, and capacitor C1. Diode D1 is electrically connected to comparator U1A. Resistors R10 and R11 are both electrically connected to pin 1 of comparator U1A. One end of capacitor C1 is electrically connected to resistor R10, and the other end of capacitor C1 is grounded. One end of diode D2 is electrically connected to resistor R11, and the other end of diode D2 is electrically connected to the collector of the IGBT.

[0010] The beneficial effects of this invention are:

[0011] The IGBT overcurrent and short-circuit protection circuit proposed in this invention is designed based on the switching characteristics of IGBTs and silicon carbide MOSFETs. When the IGBT gate voltage exceeds the Miller plateau formed by the silicon carbide MOSFET, the silicon carbide MOSFET is essentially fully turned on. Therefore, the gate voltage can be detected, and when the IGBT gate voltage exceeds a certain set value, the protection circuit is activated. This avoids the protection circuit from malfunctioning when the IGBT and silicon carbide MOSFET are in the decreasing phase of VCE and VDS from high to low during turn-on, and can activate the protection circuit in the shortest possible time. Furthermore, it can adapt to IGBTs and silicon carbide MOSFETs with different turn-on speeds. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the IGBT overcurrent and short circuit protection circuit of the present invention. Detailed Implementation

[0013] To more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings.

[0014] Please refer to Figure 1This invention proposes an IGBT overcurrent and short-circuit protection circuit, including an IGBT, a driving circuit, comparators U1A and U1B, and a silicon carbide MOSFET Q1. The gate of the IGBT is electrically connected to the driving voltage terminal of the driving circuit. The driving circuit includes resistors R12 and R13. Resistor R12 is electrically connected between the driving voltage terminal and the gate of the IGBT, and resistor R13 is energized. The gate of the IGBT is electrically connected to pin 7 of comparator U1B. Pin 6 of comparator U1B and pin 4 of comparator U1A are both electrically connected to a reference voltage terminal. Pin 5 of comparator U1A and pin 1 of comparator U1B are both electrically connected to the collector of the IGBT. One end of the silicon carbide MOSFET Q1 is electrically connected between pin 4 of comparator U1A and the reference voltage terminal, and the other end of the silicon carbide MOSFET Q1 is electrically connected to a control circuit terminal. The IGBT overcurrent and short-circuit protection circuit also includes resistors R8 and R9, and capacitor C2. Resistor R9 is electrically connected between the gate of the IGBT and pin 7 of the comparator U1B. Resistor R8 and capacitor C2 are connected in parallel at pin 7 of the comparator U1B and are both grounded. The IGBT overcurrent and short-circuit protection circuit also includes resistors R1, R2, R3, and R4. Resistor R3 is electrically connected between pin 4 of the comparator U1A and the reference voltage terminal. Resistor R4 is electrically connected between the silicon carbide MOSFET Q1 and pin 4 of the comparator U1A. Resistor R1 and resistor R2 are electrically connected, and resistor R2 is electrically connected to the silicon carbide MOSFET Q1. The IGBT overcurrent and short-circuit protection circuit also includes resistors R5, R6, and R7, and transistor Q2. One end of resistor R7 is electrically connected to pin 6 of comparator U1B, and the other end of resistor R7 is electrically connected to the collector of transistor Q2. The emitter of transistor Q2 is grounded, and the base of transistor Q2 is electrically connected to resistor R5. The IGBT overcurrent and short-circuit protection circuit also includes diodes D1 and D2, resistors R10 and R11, and capacitor C1. Diode D1 is electrically connected to comparator U1A. Resistors R10 and R11 are both electrically connected to pin 1 of comparator U1A. One end of capacitor C1 is electrically connected to resistor R10, and the other end of capacitor C1 is grounded. One end of diode D2 is electrically connected to resistor R11, and the other end of diode D2 is electrically connected to the collector of the IGBT.

[0015] In this embodiment, comparator U1B samples the gate voltage signal of the IGBT, divides it using resistors R9 and R8, and compares it with the reference voltage REF. When the IGBT drive signal Dr is low, controlling the IGBT to turn off, the signal at pin 7 of comparator U1B is lower than the signal at pin 6. Pin 1 of comparator U1B pulls pin 5 of comparator U1A to ground, ensuring that the voltage at pin 5 of comparator U1A is always lower than the voltage at pin 4. Pin 2 of comparator U1A outputs a low level, and the protection function is disabled.

[0016] When the drive signal Dr is high, driving the IGBT and the silicon carbide MOSFET Q1 to turn on, the gate voltage of the IGBT will experience a Miller plateau during its rise. When the gate voltage exceeds the Miller plateau, it can be considered that the IGBT and the silicon carbide MOSFET Q1 are essentially fully turned on. Therefore, it is only necessary to set a suitable reference voltage REF so that when the gate voltage of the IGBT and the silicon carbide MOSFET Q1 exceeds a certain value (such as 85% of the maximum value of the gate drive signal; the smaller this percentage, the faster the protection, but it must be greater than the Miller plateau voltage, because the gate drive voltage of the IGBT is only fully turned on after passing the Miller plateau; otherwise, it will cause malfunction due to excessive VCE and VDS voltages), the voltage at pin 7 of the comparator U1B is greater than the voltage at pin 6, pin 1 of the comparator U1B is cut off, and the protection function is activated. If there is no short circuit at this time, the current flows through the resistor R10, the resistor R11, the diode D2, the IGBT, and the silicon carbide MOSFET Q1, and finally returns to ground. By adjusting the resistance values ​​of the resistors R10 and R11, the voltage at pin 5 of the comparator U1A is lower than the reference voltage at pin 4. The pin 2 of the comparator U1A outputs a low level, and the IGBT and the silicon carbide MOSFET Q1 work normally.

[0017] In this embodiment, if the current increases excessively or a short circuit occurs while the IGBT and the silicon carbide MOSFET Q1 are operating normally, the voltage drop across the IGBT and the silicon carbide MOSFET Q1 will increase, causing the voltage at pin 5 of the comparator U1A to rise. When this voltage exceeds the reference voltage at pin 4 of the comparator U1A, the comparator U1A will flip, outputting a high level and triggering the subsequent drive circuit for overcurrent or short-circuit protection. If an overcurrent or short circuit occurs when the IGBT is turned on, and the gate drive voltage of the IGBT exceeds the Miller plateau, the protection function of this circuit can be activated immediately after the IGBT is fully turned on (before the gate drive voltage reaches its maximum value). Upon detecting a voltage drop exceeding a set value, protection can be initiated in the shortest possible time.

[0018] Of course, the present invention may have many other embodiments. Based on this embodiment, other embodiments obtained by those skilled in the art without any creative effort are all within the scope of protection of the present invention.

Claims

1. A protection circuit for IGBT overcurrent and short circuit, characterized in that, The IGBT overcurrent and short-circuit protection circuit includes an IGBT, a drive circuit, comparators U1A and U1B, and a silicon carbide MOSFET Q1. The gate of the IGBT is electrically connected to the drive voltage terminal of the drive circuit. The drive circuit includes resistors R12 and R13. Resistor R12 is electrically connected between the drive voltage terminal and the gate of the IGBT. The first terminal of resistor R13 is grounded, and the second terminal of resistor R13 is connected to the gate. The gate of the IGBT is electrically connected to the non-inverting input terminal (pin 7) of comparator U1B. The inverting input pin 6 of comparator U1B and the inverting input pin 4 of comparator U1A are both electrically connected to the reference voltage terminal. The non-inverting input pin 5 of comparator U1A is electrically connected to the output pin 1 of comparator U1B and both are connected to the collector of the IGBT. The drain of the silicon carbide MOSFET Q1 is electrically connected between the inverting input pin 4 of comparator U1A and the reference voltage terminal. The gate of the silicon carbide MOSFET Q1 is electrically connected to the control circuit terminal. The source of the silicon carbide MOSFET Q1 is grounded. The IGBT overcurrent and short circuit protection circuit also includes resistor R8, resistor R9, and capacitor C2. Resistor R9 is electrically connected between the gate of the IGBT and the non-inverting input terminal of pin 7 of the comparator U1B. Resistor R8 and capacitor C2 are connected in parallel at the non-inverting input terminal of pin 7 of the comparator U1B and are both grounded. The IGBT overcurrent and short circuit protection circuit also includes resistors R1, R2, R3, and R4. Resistor R3 is electrically connected between the inverting input terminal (pin 4) of comparator U1A and the reference voltage terminal. The first end of resistor R4 is electrically connected to the drain of silicon carbide MOSFET Q1. The second end of resistor R4 is connected to the inverting input terminal (pin 4) of comparator U1A. The first end of resistor R1 and the first end of resistor R2 are electrically connected. The second end of resistor R1 is connected to the power supply voltage VDD. The second end of resistor R2 is electrically connected to the gate of silicon carbide MOSFET Q1. The IGBT overcurrent and short-circuit protection circuit also includes resistors R5, R6, and R7, and transistor Q2. The first end of resistor R6 is connected to the reference voltage REF, the second end of resistor R6 is connected to the inverting input of U1B, one end of resistor R7 is electrically connected to the inverting input of pin 6 of comparator U1B, the other end of resistor R7 is electrically connected to the collector of transistor Q2, the emitter of transistor Q2 is grounded, the base of transistor Q2 is electrically connected to one end of resistor R5, and the other end of resistor R5 is connected to the anode of diode D1.

2. The IGBT overcurrent and short-circuit protection circuit according to claim 1, characterized in that, The IGBT overcurrent and short-circuit protection circuit also includes diodes D1 and D2, resistors R10 and R11, and capacitor C1. The anode of diode D1 is electrically connected to the non-inverting input terminal of comparator U1A. One end of resistor R10 and one end of resistor R11 are both electrically connected to pin 1 of comparator U1B. One end of capacitor C1 is electrically connected to the other end of resistor R10, and the other end of capacitor C1 is grounded. The anode of diode D2 is electrically connected to the other end of resistor R11, and the cathode of diode D2 is electrically connected to the collector of the IGBT.

Images