An IGBT overcurrent protection circuit

Abstract

The invention discloses an IGBT overcurrent protection circuit, comprising a decoupling protection circuit, a reference level generating circuit, a fault signal generating circuit and a hardware blocking circuit; the decoupling protection circuit is used for generating a protection voltage signal according to the collected gate and drain voltages of the IGBT lower tube; the fault signal generating circuit compares the protection voltage signal with the reference voltage signal, and forms a fault signal when the protection voltage signal is greater than the reference voltage signal; the hardware blocking circuit clamps the gate voltage of the lower tube to the negative power supply of the lower tube driving power supply under the triggering of the fault signal, so that the lower tube is turned off; the invention adopts separate analog circuit devices to configure three working modes of the decoupled overcurrent protection circuit, flexibly switches among three actual working conditions when the IGBT has an overcurrent fault, works normally and does not work, realizes overcurrent protection without using a driving chip, and can adjust the execution voltage range and response time value by adjusting circuit parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, and more specifically, relates to an IGBT overcurrent protection circuit for a frequency converter implemented by discrete device hardware. Background Art

[0002] With the popularization of frequency conversion technology, IGBT overcurrent protection circuits are increasingly used in power circuits. Existing IGBT overcurrent protection circuits are generally designed using controlled DC sources in driver chips. This software protection method has the disadvantages that the protection execution voltage range and protection response time are fixed and cannot be adjusted. After the power modules of high-power inverters are made into bare chips, connected in parallel, or the IGBT modules are replaced with silicon carbide modules, the original protection scheme based on the driver chip can no longer meet the response time requirements, and the protection voltage range cannot be set independently. Summary of the invention

[0003] In response to at least one defect or improvement need of the prior art, the present invention provides an IGBT overcurrent protection circuit, which can adjust the range of protection execution voltage and set response time by changing RC network parameters and diode selection.

[0004] To achieve the above object, according to one aspect of the present invention, an IGBT overcurrent protection circuit is provided, comprising a decoupling protection circuit, a reference level generating circuit, a fault signal generating circuit and a hardware blocking circuit;

[0005] The decoupling protection circuit is connected to the gate and drain of the lower tube of the IGBT respectively, and generates a protection voltage signal according to the collected gate voltage and drain voltage of the lower tube of the IGBT;

[0006] The reference level generating circuit is used to provide a reference voltage signal;

[0007] The fault signal generating circuit is respectively connected to the decoupling protection circuit, the reference level generating circuit and the hardware blocking circuit, and compares the protection voltage signal provided by the decoupling protection circuit with the reference voltage signal provided by the reference level generating circuit. When the value of the protection voltage signal is greater than the reference voltage signal, a fault signal is generated and sent to the hardware blocking circuit;

[0008] The hardware blocking circuit is connected to the gate of the lower tube of the IGBT, and when triggered by the fault signal, the gate voltage of the lower tube of the IGBT is clamped to the negative power supply of the lower tube driving power supply, so that the lower tube of the IGBT is turned off.

[0009] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the decoupling protection circuit comprises a first diode D1, a first resistor R1, a second diode D2, a fourth resistor R4, a third diode D3, and a fifth resistor R5;

[0010] The cathode of the first diode D1 is connected to the drain of the lower tube of the IGBT, and the cathode is connected to the anode of the second diode D2 through the first resistor R1; the cathode of the second diode D2 outputs a protection voltage signal;

[0011] The fourth resistor R4 is connected in parallel with the third diode D3, the first end of the fourth resistor R4 and the anode of the third diode D3 are connected to the anode of the first diode D1, and the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the gate of the lower tube of the IGBT;

[0012] The first end of the fifth resistor R5 is connected to the negative power supply of the lower tube driving power supply, and the second end is connected to the positive electrode of the second diode D2.

[0013] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the decoupling protection circuit has three working modes:

[0014] When the IGBT lower tube does not operate, the drain voltage of the IGBT lower tube breaks down the first diode D1, and the fourth resistor R4 is connected to the negative power supply of the lower tube driving power supply for clamping; the breakdown energy of the first diode D1 is discharged to the negative power supply of the lower tube driving power supply through the third diode D3 and the fifth resistor R5; the protection voltage signal output by the second diode D2 is limited to (-V2-V D2 +X); where -V2 represents the negative power supply of the lower tube drive power supply, V D2 represents the on-state voltage of the second diode D2, and the value of X depends on the resistance values ​​of the first resistor R1, the fourth resistor R4 and the fifth resistor R5;

[0015] When the IGBT lower tube is in operation and no short circuit occurs, the drain voltage of the IGBT lower tube is its conduction voltage drop, the first diode D1 is not broken down, the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the positive power supply of the lower tube drive power supply, and the protection voltage signal output by the second diode D2 is limited to (-V2-V D2 );

[0016] When the IGBT lower tube is in operation and short-circuited, the drain voltage of the IGBT lower tube breaks down the first diode D1, the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the positive power supply of the lower tube drive power supply, and the breakdown energy of the first diode D1 is discharged to the negative power supply of the lower tube drive power supply through the fifth resistor R5; the protection voltage signal output by the second diode D2 is limited to (V2+X*Y / Udc-V D2 ), wherein V2 represents the positive power supply of the lower tube driving power supply, Udc represents the bus voltage, and Y represents the drain voltage of the IGBT lower tube.

[0017] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the reference voltage generating circuit includes a second resistor R2 and a fifth diode D5; one end of the second resistor R2 is connected to the reference voltage of the lower tube driving power supply, and the other end is connected to the cathode of the fifth diode D5; the anode of the fifth diode D5 is connected to the negative power supply of the lower tube driving power supply.

[0018] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the fault signal generating circuit comprises a first comparator, an eighth resistor, a sixth diode and a ninth resistor;

[0019] The non-inverting input terminal of the first comparator is used to receive the protection voltage signal, and the inverting input terminal is used to receive the reference voltage signal;

[0020] The eighth resistor and the sixth diode are connected in series between the non-phase input terminal and the output terminal of the first comparator. The fault voltage signal output by the output terminal of the first comparator is transmitted to the interference removal circuit. The fault voltage signal is converted into a corresponding fault current signal through the ninth resistor and transmitted to the hardware blocking circuit.

[0021] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the hardware blocking circuit comprises a first transistor Q1, a twenty-first resistor R21, a MOS transistor Q3, an eighteenth resistor R18, and a seventh capacitor C7;

[0022] The base of the first transistor Q1 receives the fault signal output by the fault signal generating circuit, the collector receives the reference voltage of the lower tube driving power supply, and the emitter is connected to the negative power supply of the lower tube driving power supply through the twenty-first resistor R21;

[0023] The gate of the MOS tube Q3 is connected to the emitter of the first transistor Q1, the source is connected to the negative power supply of the lower tube driving power supply, and the drain is connected to the gate of the IGBT lower tube after being connected in series with the eighteenth resistor R18 and the seventh capacitor C7.

[0024] Preferably, the above-mentioned IGBT overcurrent protection circuit further includes a filter circuit; the input end of the filter circuit is connected to the decoupling protection circuit, and the output end is connected to the fault signal generation circuit;

[0025] The filter circuit performs filtering and voltage division processing on the protection voltage signal output by the decoupling protection circuit to output a protection voltage signal matching the input resistance range of the fault signal generating circuit.

[0026] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the filter circuit comprises a tenth resistor R10, a fifth capacitor C5, a thirteenth resistor R13, and an eleventh resistor R11;

[0027] The first end of the tenth resistor R10 is connected to the output end of the decoupling protection circuit to receive the protection voltage signal, and the second end is connected to the eleventh resistor R11; the other end of the eleventh resistor R11 serves as the output end of the filter circuit;

[0028] After the fifth capacitor C5 is connected in parallel with the thirteenth resistor R13, one end of the fifth capacitor C5 is connected to the second end of the tenth resistor R10, and the other end is connected to the gate of the lower tube of the IGBT;

[0029] Among them, the tenth resistor R10, the fifth capacitor C5, and the thirteenth resistor R13 constitute a first-order RC filter circuit and a resistor voltage divider circuit, which filter and divide the protection voltage signal output by the decoupling protection circuit; the eleventh resistor R11 is an output matching resistor, which ensures that the output protection voltage signal matches the input resistance range of the fault signal generating circuit.

[0030] Preferably, the above-mentioned IGBT overcurrent protection circuit also includes a controller and a reset circuit;

[0031] The controller is connected to the fault signal generating circuit, generates a reset signal according to the fault signal output by the fault signal generating circuit, and sends the reset signal to the reset circuit;

[0032] The output end of the reset circuit is connected to the fault signal generating circuit, and the protection voltage signal in the fault signal generating circuit is clamped to the negative power supply of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is discharged to the negative power supply of the lower tube driving power supply to release the fault signal.

[0033] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the reset circuit comprises an optocoupler and a second transistor Q2;

[0034] The first input end of the optocoupler receives a reset signal output by the controller, the second input end is grounded, the first output end is connected to the base of the second transistor Q2, and the second output end is connected to the emitter of the second transistor Q2; the emitter of the second transistor Q2 is connected to the negative power supply of the lower tube driving power supply, and the collector is connected to the non-inverting input end of the first comparator in the fault signal generating circuit.

[0035] Preferably, the above-mentioned IGBT overcurrent protection circuit also includes an interference elimination circuit;

[0036] The interference removal circuit is used to compare the fault signal output by the fault signal generation circuit with the reference voltage signal, and send the comparison result as a valid fault signal to the controller.

[0037] Preferably, in the above-mentioned IGBT overcurrent protection circuit, the interference elimination circuit comprises a sixteenth resistor R16, a sixth capacitor C6 and a second comparator U1B;

[0038] The sixteenth resistor R16 and the sixth capacitor C6 form a first-order RC low-pass filter circuit to filter the fault voltage signal generated by the fault signal generating circuit;

[0039] The non-inverting input terminal of the second comparator U1B is used to receive the fault voltage signal after filtering, the inverting input terminal is used to receive the reference voltage signal, and the output terminal is connected to the control to send a valid fault signal to the controller.

[0040] Preferably, the above-mentioned IGBT overcurrent protection circuit further includes an IGBT driving circuit for controlling the opening and closing of the IGBT upper tube and the IGBT lower tube;

[0041] The IGBT driving circuit includes a first capacitor C1, a third resistor R3, a fourth diode D4, a seventh resistor R7, a second capacitor C2 and a sixth resistor R6;

[0042] Among them, the first capacitor C1 and the third resistor R3 are connected in parallel to form an IGBT turn-on circuit, which is used to adjust the IGBT turn-on speed; the seventh resistor R7 and the fourth diode D4 are connected in series and then connected in parallel with the first capacitor C1 and the third resistor R3, and the seventh resistor R7 and the fourth diode D4 are connected in series to form an IGBT turn-off circuit; the common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7 is connected to the gate of the IGBT upper tube or the IGBT lower tube;

[0043] After the second capacitor C2 is connected in parallel with the sixth resistor R6, a first end thereof is connected to a common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7, a second end thereof is grounded, and a third end thereof is connected to a source of the IGBT upper tube or the IGBT lower tube;

[0044] The sixth resistor R6 and the second capacitor C2 form an IGBT internal capacitive-inductive network compensation circuit, which is used to adjust the switching waveform of the IGBT upper tube or the IGBT lower tube and ensure that the IGBT upper tube or the IGBT lower tube is reliably turned off.

[0045] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0046] The IGBT overcurrent protection circuit provided by the present invention adopts separate analog circuit devices to configure three working modes of the decoupled overcurrent protection circuit, and flexibly switches between three actual working conditions: when an overcurrent fault occurs in the IGBT, when it is working normally, and when it is not working. Overcurrent protection is achieved without using a driver chip, and the execution voltage range and response time value can be adjusted by adjusting circuit parameters and diode selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a common power circuit diagram of a frequency converter;

[0048] Figure 2 It is a schematic diagram of the composition structure of a first IGBT overcurrent protection circuit provided by an embodiment of the present invention;

[0049] Figure 3 is a circuit structure diagram of an upper tube driving circuit and a lower tube driving circuit provided by an embodiment of the present invention;

[0050] Figure 4 is a structural schematic diagram of a decoupling protection circuit provided by an embodiment of the present invention;

[0051] Figure 5 Schematic diagram of three different working modes of the decoupling protection circuit provided by an embodiment of the present invention;

[0052] Figure 6 is a schematic diagram of the structure of a filter circuit provided by an embodiment of the present invention;

[0053] Figure 7 is a schematic diagram of the structure of a reference voltage generating circuit provided by an embodiment of the present invention;

[0054] Figure 8 is a structural schematic diagram of a fault signal generating circuit provided by an embodiment of the present invention;

[0055] Fig. 9 is a schematic diagram of the structure of a hardware blocking circuit provided by an embodiment of the present invention;

[0056] Fig.10 It is a schematic diagram of the composition structure of a second IGBT overcurrent protection circuit provided by an embodiment of the present invention;

[0057] Fig.11 is a schematic diagram of the structure of a reset circuit provided by an embodiment of the present invention;

[0058] Fig.12 is a schematic diagram of the structure of an interference removal circuit provided by an embodiment of the present invention;

[0059] Fig.13 This is a schematic diagram of the inverter half-bridge drive signal position during parallel drive. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0061] Figure 1For a common inverter power circuit diagram, see Figure 1 , an IGBT overcurrent protection circuit designed for the upper and lower tubes of the A-phase half bridge is taken as an example for explanation. The IGBT overcurrent protection circuit needs to use the status signals D1 (upper tube drain voltage signal), G1 (upper tube gate voltage signal), S1 (upper tube source voltage signal), D2 (lower tube drain voltage signal), G2 (lower tube gate voltage signal), and S2 (lower tube source voltage signal) of the upper and lower tubes of the A-phase half bridge.

[0062] Figure 2 FIG. 1 is a schematic diagram of the composition structure of an IGBT overcurrent protection circuit provided in this embodiment, such as Figure 2 As shown, the IGBT overcurrent protection circuit includes an upper tube driving circuit and a lower tube driving circuit. The upper tube driving circuit is used to control the opening and closing of the IGBT upper tube, and the lower tube driving circuit is used to control the opening and closing of the IGBT lower tube.

[0063] Figure 3 is a schematic diagram of the circuit structure of the upper tube driving circuit and the lower tube driving circuit provided in this embodiment, such as Figure 3 As shown, the topological structures of the upper tube driving circuit and the lower tube driving circuit are the same, and the upper tube driving circuit is taken as an example for description below.

[0064] The upper tube driving circuit includes a first capacitor C1, a third resistor R3, a fourth diode D4, a seventh resistor R7, a second capacitor C2 and a sixth resistor R6;

[0065] The first capacitor C1 and the third resistor R3 are connected in parallel to form an IGBT turn-on circuit, which is used to adjust the IGBT turn-on speed; the seventh resistor R7 is connected in series with the fourth diode D4 and then connected in parallel with the first capacitor C1 and the third resistor R3, and the seventh resistor R7 and the fourth diode D4 are connected in series to form an IGBT turn-off circuit; wherein the fourth diode D4 is preferably a Schottky diode with a response level below 100ns. The common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7 is connected to the gate of the IGBT upper tube;

[0066] After the second capacitor C2 is connected in parallel with the sixth resistor R6, its first end is connected to the common connection end of the first capacitor C1, the third resistor R3 and the seventh resistor R7, the second end is grounded, and the third end is connected to the source of the IGBT upper tube; the sixth resistor R6 and the second capacitor C2 constitute an IGBT internal capacitive-inductive network compensation circuit, which is used to adjust the switching waveform of the IGBT upper tube and ensure that the IGBT upper tube is reliably turned off when the driving signal G1 is high-impedance.

[0067] As the core part of overcurrent protection, the IGBT overcurrent protection circuit also includes a decoupling protection circuit, a reference level generating circuit, a fault signal generating circuit and a hardware blocking circuit;

[0068] The decoupling protection circuit is used to collect the gate voltage and drain voltage of the IGBT lower tube, and generate a protection voltage signal according to the gate voltage and drain voltage;

[0069] The reference level generating circuit is used for providing a reference voltage signal;

[0070] The fault signal generating circuit is used to compare the protection voltage signal with the reference voltage signal, and generate a fault signal when the value of the protection voltage signal is greater than the reference voltage signal;

[0071] The hardware blocking circuit is used to clamp the gate voltage of the IGBT lower tube to the negative power supply of the lower tube driving power supply under the triggering of the fault signal, so that the IGBT lower tube is turned off to achieve overcurrent protection.

[0072] Figure 4 is a schematic diagram of the structure of the decoupling protection circuit provided in this embodiment, see Figure 4 , the decoupling protection circuit includes a first diode D1, a first resistor R1, a second diode D2, a fourth resistor R4, a third diode D3, and a fifth resistor R5;

[0073] The cathode of the first diode D1 is connected to the drain of the lower tube of the IGBT, and the cathode is connected to the anode of the second diode D2 through the first resistor R1; the cathode of the second diode D2 outputs the protection voltage signal SignalA;

[0074] The fourth resistor R4 is connected in parallel with the third diode D3, the first end of the fourth resistor R4 and the anode of the third diode D3 are connected to the anode of the first diode D1, and the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the gate of the lower tube of the IGBT;

[0075] A first end of the fifth resistor R5 is connected to the negative power supply of the lower tube driving power supply, and a second end thereof is connected to the anode of the second diode D2.

[0076] See also Figure 5 In this embodiment, the decoupling protection circuit has three working modes:

[0077] Working mode 1: When the IGBT lower tube is not in operation, the voltage value of the drain voltage VD2 of the IGBT lower tube is close to the voltage value Udc of the bus voltage, and the drain voltage of the IGBT lower tube breaks down the first diode D1. The fourth resistor R4 is connected to the negative power supply -V2 of the lower tube drive power supply for clamping; through the voltage division adjustment of R4 and R1, it is ensured that the voltage value of the state signal S does not reach the protection limit voltage value. The breakdown energy of the first diode D1 is discharged to the negative power supply of the lower tube drive power supply through the third diode D3 and the fifth resistor R5; finally, the voltage value of the state signal S is limited to near -V2+X, and the protection voltage signal SignalA output by the second diode D2 is limited to (-V2-V D2 +X); where -V2 represents the negative power supply of the lower tube drive power supply, V D2 represents the on-state voltage of the second diode D2, and the value of X depends on the resistance values ​​of the first resistor R1, the fourth resistor R4 and the fifth resistor R5;

[0078] Working mode 2: When the IGBT lower tube is in operation and no short circuit occurs, the drain voltage VD2 of the IGBT lower tube is the conduction voltage drop when the IGBT is turned on, which is generally very small and close to 0, so that the voltage value of the drain voltage VD2 of the IGBT lower tube is close to the reference value Ground2 of the lower tube drive power supply. At this time, the first diode D1 is not broken down, the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the positive power supply of the lower tube drive power supply, and the voltage value of the state signal S is close to the negative power supply -V2 of the lower tube drive power supply. The protection voltage signal SignalA output by the second diode D2 is limited to (-V2-V D2 );

[0079] Working mode 3: When the IGBT lower tube is in operation and an overcurrent short circuit occurs, it is necessary to send information that overcurrent protection is required to the controller MCU; at this time, the drain voltage VD2 of the IGBT lower tube is a larger value Y that is less than the bus voltage Udc, the first diode D1 is broken down, the second end of the fourth resistor R4 and the cathode of the third diode D3 are connected to the positive power supply of the lower tube drive power supply, and the breakdown energy of the first diode D1 is discharged to the negative power supply of the lower tube drive power supply through the fifth resistor R5; finally, the voltage value of the state signal S is limited to (V2+X*Y / Udc), and the protection voltage signal output by the second diode D2 is limited to (V2+X*Y / Udc-V D2 ), wherein V2 represents the positive power supply of the lower tube driving power supply, and Y represents the drain voltage of the lower tube of the IGBT.

[0080] In summary, under normal working conditions, the working state of the decoupling protection circuit switches between working mode 1 and working mode 2, and the protection voltage signal at SignalA is (-V2-V D2 ) to (-V2-V D2+X) changes.

[0081] The circuit application conditions of this example [bus voltage UDC: 600V, lower tube drive positive power supply V2 (relative to reference voltage Ground2): 15V), lower tube drive negative power supply -V2 (relative to reference voltage Ground2): -4V, the conduction voltage V D2 :0.3V];

[0082] In this example, by configuring the resistance values ​​of the first resistor R1, the fourth resistor R4 and the fifth resistor R5, X is configured to be 6V, and the protection voltage signal at SignalA varies between -4.3V and 1.7V (referenced to Ground2) in normal working conditions.

[0083] If an overcurrent fault occurs when the IGBT is turned on, the decoupling protection circuit operates in mode 3, and the protection voltage signal at SignalA is limited to 15.6V.

[0084] Through the circuit topology configuration of the present invention, the protection voltage signal SignalA is divided into clear voltage areas according to the working conditions of the IGBT.

[0085] As a preferred example, the IGBT overcurrent protection circuit also includes a filtering circuit; the filtering circuit is used to filter and divide the protection voltage signal SignalA output by the decoupling protection circuit to output a protection voltage signal A that matches the input resistance range of the fault signal generating circuit.

[0086] Figure 6 is a circuit structure diagram of the filter circuit provided in this embodiment, see Figure 6 , the filter circuit includes a tenth resistor R10, a fifth capacitor C5, a thirteenth resistor R13, and an eleventh resistor R11;

[0087] A first end of the tenth resistor R10 is connected to the output end of the decoupling protection circuit to receive the protection voltage signal SignalA, and a second end is connected to the eleventh resistor R11; the other end of the eleventh resistor R11 serves as the output end of the filter circuit;

[0088] After the fifth capacitor C5 is connected in parallel with the thirteenth resistor R13, one end of the fifth capacitor C5 is connected to the second end of the tenth resistor R10, and the other end is connected to the gate of the lower tube of the IGBT;

[0089] Among them, the tenth resistor R10, the fifth capacitor C5, and the thirteenth resistor R13 constitute a first-order RC filter circuit and a resistor voltage divider circuit, which filters and divides the protection voltage signal SignalA output by the decoupling protection circuit; the eleventh resistor R11 is an output matching resistor, which ensures that the output protection voltage signal A matches the input resistance range of the fault signal generating circuit.

[0090] As a specific example, the filtering circuit performs voltage division filtering on the protection voltage signal SignalA through resistor R10, resistor R13, and capacitor C5. The resistance value of R10 is equal to R13, and R11 is regarded as the driving resistor of the lower comparator circuit. At this time, the signal A output by the filtering circuit has a voltage value of -2.15V to 0.85V under normal working conditions and a voltage value of 7.8V in the event of a fault. In the case of mode transition, the voltage value of the filtered protection voltage signal transitions between the above three voltage values, and the transition range is (-2.15V to 7.8V).

[0091] Figure 7 is a schematic diagram of the circuit structure of the reference voltage generating circuit provided in this embodiment, see Figure 7 The reference voltage generating circuit is used to set the voltage threshold range, and includes a second resistor R2 and a fifth diode D5; one end of the second resistor R2 is connected to the reference voltage of the lower tube driving power supply, and the other end is connected to the cathode of the fifth diode D5; the anode of the fifth diode D5 is connected to the negative power supply -V2 of the lower tube driving power supply, and the fifth diode D5 is a voltage stabilizing diode, which generates a reference voltage signal B (such as 3V) relative to Ground2 through the second resistor R2 and the voltage stabilizing diode D5.

[0092] Figure 8 is a schematic diagram of the circuit structure of the fault signal generating circuit provided in this embodiment, see Figure 8 , the fault signal generating circuit includes an operational amplifier U1A, an eighth resistor R8, a sixth diode D6 and a ninth resistor R9;

[0093] The positive input terminal of the operational amplifier U1A is used to receive the protection voltage signal A, and the negative input terminal is used to receive the reference voltage signal B; when the voltage value of the protection voltage signal A is greater than the reference voltage signal B, it is considered that an overcurrent fault has occurred;

[0094] The eighth resistor R8 and the sixth diode D6 are connected in series between the non-inverting input terminal and the output terminal of the operational amplifier U1A. The output terminal of the operational amplifier U1A outputs a fault voltage signal C, which is converted into a corresponding fault current signal Fault2 through the ninth resistor R9 and transmitted to the hardware blocking circuit.

[0095] Fig. 9 is a schematic diagram of the circuit structure of the hardware blocking circuit provided in this embodiment, see Fig. 9 , the hardware blocking circuit includes a first transistor Q1, a twenty-first resistor R21, a MOS transistor Q3, an eighteenth resistor R18, and a seventh capacitor C7;

[0096] The base of the first transistor Q1 receives the fault current signal Fault2 output by the fault signal generating circuit, the collector receives the reference voltage Ground2 of the lower tube driving power supply, and the emitter is connected to the negative power supply -V2 of the lower tube driving power supply through the twenty-first resistor R21;

[0097] The gate of the MOS tube Q3 is connected to the emitter of the first transistor Q1, the source is connected to the negative power supply -V2 of the lower tube driving power supply, and the drain is connected to the gate of the IGBT lower tube after being connected in series with the eighteenth resistor R18 and the seventh capacitor C7.

[0098] The fault current signal Fault2 output by the fault signal generation circuit drives the hardware blocking circuit, turning on the first transistor Q1 in the circuit, and making the gate voltage of the MOS tube Q3 5V2 through the resistor R21. The MOS tube Q3 is turned on, and the gate signal of the lower tube is clamped to -V2, ensuring that the lower tube is turned off, and the IGBT tube is turned off before sending the final confirmation signal to the controller MCU, ensuring the safety of the IGBT and preventing damage. Among them, the role of R18 and C7 is to achieve soft shutdown, so as not to generate excessive voltage spikes to damage the IGBT.

[0099] In this embodiment, the range of the protection execution voltage is changed by adjusting the resistance values ​​of resistors R4, R1, and R5 in the decoupling protection circuit, and the response time is set by adjusting the resistance values ​​of R9 in the fault signal generating circuit and R21 and R18 in the hardware blocking circuit.

[0100] See also Fig.10 As a preferred embodiment, the above-mentioned IGBT overcurrent protection circuit also includes a controller MCU and a reset circuit;

[0101] The controller MCU is used to generate a reset signal according to the fault voltage signal C output by the fault signal generating circuit and send it to the reset circuit;

[0102] The reset circuit is used to clamp the protection voltage signal in the fault signal generating circuit to the negative power supply -V2 of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is discharged to the negative power supply of the lower tube driving power supply to release the fault signal.

[0103] Fig.11 is a schematic diagram of the circuit structure of the reset circuit provided in this embodiment, see Fig.11 , the reset circuit includes an optical coupler U507 and a second transistor Q2;

[0104] Among them, the first input terminal 1 of the optocoupler U507 receives the reset signal RESET_Sig output by the controller MCU, the second input terminal 2 is grounded, the first output terminal 4 is connected to the base of the second transistor Q2, and the second output terminal 5 is connected to the emitter of the second transistor Q2; the emitter of the second transistor Q2 is connected to the negative power supply -V2 of the lower tube drive power supply, and the collector is connected to the non-inverting input terminal of the operational amplifier U1A in the fault signal generating circuit.

[0105] When the controller MCU attempts to perform a software reset, if the overcurrent fault has disappeared, the reset circuit transmits the fault command RESET_Sig sent by the MCU to the transistor Q2 through the resistor R19, capacitor C8, optocoupler U507 and resistor R17, resistor R20, and capacitor C9, turning on the transistor Q2. At this time, the protection voltage signal A is pulled down to -V2, and the fault voltage signal C in the fault signal generation circuit is discharged to the negative power supply -V2 of the down tube drive power supply through the resistor R8 and the diode D6, so that the fault voltage signal C finally drops to -V2, thereby eliminating the overcurrent fault.

[0106] Furthermore, in order to avoid the influence of interference, the IGBT overcurrent protection circuit provided in this embodiment also includes an interference removal circuit; the interference removal circuit is used to compare the fault voltage signal output by the fault signal generating circuit with the reference voltage signal, and send the comparison result as a valid fault signal to the controller.

[0107] Fig.12 is a schematic diagram of the circuit structure of the interference removal circuit provided in this embodiment, see Fig.12 , the interference removal circuit includes a sixteenth resistor R16, a sixth capacitor C6 and a second comparator U1B;

[0108] The sixteenth resistor R16 and the sixth capacitor C6 form a first-order RC low-pass filter circuit to filter the fault voltage signal C generated by the fault signal generating circuit;

[0109] The non-inverting input terminal of the comparator U1B is used to receive the fault voltage signal C after filtering, the inverting input terminal is used to receive the reference voltage signal B, and the output terminal is connected to the controller MCU to send a valid fault signal D (high level valid) to the controller to confirm that an overcurrent fault has occurred.

[0110] Fig.13 This is a schematic diagram of the inverter half-bridge drive signal position during parallel drive, such as Fig.13As shown, when multiple tubes are connected in parallel, the lower tube status signal D2 is separated into D21 and D22. According to the structure of the above decoupling protection circuit, the same IGBT overcurrent protection circuits are respectively built for D21, G2, S2 and D22, G2, S2. The circuit structures and signal processing methods such as the decoupling protection circuit, the reference level generating circuit, the fault signal generating circuit, and the hardware blocking circuit are exactly the same as those described above. Multiple IGBT overcurrent protection circuits use the same controller MCU and send fault signals to the controller MCU through an OR gate.

[0111] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An IGBT overcurrent protection circuit, characterized in that: It includes a decoupling protection circuit, a reference level generating circuit, a fault signal generating circuit and a hardware blocking circuit; The decoupling protection circuit is connected to the gate and drain of the lower tube of the IGBT respectively, and generates a protection voltage signal according to the collected gate voltage and drain voltage of the lower tube of the IGBT; The reference level generating circuit is used to provide a reference voltage signal; The fault signal generating circuit is respectively connected to the decoupling protection circuit, the reference level generating circuit and the hardware blocking circuit, and compares the protection voltage signal provided by the decoupling protection circuit with the reference voltage signal provided by the reference level generating circuit. When the value of the protection voltage signal is greater than the reference voltage signal, a fault signal is generated and sent to the hardware blocking circuit; The hardware blocking circuit is connected to the gate of the lower tube of the IGBT, and when triggered by the fault signal, the gate voltage of the lower tube of the IGBT is clamped to the negative power supply of the lower tube driving power supply, so that the lower tube of the IGBT is turned off; The decoupling protection circuit includes a first diode, a first resistor, a second diode, a fourth resistor, a third diode, and a fifth resistor; The cathode of the first diode is connected to the drain of the lower tube of the IGBT, and the cathode is connected to the anode of the second diode through the first resistor; the cathode of the second diode outputs a protection voltage signal; The fourth resistor is connected in parallel with the third diode, the first end of the fourth resistor and the anode of the third diode are connected to the anode of the first diode, and the second end of the fourth resistor and the cathode of the third diode are connected to the gate of the lower tube of the IGBT; The first end of the fifth resistor is connected to the negative power supply of the lower tube driving power supply, and the second end is connected to the positive electrode of the second diode; The reference level generating circuit includes a second resistor and a fifth diode; one end of the second resistor is connected to the reference voltage of the lower tube driving power supply, and the other end is connected to the cathode of the fifth diode; the anode of the fifth diode is connected to the negative power supply of the lower tube driving power supply.

2. The IGBT overcurrent protection circuit according to claim 1, characterized in that: The decoupling protection circuit has three working modes: When the IGBT lower tube does not operate, the drain voltage of the IGBT lower tube breaks down the first diode, and the fourth resistor is connected to the negative power supply of the lower tube driving power supply for clamping; the breakdown energy of the first diode is discharged to the negative power supply of the lower tube driving power supply through the third diode and the fifth resistor; The protection voltage signal output by the second diode is limited to (-V2-V D2 +X); where -V2 represents the negative power supply of the lower tube drive power supply, V D2 represents the conduction voltage of the second diode, and the value of X depends on the resistance values ​​of the first resistor, the fourth resistor and the fifth resistor; When the IGBT lower tube is in operation and no short circuit occurs, the drain voltage of the IGBT lower tube is its conduction voltage drop, the first diode is not broken down, the second end of the fourth resistor and the cathode of the third diode are connected to the positive power supply of the lower tube drive power supply, and the protection voltage signal output by the second diode is limited to (-V2-V D2 ); When the IGBT lower tube is activated and short-circuited, the drain voltage of the IGBT lower tube breaks down the first diode, the second end of the fourth resistor and the cathode of the third diode are connected to the positive power supply of the lower tube drive power supply, and the breakdown energy of the first diode is discharged to the negative power supply of the lower tube drive power supply through the fifth resistor; the protection voltage signal output by the second diode is limited to (V2+X*Y / Udc-V D2 ), wherein V2 represents the positive power supply of the lower tube driving power supply, Udc represents the bus voltage, and Y represents the drain voltage of the IGBT lower tube.

3. The IGBT overcurrent protection circuit according to claim 1, characterized in that: The fault signal generating circuit comprises a first comparator, an eighth resistor, a sixth diode and a ninth resistor; The non-inverting input terminal of the first comparator is used to receive the protection voltage signal, and the inverting input terminal is used to receive the reference voltage signal; The eighth resistor and the sixth diode are connected in series between the non-inverting input terminal and the output terminal of the first comparator. The output terminal of the first comparator outputs a fault voltage signal, which is converted into a corresponding fault current signal by the ninth resistor and transmitted to the hardware blocking circuit.

4. The IGBT overcurrent protection circuit according to claim 1, characterized in that: The hardware blocking circuit includes a first transistor, a twenty-first resistor, a MOS transistor, an eighteenth resistor, and a seventh capacitor; The base of the first transistor receives the fault signal output by the fault signal generating circuit, the collector receives the reference voltage of the lower tube driving power supply, and the emitter is connected to the negative power supply of the lower tube driving power supply through the twenty-first resistor; The gate of the MOS tube is connected to the emitter of the first triode, the source is connected to the negative power supply of the lower tube driving power supply, and the drain is connected to the gate of the IGBT lower tube after being serially connected to the eighteenth resistor and the seventh capacitor.

5. The IGBT overcurrent protection circuit according to any one of claims 1 to 4, characterized in that: It also includes a filter circuit; the input end of the filter circuit is connected to the decoupling protection circuit, and the output end is connected to the fault signal generation circuit; The filter circuit performs filtering and voltage division processing on the protection voltage signal output by the decoupling protection circuit to output a protection voltage signal matching the input resistance range of the fault signal generating circuit.

6. The IGBT overcurrent protection circuit according to any one of claims 1 to 4, characterized in that: Also includes a controller and a reset circuit; The controller is connected to the fault signal generating circuit, generates a reset signal according to the fault signal output by the fault signal generating circuit, and sends the reset signal to the reset circuit; The output end of the reset circuit is connected to the fault signal generating circuit, and the protection voltage signal in the fault signal generating circuit is clamped to the negative power supply of the lower tube driving power supply according to the reset signal, so that the energy of the fault signal is discharged to the negative power supply of the lower tube driving power supply to release the fault signal.

7. The IGBT overcurrent protection circuit according to claim 6, characterized in that: It also includes an interference removal circuit, which is used to compare the fault signal output by the fault signal generation circuit with the reference voltage signal, and send the comparison result as a valid fault signal to the controller; The interference removal circuit includes a sixteenth resistor, a sixth capacitor and a second comparator; The sixteenth resistor and the sixth capacitor form a first-order RC low-pass filter circuit to filter the fault voltage signal generated by the fault signal generating circuit; The non-phase input terminal of the second comparator is used to receive the fault voltage signal after filtering, the inverting input terminal is used to receive the reference voltage signal, and the output terminal is connected to the control to send the effective fault signal to the controller.

8. The IGBT overcurrent protection circuit according to any one of claims 1 to 7, characterized in that: It also includes an IGBT drive circuit for controlling the on and off of the IGBT upper tube and the IGBT lower tube; The IGBT driving circuit includes a first capacitor, a third resistor, a fourth diode, a seventh resistor, a second capacitor and a sixth resistor; Among them, the first capacitor and the third resistor are connected in parallel to form an IGBT turn-on circuit, which is used to adjust the IGBT turn-on speed; the seventh resistor is connected in series with the fourth diode and then connected in parallel with the first capacitor and the third resistor, and the seventh resistor and the fourth diode are connected in series to form an IGBT turn-off circuit; the common connection end of the first capacitor, the third resistor and the seventh resistor is connected to the gate of the IGBT upper tube or the IGBT lower tube; After the second capacitor is connected in parallel with the sixth resistor, its first end is connected to the common connection end of the first capacitor, the third resistor and the seventh resistor, its second end is grounded, and its third end is connected to the source of the IGBT upper tube or the IGBT lower tube.

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