Test method relating to bipolar degradation of large-current SiC power semiconductor device
By using IGBT or MOSFET modules to generate large current and apply it to SiC MOSFET samples, combined with overheating and overcurrent protection circuits, the problem of difficulty in conducting bipolar degradation tests of high-current SiC bipolar power semiconductor devices in the prior art is solved, and efficient aging efficiency and accelerated degradation effect are achieved.
Patent Information
- Application Number
- CN202311735747.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-18
- Publication Date
- 2025-06-20
AI Technical Summary
The prior art is difficult to effectively carry out bipolar degradation tests of high-current SiC bipolar power semiconductor devices, resulting in the inability to accurately evaluate the long-term reliability of the device.
Using the output characteristics of the IGBT or MOSFET module, by building a pulsed high current test device, a large current of 100 amps or above is generated, and this current is applied to the SiC MOSFET sample, combining overheating protection and overcurrent protection circuits to ensure the safety and controllability of the test.
It has realized efficient high-current bipolar degradation tests for SiC bipolar power semiconductor devices, which improves the aging efficiency and accelerates bipolar degradation, and provides a new aging method to help study the degradation mechanism of the device at high temperature.
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Figure CN120177974A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor device testing, and in particular to a test method for bipolar degradation of a high-current SiC power semiconductor device. Background Art
[0002] Under bipolar operating conditions, any type of SiC (silicon carbide) device may experience bipolar degradation effects, which are mainly triggered by the basal plane bit (BPD) present on the SiC crystal. During bipolar operation, the energy released by the recombination of electrons and holes causes stacking faults to propagate at the BPD, which will propagate to the surface of the chip and then stop. This degradation phenomenon seriously affects the performance of SiC bipolar power devices, such as the reduction of minority carrier lifetime and the drift of on-state voltage drop, which is extremely unfavorable to the long-term reliability of SiC bipolar power devices.
[0003] The current bipolar degradation reliability evaluation adopts the method of applying forward current to the body diode for testing. There are two main modes for applying test current to the body diode: DC mode and pulse mode. When the DC mode is used for testing, a DC current is applied to the body diode, and the body diode is always in working state. When the pulse mode is used for testing, a pulse current is applied to the body diode. From the actual working conditions of the device, the body diode of the SiC bipolar power semiconductor device is mainly used for freewheeling, absorbing the current induced in the circuit during the device shutdown process. The pulse mode is closer to the actual working conditions of the device.
[0004] However, at present, no matter whether the DC mode or the pulse mode is used for bipolar testing, the applied current is relatively small. There is currently no practical method for bipolar degradation testing of SiC bipolar power semiconductor devices that requires the application of extremely large currents. How to design a bipolar degradation test method involving large current SiC bipolar power semiconductor devices has become a new market demand.
[0005] Currently, there are methods in the market to use transistors to provide large pulse currents, but the generation of large pulse currents is not only affected by the input characteristics of the transistor, but also by the applied pulse signal frequency, the charging current of the loop energy storage capacitor, the heating of the loop components, etc. The greater the applied pulse signal frequency, the greater the average effective current in the loop. When the power supply voltage applied to the loop is constant, the charging current of the loop energy storage capacitor will be greater, which will further cause the heating of the loop components, resulting in unnecessary energy loss and overheating. Summary of the invention
[0006] The object of the present invention is to overcome the disadvantages and deficiencies of the prior art, and to provide a test method for bipolar degradation of high-current SiC power semiconductor devices. By using the output characteristics of IGBT or MOSFET modules, high currents in the hundreds of amperes or even above thousands of amperes are generated, and the high currents are applied to SiC MOSFET samples, improving the aging efficiency and accelerating bipolar degradation.
[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:
[0008] A test method for bipolar degradation of high-current SiC power semiconductor devices, comprising the following steps:
[0009] S1: Build a pulsed high-current test device. The test device includes a drive circuit and a main circuit. The main circuit includes a power device under test, a companion device, a support capacitor, a charging resistor, a power supply, and a contactor;
[0010] S2: According to the specification parameters of the companion device, adjust the gate turn-on voltage and gate turn-off voltage of the companion device through the drive circuit, apply a reverse voltage between the gate and source of the power device under test, and make the power device under test in a fully off state;
[0011] S3: Apply a positive pulse voltage with a determined frequency and duty cycle between the GE poles of the companion device;
[0012] S4: Set the contactor to the closed state, gradually increase the power supply voltage, the power supply charges the support capacitor through the charging resistor, and the power device under test, the companion device, and the support capacitor form a loop, and pulsed high currents are generated by using the output characteristics of the companion device.
[0013] Further, the power device under test is a SiC MOSFET sample, and the companion device is an IGBT module or a MOSFET module. High currents are generated by using the output characteristics of the IGBT module or the MOSFET module, and the high currents are applied to the SiC MOSFET sample to be tested.
[0014] Further, the test device further includes an overheat protection unit and an overcurrent protection unit. Both protection units include a DC-DC power supply circuit, an amplification and comparison circuit, and a relay control circuit. The two protection units share the DC-DC power supply circuit, and the DC-DC power supply circuit includes WRA2412CS and WRB2405CS isolation power modules.
[0015] Further, for overheat protection, a thermistor is used for sampling, and the thermistor selected is a PT100 thermistor; the overheat amplification and comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. The small signal collected by the thermistor is amplified and compared through the amplification and comparison circuit, and then isolated through the HCPL181 optocoupler device.
[0016] Further, the overheat amplification comparison circuit includes a sample amplification comparison circuit for the SiC MOSFET sample part and a capacitance amplification comparison circuit for the support capacitor CE1 part.
[0017] Further, the overheat relay control circuit includes relay K1, relay K2, and a Darlington transistor. Relay K1 and relay K2 are G5V-2-DC24 signal relays, and the Darlington transistor is an ULN2803 Darlington transistor. The signals after amplification and comparison processing control the on / off of relay K1 and relay K2 through the Darlington transistor.
[0018] Further, the overheat protection wiring method includes:
[0019] The equivalent voltage of the coil rated voltage of contactor K0 is connected to the K1-6 contact of relay K1 and the K2-6 contact of relay K2. The K1-4 contact of relay K1 and the K2-4 contact of relay K2 are connected in parallel to the coil terminal of contactor K0.
[0020] Thermistors are respectively attached to the surfaces of the SiC MOSFET sample and the support capacitor CE1. The leads at both ends of the thermistor on the SiC MOSFET sample are led out and connected to the X2 terminal of the sample amplification comparison circuit. The leads at both ends of the thermistor on the support capacitor CE1 are led out and connected to the X4 terminal of the capacitance amplification comparison circuit. The data sampled by the thermistors are amplified and compared, and then respectively control the opening and closing of the relevant contacts of relay K1 and relay K2, and further control the opening and closing of contactor K0 in the main circuit, turning on or cutting off the power supply to play the role of overheat protection.
[0021] Further, for overcurrent protection, a shunt is connected in series in the main circuit for sampling. The shunt is connected in series with the charging resistor, the support capacitor, and the SiC MOSFET sample. The overcurrent amplification comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. The small signal collected by the shunt is amplified and compared through an amplifier circuit and then isolated by the HCPL181 optocoupler device.
[0022] Further, the overcurrent relay control circuit includes relay K3 and a Darlington transistor. Relay K3 is a G5V-2-DC24 signal relay, and the Darlington transistor is an ULN2803 Darlington transistor. The two relay control circuits share the Darlington transistor. The signals after amplification and comparison processing control the on / off of relay K3 through the Darlington transistor.
[0023] Further, the overcurrent protection wiring method includes:
[0024] The coil rated voltage of contactor K0 in the main circuit is connected to the K3-6 contact of relay K3, and the coil terminal of contactor K0 in the main circuit is connected to the K3-4 contact of relay K3.
[0025] The leads at both ends of the shunt in the main circuit are connected to terminal X6 of the overcurrent amplification and comparison circuit. After the data sampled by the shunt is amplified and compared, it controls the opening and closing of the relevant contacts of relay K3, and then controls the opening and closing of contactor K0 in the main circuit to turn on or cut off the power supply, playing the role of overcurrent protection.
[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0027] 1. The present invention utilizes the output characteristics of IGBT or MOSFET modules to generate large currents of hundreds of amperes or even more than thousands of amperes. The current is controllable and can be carried out in a high-temperature environment, improving the aging efficiency and accelerating the bipolar degradation.
[0028] 2. The present invention introduces an overheat protection and an overcurrent protection circuit. The circuit has high sampling accuracy and small offset voltage, and has an isolation function when sampling large currents, ensuring that the subsequent circuit is not damaged by high voltage breakdown due to circuit failure. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 It is a schematic diagram of the MOSFET output characteristic curve.
[0030] Figure 2 It is a schematic diagram of the drive circuit.
[0031] Figure 3 It is a schematic diagram of the main circuit.
[0032] Figure 4 It is a schematic diagram of the pulse waveform.
[0033] Figure 5 It is a schematic diagram of the DC-DC power supply circuit.
[0034] Figure 6 It is a schematic diagram of the sample amplification and comparison circuit.
[0035] Figure 7 It is a schematic diagram of the capacitor amplification and comparison circuit.
[0036] Figure 8 It is a schematic diagram of the overheat relay control circuit.
[0037] Figure 9 It is a schematic diagram of the overcurrent amplification and comparison circuit.
[0038] Figure 10 It is a schematic diagram of the overcurrent relay control circuit. DETAILED DESCRIPTION OF THE INVENTION
[0039] The test method for bipolar degradation of high-current SiC power semiconductor devices involved in the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0040] The present invention overcomes the limitation of the current magnitude in the DC or pulsed current stress power cycle test of the body diode of SiC bipolar power semiconductor devices, can achieve high-current tests of hundreds of amperes or even more than thousands of amperes, has controllable current, can be carried out in a high-temperature environment, improves the aging efficiency, accelerates bipolar degradation, and provides a new aging means for studying the bipolar degradation mechanism of SiC bipolar power semiconductor devices at high temperatures and dislocation defects in SiC materials.
[0041] At the same time, considering the problems of pulse frequency magnitude, loop charging current, and overcurrent and overheating that may occur in the device, the relationships between various factors are described in detail, and relevant parameter selections and device selections are given.
[0042] When the forward pulse width remains unchanged, the higher the pulse frequency, the greater the energy required from the energy storage capacitor to generate a test current of the same amplitude, the higher the applied power supply voltage (charging voltage), and the higher the requirements for the equipment. When conducting the bipolar degradation test, if a high-current of thousands of amperes is to be generated, it is recommended to select a forward pulse width of about 20 us and a pulse frequency not exceeding 100 Hz.
[0043] The greater the charging current of the energy storage capacitor in the loop, the higher the requirements for the energy storage capacitor and the power supply equipment, and at the same time, greater energy losses will be generated in the circuit. Therefore, a charging resistor can be connected in series between the power supply and the energy storage capacitor to alleviate the situation of excessive charging current during the test. When the pulse frequency and the forward pulse width remain unchanged, the greater the resistance value of the charging resistor used, the greater the power supply voltage required to generate the same pulse current value, and the greater the charging current of the capacitor. Therefore, a charging resistor with an appropriate resistance value should be selected to ensure that a continuous pulsed high current can be generated under an applied power supply voltage that is not too high, and at the same time, the charging current can be minimized as much as possible to avoid unnecessary energy losses.
[0044] According to the bipolar degradation test, when other test conditions remain unchanged, when the charging resistor is 50 Ω and the externally applied power supply voltage is 100 V, the test current can reach 1127 A, meeting the test requirements for the bipolar degradation test of high-current SiC bipolar power semiconductor devices of thousands of amperes. In addition, its charging current is 1.5092 A, the charging current value is within an acceptable range, and the heating of the charging resistor is not obvious.
[0045] Since the current applied in the test is above the kiloampere level, the current is relatively large, and the test is arranged to be carried out at high temperature. In order to prevent the sample and the IGBT or MOSFET module under test from failing due to short circuits or other problems during the test process or continuous heat accumulation during the test, resulting in thermal runaway, thus making the test have potential safety hazards, the present invention introduces an overheat protection circuit and an overcurrent protection circuit.
[0046] The present invention utilizes the output characteristics of IGBT or MOSFET modules to generate large currents above the hundred-ampere level or even above the kiloampere level, and with the corresponding software and hardware test platforms, applies the large current to SiC bipolar power semiconductor devices to conduct bipolar degradation tests of large currents on SiC bipolar power semiconductor devices.
[0047] Please refer to Figure 1 , taking MOSFET as an example to explain its output characteristics. The output characteristics of MOSFET usually represent the relationship curve between the drain current ID and the drain-source voltage VDS with the gate-source voltage VGS as a parameter variable.
[0048] Among them, when VDS > 0 and is relatively small, ID increases with the increase of VDS. This part of the region is called the variable resistance region in MOSFET and the non-saturation region in IGBT; when VDS continues to increase and the slope of ID-VDS gradually decreases to 0, this part of the region is called the constant current region in MOSFET and the saturation region in IGBT; when VDS increases to avalanche breakdown, this region is called the breakdown region in both MOSFET and IGBT. The gate-emitter voltage VGE of IGBT is similar to the gate-source voltage VGS of MOSFET, the collector current IC is similar to the drain current ID, and the collector-emitter voltage VCE is similar to the drain-source voltage VDS.
[0049] Select an IGBT with a sufficiently large collector current IC or a MOSFET with a sufficiently large drain current ID as the device under test, adjust the gate voltage of the IGBT / MOSFET to an appropriate value, and according to the output characteristic curve in the device data sheet of the device under test, apply an appropriate collector-emitter voltage VCE or drain-source voltage VDS to control the device under test in the constant current region of MOSFET or the saturation region of IGBT. At this time, the required large output current can be obtained.
[0050] Please refer to Figure 2 and Figure 3 , the present invention discloses a test method for bipolar degradation of large current SiC power semiconductor devices, including the following steps:
[0051] S1: Build a pulsed high-current test device. The test device includes a drive circuit and a main circuit. The main circuit includes a power device under test, a companion device Q1, a support capacitor CE1, a charging resistor, a power supply, and a contactor K0.
[0052] S2: According to the specification parameters of the companion device Q1, adjust the gate turn-on voltage and gate turn-off voltage of the companion device Q1 through the drive circuit, and apply a reverse voltage between the gate and source of the power device under test to make the power device under test in a fully off state.
[0053] S3: Apply a forward pulse voltage with a determined frequency and duty cycle between the GE poles of the companion device Q1.
[0054] S4: Set the contactor K0 to the closed state, gradually increase the power supply voltage, and the power supply charges the support capacitor CE1 through the charging resistor. The power device under test, the companion device Q1, and the support capacitor CE1 form a loop, and use the output characteristics of the companion device Q1 to generate a pulsed high current.
[0055] The power device under test is a SiC MOSFET sample ( Figure 3 DUT), and the companion device Q1 is an IGBT module or a MOSFET module. Use the output characteristics of the IGBT module or MOSFET module to generate a large current, and apply the large current to the SiC MOSFET sample to be tested. The drive circuit provides a gate voltage for the companion device Q1. Referring to the specification parameters of the companion device Q1, first adjust the gate turn-on voltage of the companion device Q1 to about 11V and the gate turn-off voltage to about -5V through the drive circuit, and apply a reverse voltage between the gate and source of the SiC MOSFET sample to be tested to ensure that the SiC MOSFET sample is in a fully off state.
[0056] Please refer to Figure 3 and Figure 4 , the SiC MOSFET sample (DUT) to be tested, the companion device Q1, and the support capacitor CE1 form a loop, and use the output characteristics of the companion IGBT module to generate a pulsed current. The current waveform on the loop is like Figure 4 I1 in. When the parameters such as the externally applied pulse frequency and the forward pulse width of the pulse are within a reasonable range and a sufficiently large power supply voltage is provided, the required large current can be generated (the large current waveform refers to Figure 4 I1 in).
[0057] The test device also includes an overheat protection unit and an overcurrent protection unit. The overheat protection unit includes a DC-DC power supply circuit, an overheat amplification and comparison circuit, and an overheat relay control circuit. The overcurrent protection unit includes a DC-DC power supply circuit, an overcurrent amplification and comparison circuit, and an overcurrent relay control circuit. The overheat protection unit and the overcurrent protection unit share the DC-DC power supply circuit.
[0058] Please refer to Figure 5 , the DC-DC power circuit includes a WRA2412CS isolated power module and a WRB2405CS isolated power module, with a wide voltage input, input-output isolation, and reduced interference between signals. The DC-DC power circuit can provide power for the subsequent amplification and comparison circuit and the relay control circuit.
[0059] Please refer to Figure 6 and Figure 7 , the overheat amplification and comparison circuit includes a sample amplification and comparison circuit for the SiC MOSFET sample part and a capacitance amplification and comparison circuit for the support capacitor CE1 part. The amplification and comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. Overheat protection uses a thermistor for sampling, and the PT100 thermistor is selected. The small signal collected by the thermistor is amplified by the amplification circuit and then isolated by the HCPL181 optocoupler device to achieve secondary isolation and further reduce the interference between input and output signals.
[0060] Please refer to Figure 8 , the overheat relay control circuit includes relay K1, relay K2, and a Darlington tube. Relay K1 and relay K2 are G5V-2-DC24 signal relays, and the Darlington tube is a ULN2803 Darlington tube. The signal after amplification and comparison processing controls the on and off of relay K1 and relay K2 through the Darlington tube.
[0061] The overheat protection wiring method includes:
[0062] At the K1-6 contact of relay K1 and the K2-6 contact of relay K2, an equivalent voltage of the coil rated voltage of the main circuit contactor K0 is connected. The K1-4 contact of relay K1 and the K2-4 contact of relay K2 are connected in parallel to the coil (V+) terminal of the main circuit contactor K0.
[0063] The thermistors are respectively attached to the surfaces of the SiC MOSFET sample and the support capacitor CE1. The leads at both ends of the thermistor on the SiC MOSFET sample are led out and connected to Figure 5 the X2 terminal of the sample amplification and comparison circuit, and the leads at both ends of the thermistor on the support capacitor CE1 are led out and connected to Figure 7 the X4 terminal of the capacitance amplification and comparison circuit. The data sampled by the thermistor are amplified and compared, and then respectively control the opening and closing of the relevant contacts of relay K1 and relay K2, thereby controlling the opening and closing of the main circuit contactor K0, turning on or cutting off the power supply, and playing an overheat protection role.
[0064] The DC-DC power circuit of the overcurrent protection unit is the same as that of the overheat protection unit. The DC-DC power circuit includes a WRA2412CS isolated power module and a WRB2405CS isolated power module, with wide voltage input and input-output isolation, reducing interference between signals. The DC-DC power circuit provides power for the subsequent amplification and comparison circuit and the relay control circuit.
[0065] Please refer to Figure 9 , for overcurrent protection, a shunt is connected in series in the main circuit for sampling, and the shunt model is "1500A / 75mV". The overcurrent amplification and comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. The small signal collected by the shunt is amplified by the amplification circuit and then isolated by the HCPL181 optocoupler device to achieve secondary isolation, further reducing interference between input and output signals.
[0066] Please refer to Figure 10 , the overcurrent relay control circuit includes a relay K3 and a Darlington tube. The relay K3 is a G5V-2-DC24 signal relay, and the Darlington tube is a ULN2803. The overheat relay control circuit and the overcurrent relay control circuit share the same Darlington tube, and the signal after amplification and comparison controls the on / off of the relay K3 through the Darlington tube.
[0067] The overcurrent protection wiring method includes:
[0068] At the K3-6 contact of the relay K3, the rated voltage of the coil of the contactor K0 in the main circuit is connected, and the K3-4 contact of the relay K3 is connected to the coil (V+) terminal of the contactor K0 in the main circuit. The leads at both ends of the shunt in the main circuit are connected to Figure 9 the X6 terminal in the overcurrent amplification and comparison circuit. The data sampled by the shunt is amplified and compared, and then the relevant contacts of the relay K3 are controlled to open and close, thereby controlling the opening and closing of the contactor K0 in the main circuit, turning on or cutting off the power supply, and playing the role of overcurrent protection.
[0069] In summary, the present invention has the following advantages and beneficial effects:
[0070] 1. The present invention utilizes the output characteristics of IGBT or MOSFET modules to generate large currents of hundreds of amperes or even more than thousands of amperes. The current is controllable and can be carried out in a high-temperature environment, improving the aging efficiency and accelerating the bipolar degradation.
[0071] 2. The present invention introduces an overheat protection and an overcurrent protection circuit. The circuit has high sampling accuracy and small offset voltage, and has an isolation function when sampling large currents, ensuring that the subsequent circuit is not damaged by high voltage breakdown due to circuit failure.
[0072] The above description is a detailed description of the preferred and feasible embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the scope of the patent covered by the present invention.
Claims
1. A test method for bipolar degradation of high-current SiC power semiconductor devices, characterized in that, It includes the following steps: S1: Build a pulsed high-current test device. The test device includes a drive circuit and a main circuit. The main circuit includes a power device under test, a companion device, a support capacitor, a charging resistor, a power supply, and a contactor; S2: According to the specification parameters of the companion device, adjust the gate turn-on voltage and gate turn-off voltage of the companion device through the drive circuit, apply a reverse voltage between the gate and source of the power device under test, and make the power device under test in a fully off state; S3: Apply a positive pulse voltage with a determined frequency and duty cycle between the GE poles of the companion device; S4: Set the contactor to the closed state, gradually increase the power supply voltage, the power supply charges the support capacitor through the charging resistor, the power device under test, the companion device, and the support capacitor form a loop, and use the output characteristics of the companion device to generate a pulsed high current.
2. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 1, characterized in that, The power device under test is a SiC MOSFET sample, and the companion device is an IGBT module or a MOSFET module. Use the output characteristics of the IGBT module or MOSFET module to generate a large current, and apply the large current to the SiC MOSFET sample to be tested.
3. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 1, characterized in that, The test device also includes an overheat protection unit and an overcurrent protection unit. Both protection units include a DC-DC power supply circuit, an amplification and comparison circuit, and a relay control circuit. The two protection units share the DC-DC power supply circuit. The DC-DC power supply circuit includes WRA2412CS and WRB2405CS isolated power supply modules.
4. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 3, characterized in that, For overheat protection, a thermistor is used for sampling, and the thermistor selected is a PT100 thermistor; the overheat amplification and comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. The small signal collected by the thermistor is amplified and compared through the amplification and comparison circuit, and then isolated through the HCPL181 optocoupler device.
5. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 4, characterized in that, The overheat amplification and comparison circuit includes a sample amplification and comparison circuit for the SiC MOSFET sample part and a capacitor amplification and comparison circuit for the support capacitor CE1 part.
6. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 5, characterized in that, The overheat relay control circuit includes relay K1, relay K2, and a Darlington tube. Relay K1 and relay K2 are G5V-2-DC24 signal relays, and the Darlington tube is a ULN2803 Darlington tube. The signal after amplification and comparison processing controls the on and off of relay K1 and relay K2 through the Darlington tube.
7. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 6, characterized in that, The overheat protection wiring method includes: Connect the equivalent voltage of the coil rated voltage of contactor K0 at the K1-6 contact of relay K1 and the K2-6 contact of relay K2, and connect the K1-4 contact of relay K1 and the K2-4 contact of relay K2 in parallel to the coil terminal of contactor K0; The thermistors are respectively attached to the surfaces of the SiC MOSFET sample and the support capacitor CE1. The leads at both ends of the thermistor on the SiC MOSFET sample are led out and connected to the X2 terminal of the sample amplification and comparison circuit. The leads at both ends of the thermistor on the support capacitor CE1 are led out and connected to the X4 terminal of the capacitance amplification and comparison circuit. The data sampled by the thermistors are amplified and compared, and then the relevant contacts of the relay K1 and the relay K2 are controlled to open and close, thereby controlling the opening and closing of the contactor K0 of the main circuit, turning on or cutting off the power supply, and playing a role in overheat protection.
8. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 3, characterized in that, For overcurrent protection, a shunt is connected in series in the main circuit for sampling. The shunt is connected in series with the charging resistor, the support capacitor, and the SiC MOSFET sample. The overcurrent amplification and comparison circuit includes an OP07A operational amplifier and an HCPL181 optocoupler device. The small signal collected by the shunt is amplified and compared through the amplification circuit and then isolated by the HCPL181 optocoupler device.
9. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 8, characterized in that, The overcurrent relay control circuit includes a relay K3 and a Darlington transistor. The relay K3 is a G5V-2-DC24 signal relay, and the Darlington transistor is a ULN2803 Darlington transistor. The two relay control circuits share the Darlington transistor, and the signal after amplification and comparison processing controls the on and off of the relay K3 through the Darlington transistor.
10. The test method for bipolar degradation of high-current SiC power semiconductor devices according to claim 9, characterized in that, The overcurrent protection wiring method includes: The rated voltage of the coil of the contactor K0 of the main circuit is connected to the K3-6 contact of the relay K3, and the K3-4 contact of the relay K3 is connected to the coil terminal of the contactor K0 of the main circuit. The leads at both ends of the shunt of the main circuit are connected to the X6 terminal of the overcurrent amplification and comparison circuit. The data sampled by the shunt are amplified and compared, and then the relevant contacts of the relay K3 are controlled to open and close, thereby controlling the opening and closing of the contactor K0 of the main circuit, turning on or cutting off the power supply, and playing a role in overcurrent protection.