CN115144719A - Power device testing device - Google Patents

Abstract

The application relates to a power device testing device. The device comprises: the device comprises a controller, an energy storage circuit, a power supply, a first inductance circuit, a power device to be tested and computer equipment; the controller is used for receiving a periodic test instruction sent by the computer equipment and controlling the power device to be tested to be switched off and the power supply to charge the energy storage circuit according to the test instruction; the controller is further used for stopping charging the energy storage circuit if the charging voltage of the energy storage circuit is greater than or equal to a preset voltage threshold, controlling the energy storage circuit to charge the first inductance circuit and controlling the power device to be tested to be conducted; the controller is further used for detecting the drain current of the power device to be tested, and if the drain current is larger than or equal to a preset current threshold, the power device to be tested is controlled to be turned off, so that the first inductance circuit applies voltage to the power device to be tested within a preset time period to obtain an avalanche test result. By adopting the device, the avalanche test can be automatically and repeatedly carried out on the power device, and the test efficiency is improved.

Description

Power device test equipment

technical field

The present application relates to the technical field of semiconductor device reliability testing, and in particular, to a power device testing device.

Background technique

Power devices are widely used in automotive electronics, consumer electronics, aerospace and other fields due to their good electrical properties and low price. The large-scale use of power devices in power electronic circuits makes the research on their reliability particularly important. In industrial applications of power devices, voltage surges or current surges often occur due to inductive loads at the moment of turn-off, resulting in avalanche failure of power devices, and this failure is usually irreversible, so the avalanche withstand capability of power devices will affect Therefore, it is necessary to study the avalanche withstand characteristics of power devices.

In the traditional technology, the research on the avalanche withstand characteristics of power devices is to repeat the Unclamped Inductive Switching UIS (Unclamped Inductive Switching UIS) test to simulate the actual working environment of the power device. In the existing UIS test method, the avalanche test can only be achieved by manually controlling the gate pulse generator.

However, since only a single avalanche test can be achieved by manually controlling the gate pulse generator, if multiple avalanche tests are to be performed, the gate pulse generator needs to be manually controlled multiple times, so the test is time-consuming and labor-intensive, and the test efficiency is relatively low. Low.

Because power devices usually have repeated voltage surges or current surges in practical applications, traditional technologies cannot automatically and repeatedly perform avalanche tests on power devices, and the test efficiency is low.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a power device testing apparatus that can improve the testing efficiency in view of the above technical problems.

The present application provides a power device testing apparatus. The device includes: a controller, an energy storage circuit, a power supply, a first inductance circuit, a power device to be measured, and computer equipment;

The controller is configured to receive periodic test instructions sent by the computer equipment, and control the power device to be tested to turn off and the power supply to charge the energy storage circuit according to the test instructions;

The controller is further configured to stop charging the energy storage circuit if the charging voltage of the energy storage circuit is greater than or equal to a preset voltage threshold, and control the energy storage circuit to charge the first inductance circuit , and control the power device to be tested to be turned on;

The controller is further configured to detect the drain current of the power device under test, and if the drain current is greater than or equal to a preset current threshold, control the power device under test to be turned off, so that the power device under test is turned off within a preset time period The avalanche test result is obtained by applying a voltage to the power device to be tested by the first inductance circuit.

In one embodiment, the device further includes a first switch and a second switch, the first switch is disposed between the energy storage circuit and the power supply, and the first end of the second switch is connected to The source of the power device to be tested is connected, and the second end of the second switch is grounded;

The controller is configured to control the first switch to be closed and the second switch to be opened according to the test instruction, so as to charge the energy storage circuit through the power supply when the first switch is closed , and turn off the power device under test when the second switch is turned off.

In one embodiment, the controller is further configured to turn off the first switch if the charging voltage of the energy storage circuit is greater than or equal to a preset voltage threshold, so as to stop charging the energy storage circuit, and controlling the energy storage circuit to charge the first inductive circuit, and controlling the second switch to be closed to turn on the power device to be tested.

In one of the embodiments, the device further comprises a constant current controller, the constant current controller is respectively connected with the controller and the energy storage circuit;

The constant current controller is used to control the current when the energy storage circuit charges the first inductance circuit to reach a set current value.

In one embodiment, the device further includes a current probe and an oscilloscope, a first end of the current probe is grounded, a second end of the current probe is connected to the second switch, and a third end of the current probe is connected to the second switch. The terminal is connected with the computer equipment through the oscilloscope;

the current probe, configured to detect an avalanche current generated when a voltage is applied to the power device under test by the first inductance circuit within the preset time period, wherein the avalanche test result includes the avalanche current;

The oscilloscope is used to measure the waveform of the avalanche current.

In one embodiment, the device further includes a voltage probe, a first end of the voltage probe is connected to the drain of the power device to be tested, and a second end of the voltage probe is connected to the drain of the second switch. The second end is connected to the second end of the current probe, and the third end of the voltage probe is connected to the computer device through the oscilloscope;

the voltage probe, configured to detect an avalanche voltage generated when a voltage is applied to the power device under test by the first inductance circuit within the preset time period, wherein the avalanche test result includes the avalanche voltage;

The oscilloscope is also used for measuring the waveform of the avalanche voltage.

In one embodiment, the device further includes a resistor, the controller includes a drain current detection circuit, a processing circuit and a gate control circuit, a first end of the resistor is connected to the drain current detection circuit and the gate control circuit. the source of the power device to be tested is connected, and the second end of the resistor is grounded;

The drain current detection circuit and the gate control circuit are connected to the processing circuit.

In one embodiment, the controller further includes an interface circuit and a driving circuit, the interface circuit is connected with the computer device, and the interface circuit and the driving circuit are connected with the processing circuit;

The interface circuit is configured to receive a periodic test instruction sent by the computer device, and send the test instruction to the drive circuit, so that the drive circuit controls the first switch according to the test instruction closed and the second switch is open.

In one of the embodiments, the controller further includes a voltage measurement circuit, the voltage measurement circuit is connected to the processing circuit;

The voltage measurement circuit is used to measure the charging voltage of the energy storage circuit and send the charging voltage to the processing circuit, so that the processing circuit can determine the charging of the energy storage circuit according to the charging voltage Whether the voltage is greater than or equal to the preset voltage threshold.

In one embodiment, the device further includes a second inductive circuit, a third switch and a fourth switch, a first end of the third switch is connected to the first end of the second inductive circuit, and the first end of the third switch is connected to the first end of the second inductive circuit. The second end of the two inductance circuits is connected to the first end of the voltage probe and the drain of the device under test;

The second end of the third switch is connected to the fourth switch and the constant current controller.

The above-mentioned power device testing device, wherein the device includes a controller, an energy storage circuit, a power supply, a first inductance circuit, a power device to be tested, and computer equipment; the controller is used to receive periodic test instructions sent by the computer equipment, And according to the test instruction, control the power device to be tested to turn off and the power supply to charge the energy storage circuit; the controller is also used to stop charging the energy storage circuit if the charging voltage of the energy storage circuit is greater than or equal to the preset voltage threshold, and The energy storage circuit is controlled to charge the first inductance circuit, and the power device to be tested is turned on; the controller is also used to detect the drain current of the power device to be tested, and if the drain current is greater than or equal to the preset current threshold, control The power device to be tested is turned off, so that a voltage is applied to the power device to be tested by the first inductance circuit within a preset time period to obtain an avalanche test result. That is to say, in this embodiment of the present application, the controller receives the periodic test instructions sent by the computer equipment, and controls the power device to be tested to turn off and the power supply to charge the energy storage circuit according to the test instructions, and the charging voltage of the energy storage circuit is greater than When it is equal to the preset voltage threshold, the controller controls the power supply to stop charging the energy storage circuit, controls the energy storage circuit to charge the first inductance circuit, and controls the power device to be tested to be turned on, and then the controller detects the power to be measured by detecting the power Whether the drain current of the device is greater than or equal to the preset current threshold, so as to control the power device under test to be turned off, so as to apply a voltage to the power device under test from the first inductance circuit within a preset time period to obtain the avalanche test result, because the controller can receive Periodic test instructions sent to the computer equipment, so that the power device under test can be controlled on and off according to the test instructions, so that the power device under test is in the process of repeated avalanche testing, so that the power device under test can be automatically repeated. Avalanche testing to improve testing efficiency. For example, the controller will receive a test instruction at a certain period of time, for example, the certain period of time is equal to 1 minute. After receiving the first test instruction at 10 o'clock, the controller executes a test instruction according to the method provided in this embodiment. test to get the avalanche test result corresponding to this test. After that, the controller will receive a test instruction again at 10:01, and then execute a test according to the method provided in this embodiment to obtain the avalanche test result corresponding to the test, and automatically repeat the test in this way, This saves manpower and improves test efficiency.

Description of drawings

1 is a schematic diagram of a circuit for performing avalanche testing on a power device in the prior art;

FIG. 2 is a schematic structural diagram of a power device testing apparatus provided by an embodiment of the present application;

3 is a schematic circuit diagram of a power device testing apparatus provided by an embodiment of the present application;

FIG. 4 is a schematic structural diagram of the interior of a controller according to an embodiment of the present application;

FIG. 5 is a schematic circuit diagram of a power device testing apparatus provided by another embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

In practical application circuits of power devices, the inductive load often causes the circuit to generate a large induced electromotive force at the moment of turn-off, and all the energy stored in the induced electromotive force is released by the power device. For example, when the motor starts When the motor is connected to an inductive load, a peak current will be generated, which will cause the power device to bear a large current or voltage shock. However, power devices are prone to failure under high voltage and strong current, namely avalanche failure, and this avalanche failure is usually irreversible. Therefore, the avalanche withstand capability of a power device will affect the safe operating area and service life of the device.

In the traditional technology, when the power device to be tested is tested for UIS, an external signal generator is required, such as a gate pulse generator, and a single avalanche test can be realized by manually controlling the gate pulse generator to issue voltage pulses. Refer to Figure 1, Figure 1 It is a schematic circuit diagram of performing avalanche testing on power devices in the prior art, and the specific testing process is as follows:

First set the test environment temperature to the specified value, and set the power supply voltage V _DD to the specified value, then manually adjust the voltage pulse width generated by the gate pulse generator V _GG , and then adjust the turn-on time of the power device DUT to be tested, and According to the monitored drain current I _d value, it is determined to make the drain current I _d value reach the specified avalanche current. Therefore, under the specified avalanche current conditions, by manually controlling the gate pulse generator V _GG many times, the DUT of the power device to be tested can perform avalanche testing with the specified number of pulses and repetition rate. After performing multiple avalanche tests, confirm whether the characteristics of the DUT of the power device to be tested are normal according to the failure criterion of the power device.

However, due to the practical application of power devices, systems with inductive loads usually experience repeated voltage surges or current surges, and manual control of the gate pulse generator can only achieve a single avalanche test at a time. For the second avalanche test, the gate pulse generator needs to be manually controlled many times, resulting in low test efficiency.

In order to solve the above technical problem, an embodiment of the present application provides a power device testing apparatus. Referring to FIG. 2 , FIG. 2 is a schematic structural diagram of a power device testing device provided by an embodiment of the present application. The device includes: a controller 21 , an energy storage circuit 24 , a power supply 25 , a first inductance circuit 23 , and a power device to be tested. 22 and the computer equipment 20; the controller 21 is used to receive the periodic test instructions sent by the computer equipment 20, and according to the test instructions, control the power device 22 to be tested to be turned off and the power supply 25 to charge the energy storage circuit 24; the controller 21, is also used to stop charging the energy storage circuit 24 if the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold, and control the energy storage circuit 24 to charge the first inductance circuit 23, and control the power device to be tested. 22 is turned on; the controller 21 is also used to detect the drain current of the power device 22 to be tested, and if the drain current is greater than or equal to the preset current threshold, the power device 22 to be tested is controlled to be turned off, so that the power device 22 to be tested is turned off within a preset time period. The first inductance circuit 23 applies a voltage to the power device 22 under test to obtain the avalanche test result.

The drain current is the current flowing from the drain of the power device DUT22 to be tested to the source of the power device DUT22 to be tested, that is, the leakage current.

Optionally, the power supply 25 may be, for example, a high-voltage programmable power supply HVG, and the energy storage circuit 24 may be an energy storage capacitor C1. The controller 21 receives the periodic test instructions sent by the computer equipment 20, and controls the gate-source voltage V _gs of the power device under test DUT22 to be less than or equal to the threshold voltage according to the test instructions, so that the power device under test DUT22 is turned off, and at the same time controls the high voltage The program-controlled adjustable power supply HVG charges the energy storage capacitor C1.

Optionally, it will be described with reference to the above example. After the charging voltage of the energy storage capacitor C1 reaches the preset voltage threshold, the controller 21 controls the high-voltage programmable power supply HVG to stop charging the energy storage capacitor C1, and controls the power device DUT22 to be tested. The gate-source voltage V _gs is greater than the threshold voltage, so that the power device DUT22 to be tested is turned on, and the energy storage capacitor C1 is controlled to discharge through the first inductance circuit 23 , that is, the first inductance circuit 23 is charged.

Optionally, the controller 21 detects that the drain current of the power device under test DUT22 reaches a preset current threshold, and the controller 21 controls the gate-source voltage V _gs of the power device under test DUT22 to be less than or equal to the threshold voltage, so that the power device under test DUT22 When turned off, since the current of the first inductance circuit 23 cannot be abruptly changed, a voltage surge occurs at both ends of the first inductance circuit 23 within a preset time period, and the avalanche test result is obtained through the power device DUT22 to be tested.

It should be noted that: if the gate-source voltage V _gs of the power device to be tested 22 is less than or equal to the threshold voltage, the power device to be tested 22 is turned off; if the gate-source voltage V _gs of the power device to be tested 22 is greater than the threshold voltage, the power device to be tested is 22 is on.

The above-mentioned power device testing device, wherein the device includes a controller 21, an energy storage circuit 24, a power supply 25, a first inductance circuit 23, a power device to be tested 22, and a computer device 20; the controller 21 is used to receive the computer device 20. The periodic test instructions sent, and according to the test instructions, control the power device 22 to be tested to be turned off and the power supply 25 to charge the energy storage circuit 24; the controller 21 is also used for if the charging voltage of the energy storage circuit 24 is greater than or equal to the preset value. If the voltage threshold is set, the charging of the energy storage circuit 24 is stopped, and the energy storage circuit 24 is controlled to charge the first inductance circuit 23, and the power device 22 to be tested is controlled to be turned on; the controller 21 is also used to detect the power device to be tested. 22, if the drain current is greater than or equal to the preset current threshold, the power device under test 22 is controlled to be turned off, so that the first inductance circuit 23 applies a voltage to the power device under test 22 within a preset time period to obtain an avalanche test. result. That is to say, in this embodiment, the controller 21 receives the periodic test instructions sent by the computer equipment 20, and controls the power device 22 to be tested to turn off and the power supply 25 to charge the energy storage circuit 24 according to the test instructions. When the charging voltage of 24 is greater than or equal to the preset voltage threshold, the controller 21 controls the power supply 25 to stop charging the energy storage circuit 24, controls the energy storage circuit 24 to charge the first inductance circuit 23, and controls the power device 22 to be tested. is turned on, and then the controller 21 controls the power device 22 to be turned off by detecting whether the drain current of the power device 22 to be tested is greater than or equal to the preset current threshold, so that the power device 22 to be tested is turned off by the first inductance circuit 23 within a preset time period. The power measuring device 22 applies a voltage to obtain the avalanche test result. Because the controller 21 can receive the periodic test instructions sent by the computer equipment 20, it can control the power device 22 to be turned on and off according to the test instructions, so that the power device 22 to be tested is in the process of repeated avalanche testing, Therefore, the avalanche test can be automatically and repeatedly performed on the power device 22 to be tested, thereby improving the test efficiency. For example, the controller 21 will receive a test instruction at a certain period of time, for example, the certain period of time is equal to 1 minute. After receiving the first test instruction at 10 o'clock, the controller 21 will follow the method provided in this embodiment. Execute a test to get the avalanche test result corresponding to the test. After that, the controller 21 will receive a test instruction again at 10:01, and then execute a test according to the method provided in this embodiment to obtain the avalanche test result corresponding to the test, and automatically repeat the test in this way. , thereby saving manpower and improving test efficiency.

In one of the embodiments, as shown in FIG. 3 , FIG. 3 is a schematic circuit diagram of a power device testing apparatus provided in an embodiment of the application, the apparatus further includes a first switch 31 and a second switch 32 , and the first switch 31 Set between the energy storage circuit 24 and the power supply 25, the first end of the second switch 32 is connected to the source of the power device 22 to be tested, and the second end of the second switch 32 is grounded; the controller 21 is used for testing according to the Command, control the first switch 31 to close and the second switch 32 to open, so that when the first switch 31 is closed, the energy storage circuit 24 is charged through the power supply 25, and when the second switch 32 is open, the power device to be tested is turned off twenty two.

The controller 21 controls the first switch 31 to close and the second switch 32 to open according to the test command, and controls the gate-source voltage V _gs of the power device DUT22 to be tested to be less than or equal to the threshold voltage, so that the power device to be tested is less than or equal to the threshold voltage. The power device DUT22 is turned off, and the energy storage capacitor C1 is charged through the high-voltage programmable power supply HVG.

In the embodiment of the present application, the device further includes a first switch 31 and a second switch 32, the first switch 31 is disposed between the energy storage circuit 24 and the power supply 25, and the first end of the second switch 32 is connected to the power device 22 to be tested. The source of the second switch 32 is connected to the ground, and the second end of the second switch 32 is grounded; the controller 21 is used to control the first switch 31 to be closed and the second switch 32 to be opened according to the test instruction, so as to pass the power supply when the first switch 31 is closed. 25 charges the tank circuit 24 and turns off the power device 22 under test when the second switch 32 is turned off. That is to say, the controller 21 in this embodiment controls the first switch 31 to close and the second switch 32 to open according to the test instruction, so as to make the power supply 25 charge the energy storage circuit, so that the energy storage circuit 24 can charge the first switch 32 to the first switch 32 . The inductance circuit 23 is charged, so that the first inductance circuit 23 can apply a voltage to the power device 22 under test to obtain the avalanche test result.

In one embodiment, the controller 21 is further configured to turn off the first switch 31 if the charging voltage of the energy storage circuit 24 is greater than or equal to a preset voltage threshold, so as to stop charging the energy storage circuit 24 and control the energy storage The circuit 24 charges the first inductance circuit 23 and controls the second switch 32 to be closed to turn on the power device 22 under test.

Optionally, referring to FIG. 3 , if the charging voltage of the storage capacitor C1 is greater than or equal to the preset voltage threshold, the controller 21 controls the first switch 31 to be turned off, the second switch 32 is turned on, and controls the power device DUT22 to be tested. The gate-source voltage V _gs is greater than the threshold voltage, so that the power device DUT22 to be tested is turned on, and the energy storage capacitor C1 discharges constant current through the first inductance circuit 23 , that is, the first inductance circuit 23 is charged.

Optionally, the first inductance circuit 23 includes a plurality of inductances in series, a plurality of inductance selection switches connected in parallel with each inductance, and before the device performs the avalanche test, the controller 21 controls the number of closed inductance selection switches, The inductance of the first inductance circuit 23 is made to reach the set value. For example, taking FIG. 3 as an example for illustration, the inductance of the first inductance circuit 23 for performing the avalanche test needs to be 180mH, then the controller 21 controls S11 and S12 corresponding to L1 with a specification of 120mH and L2 with a specification of 60mH to close, respectively, The other inductive selector switches are open.

Optionally, the first inductance circuit 23 includes fixed inductances (L1-L7), 100μH group tapped inductances (L8) and 10μH group tapped inductances (L9), then the inductance selection switches corresponding to L1-L7 are S11-S17, and L8 corresponds to The inductance selection switches of 1 are S20~S28, and the corresponding inductance selection switches of L9 are S30~S38, among which, L1~L9 are used for the avalanche energy storage inductance.

In the embodiment of the present application, the controller 21 is further configured to turn off the first switch 31 if the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold, so as to stop charging the energy storage circuit 24 and control the energy storage circuit 24 charges the first inductance circuit 23, and controls the second switch 32 to be closed to turn on the power device 22 under test. That is to say, when the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold, the controller 21 in this embodiment controls the first switch 31 to be turned off, the second switch 32 to be turned on, and controls the power device 22 to be tested to conduct so that the tank circuit 24 can charge the first inductance circuit 23 .

In one embodiment, the device further includes a constant current controller 39, which is respectively connected to the controller 21 and the energy storage circuit 24; the constant current controller 39 is used to control the energy storage circuit 24 to the first inductance The current when the circuit 23 is charged reaches the set current value.

3, one end of the constant current controller 39 is connected to the controller 21, the other end of the constant current controller 39 is connected to the energy storage circuit 24, and the other end of the constant current controller 39 is also connected to the discharge resistor 40. One end is connected, the other end of the discharge resistor 40 is connected to the discharge switch, and the energy storage circuit 24 is connected in parallel with the discharge resistor 40 .

In the embodiment of the present application, the device further includes a constant current controller 39, which is respectively connected to the controller 21 and the energy storage circuit 24; the constant current controller 39 is used to control the energy storage circuit 24 to the first inductance circuit 23 The current during charging reaches the set current value. That is to say, the constant current controller 39 in this embodiment can control the current when the energy storage circuit 24 charges the first inductance circuit 23 to reach the set current value, and can also control the energy storage circuit 24 to charge the first inductance circuit 23 with a constant current. An inductive circuit 23 is charged.

In one embodiment, the device further includes a current probe 33 and an oscilloscope 35 , the first end of the current probe 33 is grounded, the second end of the current probe 33 is connected to the second switch 32 , and the third end of the current probe 33 passes through the oscilloscope 35 connected with the computer equipment 20; the current probe 33 is used to detect the avalanche current generated when the voltage is applied to the power device 22 to be tested by the first inductance circuit 23 within a preset time period, wherein the avalanche test result includes the avalanche current; the oscilloscope 35, Waveform used to measure avalanche current.

3 , the controller 21 detects that the drain current value of the power device DUT22 to be tested is greater than or equal to a preset current threshold, and the controller 21 controls the gate-source voltage V _gs of the power device DUT22 to be tested to be less than or equal to the threshold voltage, The power device DUT22 to be tested is turned off. Since the current on the first inductance circuit 23 cannot be abruptly changed, a high voltage is generated at both ends of the first inductance circuit 23, and the first inductance circuit 23 sends the power device DUT22 to the test within a preset period of time. The avalanche current generated when the voltage is applied, the current probe 33 connected in series with the power device DUT22 to be tested measures the avalanche current, the waveform of the avalanche current is measured by the oscilloscope 35 connected to the current probe 33, and the current I curve is recorded and stored in the computer equipment 20.

In the embodiment of the present application, the device further includes a current probe 33 for detecting an avalanche current generated when a voltage is applied to the power device 22 under test by the first inductance circuit 23 within a preset time period, and an oscilloscope 35 for measuring the avalanche current waveform , the first end of the current probe 33 is grounded, the second end of the current probe 33 is connected to the second switch 32 , and the third end of the current probe 33 is connected to the computer equipment 20 through the oscilloscope 35 . That is to say, in this embodiment, the avalanche current generated when the voltage is applied to the power device 22 under test by the first inductance circuit 23 within a preset time period is detected by the current probe 33, and the waveform of the avalanche current is measured by the oscilloscope 35, thereby It can measure the value and waveform of avalanche current, and then convert the current signal invisible to the naked eye into a current curve visible to the naked eye, which is convenient for researchers to study the changing process of avalanche current. Record.

In one embodiment, the device further includes a voltage probe 34, the first end of the voltage probe 34 is connected to the drain of the power device 22 to be tested, the second end of the voltage probe 34 is connected to the second end of the second switch 32 and the current The second end of the probe 33 is connected, and the third end of the voltage probe 34 is connected to the computer equipment 20 through the oscilloscope 35; the voltage probe 34 is used to detect the voltage applied to the power device 22 under test by the first inductance circuit 23 within a preset time period The avalanche voltage is generated during the avalanche test, wherein the avalanche test result includes the avalanche voltage; the oscilloscope 35 is also used to measure the waveform of the avalanche voltage.

3 , the controller 21 detects that the drain current value of the power device DUT22 to be tested is greater than or equal to a preset current threshold, and the controller 21 controls the gate-source voltage V _gs of the power device DUT22 to be tested to be less than or equal to the threshold voltage, The power device DUT22 to be tested is turned off. Since the current on the first inductance circuit 23 cannot be abruptly changed, a high voltage is generated at both ends of the first inductance circuit 23, and the first inductance circuit 23 sends the power device DUT22 to the test within a preset period of time. The avalanche voltage generated when the voltage is applied, the voltage probe 34 connected in parallel at both ends of the power device DUT22 to be tested measures the avalanche voltage, the waveform of the avalanche voltage is measured by the oscilloscope 35 connected to the voltage probe 34, and the voltage V curve is recorded and stored in the computer device 20.

In the embodiment of the present application, the apparatus further includes a voltage probe 34 for detecting an avalanche voltage generated when a voltage is applied to the power device 22 under test by the first inductance circuit 23 within a preset time period, and an oscilloscope 35 for measuring the avalanche voltage waveform , the first end of the voltage probe 34 is connected to the drain of the power device 22 to be tested, the second end of the voltage probe 34 is connected to the second end of the second switch 32 and the second end of the current probe 33, and the second end of the voltage probe 34 The three terminals are connected to the computer equipment 20 through the oscilloscope 35 . That is to say, in this embodiment, the voltage probe 34 is used to detect the avalanche voltage generated when the voltage is applied to the power device 22 under test by the first inductance circuit 23 within a preset time period, and the oscilloscope 35 is used to measure the waveform of the avalanche voltage, thereby It can measure the value and waveform of avalanche voltage, and then convert the invisible voltage signal into a voltage curve visible to the naked eye, which is convenient for researchers to study the change process of avalanche voltage. Record.

In one embodiment, the device further includes a resistor 38, the controller 21 includes a drain current detection circuit 43, a processing circuit 41 and a gate control circuit 44, the first end of the resistor 38 is connected to the drain current detection circuit 43 and the circuit to be tested The source of the power device 22 is connected, and the second end of the resistor 38 is grounded; the drain current detection circuit 43 and the gate control circuit 44 are connected to the processing circuit 41 .

Optionally, FIG. 4 is a schematic diagram of the internal structure of a controller provided by an embodiment of the present application. As shown in FIG. 4 , the controller 21 includes a drain current detection circuit 43 , a processing circuit 41 and a gate control circuit 44 . The pole current detection circuit 43 and the gate control circuit 44 are connected to the processing circuit 41 .

Optionally, since the current flows from the drain of the power device under test DUT22 to the source of the power device under test DUT22, the drain current detection circuit 43 detects the drain current of the power device under test DUT22 through the resistor R2. If the current exceeds the allowable drain current of the power device under test DUT22, it is determined that the power device under test DUT22 or the test socket used to carry the power device under test DUT22 is short-circuited, that is to say, the power device under test DUT22 or the test socket is damaged and the avalanche test is terminated. .

Optionally, the drain current detection circuit 43 detects the drain current of the power device under test DUT22 through the resistor R2, and if the drain current does not exceed the allowable drain current of the power device under test DUT22, it is determined that the power device under test DUT22 or use If the test socket carrying the power device under test DUT22 is not short-circuited, that is to say, the power device under test DUT22 or the test socket is intact, then when the drain current detection circuit 43 detects that the drain current of the power device under test DUT22 is greater than or equal to the preset current threshold value, and send the drain current information that the drain current is greater than or equal to the preset current threshold value to the processing circuit 41, the processing circuit 41 receives the drain current information, and sends it to the gate control circuit 44, and the gate control circuit 44 according to the drain current information The pole current information controls the gate-source voltage V _gs of the power device under test DUT22 to be less than or equal to the threshold voltage, so that the power device under test DUT22 is turned off. The two ends of 23 generate a voltage shock, and the avalanche test result is obtained through the power device DUT22 to be tested.

In this embodiment of the present application, the controller 21 includes a processing circuit respectively connected to the drain current detection circuit 43 and the gate control circuit 44 , and the first end of the resistor 38 is connected to the drain current detection circuit 43 and the source of the power device 22 under test. connected, the second end of resistor 38 is grounded. That is to say, in this embodiment, through the processing circuit 41 connected to the drain current detection circuit 43 and the gate control circuit 44 respectively, the controller 21 can control the gate-source voltage V _gs of the power device 22 under test to be between positive and negative The continuous conversion enables the power device 22 to be tested to be in a repeated avalanche process, so that the avalanche test can be automatically and repeatedly performed, which is convenient for evaluating the reliability of the avalanche current of the power device 22 to be tested.

In one embodiment, the controller 21 further includes an interface circuit 42 and a drive circuit 46, the interface circuit 42 is connected to the computer device 20, the interface circuit 42 and the drive circuit 46 are connected to the processing circuit 41; the interface circuit 42 is used to receive the computer The device 20 sends the periodic test command, and sends the test command to the driving circuit 46, so that the driving circuit 46 controls the first switch 31 to be closed and the second switch 32 to be turned off according to the test command.

4 , the controller 21 further includes an interface circuit 42 and a drive circuit 46 , the interface circuit 42 is connected to the computer device 20 , and both the interface circuit 42 and the drive circuit 46 are connected to the processing circuit 41 .

Optionally, the interface circuit 42 receives the periodic test instruction sent by the computer device 20, and the driving circuit 46 controls the first switch 31 to close and the second switch 32 to open according to the periodic test instruction sent by the interface circuit 42, and to The switch state signal that the first switch 32 is closed and the second switch 32 is disconnected is sent to the processing circuit 41, and the processing circuit 41 sends the switch state signal to the gate control circuit 44, and the gate control circuit 44 controls the power to be measured according to the switch state signal. When the gate-source voltage V _gs of the device DUT22 is less than or equal to the threshold voltage, the power device DUT22 to be tested is turned off, and the energy storage capacitor C1 is charged through the high-voltage programmable power supply HVG.

Optionally, the interface circuit 42 receives the periodic test instructions sent by the computer device 20, and sends the test instructions to the processing circuit 41, the processing circuit 41 receives the test instructions and sends the test instructions to the drive circuit 46, and the drive circuit 46 according to the test instructions. , control the first switch 31 to close and the second switch 32 to open, and send the switch state signal of the first switch 31 closed and the second switch 32 open to the processing circuit 41, and the processing circuit 41 sends the switch state signal to the gate The control circuit 44, the gate control circuit 44 controls the gate-source voltage V _gs of the power device under test DUT22 to be less than or equal to the threshold voltage according to the switch state signal, so that the power device under test DUT22 is turned off, and the energy storage capacitor C1 is connected to the energy storage capacitor C1 by the process-controlled adjustable power supply HVG to charge.

In this embodiment of the present application, the controller 21 further includes an interface circuit 42 and a drive circuit 46 connected to the computer device 20 , and the interface circuit 42 and the drive circuit 46 are connected to the processing circuit 41 ; the interface circuit 42 receives the periodic test sent by the computer device 20 . instruction, and send a test instruction to the drive circuit 46, so that the drive circuit 46 controls the first switch 31 to close and the second switch 32 to open according to the test instruction. That is to say, in this embodiment, the interface circuit 42 receives the periodic test instructions sent by the computer device 20, and sends the test instructions to the drive circuit 46, so that the drive circuit 46 controls the first switch 31 to close and close the first switch 31 according to the test instructions. The second switch 32 is turned off.

In one embodiment, the controller 21 further includes a voltage measurement circuit 45, which is connected to the processing circuit 41; the voltage measurement circuit 45 is used to measure the charging voltage of the energy storage circuit 24 and send the charging voltage to the processing circuit 41. voltage, so that the processing circuit 41 determines whether the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold according to the charging voltage.

4 , the voltage measurement circuit 45 in the controller 21 is connected to the processing circuit 41 , and the processing circuit 41 is connected to the gate control circuit 44 .

In combination with the above example, the voltage measurement circuit 45 measures the charging voltage of the energy storage capacitor C1, and sends the charging voltage to the processing circuit 41. When the processing circuit 41 determines that the charging voltage of the energy storage capacitor C1 reaches the preset voltage threshold, it will The charging voltage information whose charging voltage reaches the preset voltage threshold is sent to the gate control circuit 44 and the driving circuit 46, and the gate control circuit 44 controls the gate-source voltage V _gs of the power device DUT22 to be tested to be greater than the threshold voltage according to the charging voltage information, so that the The power measuring device DUT22 is turned on, and at the same time, the driving circuit 46 controls the first switch 31 to be turned off and the second switch 32 to be closed according to the charging voltage information, and then the energy storage capacitor C1 discharges the constant current through the first inductance circuit 23, that is, the first inductance Circuit 23 is charged.

In the implementation of this application, the controller 21 further includes a voltage measurement circuit 45, which is connected to the processing circuit 41; the voltage measurement circuit 45 is used to measure the charging voltage of the energy storage circuit 24, and send the charging voltage to the processing circuit 41, The processing circuit 41 determines whether the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold according to the charging voltage. That is to say, in this embodiment, the voltage measurement circuit 45 is connected to the processing circuit 41 , so that the controller 21 can determine whether the charging voltage of the energy storage circuit 24 is greater than or equal to the preset voltage threshold.

In one embodiment, the device further includes a second inductive circuit, a third switch 37 and a fourth switch 36, the first end of the third switch 37 is connected to the first end of the second inductive circuit, and the first end of the second inductive circuit is connected to the first end of the second inductive circuit. The two terminals are connected to the first terminal of the voltage probe 34 and the drain of the power device 22 to be tested; the second terminal of the third switch 37 is connected to the fourth switch 36 and the constant current controller 39 .

The second inductance circuit is connected to the second inductance circuit through an external inductance connection terminal when the inductance value of the first inductance circuit 23 is not large enough.

Optionally, the device further includes a diode, the first end of the diode is connected to the fourth switch 36, and the second end of the diode is connected to the power supply 25, wherein the specification of the diode is a 200A rectifier diode.

Optionally, the third switch 37 is, for example, an external inductance selection switch, the second inductance circuit is, for example, an external inductance, and the fourth switch 36 is, for example, an internal inductance selection switch, and both the external inductance selection switch and the internal inductance selection switch are 200A DC contacts. device.

It should be noted that, after the avalanche test is completed, the voltage measurement circuit 45 detects whether the charging voltage in the energy storage circuit 24 is emptied. The drive circuit 46 controls the energy storage circuit 24 to turn off the third switch 37 or the fourth switch 36 that is in the closed state when the first inductive circuit 23 or the second inductive circuit is charged according to the unemptied charging voltage sent by the processing circuit 41 , and The discharge switch 40 is controlled to close to empty the charge in the tank circuit 24 .

Optionally, the apparatus further includes: a liquid crystal display, where the liquid crystal display is connected to the computer equipment 20 . The computer device 20 and the liquid crystal display are used to set test parameters and display test parameters and curves during the avalanche test. Among them, the test parameters are specifically shown in Table 1, the test interval is the time interval for each avalanche test, and the number of tests is the number of times the avalanche test is repeated. The number of tests and the test interval can be preset before the test, and the test is repeated based on the number of tests and the test interval.

Table 1 Description of test parameters

Test parameter name Numerical value illustrate The output voltage of the power supply 1～400V Adjustable in steps of 1V The output current of the power supply 0.5A / tank circuit 220μF/400V / Gate-source voltage V_gs -15～+20V Adjustable in steps of 1V The current output by the constant current controller 4～200A 2A is step size adjustable first inductive circuit 0.01～239.99mH Step 0.01mH adjustable preset duration 1～200μs Adjustable in 1μs steps allowable drain current 1μA～2mA Adjustable in 1μA steps test interval 10～9999s / Testing frequency 1～9999 times /

In the embodiment of the present application, the device further includes a second inductive circuit, a third switch 37 and a fourth switch 36, the first end of the third switch 37 is connected to the first end of the second inductive circuit, and the second end of the second inductive circuit The terminal is connected to the first terminal of the voltage probe 34 and the drain of the power device 22 to be tested, and the second terminal of the third switch 37 is connected to the fourth switch 36 and the constant current controller 39 . That is to say, in this embodiment, through the second inductance circuit, the problem that the avalanche test cannot be performed due to insufficient inductance of the first inductance circuit 23 can be avoided.

In one embodiment, for example, the capacitor C is used as the tank circuit 24, the internal inductance L1 with a specification of 120mH and L2 with a specification of 60mH are used as the first inductance circuit 23, the resistor 38 is R2, and the controller 21 is the central control The first switch 31 is S01, the second switch 32 is S04, the third switch 37 is S03, the fourth switch 36 is S02, the discharge switch is S05, the power supply 25 is a high-voltage programmable power supply HVG, a constant current controller 39 is the constant current source CS1, the current probe 33 is the current probe P1, the voltage probe 34 is the high-voltage differential probe P2, the drive circuit 46 is the relay array drive circuit, the interface circuit 42 is the host computer communication interface circuit, and the voltage measurement circuit 45 is a capacitor bank The voltage measurement circuit, the drain current detection circuit 43 is the leakage current detection circuit of the device under test, the gate control circuit 44 is the gate control circuit of the device under test, and the processing circuit 41 is an MCU+FPGA processing unit as an example, as shown in FIG. 5 5 is a schematic circuit diagram of a power device testing device provided by another embodiment of the present application, and the power device testing device provided by the embodiment of the present application is described in detail, including the following steps:

S501. Before the test starts, adjust the inductance of the inductance group according to the set value. The central controller controls S02 to close to select the internal inductance, and controls S11 and S12 to close, so that the inductance value of the internal inductance is 180mH.

S502, the host computer communication interface circuit in the central controller receives the test instruction of the computer, and sends the test instruction to the relay array drive circuit, and the relay array drive circuit controls S01 to be closed and S04 to be disconnected, and S01 to be closed and S04 to be disconnected The switch status signal is sent to the MCU+FPGA processing unit, and the MCU+FPGA processing unit sends the switch status signal to the gate control circuit of the device under test, and the gate control circuit of the device under test controls the gate of the power device DUT under test according to the switch status signal. When the source voltage V _gs is less than the threshold voltage, the DUT of the power device to be tested is disconnected, and the high-voltage programmable power supply HVG charges the capacitor C.

S503, the leakage current detection circuit of the device to be tested detects the leakage current of the DUT of the power device to be tested through R2, and if the leakage current exceeds the allowable value, it is determined that the DUT of the power device to be tested is damaged and the test is terminated.

S504, the capacitor bank voltage measurement circuit detects that the charging voltage of the capacitor C reaches the preset voltage threshold, and sets the current value of the constant current source CS1 through the MCU+FPGA processing unit, and the MCU+FPGA processing unit sends the current value of the constant current source CS1 to the relay The array drive circuit and the gate control circuit of the device under test, the relay array drive circuit controls S01 to open and S04 to close according to the current value of the constant current source CS1, at the same time, the gate control circuit of the device under test controls the under test according to the current value of the constant current source CS1 When the gate-source voltage V _gs of the power device DUT is greater than the threshold voltage, the DUT of the power device to be tested is turned on, and the capacitor C1 discharges with constant current through the internal inductor.

S505 , the leakage current detection circuit of the device under test detects that the drain current value of the power device under test reaches a preset current threshold, and the MCU+FPGA processing unit receives the drain current of the power device under test sent by the leakage current detection circuit of the device under test The drain current information whose value reaches the preset current threshold is sent to the gate control circuit of the _device under test. The DUT of the power measurement device is turned off. Since the current of the internal inductor cannot be abruptly changed, a high voltage is generated at both ends of the internal inductor and an avalanche test is performed through the DUT of the power device to be tested. The current probe P1 connected in series on the circuit and the DUT of the power device to be tested are connected in parallel. The high-voltage differential probes P2 on both sides detect the avalanche current and avalanche voltage in the avalanche test and record the V/I curve, which is stored in the computer.

S506. After a preset time period, the avalanche test is completed.

S507 , controlling the entire testing device through the computer, the gate control circuit of the device under test controls the gate-source voltage V _gs of the power device under test DUT to be continuously transformed to be greater than or equal to and less than the threshold voltage, so that the power device under test DUT is in the process of repeated avalanche testing .

S508 , after all avalanche tests are completed, turn off S02 and turn on S05 to clear the internal charge in the capacitor C1 .

The above-mentioned power device testing device, wherein the device includes a controller, an energy storage circuit, a power supply, a first inductance circuit, a power device to be tested, and computer equipment; the controller is used to receive periodic test instructions sent by the computer equipment, And according to the test instruction, control the power device to be tested to turn off and the power supply to charge the energy storage circuit; the controller is also used to stop charging the energy storage circuit if the charging voltage of the energy storage circuit is greater than or equal to the preset voltage threshold, and The energy storage circuit is controlled to charge the first inductance circuit, and the power device to be tested is turned on; the controller is also used to detect the drain current of the power device to be tested, and if the drain current is greater than or equal to the preset current threshold, control The power device to be tested is turned off, so that a voltage is applied to the power device to be tested by the first inductance circuit within a preset time period to obtain an avalanche test result. That is to say, in this embodiment of the present application, the controller receives the periodic test instructions sent by the computer equipment, and controls the power device to be tested to turn off and the power supply to charge the energy storage circuit according to the test instructions, and the charging voltage of the energy storage circuit is greater than When it is equal to the preset voltage threshold, the controller controls the power supply to stop charging the energy storage circuit, controls the energy storage circuit to charge the first inductance circuit, and controls the power device to be tested to be turned on, and then the controller detects the power to be measured by detecting the power Whether the drain current of the device is greater than or equal to the preset current threshold, so as to control the power device under test to be turned off, so as to apply a voltage to the power device under test from the first inductance circuit within a preset time period to obtain the avalanche test result, because the controller can receive Periodic test instructions sent to the computer equipment, so that the power device under test can be controlled on and off according to the test instructions, so that the power device under test is in the process of repeated avalanche testing, so that the power device under test can be automatically repeated. Avalanche testing to improve testing efficiency. For example, the controller will receive a test instruction at a certain period of time, for example, the certain period of time is equal to 1 minute. After receiving the first test instruction at 10 o'clock, the controller executes a test instruction according to the method provided in this embodiment. test to get the avalanche test result corresponding to this test. After that, the controller will receive a test instruction again at 10:01, and then execute a test according to the method provided in this embodiment to obtain the avalanche test result corresponding to the test, and automatically repeat the test in this way, This saves manpower and improves test efficiency.

It should be understood that, although the steps in the flowcharts involved in the above embodiments are sequentially displayed according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, the execution of these steps is not strictly limited to the order, and these steps may be performed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but may be performed at different times The execution order of these steps or phases is not necessarily sequential, but may be performed alternately or alternately with other steps or at least a part of the steps or phases in the other steps.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented by instructing relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage In the medium, when the computer program is executed, it may include the processes of the above-mentioned method embodiments. Wherein, any reference to a memory, a database or other media used in the various embodiments provided in this application may include at least one of a non-volatile memory and a volatile memory. Non-volatile memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetic variable memory (Magnetoresistive Random Memory) Access Memory (MRAM), Ferroelectric Random Access Memory (FRAM), Phase Change Memory (PCM), graphene memory, and the like. Volatile memory may include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration and not limitation, the RAM may be in various forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM). The database involved in the various embodiments provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a blockchain-based distributed database, etc., but is not limited thereto. The processors involved in the various embodiments provided in this application may be general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, data processing logic devices based on quantum computing, etc., and are not limited to this.

The technical features of the above embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features It is considered to be the range described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as a limitation on the scope of the patent of the present application. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the present application should be determined by the appended claims.

Claims (10)

1. a power device testing device, characterized in that the device comprises a controller, an energy storage circuit, a power supply, a first inductance circuit, a power device to be tested and a computer device; The controller is configured to receive periodic test instructions sent by the computer equipment, and control the power device to be tested to turn off and the power supply to charge the energy storage circuit according to the test instructions; The controller is further configured to stop charging the energy storage circuit if the charging voltage of the energy storage circuit is greater than or equal to a preset voltage threshold, and control the energy storage circuit to charge the first inductance circuit , and control the power device to be tested to be turned on; The controller is further configured to detect the drain current of the power device under test, and if the drain current is greater than or equal to a preset current threshold, control the power device under test to be turned off, so that the power device under test is turned off within a preset time period The avalanche test result is obtained by applying a voltage to the power device to be tested by the first inductance circuit. 2 . The device according to claim 1 , wherein the device further comprises a first switch and a second switch, the first switch is provided between the energy storage circuit and the power supply, and the The first end of the second switch is connected to the source of the power device to be tested, and the second end of the second switch is grounded; The controller is configured to control the first switch to be closed and the second switch to be opened according to the test instruction, so as to charge the energy storage circuit through the power supply when the first switch is closed , and turn off the power device under test when the second switch is turned off. 3 . The device according to claim 2 , wherein the controller is further configured to turn off the first switch to stop if the charging voltage of the energy storage circuit is greater than or equal to a preset voltage threshold. 4 . The energy storage circuit is charged, and the energy storage circuit is controlled to charge the first inductance circuit, and the second switch is controlled to be closed to turn on the power device to be tested. 4. The device according to claim 3, characterized in that, the device further comprises a constant current controller, and the constant current controller is respectively connected with the controller and the energy storage circuit; The constant current controller is used to control the current when the energy storage circuit charges the first inductance circuit to reach a set current value. 5. The device according to claim 4, wherein the device further comprises a current probe and an oscilloscope, the first end of the current probe is grounded, and the second end of the current probe is connected to the second switch , the third end of the current probe is connected with the computer equipment through the oscilloscope; the current probe, configured to detect an avalanche current generated when a voltage is applied to the power device under test by the first inductance circuit within the preset time period, wherein the avalanche test result includes the avalanche current; The oscilloscope is used to measure the waveform of the avalanche current. 6 . The device according to claim 5 , wherein the device further comprises a voltage probe, the first end of the voltage probe is connected to the drain of the power device to be tested, and the second end of the voltage probe is connected to the drain of the power device to be measured. 7 . The end is connected with the second end of the second switch and the second end of the current probe, and the third end of the voltage probe is connected with the computer equipment through the oscilloscope; the voltage probe, configured to detect an avalanche voltage generated when a voltage is applied to the power device under test by the first inductance circuit within the preset time period, wherein the avalanche test result includes the avalanche voltage; The oscilloscope is also used for measuring the waveform of the avalanche voltage. 7. The device according to any one of claims 1-6, wherein the device further comprises a resistor, the controller comprises a drain current detection circuit, a processing circuit and a gate control circuit, the resistor The first end is connected to the drain current detection circuit and the source of the power device to be tested, and the second end of the resistor is grounded; The drain current detection circuit and the gate control circuit are connected to the processing circuit. 8 . The apparatus according to claim 7 , wherein the controller further comprises an interface circuit and a drive circuit, the interface circuit is connected to the computer equipment, and the interface circuit and the drive circuit are connected to the computer device. 9 . processing circuit connections; The interface circuit is configured to receive a periodic test instruction sent by the computer device, and send the test instruction to the drive circuit, so that the drive circuit controls the first switch according to the test instruction closed and the second switch is open. 9. The device according to claim 8, wherein the controller further comprises a voltage measurement circuit, the voltage measurement circuit is connected with the processing circuit; The voltage measurement circuit is used to measure the charging voltage of the energy storage circuit and send the charging voltage to the processing circuit, so that the processing circuit can determine the charging of the energy storage circuit according to the charging voltage Whether the voltage is greater than or equal to the preset voltage threshold. 10 . The device according to claim 6 , wherein the device further comprises a second inductive circuit, a third switch and a fourth switch, wherein the first end of the third switch is connected to the second inductive circuit. 11 . the first end is connected, and the second end of the second inductance circuit is connected with the first end of the voltage probe and the drain of the power device to be tested; The second end of the third switch is connected to the fourth switch and the constant current controller.

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