Power device testing device

Abstract

The utility model relates to the technical field of electronic testing devices, in particular to a power device testing device. The device comprises a controller, a data acquisition card, a step-down circuit, a differential amplification circuit, a test clamp, a first test branch, a second test branch, a plurality of electric control change-over switches, a constant current power supply and a constant voltage power supply. Output or input interfaces of all the devices are connected and combined through wires and electric control change-over switches, when different parameters of the power device are measured, switching of needed test circuits is achieved by controlling change of on-off states of all the electric control change-over switches, and finally data obtained through testing are collected by a data collection card. The method has the advantages of simple operation, low cost and high test efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic testing devices, in particular to a power device testing device. Background Art

[0002] Power semiconductor devices, as electronic components for power processing, have the ability to control high voltages and large currents through smaller voltages or currents. Power device parameters directly impact their applications, so various parameter tests are required for power devices, including gate-controlled switching voltages (VGSTH, VGSON, VGSOFF), drain-source breakdown voltage (VDSS), zero gate voltage drain current (IDSS), gate-source leakage current (IGSS), on-state internal resistance (RDSON), and parasitic capacitance (including input capacitance Ciss, output capacitance Coss, and forward transfer capacitance Crss).

[0003] Currently, power device testing requires different measurement circuits depending on the measurement parameter. Some require a series ammeter to read the current of the device under test, or a parallel voltmeter to read the voltage. This requires manual soldering of the test circuit throughout the entire process, and only one function can be tested and the data recorded at a time. After completing one test, re-soldering the test circuit is required to test another parameter, which is extremely inefficient. There are currently commercially available devices that can automatically test power device parameters, but they are relatively expensive.

[0004] In view of this, there is a need for a test device that can automatically perform various parameter tests on power devices, simplify the operation of testers, and reduce testing costs. Utility Model Content

[0005] In view of the deficiencies in the prior art, the present invention provides a power device testing device, which solves the problem that current power device parameter testing equipment is expensive and also solves the problem that circuits need to be rearranged when testing power device parameters.

[0006] The utility model discloses a power device test device through an embodiment, comprising: a controller, a data acquisition card, a step-down circuit, a differential amplifier circuit, and a test fixture. The controller is communicatively connected to the data acquisition card; the test fixture is used to place a MOS power tube under test; the power device test device also includes a first test branch and a second test branch, the first test branch includes a plurality of electrically controlled switching switches and a constant current power supply, and the second test branch includes a plurality of electrically controlled switching switches and a constant voltage power supply; the first test branch is used to short-circuit the gate and source of the MOS power tube under test, and load current on the drain of the MOS power tube under test through the constant current power supply, and then transmit the electrical signal of the source of the MOS power tube under test to the first signal input terminal of the data acquisition card through the step-down circuit; the second test branch is used to short-circuit the drain and source of the MOS power tube under test, and load voltage on the gate of the MOS power tube under test through the constant voltage power supply, and then transmit the electrical signal of the gate and source of the MOS power tube under test to the second signal input terminal of the data acquisition card through the differential amplifier circuit; the electrically controlled switching switch is used to control the conduction or disconnection of the circuit required for power device testing.

[0007] Furthermore, the power device testing apparatus further includes a first drive circuit; a first signal output terminal of the data acquisition card is connected to a control terminal of the first drive circuit for controlling the output of the first drive circuit; the first drive circuit is configured to control the opening or closing of an electrically controlled switching switch. The control signal output by the first drive circuit can control the opening or closing of each electrically controlled switching switch, thereby changing the conduction or closure of the circuits between the various interfaces. This method pre-assembles the electrically controlled switching switches and wires to form the circuit required for power device testing. When testing a parameter of a power device (such as VDSS), the circuit required for measuring that parameter is achieved by controlling the closing or opening of the electrically controlled switching switches. When measuring other parameters of the device under test (such as switching from VDSS to IGSS), the required circuit for measuring the parameter is achieved by simply controlling the on / off state of the electrically controlled switching switches to switch the circuit connection mode (i.e., switching between the first test branch and the second test branch). This method eliminates the need for rewiring and allows for efficient measurement.

[0008] Furthermore, the power device testing device also includes a second drive circuit; the second signal output end of the data acquisition card is connected to the control end of the second drive circuit, for controlling the output of the second drive circuit; the second drive circuit is used to provide the constant voltage power supply with a voltage of the power required by the device under test during testing; the second drive circuit is used to provide the constant current power supply with a current of the power required by the device under test during testing.

[0009] Furthermore, the third signal output terminal of the data acquisition card is connected to the constant current power supply to provide a reference voltage to the constant current source; the fourth signal output terminal of the data acquisition card is connected to the constant voltage power supply to provide a reference voltage to the constant current source.

[0010] Furthermore, the electronically controlled switching switch includes a relay.

[0011] Furthermore, the test fixture includes a first interface, a second interface, and a third interface. The first interface of the test fixture is respectively connected to the output interface of the constant voltage power supply, the first input interface of the differential amplifier circuit, and the third interface of the test fixture; the second interface of the test fixture is respectively connected to the input interface of the step-down circuit and the third interface of the test fixture; the third interface of the test fixture is respectively connected to the output interface of the constant current power supply and the second input interface of the differential amplifier circuit; the output interface of the differential amplifier circuit is connected to the first signal input terminal of the data acquisition card, and the output interface of the step-down circuit is connected to the second signal input terminal of the data acquisition card.

[0012] Furthermore, the step-down circuit includes a first resistor and a second resistor; the first end of the first resistor is connected to the second interface of the test fixture, and the second end is connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the output interface of the step-down circuit.

[0013] Furthermore, the differential amplifier circuit includes an operational amplifier and a sampling resistor, the sampling resistor is connected between a first input interface and a second input interface of the operational amplifier, the first input interface of the operational amplifier is connected to a first interface of the test fixture, and the second input interface is connected to a third interface of the test fixture.

[0014] Furthermore, the differential amplifier circuit also includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor; the third resistor is connected to the circuit between the first input interface of the operational amplifier and the sampling resistor; the fourth resistor is connected to the circuit between the second input interface of the operational amplifier and the sampling resistor; one end of the fifth resistor is connected to the second input interface of the operational amplifier and the other end is connected to the output interface of the operational amplifier; one end of the sixth resistor is connected to the first input interface of the operational amplifier and the other end is grounded. The end of the sampling resistor connected to the third resistor serves as the first input interface of the differential amplifier circuit, and the end of the sampling resistor connected to the fourth resistor serves as the second input interface of the differential amplifier circuit.

[0015] It's worth noting that while the data acquisition card is currently available, the one used in this article includes at least a data acquisition control unit, a communication unit, an AD conversion module, multiple output interfaces, and multiple input interfaces for the DA conversion module. The output of the data acquisition control unit is connected to the input of the DA conversion module, which in turn is connected to the output interface (or to the interface via a voltage follower); the input interface is connected to the input of the AD conversion module, which in turn is connected to the input of the data acquisition control unit; and the data acquisition control unit is connected to the controller via the communication unit.

[0016] Furthermore, the controller includes a computer host, and the data acquisition card is connected to the computer host. The data acquisition card is controlled by the computer to further control the above-mentioned drive circuit or electronically controlled switch, or receive and process data.

[0017] It's worth noting that the above circuit description only describes the connections between the various components of the circuit and does not cover basic circuit knowledge. For example, components such as the controller, operational amplifier, constant voltage power supply, and constant current power supply must be connected to a power supply and grounded when in use.

[0018] The technical principle of the utility model is: the controller controls the connection combination of the electronically controlled switching switches between the output or input interfaces of each device through the data acquisition card. When measuring different parameters of the power device, the required test circuit is switched by controlling the change of the on-off state of each electronically controlled switching switch. After switching different test branches, the data obtained by the test is collected by the data acquisition card.

[0019] Compared with the existing technology, the utility model has the following beneficial effects: it can control the opening or closing of the electronically controlled switching switch through the controller, thereby realizing the circuit required for different parameter tests of the power device, and has the advantages of simple operation, low cost and efficient testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention and facilitate a further understanding of the technical effects, technical features and purposes of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings. The accompanying drawings constitute an essential part of the specification and are used together with the embodiments of the present invention to illustrate the technical solution of the present invention, but do not constitute a limitation to the present invention.

[0021] Figure 1 This is a functional block diagram of the test device described in this utility model;

[0022] Figure 2 This is a schematic diagram of the connection between the first drive circuit and the electronically controlled switch in the test device described in the present utility model;

[0023] Figure 3 This is a schematic diagram of the connection between the second drive circuit, the constant current power supply, and the constant voltage power supply in the test device described in the present utility model;

[0024] Figure 4 This is a circuit diagram of the test device in the embodiment of the present utility model;

[0025] Figure 5 This is a circuit diagram of the first test branch in the test device in an embodiment of the present utility model;

[0026] Figure 6This is a circuit diagram of the second test branch in the test device in an embodiment of the present utility model;

[0027] Figure 7 Schematic diagram of a step-down circuit in an embodiment of the present utility model;

[0028] Figure 8 Schematic diagram of a circuit of a differential amplifier in an embodiment of the present utility model;

[0029] Figure 9 This is a circuit diagram for measuring the VDSS parameters of a MOS tube in an embodiment of the present utility model;

[0030] Figure 10 This is a circuit diagram for measuring the IGSS parameters of a MOS tube in an embodiment of the present utility model;

[0031] Among them, 1-first test branch, 2-second test branch, J1-first electronically controlled switching switch, J2-second electronically controlled switching switch, J3-third electronically controlled switching switch, J4-fourth electronically controlled switching switch, J5-fifth electronically controlled switching switch, J6-sixth electronically controlled switching switch, J7-seventh electronically controlled switching switch, G-first interface, D-second interface, S-third interface, R0-sampling resistor, R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, R7-seventh resistor, U8A-operational amplifier. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described below are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Furthermore, the portions described in the embodiments or drawings are merely illustrative of the relevant portions of the present invention and are not intended to be exhaustive. All other embodiments derived by those of ordinary skill in the art based on the embodiments of the present invention are intended to fall within the scope of protection of the present invention.

[0033] like Figure 1-6 As shown in , the utility model proposes a power device test device through the following embodiments, including: a controller U1, a data acquisition card U2, a step-down circuit U9, a differential amplifier circuit U8 and a test fixture U3, wherein the controller U1 is in communication with the data acquisition card U2, and the controller U1 is used to output control instructions during power device testing or receive data of various parameters measured. The test fixture U3 is used to place the MOS power tube to be tested. The power device test device also includes Figure 5 The first test branch shown and Figure 6The first test branch includes several electronically controlled switches and a constant current power supply U6, and the second test branch includes several electronically controlled switches and a constant voltage power supply U7.

[0034] The data acquisition card U2 includes multiple signal output terminals and multiple signal input terminals. The first test branch is used to short-circuit the gate and source of the MOS power tube under test, load current on the drain of the MOS power tube under test, and transmit the electrical signal of the source of the MOS power tube under test to the first input terminal of the data acquisition card through the step-down circuit U9. The second test branch is used to short-circuit the drain and source of the MOS power tube under test, load voltage on the gate of the MOS power tube under test, and transmit the electrical signal of the gate and source of the MOS power tube under test to the second input terminal of the data acquisition card through the differential amplifier circuit U8. The constant current power supply U7 is used to load current to the drain of the MOS power tube under test; the constant voltage power supply U6 is used to load voltage to the gate of the MOS power tube under test; and the electronically controlled switching switch is used to control the conduction or disconnection of the first test branch or the second test branch.

[0035] like Figure 2 As shown, in this embodiment, the power device testing apparatus further includes a first drive circuit U4. The first signal output terminal of the data acquisition card is connected to the control terminal of the first drive circuit U4 for controlling the output of the first drive circuit U4. The first drive circuit U4 is used to control the opening or closing of the electronically controlled switches. The control signal output by the first drive circuit U4 can control the opening or closing of each electronically controlled switch, thereby changing the conduction or closure of the circuits between the various interfaces.

[0036] like Figure 3 As shown, in this embodiment, the power device testing device further includes a second drive circuit U5; the second signal output terminal of the data acquisition card is connected to the control terminal of the second drive circuit U5, for controlling the output of the second drive circuit U5; the second drive circuit 5U is used to provide the constant voltage power supply U6 with the voltage required by the device under test during the test; the second drive circuit U5 is used to provide the constant current power supply U7 with the current required by the device under test during the test.

[0037] like Figure 4 As shown, in this embodiment, the third signal output terminal of the data acquisition card is connected to the constant current power supply U7, which is used to provide a reference voltage to the constant current source U7; the fourth signal output terminal of the data acquisition card is connected to the constant voltage power supply U6, which is used to provide a reference voltage to the constant current source U6.

[0038] In this embodiment, the electrically controlled switching switch is a relay. The on / off state of the relay can be controlled by an electrical signal. Therefore, using a relay to control circuit switching has the advantages of simple control and fast switching. This method pre-assembles the circuit required for power device testing by combining the electrically controlled switching switch and wires. When testing a parameter of a power device (such as VDSS), the circuit required to measure the power device parameter is realized by controlling the closing or opening of the electrically controlled switching switch. When it is necessary to measure other parameters of the device under test (such as switching from measuring VDSS to measuring IGSS), the circuit connection mode is switched by simply controlling the on / off state of the electrically controlled switching switch to realize the circuit required for measuring the parameter (i.e., switching between the first test branch and the second test branch). This method has the advantages of not requiring rewiring and enabling efficient measurement.

[0039] like Figure 4 As shown, in this embodiment, the test fixture U3 includes a first interface G, a second interface D, and a third interface S. The third interface S of the test fixture U3 is grounded and connected to a grounded resistor R. The first interface of the test fixture is respectively connected to the output interface of the constant voltage power supply U6, the first input interface of the differential amplifier circuit U8, and the third interface of the test fixture U3; the second interface of the test fixture U3 is respectively connected to the input interface of the step-down circuit U9 and the third interface of the test fixture U8; the third interface of the test fixture U3 is respectively connected to the output interface of the constant current power supply U7 and the second input interface of the differential amplifier circuit U8; the output interface of the differential amplifier circuit U8 is connected to the first signal input terminal of the data acquisition card, and the output interface of the step-down circuit U9 is connected to the second signal input terminal of the data acquisition card U2.

[0040] like Figure 4 As shown, in this embodiment, the electronically controlled switching switches include a first electronically controlled switching switch J1, a second electronically controlled switching switch J2, a third electronically controlled switching switch J3, a fourth electronically controlled switching switch J4, a fifth electronically controlled switching switch J5, a sixth electronically controlled switching switch J6, and a seventh electronically controlled switching switch J7. It should be noted that the connections between the first drive circuit U4 and each electronically controlled switching switch would complicate the diagram, so the connections are not shown in the figure. The electronically controlled switching switches are used to control the circuit conduction or closure between the output interface of the constant voltage power supply U6, the output interface of the constant current power supply U7, the first input interface of the differential amplifier circuit U8, the second input interface of the differential amplifier circuit U8, the input interface of the step-down circuit U9, the first interface G of the test fixture U3, the second interface D of the test fixture U3, and the third interface S of the test fixture U3. The control signal output by the first drive circuit U4 can control the opening or closing of each electronically controlled switching switch, thereby changing the circuit conduction or closure between each interface to implement the first test branch or the second test branch.

[0041] like Figure 5 As shown, in this embodiment, the step-down circuit U9 includes a first resistor R1 and a second resistor R2; the first end of the first resistor R1 is connected to the second interface D of the test fixture U3, and the second end is connected to the first end of the second resistor R2; the second end of the second resistor R2 is grounded; the second end of the first resistor R1 serves as the output interface of the step-down circuit U9.

[0042] like Figure 6 As shown, in this embodiment, the differential amplifier circuit U8 includes an operational amplifier U8A and a sampling resistor R0. The sampling resistor R0 is connected between the first input interface and the second input interface of the operational amplifier U8A. When in use, the first input interface of the operational amplifier U8A is connected to the first interface G of the test fixture U3, and the second input interface is connected to the third interface S of the test fixture U3.

[0043] like Figure 6 As shown, in this embodiment, the operational amplifier U8A further includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6. The third resistor R3 is connected to the circuit between the non-inverting input terminal of the operational amplifier and the sampling resistor. The fourth resistor R3 is connected to the circuit between the inverting input terminal of the operational amplifier and the sampling resistor R0. One end of the fifth resistor R5 is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier. One end of the sixth resistor R6 is connected to the non-inverting input terminal of the operational amplifier, and the other end is grounded. The end of the sampling resistor connected to the third resistor serves as the first input interface of the differential amplifier circuit U8, and the end of the sampling resistor connected to the fourth resistor serves as the second input interface of the differential amplifier circuit U8.

[0044] In this embodiment, the controller U1 adopts a computer host, and the data acquisition card U2 is connected to the computer host. The data acquisition card is controlled by the computer to further control the above-mentioned drive circuit or electronically controlled switch, or receive and process data.

[0045] It is worth noting that the data acquisition card adopts existing technology, but the data acquisition card used in this article at least includes a data acquisition control unit, a communication unit, an AD conversion module, a DA conversion module, multiple output interfaces and multiple input interfaces. Among them, the output of the data acquisition control unit is connected to the input of the DA conversion module, and the output of the DA conversion module is connected to the output interface (or connected to the interface after passing through a voltage follower); the input interface is connected to the input of the AD conversion module, and the output of the AD conversion module is connected to the input of the data acquisition control unit; the data acquisition control unit is connected to the controller through the communication unit. At the same time, the above description of the circuit only describes the connection method between the various components of this circuit, and does not describe the basic common sense of the circuit. For example, components such as the controller, operational amplifier, constant voltage power supply and constant current power supply need to be connected to the power supply and grounded when in use.

[0046] The following describes the circuit usage using the example of testing the VDSS parameters of a MOS tube.

[0047] As shown in Figures 5 and 9, the first test branch is used to test the power device. The device under test is connected to the test fixture U3, where the gate of the device under test is connected to the first interface G of the test fixture U3, the drain is connected to the second interface D of the test fixture U3, and the source is connected to the third interface S of the test fixture U3. Controller U1 sends a signal to the first drive circuit U4, turning on the first, fourth, and fifth electronically controlled switches J1, J4, and J5, and disconnecting the second, third, sixth, and seventh electronically controlled switches J2, J3, J6, and J7. At this point, in this circuit, the gate and source of the device under test are short-circuited. Controller U1 outputs a signal to cause constant-current power supply U7 to output a stable current, which flows through the drain and source of the device under test. The drain is also connected to a step-down circuit U9, which collects the voltage signal and outputs it to the data acquisition card U2. The data acquisition card U2 transmits the signal to controller U1. Finally, controller U1 calculates the VDSS voltage of the power device based on the step-down factor and displays it on a display. This allows the VDSS parameters of the power device to be measured.

[0048] The circuit usage is explained by taking the IGSS parameter test of MOS tube as an example.

[0049] like Figure 6 、 10 As shown, the second test branch is used to test the power device. The device under test is connected to the test fixture U3, wherein the gate of the device under test is connected to the first interface G of the test fixture U3, the drain is connected to the second interface D of the test fixture U3, and the source is connected to the third interface S of the test fixture U3. The controller sends a signal to the first drive circuit, disconnecting the first, fourth, and fifth electronically controlled switches J1, J4, and J5, and closing the second, third, sixth, and seventh electronically controlled switches J2, J3, J6, and J7. At this point, in this circuit, the drain and source of the device under test are short-circuited. Controller U1 outputs a signal to cause constant-voltage power supply U6 to output a stable voltage. Current then flows through the gate and source of the MOS transistor, which is also connected to a differential amplifier U8. The differential amplifier U8 collects the voltage signal, and the output of the differential amplifier U8 is connected to a data acquisition card U2. The data acquisition card U2 transmits the voltage to controller U1. Based on the voltage, sampling resistor R0, and amplification factor of differential amplifier U8, controller U1 determines the current between the gate and source of the MOS transistor. This allows for measurement of the IGSS parameters of the power device.

[0050] Similarly, the above-mentioned testing device can also perform other parameter tests. When performing the IDSS test of the MOS tube, the operation of measuring the IGSS parameter can be referred to. When performing the VGS test of the MOS tube, the operation of measuring the VDSS parameter can be referred to. When performing the Rds test of the MOS tube, the above-mentioned IGSS measurement and VDSS measurement can be combined to obtain the Rds value. Specifically, the constant voltage power supply is controlled to supply power to Vgs, and the constant current power supply is controlled to supply power to the drain and source of the MOS tube. Then, the voltage of the drain and source is collected, and finally the voltage is calculated by Ohm's law.

[0051] It should be noted that the above embodiments are only for more clearly illustrating the technical solutions of the present invention. Those skilled in the art will understand that the implementation methods of the present invention are not limited to the above contents, and obvious changes, replacements or substitutions based on the above contents do not exceed the scope covered by the technical solutions of the present invention; without departing from the concept of the present invention, other implementation methods will naturally fall within the scope of the present invention.

Claims

1. A power device testing device, comprising a controller, a data acquisition card, a step-down circuit, a differential amplifier circuit, and a test fixture, wherein the controller is in communication with the data acquisition card; and the test fixture is used to place a MOS power transistor under test, characterized in that: It also includes a first test branch and a second test branch; the first test branch includes a plurality of electronically controlled switching switches and a constant current power supply, and the second test branch includes a plurality of electronically controlled switching switches and a constant voltage power supply; The first test branch is used to short-circuit the gate and source of the MOS power tube under test, and load current on the drain of the MOS power tube under test through the constant current power supply, and then transmit the electrical signal of the source of the MOS power tube under test to the first signal input terminal of the data acquisition card through the step-down circuit; The second test branch is used to short-circuit the drain and source of the MOS power tube under test, and apply a voltage to the gate of the MOS power tube under test through the constant voltage power supply, and then transmit the electrical signals of the gate and source of the MOS power tube under test to the second signal input terminal of the data acquisition card through the differential amplifier circuit; The electronically controlled switch is used to control the conduction or disconnection of the circuit required for power device testing.

2. A power device testing device according to claim 1, characterized in that: Also comprising a first drive circuit; The first signal output terminal of the data acquisition card is connected to the control terminal of the first driving circuit, and is used to control the output of the first driving circuit; The first driving circuit is used to control the opening or closing of the electronically controlled switch.

3. A power device testing device according to claim 1, characterized in that: Also comprising a second drive circuit; The second signal output terminal of the data acquisition card is connected to the control terminal of the second drive circuit, and is used to control the output of the second drive circuit; The second driving circuit is used to provide the constant voltage power supply with a voltage corresponding to the power required by the device under test during testing; The second driving circuit is used to provide the constant current power supply with a current of the power required by the device under test during testing.

4. A power device testing device according to claim 1, characterized in that: The third signal output terminal of the data acquisition card is connected to the constant current power supply, and is used to provide a reference voltage to the constant current source; The fourth signal output terminal of the data acquisition card is connected to the constant voltage power supply and is used to provide a reference voltage to the constant current source.

5. A power device testing device according to claim 2, characterized in that: The electronically controlled switching switch includes a relay.

6. A power device testing device according to claim 1, characterized in that: The test fixture includes a first interface, a second interface and a third interface; The first interface of the test fixture is connected to the output interface of the constant voltage power supply, the first input interface of the differential amplifier circuit, and the third interface of the test fixture respectively; the second interface of the test fixture is connected to the input interface of the step-down circuit and the third interface of the test fixture respectively; the third interface of the test fixture is connected to the output interface of the constant current power supply and the second input interface of the differential amplifier circuit respectively; The output interface of the differential amplifier circuit is connected to the first signal input terminal of the data acquisition card, and the output interface of the step-down circuit is connected to the second signal input terminal of the data acquisition card.

7. A power device testing device as claimed in claim 6, characterized in that: The step-down circuit includes a first resistor and a second resistor; the first end of the first resistor is connected to the second interface of the test fixture, and the second end is connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the output interface of the step-down circuit.

8. A power device testing device according to claim 6, characterized in that: The differential amplifier circuit includes an operational amplifier and a sampling resistor, the sampling resistor is connected between a first input interface and a second input interface of the operational amplifier, the first input interface of the operational amplifier is connected to a first interface of the test fixture, and the second input interface is connected to a third interface of the test fixture.

9. A power device testing device according to claim 8, characterized in that: The differential amplifier circuit further includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor; the third resistor is connected to the circuit between the first input interface of the operational amplifier and the sampling resistor; the fourth resistor is connected to the circuit between the second input interface of the operational amplifier and the sampling resistor; one end of the fifth resistor is connected to the second input interface of the operational amplifier, and the other end is connected to the output interface of the operational amplifier; one end of the sixth resistor is connected to the first input interface of the operational amplifier, and the other end is grounded; One end of the sampling resistor connected to the third resistor serves as a first input interface of the differential amplifier circuit, and one end of the sampling resistor connected to the fourth resistor serves as a second input interface of the differential amplifier circuit.

10. A power device testing device according to any one of claims 1 to 9, characterized in that: The controller includes a computer host.

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