A silicon carbide device power cycle test circuit and control method

Abstract

The application provides a silicon carbide MOSFET device power cycle test circuit and a control method, which is aimed at the MOSFET heating (forward current heating) and body diode temperature measurement (reverse current temperature measurement) mode, and simultaneously realizes the rapid response and stable output of the heating current and the measurement current, and overcomes the problems of slow current recovery speed, large current impact and inaccurate temperature measurement caused by the intermittent heating current and measurement current in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of power semiconductors, and in particular relates to a power cycle test circuit and a control method for a silicon carbide MOSFET device. Background Art

[0002] Thermally sensitive electrical parameters (TSEP) refer to device electrical parameters that have a specific functional relationship with temperature. By pre-calibrating the relationship between TSEP and temperature, the device junction temperature can be inversely calculated by measuring these parameters. Power cycling testing of power semiconductor devices such as diodes, field-effect transistors (MOSFETs), and insulated-gate bipolar transistors (IGBTs) uses TSEP to determine the chip junction temperature. Commonly used TSEP parameters include on-state voltage drop and threshold voltage. To minimize device overheating, TSEP is typically a voltage signal generated by a small current (10mA to 100mA) flowing through the device, exhibiting a negative temperature coefficient. Due to the low forward resistance of MOSFET devices, forward voltage drop is generally not used as a thermally sensitive parameter. Instead, threshold voltage or body diode voltage drop is used as the TSEP. Unlike silicon (Si)-based MOSFET devices, silicon carbide (SiC)-based MOSFET devices are compound semiconductors. In addition to Si, they also contain carbon. During gate processing, residual carbon is unavoidable. The presence of carbon clusters causes the number of trapped charges in the gate oxide layer of SiC devices to be 1 to 2 orders of magnitude higher than that of silicon devices. Gate voltage, channel current, and temperature all have a significant impact on the charge distribution in the gate oxide layer, and there is a significant hysteresis characteristic. For example, when a positive gate voltage is applied, the trapped charges in the gate oxide layer capture electrons, causing the device's threshold voltage to increase. This increase in threshold voltage in turn causes an increase in forward voltage drop. When the gate voltage is removed, the device parameters take a long time to return to their pre-voltage state. This characteristic of SiC devices makes it impossible to use the forward threshold voltage as a thermal parameter for power cycling testing, as is the case with Si-based devices. Junction temperature can only be measured using the body diode voltage drop.

[0003] Existing research results indicate that SiC MOSFET devices can only achieve accurate junction temperature measurement through two methods: MOSFET heating (forward current heating) and body diode temperature measurement (reverse current temperature measurement), or body diode heating (reverse current heating) and body diode temperature measurement (reverse current temperature measurement). Therefore, the key to implementing power cycling testing of SiC devices is "reverse current temperature measurement." Compared to conventional forward current temperature measurement, reverse current temperature measurement requires precise control of the device's gate voltage, switching the gate voltage between positive and negative gate voltages in a strict timing sequence. Furthermore, the timing of the heating and measurement currents must be precisely controlled. When heating is in progress, only the heating current is enabled. When measurement is required, the heating current must be rapidly shut off within microseconds and the measurement current must be quickly turned on within microseconds to ensure accurate junction temperature measurement. These functions place high demands on power supply response speed, control algorithms, data acquisition speed, and accuracy.

[0004] The aforementioned body diode heating and temperature measurement methods are essentially the same as those used for conventional diode power cycling. The only difference is that the SiC MOSFET's forward channel is completely shut off by simply setting the device's gate voltage to a negative voltage, such as below -6V. This allows the device to be tested completely as a diode, making the technical implementation relatively easy. However, this method has its drawbacks: reverse current flow is not the primary operating mode of the device, and the resulting stresses differ from those associated with forward current flow. Furthermore, with this heating method, the device exhibits a negative temperature coefficient (TTC), meaning the heat generation decreases with increasing temperature. As device degradation progresses, reverse heating "automatically" reduces TTC, slowing the degradation process. In contrast, forward heating exhibits a positive TTC, increasing TTC with increasing device degradation, accelerating degradation. Because forward heating is more demanding and more realistic than reverse heating and better reflects actual operating conditions, the industry generally prefers forward heating for power cycling tests of SiC MOSFETs to more accurately reflect device reliability. Summary of the Invention

[0005] The present invention aims at MOSFET heating (forward current heating) and body diode temperature measurement (reverse current temperature measurement) methods, and proposes a power cycle test circuit and control method for silicon carbide MOSFET devices. The circuit can simultaneously achieve rapid response and stable output of heating current and measurement current, overcoming the problems of slow current recovery, large current shock and inaccurate temperature measurement caused by the intermittent heating current and measurement current in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A power cycle test circuit for a silicon carbide MOSFET device comprises a heating power supply, a measuring current source, a first branch heating switch, a first branch measuring switch, a second branch heating switch, a second branch measuring switch, and several devices under test;

[0008] One end of the first branch heating switch is respectively connected to one end of the second branch heating switch and the positive electrode of the heating power supply, and the other end of the first branch heating switch is respectively connected to one end of the first branch measuring switch and the drain electrode of the first device under test; the other end of the first branch measuring switch is respectively connected to the negative electrode of the measuring current source and one end of the second branch measuring switch; the first, second, and third devices under test are connected in series end to end to form a first branch, and the source electrode of the third device under test is respectively connected to the positive electrode of the measuring current source, the source electrode of the sixth device under test, and the negative electrode of the heating power supply;

[0009] One end of the second branch heating switch is respectively connected to one end of the first branch heating switch and the positive electrode of the heating power supply, and the other end of the second branch heating switch is respectively connected to one end of the second branch measuring switch and the drain of the fourth device under test; the other end of the second branch measuring switch is respectively connected to the negative electrode of the measuring current source and one end of the first branch measuring switch; the fourth device under test, the fifth device under test, and the sixth device under test are connected in series end to end to form a second branch, and the source electrode of the sixth device under test is respectively connected to the positive electrode of the measuring current source, the source electrode of the third device under test, and the negative electrode of the heating power supply.

[0010] The present invention also provides another silicon carbide MOSFET device power cycle test circuit, which comprises a heating power supply, a measuring current source, a first branch heating switch, a first branch measuring switch, a second branch heating switch, a second branch measuring switch, and a plurality of devices under test; one end of the first branch heating switch is respectively connected to one end of the second branch heating switch and the negative electrode of the heating power supply, and the other end of the first branch heating switch is respectively connected to one end of the first branch measuring switch and the source electrode of the third device under test; the other end of the first branch measuring switch is respectively connected to the positive electrode of the measuring current source and one end of the second branch measuring switch; the first, second, and third devices under test are connected in series from left to right to form a first branch, and the drain electrode of the first device under test is respectively connected to the negative electrode of the measuring current source, the drain electrode of the fourth device under test, and the positive electrode of the heating power supply;

[0011] One end of the second-branch heating switch is connected to one end of the first-branch heating switch and the negative electrode of the heating power supply, respectively. The other end of the second-branch heating switch is connected to one end of the second-branch measurement switch and the source electrode of the sixth device under test, respectively. The other end of the second-branch measurement switch is connected to the positive electrode of the measurement current source and one end of the first-branch measurement switch, respectively. The fourth, fifth, and sixth devices under test are connected in series from left to right, end to end, to form a second branch. The drain electrode of the fourth device under test is connected to the negative electrode of the measurement current source, the drain electrode of the first device under test, and the positive electrode of the heating power supply, respectively.

[0012] Furthermore, a third branch heating switch, a third branch measuring switch, a fourth branch heating switch, a fourth branch measuring switch, another measuring current source and seventh to twelfth devices under test are provided.

[0013] The present invention also provides a control method for a power cycle test circuit of a silicon carbide MOSFET device, comprising the following steps:

[0014] Step (1) applying a positive gate voltage to all the devices under test on the first branch to put the devices under test in a forward conduction state, then closing the first branch heating switch, so that the heating current generated by the heating power supply flows through the first branch, causing all the devices under test on the first branch to heat up;

[0015] Step (2) When all the DUTs on the first branch are in a heating state, the second branch heating switch and the first branch measuring switch are closed, and a negative gate voltage is applied to all the DUTs on the second branch, so that the DUTs on the second branch are in a forward blocking state. Then, the second branch measuring switch is closed, so that the measuring current source applies a measuring current to the body diode of the DUT on the second branch, and the voltage signals generated by the measuring current flowing through the body diode of the DUT on the second branch are respectively detected. Thus, the temperature curves of all the DUTs on the second branch can be obtained based on the pre-calibrated temperature-sensitive parameter curves.

[0016] Step (3) When the set first branch heating time ends, the first branch heating switch and the second branch measuring switch are immediately disconnected to cut off the first branch heating, and then the second branch heating switch is closed. At the same time, a positive gate voltage is applied to all the DUTs on the second branch, so that the DUTs on the second branch are in a forward conduction state. The heating current generated by the heating power supply flows through all the DUTs on the second branch, and the second branch heating begins.

[0017] Step (4) When the heating of the second branch begins, the temperature of all the DUTs on the first branch is immediately measured. At this time, a negative gate voltage is simultaneously applied to all the DUTs on the first branch, so that the DUTs on the first branch are in a forward blocking state. Then, the measurement switch of the first branch is closed, so that the measurement current source applies a measurement current to the body diode of the DUT on the first branch. The voltage signals generated by the measurement current flowing through the body diode of the DUT on the first branch are respectively detected. The temperature curve of the DUT on the first branch can be obtained based on the pre-calibrated temperature-sensitive parameter curve.

[0018] Step (5) When the set second branch heating time ends, immediately disconnect the second branch heating switch and the first branch measuring switch to cut off the second branch heating; then close the first branch heating switch and the second branch measuring switch, heat the first branch again according to steps (1) to (2), and measure the temperature curves of all the test pieces on the second branch;

[0019] Step (6) continuously repeats steps (1) to (5), reciprocatingly heating and measuring the temperature of all the tested parts until the preset end condition is reached, thus completing the power cycle test.

[0020] Beneficial effects:

[0021] The present invention adopts a method of connecting no less than two groups of current branches in parallel and provides multiple switching switches, so that the heating power supply and the measuring current source always maintain a stable output state, overcoming the shortcomings of the existing technology such as slow current recovery speed, large current impact and inaccurate temperature measurement caused by the intermittent state of current. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of a field effect transistor device;

[0023] Figure 2 This is a schematic diagram of a power cycle test circuit according to the first embodiment;

[0024] Figure 3 This is a schematic diagram of a power cycle test circuit according to a second embodiment;

[0025] Figure 4 This is the control logic diagram of the power cycle test circuit;

[0026] Figure 5 FIG. 4 is a schematic diagram of a power cycle test circuit according to a third embodiment. DETAILED DESCRIPTION

[0027] The present invention adopts a method of connecting no less than two groups of current branches in parallel and provides multiple switching switches, so that the heating power supply and the measuring current source always maintain a stable output state, overcoming the shortcomings of the existing technology such as slow current recovery speed, large current impact and inaccurate temperature measurement caused by the intermittent state of current.

[0028] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 Figure 2 is a schematic diagram of the structure of a typical field-effect transistor (DUT). A field-effect transistor (DUT) has three electrodes: gate G, drain D, and source S. A parasitic body diode exists between drain D and source S. When a certain positive voltage is applied between gate G and source S, the forward conduction channel inside the device opens, allowing current to flow from drain D to source S, forming a forward current. When a certain negative voltage is applied between gate G and source S, the forward conduction channel inside the device closes, and current can only flow from source S to drain D, forming a reverse current.

[0030] The power cycle test circuit used in the first embodiment of the present invention is as follows: Figure 2 As shown, the power cycling test circuit comprises a first-branch heating switch HS1, a first-branch measurement switch SS1, a second-branch heating switch HS2, a second-branch measurement switch SS2, a measurement current source Im1, a heating power source Ih1, and first to sixth DUTs DUT1 to DUT6. The first branch comprises the first to third DUTs DUT1 to DUT3 connected in series, while the second branch comprises the fourth to sixth DUTs DUT4 to DUT6 connected in series. The number of DUTs connected in series in each branch can be adjusted as needed; in this embodiment, there are six DUTs.

[0031] like Figure 2 As shown, in the power cycling test circuit used in the present invention, one end of the first branch heating switch HS1 is respectively connected to one end of the second branch heating switch HS2 and the positive electrode of the heating power supply Ih1, and the other end of the first branch heating switch HS1 is respectively connected to one end of the first branch measurement switch SS1 and the drain of the first device under test DUT1. The other end of the first branch measurement switch SS1 is respectively connected to the negative electrode of the measurement current source Im1 and one end of the second branch measurement switch SS2; the first device under test DUT1, the second device under test DUT2, and the third device under test DUT3 are connected in series from left to right to form a first branch, and the source of the third device under test DUT3 is respectively connected to the positive electrode of the measurement current source Im1, the source of the sixth device under test DUT6, and the negative electrode of the heating power supply Ih1.

[0032] One end of the second-branch heating switch HS2 is connected to one end of the first-branch heating switch HS1 and the positive electrode of the heating power supply Ih1, respectively. The other end of the second-branch heating switch HS2 is connected to one end of the second-branch measurement switch SS2 and the drain of the fourth device under test DUT4, respectively. The other end of the second-branch measurement switch SS2 is connected to the negative electrode of the measurement current source Im1 and one end of the first-branch measurement switch SS1, respectively. The fourth device under test DUT4, the fifth device under test DUT5, and the sixth device under test DUT6 are connected in series from left to right, end to end, to form a second branch. The source of the sixth device under test DUT6 is connected to the positive electrode of the measurement current source Im1, the source of the third device under test DUT3, and the negative electrode of the heating power supply Ih1, respectively.

[0033] The power cycle test circuit used in the second embodiment of the present invention is as follows: Figure 3 As shown. One end of the first branch heating switch HS1 is connected to one end of the second branch heating switch HS2 and the negative electrode of the heating power supply Ih1, respectively. The other end of the first branch heating switch HS1 is connected to one end of the first branch measurement switch SS1 and the source electrode of the third device under test DUT3, respectively. The other end of the first branch measurement switch SS1 is connected to the positive electrode of the measurement current source Im1 and one end of the second branch measurement switch SS2, respectively. The first device under test DUT1, the second device under test DUT2, and the third device under test DUT3 are connected in series from left to right to form the first branch. The drain electrode of the first device under test DUT1 is connected to the negative electrode of the measurement current source Im1, the drain electrode of the fourth device under test DUT4, and the positive electrode of the heating power supply Ih1, respectively.

[0034] One end of the second-branch heating switch HS2 is connected to one end of the first-branch heating switch HS1 and the negative electrode of the heating power supply Ih1, respectively. The other end of the second-branch heating switch HS2 is connected to one end of the second-branch measurement switch SS2 and the source electrode of the sixth device under test DUT6, respectively. The other end of the second-branch measurement switch SS2 is connected to the positive electrode of the measurement current source Im1 and one end of the first-branch measurement switch SS1, respectively. The fourth device under test DUT4, the fifth device under test DUT5, and the sixth device under test DUT6 are connected in series from left to right, end to end, to form a second branch. The drain electrode of the fourth device under test DUT4 is connected to the negative electrode of the measurement current source Im1, the drain electrode of the first device under test DUT1, and the positive electrode of the heating power supply Ih1, respectively.

[0035] The control method of the power cycle test circuit of the present invention comprises the following steps:

[0036] Step (1) First, a positive gate voltage is applied to the first DUT1, the second DUT2, and the third DUT3 simultaneously, so that the three DUTs are in a forward conduction state. Then, the first branch heating switch HS1 is closed, and the heating current generated by the heating power supply Ih1 flows through DUT1 to DUT3, starting to heat the three DUTs on the first branch.

[0037] Step (2) When the first branch starts heating, immediately close the second branch heating switch HS2 and the first branch measurement switch SS1, and simultaneously apply a negative gate voltage to the fourth DUT4, the fifth DUT5, and the sixth DUT6, so that the above three DUTs are in a forward blocking state. Then close the second branch measurement switch SS2, so that the measurement current source Im1 applies a measurement current to the body diodes of DUT4 to DUT6, and respectively detects the voltage signals generated by the measurement current flowing through the body diodes of DUT4 to DUT6. Then, the temperature curves of DUT4 to DUT6 can be obtained based on the pre-calibrated temperature-sensitive parameter curves.

[0038] Step (3) When the set heating time of the first branch ends, the first branch heating switch HS1 and the second branch measurement switch SS2 are immediately disconnected to cut off the heating of the first branch, and then the second branch heating switch HS2 is closed. At the same time, a positive gate voltage is applied to the fourth device under test DUT4, the fifth device under test DUT5, and the sixth device under test DUT6, so that the above three devices under test are in a forward conduction state, and the heating current generated by the heating power supply Ih1 flows through DUT4~DUT6, and the heating of the second branch begins; since the second branch is immediately "opened" after the first branch heating switch HS1 is disconnected, the output current of the heating power supply Ih1 will not be intermittent, but will always maintain a stable current output, avoiding the large current shock caused by the heating current being first disconnected and then connected in the prior art, which will cause additional damage to the device.

[0039] Step (4) When the heating of the second branch begins, the temperature of all the DUTs on the first branch must be measured immediately. At this time, a negative gate voltage is applied to the first DUT1, the second DUT2, and the third DUT3, so that the three DUTs are in a forward blocking state. Then the first branch measurement switch SS1 is closed, so that the measurement current source Im1 applies a measurement current to the body diodes of DUT1 to DUT3, and the voltage signals generated by the measurement current flowing through the body diodes of DUT1 to DUT3 are detected respectively. The temperature curve of DUT1 to DUT3 can be obtained according to the pre-calibrated temperature-sensitive parameter curve; since the first branch measurement switch SS1 is immediately closed after the second branch measurement switch SS2 is disconnected, the output current of the measurement current source Im1 will not be intermittent, but will always maintain a stable current output, thus avoiding the problem of slow current recovery speed caused by the measurement current being disconnected first and then connected in the prior art. The slow current recovery speed will directly lead to the inability to accurately measure the maximum temperature of the DUT at the moment the heating current is cut off. Generally, the recovery time of the measurement current should not exceed 0.5 milliseconds;

[0040] Step (5) When the set second branch heating time ends, immediately disconnect the second branch heating switch HS2 and the first branch measuring switch SS1 to cut off the second branch heating; then close the first branch heating switch HS1 and the second branch measuring switch SS2, heat the first branch again according to steps (1) to (2), and measure the temperature curves of all the test pieces on the second branch;

[0041] Step (6) Repeat steps (1) to (5) to perform reciprocating heating and temperature measurement on all the tested parts until the preset end condition is reached, thus completing the power cycle test.

[0042] The control logic of the power cycle test circuit of the embodiment of the present invention is as follows Figure 4 As shown, "1" indicates that the switches (HS1, HS2, SS1, SS2) are closed or the devices under test (DUT1 to DUT6) are turned on, and "0" indicates that the switches (HS1, HS2, SS1, SS2) are open or the devices under test (DUT1 to DUT6) are turned off.

[0043] It should be further explained that, in order to increase the number of devices under test as much as possible, in addition to adopting the aforementioned method of connecting more devices under test in series on the two branches, the capacity can also be expanded by adding a heating branch. The specific implementation method is as follows: Figure 5 shown. Figure 5 Compared Figure 2 A third branch heating switch HS3, a third branch measurement switch SS3, a fourth branch heating switch HS4, a fourth branch measurement switch SS4, another measurement current source Im2 and the seventh to twelfth devices under test DUT7 to DUT12 are added. The connection method of the added components is the same as Figure 2Analogous.

[0044] It is to be understood that the above description is intended to be illustrative and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading the above description. The scope of the application should therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with their full scope of equivalents. The disclosure of all articles and references referred to herein are incorporated by reference in their entirety.

Claims

1. A power cycle test circuit for a silicon carbide MOSFET device, characterized in that: It consists of a heating power supply, a measuring current source, a first branch heating switch, a first branch measuring switch, a second branch heating switch, a second branch measuring switch and several measured devices; One end of the first branch heating switch is respectively connected to one end of the second branch heating switch and the positive electrode of the heating power supply, and the other end of the first branch heating switch is respectively connected to one end of the first branch measuring switch and the drain electrode of the first device under test; the other end of the first branch measuring switch is respectively connected to the negative electrode of the measuring current source and one end of the second branch measuring switch; the first, second, and third devices under test are connected in series end to end to form a first branch, and the source electrode of the third device under test is respectively connected to the positive electrode of the measuring current source, the source electrode of the sixth device under test, and the negative electrode of the heating power supply; One end of the second branch heating switch is respectively connected to one end of the first branch heating switch and the positive electrode of the heating power supply, and the other end of the second branch heating switch is respectively connected to one end of the second branch measuring switch and the drain of the fourth device under test; the other end of the second branch measuring switch is respectively connected to the negative electrode of the measuring current source and one end of the first branch measuring switch; the fourth device under test, the fifth device under test, and the sixth device under test are connected in series end to end to form a second branch, and the source electrode of the sixth device under test is respectively connected to the positive electrode of the measuring current source, the source electrode of the third device under test, and the negative electrode of the heating power supply.

2. A power cycle test circuit for a silicon carbide MOSFET device, characterized in that: The device comprises a heating power supply, a measuring current source, a first-branch heating switch, a first-branch measuring switch, a second-branch heating switch, a second-branch measuring switch, and several DUTs; one end of the first-branch heating switch is respectively connected to one end of the second-branch heating switch and the negative electrode of the heating power supply, and the other end of the first-branch heating switch is respectively connected to one end of the first-branch measuring switch and the source electrode of the third DUT; the other end of the first-branch measuring switch is respectively connected to the positive electrode of the measuring current source and one end of the second-branch measuring switch; the first, second, and third DUTs are connected in series from left to right to form a first branch, and the drain electrode of the first DUT is respectively connected to the negative electrode of the measuring current source, the drain electrode of the fourth DUT, and the positive electrode of the heating power supply; One end of the second branch heating switch is respectively connected to one end of the first branch heating switch and the negative electrode of the heating power supply, the other end of the second branch heating switch is respectively connected to one end of the second branch measuring switch and the source electrode of the sixth device under test, and the other end of the second branch measuring switch is respectively connected to the positive electrode of the measuring current source and one end of the first branch measuring switch; the fourth device under test, the fifth device under test, and the sixth device under test are connected in series from left to right to form a second branch, and the drain electrode of the fourth device under test is respectively connected to the negative electrode of the measuring current source, the drain electrode of the first device under test, and the positive electrode of the heating power supply.

3. A power cycle test circuit for a silicon carbide MOSFET device according to claim 2, characterized in that: A third branch heating switch, a third branch measuring switch, a fourth branch heating switch, a fourth branch measuring switch, another measuring current source and seventh to twelfth tested devices are provided.

4. A control method for a power cycle test circuit of a silicon carbide MOSFET device according to any one of claims 1 to 3, characterized in that: The steps include: Step (1) applying a positive gate voltage to all the devices under test on the first branch to put the devices under test in a forward conduction state, then closing the first branch heating switch, so that the heating current generated by the heating power supply flows through the first branch, causing all the devices under test on the first branch to heat up; Step (2) When all the DUTs on the first branch are in a heating state, the second branch heating switch and the first branch measuring switch are closed, and a negative gate voltage is applied to all the DUTs on the second branch, so that the DUTs on the second branch are in a forward blocking state. Then, the second branch measuring switch is closed, so that the measuring current source applies a measuring current to the body diode of the DUT on the second branch, and the voltage signals generated by the measuring current flowing through the body diode of the DUT on the second branch are respectively detected. Thus, the temperature curves of all the DUTs on the second branch can be obtained based on the pre-calibrated temperature-sensitive parameter curves. Step (3) When the set first branch heating time ends, the first branch heating switch and the second branch measuring switch are immediately disconnected to cut off the first branch heating, and then the second branch heating switch is closed. At the same time, a positive gate voltage is applied to all the DUTs on the second branch, so that the DUTs on the second branch are in a forward conduction state. The heating current generated by the heating power supply flows through all the DUTs on the second branch, and the second branch heating begins. Step (4) When the heating of the second branch begins, the temperature of all the DUTs on the first branch is immediately measured. At this time, a negative gate voltage is simultaneously applied to all the DUTs on the first branch, so that the DUTs on the first branch are in a forward blocking state. Then, the measurement switch of the first branch is closed, so that the measurement current source applies a measurement current to the body diode of the DUT on the first branch. The voltage signals generated by the measurement current flowing through the body diode of the DUT on the first branch are respectively detected. The temperature curve of the DUT on the first branch can be obtained based on the pre-calibrated temperature-sensitive parameter curve. Step (5) When the set second branch heating time ends, the second branch heating switch and the first branch measuring switch are immediately disconnected to cut off the second branch heating; then the first branch heating switch and the second branch measuring switch are closed, and the first branch is heated again according to steps (1) to (2), and the temperature curves of all the test pieces on the second branch are measured; Step (6) continuously repeats steps (1) to (5), reciprocatingly heating and measuring the temperature of all the tested parts until the preset end condition is reached, thus completing the power cycle test.

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