AC power cycle test circuit, apparatus and method

Abstract

The invention discloses an AC power cycle test circuit, device and method, and relates to the technical field of electronics. The circuit comprises an IGBT and a to-be-tested device, one end of the to-be-tested device is electrically connected with an emitter of the IGBT, and a collector of the IGBT and the other end of the to-be-tested device are electrically connected with two ends of a voltage source respectively; wherein the to-be-tested device comprises three to-be-tested units which are connected in parallel, and each to-be-tested unit comprises two switch tubes which are connected in series; the collector and the emitter of the switch tube of the upper bridge arm of one to-be-measured unit are connected with the two ends of the measuring current source; the series connection end of the switch tube of the upper bridge arm and the switch tube of the lower bridge arm of each to-be-tested unit is electrically connected with a load, and the other end of the load is grounded. The aging of the device can be monitored on line, so that the test result for evaluating the to-be-tested device is more accurate.

Description

Technical Field

[0001] The present application relates to the field of electronic technologies, and particularly to an AC power cycle test circuit, device, and method. Background Art

[0002] Power devices are the core components of power electronic converters and are widely used in high-voltage commutation valves and DC converters. With the large-scale development of flexible DC transmission technology in recent years, the reliability issue of power devices has become increasingly prominent and has received wide attention. However, harsh working conditions such as high voltage and large current will affect the actual life of the devices and increase the failure rate of the power system. Therefore, testing the long-term life of power devices under actual working conditions has become a necessary test to ensure their reliability.

[0003] According to the design requirements of the device, its actual service life can usually be determined by actual test conditions for decades. At present, the tests for evaluating the device life mainly rely on traditional direct current (DC) power cycle test devices. Among them, power cycle has always been regarded by the industrial community and academia as an important test for evaluating the packaging reliability of power devices. However, the current test methods and circuits for conventional power cycles are still questioned by many scholars and technicians. The reason for the question is that the device under test in the conventional power cycle test has been in the conducting state all the time (sometimes this power cycle test method is called DC power cycle). However, in actual inverter, rectifier, frequency conversion, and chopper full-control circuits, power devices often take a high-voltage source as the load and switch frequently under inductive load or resistive-inductive load (motor) conditions. Taking the IGBT device as an example below, within one current output cycle of the inverter circuit, the device needs to perform switching control during the positive half cycle of the output current, while the IGBT is in the off state during the negative half cycle of the output current. Therefore, for any IGBT device in the inverter circuit topology (when the factor of freewheeling is not considered), the junction temperature inside it can only show an upward trend during the positive half cycle, and due to the influence of switching losses during the switching process, the junction temperature curve has certain fluctuations. During the negative half cycle of the output, the IGBT module is cooled and the junction temperature drops accordingly, resulting in a large measurement error. Summary of the Invention

[0004] The present application aims to at least solve the problem of large measurement error of the junction temperature of power devices in the prior art, so as to make the measured junction temperature more accurate.

[0005] The solution of the example of the present application is implemented through the following content.

[0006] In a first aspect of the present application, an AC power cycle test circuit is provided, including an IGBT and a device under test. One end of the device under test is electrically connected to the emitter of the IGBT, and the collector of the IGBT and the other end of the device under test are respectively electrically connected to both ends of a voltage source; wherein: The device under test includes three parallel-connected units under test, and each unit under test includes two switching tubes connected in series; the collector and emitter of the switching tube of the upper arm of one unit under test are connected to both ends of the measurement current source; the series connection ends of the switching tubes of the upper arm and the lower arm of each unit under test are electrically connected to a load, and the other end of the load is grounded.

[0007] Six switching tubes are connected in series in pairs to form three parallel units under test. With the basic circuit of the inverter topology as the core, it conforms to the actual three-phase inverter working conditions, can monitor the aging of the device online, and makes the evaluation of the test results of the device under test more accurate.

[0008] For the AC power cycle test circuit as described above, optionally, the switching tubes of the upper arm and the lower arm of each unit under test are in opposite working states; where the working states include open and closed.

[0009] By reasonably controlling the timing of the switching tubes of the upper arm and the lower arm of the three units under test, which conforms to the three-phase inverter situation, to realize online monitoring of the aging of the device under test and make the evaluation of the test results of the device under test more accurate.

[0010] For the AC power cycle test circuit as described above, optionally, the device under test includes a first unit under test, a second unit under test, and a third unit under test connected in parallel, and the collector and emitter of the switching tube of the upper arm of the first unit under test are connected to both ends of the measurement current source; Before the first time node, the IGBT is turned off, the switching tubes of the upper arm of the first unit under test and the switching tubes of the lower arm of the second unit under test are in the off state, and the state of the switching tube of the upper arm of the third unit under test is adjusted from the on state to the off state.

[0011] For the AC power cycle test circuit as described above, optionally, between the first time node and the second time node, the IGBT is turned on, the state of the switching tube of the upper arm of the first unit under test is adjusted from the on state to the off state, and the switching tubes of the upper arm of the second unit under test and the switching tubes of the lower arm of the third unit under test are in the on state.

[0012] For the AC power cycle test circuit as described above, optionally, between the second time node and the third time node, the IGBT is turned on, the state of the switching tube of the upper arm of the first unit under test is switched from the off state to a periodic switching state, and the states of the switching tubes of the upper arm of the second unit under test and the switching tubes of the lower arm of the third unit under test are adjusted from the on state to a periodic switching state.

[0013] For the AC power cycle test circuit described above, optionally, from the third time node to the fourth time node, the IGBT is turned on, the switch of the upper arm of the first device under test is in the on state, and the switches of the upper arms of the second device under test and the lower arms of the third device under test are in a state of periodic switching.

[0014] The control timing is used to control the switching of the IGBT and the devices under test, accelerating the aging of the devices under test and conforming to the actual working conditions; the current measured in this state can online monitor the current of the devices under test under different working conditions and aging conditions, facilitating the acquisition of the corresponding junction temperature and making the evaluation of the test results of the devices under test more accurate.

[0015] The second aspect of the present application provides an AC power cycle test device, including: The AC power cycle test circuit according to any one of the above first aspects; A voltage source, the two ends of which are respectively electrically connected to the collector of the IGBT and the emitter of the switch of the lower arm in the device under test; A control cabinet, which is electrically connected to the bases of the IGBT and each switch in the device under test, is used to control the switching states of the IGBT and the devices under test according to the preset AC power cycle timing, and is electrically connected to the collectors and emitters of each switch to collect voltage values; An upper computer, which is used to control the start and stop of the AC power cycle test device and receive the voltage values collected by the control cabinet.

[0016] The power cycle test device has a simple structure and few components, so it is convenient to disassemble and install. Moreover, it has multiple control branches and can be expanded according to needs, with strong adaptability; it can provide power cycle tests that conform to the actual inverter working conditions for all high-voltage high-power devices including IGBT devices and MOSFET devices; in addition, the power cycle test device can perform power cycle tests with various different switching loss ratios, propose measurements for a scheme that meets a high junction temperature change rate on the basis of low conduction loss, filling the gap in the lack of power cycle test methods that conform to the actual working conditions; and the method of monitoring the junction temperature through the small current saturation voltage drop of this platform can ensure that the junction temperature and junction temperature fluctuation of the device under test are online monitored and real-time monitored, and the test results are more accurate.

[0017] For the AC power cycle test device described above, optionally, the control cabinet includes a collection port and a control port, where: The collection port is electrically connected to the collectors and emitters of each switch in the device under test to obtain voltage values; The control port is electrically connected to the bases of the IGBT and each switch in the device under test.

[0018] The control and acquisition functions are realized through different ports, which is convenient for controlling and detecting the device under test in real time, and ensuring that the test results of the device under test are more accurate.

[0019] The AC power cycle test device as described above may optionally further include a heat exchanger and a water-cooled plate, which are respectively used for heating and cooling the device under test, so that the junction temperature of the device under test changes.

[0020] The heat exchanger and the water-cooled plate are used to realize rapid junction temperature fluctuations of the device under test to meet the test requirements at different junction temperatures.

[0021] The third aspect of the present application provides an AC power cycle test method, which is applied to the AC power cycle test device described in any item of the second aspect above. The method includes: Applying a current signal to the device under test and heating it, and recording in real time the corresponding relationship between the junction temperature and the measured current corresponding to each temperature of the device under test; Controlling the switching states of the IGBT and the device under test according to a preset AC power cycle timing sequence, and collecting the voltage values of the collector and emitter of each switching transistor; Determining the corresponding measured junction temperature according to the voltage value and the corresponding relationship.

[0022] The AC power cycle test method can ensure a test environment with high junction temperature fluctuations while having low conduction losses, and can monitor the aging of the device online, making the evaluation of the test results of the power device more accurate; and on the basis of the traditional power cycle control method, the control method of the actual inverter circuit is incorporated, which is consistent with the most widely used power cycle test steps at present, so it has strong popularization; in addition, the AC power cycle test method based on the traditional abcd four-point method can solve the problem that the device aging cannot be accelerated under the condition of low conduction losses of the current power device, and can monitor the thermal resistance and the saturation voltage drop under large current, providing more accurate reliability evaluation results for semiconductor manufacturers. Description of the Drawings

[0023] By reading the following detailed description with reference to the drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the drawings, several embodiments of the present application are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein: Figure 1 It is a schematic diagram of an AC power cycle test circuit according to an embodiment of the present application; Figure 2 It is a schematic diagram of the switching timing of an IGBT and a device under test according to an embodiment of the present application; Figure 3Schematic diagram of an AC power cycle test device according to an embodiment of the present application; Figure 4 Flow schematic diagram of an AC power cycle test method according to an embodiment of the present application.

[0024] Description of reference numerals: 1 - Control cabinet, 2 - Water-cooled plate, 3 - Control switch, 4 - Voltage source, 5 - Host computer, 6 - Heat exchanger. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present disclosure.

[0026] To solve the problems of inaccurate power cycle testing, inability to simulate device aging, and aging state testing in the prior art, the present application takes the basic circuit of the inverter topology as the core, integrates the key technology of the test principle of DC power cycle into it, and designs an improved AC power cycle test circuit that fits the actual three-phase inverter working conditions.

[0027] As Figure 1 shown, this embodiment provides an AC power cycle test circuit, including IGBTs and a device under test. One end of the device under test is electrically connected to the emitter of the IGBT, and the collector of the IGBT and the other end of the device under test are respectively electrically connected to both ends of a voltage source; wherein: the device under test includes 3 parallel-connected units under test, and each unit under test includes two switch tubes connected in series; the collector and emitter of the switch tube on the upper bridge arm of one unit under test are connected to both ends of a measurement current source; the series connection ends of the switch tubes on the upper bridge arm and the lower bridge arm of each unit under test in each path are all electrically connected to a load, and the other end of the load is grounded.

[0028] The device under test in this embodiment is 6 switch tubes (DUT1, DUT2, DUT3, DUT4, DUT5, DUT6). During the test, multiple switch tubes are tested; specifically, 2 series-connected switch tubes are used to form a unit under test (DUT1 - DUT4, DUT2 - DUT5, DUT3 - DUT6), and 3 units under test are connected in parallel to form the style of the basic circuit of the inverter topology, and the test is carried out in accordance with the actual three-phase inverter working conditions. The two series-connected switch tubes serve as the upper bridge arm and the lower bridge arm of each unit under test.

[0029] Three units under test are connected in parallel to the emitter of an IGBT. The measurement of the three units under test can be controlled simultaneously by the switching of the IGBT. When the IGBT is turned off, the switching transistors in the units under test are turned on and off according to a set time sequence to achieve different working conditions, and a measurement current source is used to measure the current of the switching transistors under the corresponding working conditions, so as to determine the junction temperature of the switching transistors under different working conditions through the measured current. In addition, by periodically switching the state of the switching transistors to accelerate the aging of the switching transistors and measuring the junction temperature at this time, it can provide an accurate basis for the reliability evaluation of the device under test.

[0030] Among them, the device under test in this embodiment can be a fully controlled power device such as an IGBT or a MOSFET, or other semi-controlled power devices, and they can be connected according to the circuit in the appendix. Figure 1 That's it.

[0031] In addition, the result measured by the measurement current source in this application is the current value passing through the device under test, and the junction temperature of the device under test can be obtained through this current value.

[0032] The power cycle test circuit of this application uses six switching transistors connected in series in pairs to form three parallel units under test. With the basic circuit of the inverter topology as the core, it conforms to the actual three-phase inverter working conditions, can monitor the aging of the device online, and makes the evaluation of the test results of the device under test more accurate.

[0033] In this embodiment, when measuring the device under test, the working states of the switching transistors on the upper bridge arm and the lower bridge arm of each unit under test are opposite; the working states include on and off. For example, during measurement, if the switching transistor on the upper bridge arm of each unit under test is in the on state, the switching transistor on the lower bridge arm of this unit under test is in the off state; if the switching transistor on the upper bridge arm of each unit under test is in the off state, the switching transistor on the lower bridge arm of this unit under test is in the on state. Through the opposite working states, the switching transistors on the upper bridge arm and the lower bridge arm of each measurement unit are complementary-conducted, and then three parallel units under test are used. By reasonably controlling the time sequence of the switching transistors on the upper bridge arm and the lower bridge arm of the three units under test, it conforms to the three-phase inverter situation to realize online monitoring of the aging of the device under test and make the evaluation of the test results of the device under test more accurate.

[0034] Specifically, taking Figure 2 the schematic diagram of the switching time sequence of the exemplary IGBT and the device under test as an example, the junction temperature test under the three-phase inverter working conditions is described in detail. The device under test includes a first unit under test, a second unit under test, and a third unit under test connected in parallel. The collector and emitter of the switching transistor on the upper bridge arm of the first unit under test are connected to both ends of the measurement current source.

[0035] As Figure 2As shown, when testing the device under test, it includes multiple time nodes, such as a, b, c, d; among them, a in this embodiment is the first time node, b is the second time node, c is the third time node, and d is the fourth time node. At different time nodes and time periods, the states of the IGBT and each switching tube are different. In addition, before the second time node, the device under test is in a cooling state, and after the second time node, the device under test is in a heating state; the heating source can use a heater or other equipment; by performing periodic switching on each device under test in the heating state, the aging of the device under test is accelerated to ensure that an evaluation of the reliability of the device under test can be obtained.

[0036] For example, before the first time node, the IGBT is turned off, the switching tube DUT1 of the upper bridge arm of the first unit under test and the switching tube DUT6 of the lower bridge arm of the second unit under test are in the off state, and the state of the switching tube DUT5 of the upper bridge arm of the third unit under test is adjusted from the on state to the off state. At this time, the voltage source is turned off, the load current is loaded, the device under test is in a cooling state, and the current flowing through the PN junction inside the device under test is measured by the measuring current source.

[0037] Between the first time node and the second time node, the IGBT is turned on, the state of the switching tube DUT1 of the upper bridge arm of the first unit under test is adjusted from the on state to the off state, and the switching tubes of the upper bridge arm DUT3 of the second unit under test and the lower bridge arm DUT2 of the third unit under test are in the on state. At this time, after the IGBT is turned on, it is in the conducting state, and the load current is passed through the device under test in the cooling state. At this time, the first unit under test generates a current in a constant direction.

[0038] Between the second time node and the third time node, the IGBT is turned on, the state of the switching tube DUT1 of the upper bridge arm of the first unit under test is switched from the off state to a state of periodic switching, and the states of the switching tubes of the upper bridge arm DUT3 of the second unit under test and the lower bridge arm DUT2 of the third unit under test are adjusted from the on state to a state of periodic switching. At this time, the state of the switching tube DUT1 of the upper bridge arm of the first unit under test performs periodic switching. The states of the switching tubes of the upper bridge arm of the second unit under test and the lower bridge arm of the third unit under test are first in the on state and also perform state periodic switching after a period of time; so that each unit under test generates currents in opposite directions and repeatedly switches like alternating current, which is used to accelerate the aging of the device under test and conform to the actual working conditions; the current measured in this state can online monitor the current of the device under test under different working conditions and aging conditions, which is convenient to obtain the corresponding junction temperature and make the evaluation of the test result of the device under test more accurate.

[0039] From the third time node to the fourth time node, the IGBT is turned on. The switch DUT1 of the upper arm of the first device under test is in the on state, and the states of the switch DUT3 of the upper arm of the second device under test and the switch DUT2 of the lower arm of the third device under test are switched in a state cycle.

[0040] At this time, the switch DUT1 of the upper arm of the first device under test is in the on state, and the states of the switch of the upper arm of the second device under test and the switch of the lower arm of the third device under test continue to be switched in a state cycle; this causes opposite-direction currents to be generated in each device under test, which repeatedly switch like alternating current, used to accelerate the aging of the device under test and conform to the actual working conditions; the current measured in this state can be used to online monitor the current of the device under test under different working conditions and aging conditions, facilitating the acquisition of the corresponding junction temperature, making the evaluation of the test results of the device under test more accurate.

[0041] It should be added that in the above 4 working condition descriptions, for each of the two switches in each device under test, the state of 1 switch is described, and the state of the other switch can be controlled according to the opposite state.

[0042] As Figure 3 shown, based on the same application concept, this embodiment also provides an AC power cycle test device, including: the AC power cycle test circuit as described in any one of the above, a voltage source 4, a control cabinet 1, and a host computer 5. Specifically, the two ends of the voltage source are electrically connected to the collector of the IGBT and the emitter of the switch of the lower arm in the device under test; the control cabinet is electrically connected to the base of the IGBT and each switch in the device under test, used to control the switch states of the IGBT and the device under test according to the preset AC power cycle time sequence, and is electrically connected to the collector and emitter of each switch to collect voltage values; the host computer is used to control the start and stop of the AC power cycle test device and receive the voltage values collected by the control cabinet.

[0043] Among them, the control switch 3 is the IGBT in Figure 1 , used to control the states of the switches in the 3 devices under test. The positive pole of the voltage source 4 is connected to the C terminal (collector) of the control switch (IGBT), and the E terminal (emitter) of the control switch 3 is connected to the C terminal (collector) of the switch of the upper arm in the 3 devices under test. A small current is passed at the first time node and the fourth time node when the DUT1 device is turned on to collect the voltage value across the CE of the device under test; at the second time node and the third time node, the switches are controlled according to the time sequence in Figure 2 to pass a large current through DUT1, and the voltage value across the CE of the device under test is collected; and the collected voltage value is compared with the corresponding relationship between the preset junction temperature and voltage to obtain the corresponding junction temperature.

[0044] The control cabinet 1 is electrically connected to the bases of each switching tube in the IGBT and the device under test, for controlling the switching of each device; in addition, the control cabinet 1 is also used to collect the voltage values between the collector and the emitter of each switching tube in the device under test. When using the control cabinet 1 for control and collection, it is controlled by the host computer 5. By operating the host computer 5, the startup of the test equipment and the voltage value collection are realized, and the aging process of the device under test is analyzed according to the collection results.

[0045] The power cycle test equipment in this embodiment has a simple structure and few components, so it is convenient to disassemble and install. Moreover, it has multiple control branches and can be expanded according to requirements, with strong adaptability; it can provide power cycle tests that fit the actual inverter working conditions for all high-voltage and high-power devices including IGBT devices and MOSFET devices; in addition, the power cycle test equipment can perform power cycle tests with various different switching loss ratios, and propose a measurement method to meet the high junction temperature change rate scheme on the basis of low conduction loss, filling the gap in the lack of power cycle test methods that fit the actual working conditions; and the platform can ensure that the junction temperature and junction temperature fluctuation of the device under test are monitored online and in real time through the method of monitoring the junction temperature by the small current saturation voltage drop, and the test results are more accurate.

[0046] Exemplarily, the control cabinet 1 includes a collection port (not shown in the drawings) and a control port (not shown in the drawings), where: the collection port is electrically connected to the collector and the emitter of each switching tube in the device under test to obtain voltage values; the control port is electrically connected to the IGBT and the bases of each switching tube in the device under test. The control and collection functions are realized through different ports, which is convenient for controlling and detecting the device under test in real time, and ensuring that the test results for evaluating the device under test are more accurate.

[0047] In addition, the AC power cycle test equipment further includes a heat exchanger 6 and a water-cooled plate 2, which are respectively used to heat and cool the device under test, so that the junction temperature of the device under test changes; to realize the rapid junction temperature fluctuation of the device under test to meet the test requirements at different junction temperatures.

[0048] Based on the same application concept, this embodiment also provides an AC power cycle test method, which is applied to the AC power cycle test equipment described in any one of the above, and the method includes the following steps.

[0049] Step S10: Apply a current signal to the device under test and heat it, and record in real time the corresponding relationship between the junction temperature and the measured current corresponding to each temperature of the device under test.

[0050] Step S20: Control the switching states of the IGBT and the device under test according to the preset AC power cycle timing, and collect the voltage values between the collector and the emitter of each switching tube.

[0051] Step S30: Determine the corresponding measured junction temperature according to the voltage value and the corresponding relationship.

[0052] Before performing the power cycle test, calibrate the device under test using the small-current Vce(T) method. Specifically, heat the device under test using a heat exchanger, apply a small-current signal to the device under test, and record the voltage value at each temperature in real time to obtain the corresponding relationship between the measured current and the junction temperature. Then, control the switching state of the device under test through a preset AC power cycle timing sequence to achieve different working conditions, and use a control cabinet to collect the voltage values of the collector and emitter of each switching device. Finally, compare the collected voltage values with the corresponding relationship to determine the corresponding measured junction temperature.

[0053] The AC power cycle test method of this embodiment can ensure a test environment with high junction temperature fluctuation while having low conduction loss. At the same time, it can monitor the aging of the device online, making the evaluation of the test results of the power device more accurate; and on the basis of the traditional power cycle control method, it incorporates the control method of the actual inverter circuit, which is consistent with the most widely used power cycle test steps currently, so it has strong popularization; in addition, the AC power cycle test method based on the traditional abcd four-point method can solve the problem that the device aging cannot be accelerated under the condition of low conduction loss of the current power device, and can monitor the thermal resistance and the saturation voltage drop under large current of the device, providing more accurate reliability evaluation results for semiconductor manufacturers.

[0054] According to the above description of the present application, those skilled in the art can also understand the following terms used, such as terms indicating orientation or positional relationship, such as "upper", "lower", "length", "width", "top", "bottom", "inner", "outer", "axial", "longitudinal", "transverse", "clockwise" or "counterclockwise", etc., are based on the orientation or positional relationship shown in the drawings of the present application. It is only for the purpose of facilitating the description of the solution of the present application and simplifying the description, rather than explicitly or implicitly indicating that the device or element involved must have the specific orientation, be constructed and operate in the specific orientation, so the above orientation or positional relationship terms cannot be understood or interpreted as a limitation to the solution of the present application.

[0055] In the above description of the present application, the terms "first" or "second", etc., used to refer to numbers or ordinals are only for convenience of description, and cannot be understood as explicitly or implicitly indicating relative importance or implicitly indicating the quantity of the indicated technical features. At the same time, the features defined with "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three or more, etc., unless otherwise specifically and clearly defined.

[0056] Although several embodiments of the present application have been shown and described herein, those skilled in the art will appreciate that such embodiments are provided by way of example only. Those skilled in the art can conceive of many changes, alterations, and alternative ways without departing from the spirit and scope of the present application. It should be understood that various alternatives to the embodiments of the present application described herein may be employed in practicing the present application. The appended claims are intended to define the scope of protection of the present application and thus cover equivalents or alternatives within the scope of these claims.

Claims

1. An AC power cycle test circuit, characterized in that, It includes an IGBT and a device under test. One end of the device under test is electrically connected to the emitter of the IGBT, and the collector of the IGBT and the other end of the device under test are respectively electrically connected to both ends of a voltage source; wherein: The device under test includes three parallel-connected units under test. Each unit under test includes two switching tubes connected in series; the collector and emitter of the switching tube of the upper bridge arm of one unit under test are connected to both ends of a measurement current source; the series connection ends of the switching tubes of the upper bridge arm and the lower bridge arm of each unit under test are all electrically connected to a load, and the other end of the load is grounded.

2. The AC power cycle test circuit according to claim 1, wherein The working states of the switching tubes of the upper bridge arm and the lower bridge arm in each unit under test are opposite; wherein the working states include on and off.

3. The AC power cycle test circuit according to claim 2, wherein The device under test includes a first unit under test, a second unit under test, and a third unit under test connected in parallel. The collector and emitter of the switching tube of the upper bridge arm of the first unit under test are connected to both ends of a measurement current source; Before the first time node, the IGBT is off, the switching tubes of the upper bridge arm of the first unit under test and the lower bridge arm of the second unit under test are in the off state, and the state of the switching tube of the upper bridge arm of the third unit under test is adjusted from the on state to the off state.

4. The AC power cycle test circuit according to claim 2, characterized in that, Between the first time node and the second time node, the IGBT is on, the state of the switching tube of the upper bridge arm of the first unit under test is adjusted from the on state to the off state, and the switching tubes of the upper bridge arm of the second unit under test and the lower bridge arm of the third unit under test are in the on state.

5. The AC power cycle test circuit according to claim 2, wherein Between the second time node and the third time node, the IGBT is on, the state of the switching tube of the upper bridge arm of the first unit under test is switched from the off state to a state cycle switch, and the states of the switching tubes of the upper bridge arm of the second unit under test and the lower bridge arm of the third unit under test are adjusted from the on state to a state cycle switch.

6. The AC power cycle test circuit according to claim 2, characterized in that, Between the third time node and the fourth time node, the IGBT is on, the state of the switching tube of the upper bridge arm of the first unit under test is in the on state, and the states of the switching tubes of the upper bridge arm of the second unit under test and the lower bridge arm of the third unit under test are in a state cycle switch.

7. An AC power cycle test device, characterized in that, It includes: The AC power cycle test circuit according to any one of claims 1-6; A voltage source, both ends of which are respectively electrically connected to the collector of the IGBT and the emitter of the switching tube of the lower bridge arm in the device under test; A control cabinet, which is electrically connected to the base of the IGBT and each switching tube in the device under test, is used to control the switching states of the IGBT and the device under test according to a preset AC power cycle timing sequence, and is electrically connected to the collector and emitter of each switching tube to collect voltage values; An upper computer, which is used to control the start and stop of the AC power cycle test equipment and receive the voltage values collected by the control cabinet.

8. The AC power cycle test device according to claim 7, characterized in that, The control cabinet includes a collection port and a control port, wherein: The collection port is electrically connected to the collector and emitter of each switching tube in the device under test to obtain voltage values; The control port is electrically connected to the base of the IGBT and each switching tube in the device under test.

9. The AC power cycle test device according to claim 7, characterized in that, It further includes a heat exchanger and a water-cooled plate, which are respectively used to heat and cool the device under test, so as to cause the junction temperature of the device under test to change.

10. An AC power cycle test method, characterized in that, Applied to the AC power cycle test equipment according to any one of claims 7-9, the method includes: Applying a current signal to the device under test and heating it, and recording in real time the corresponding relationship between the junction temperature and the measured current corresponding to each temperature of the device under test; Controlling the switching states of the IGBT and the device under test according to a preset AC power cycle timing sequence, and collecting the voltage values of the collector and emitter of each switching transistor; Determining the corresponding measured junction temperature according to the voltage value and the corresponding relationship.

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