A test circuit and test method suitable for continuous switching conditions of power semiconductor devices
By decoupling voltage and current stress in the IGBT test circuit and utilizing energy circulation loops, the complexity and energy loss problems of the IGBT test system under the MMC topology are solved, and a more efficient test method is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTH CHINA ELECTRIC POWER UNIV
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies for IGBT testing systems in Modular Multilevel Converter (MMC) topologies suffer from problems such as complex and bulky equipment, high manufacturing costs, and significant energy loss during testing.
By designing a test circuit suitable for power semiconductor devices, voltage and current stress are decoupled, and an energy circulation loop is formed by the transformer's negative terminal inductor, the first diode, and the capacitor, thereby realizing the cyclic flow of energy, reducing capacitor requirements and the complexity of the test circuit.
This reduces the complexity and cost of test circuits, while also reducing energy consumption and improving the economy and accuracy of testing.
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Figure CN122085072A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic device testing technology, and in particular to a test circuit and test method suitable for continuous switching conditions of power semiconductor devices. Background Technology
[0002] In power electronic systems, the Insulated Gate Bipolar Transistor (IGBT) serves as the core switching element, operating with a high-frequency switching state, alternating between conduction and turn-off processes. This periodic switching generates significant power losses, including switching losses and conduction losses, which in turn cause periodic changes in the chip junction temperature.
[0003] To efficiently assess IGBT reliability, the industry commonly employs power cycling accelerated aging testing. This method artificially creates temperature cycling stress by periodically applying large current pulses, thereby rapidly verifying the durability of power semiconductor devices under thermomechanical stress. In equivalent test design, the focus is on accurately reproducing the switching transient characteristics during actual operation, including maintaining current amplitude and switching frequency matching actual operating conditions. Current mainstream series valve test systems use pulse width modulation (PWM) technology to achieve high-frequency switching action, effectively simulating bridge arm current characteristics. However, for the special operating conditions of Modular Multilevel Converter (MMC) topologies, due to the relatively low operating frequency of IGBTs, conduction losses become the main heat source, requiring the test system to have the capability to output high voltage and high current.
[0004] However, developing test power supplies that meet such stringent requirements faces significant technical obstacles, primarily due to the complex and bulky size of the equipment, extremely high manufacturing costs, and immense difficulty in practical engineering implementation. This technical bottleneck has become a major obstacle restricting the development of IGBT equivalent testing in MMC application scenarios. Furthermore, during continuous switching tests of power semiconductor devices, the energy generated during the turn-on and turn-off processes is enormous because the devices operate at high voltage and high current. Current testing processes dissipate this energy through discharge circuits, resulting in energy loss and resource waste. Summary of the Invention
[0005] The purpose of this application is to provide a test circuit and test method suitable for continuous switching conditions of power semiconductor devices. By decoupling voltage and current stress, the complexity of continuous switching condition testing of power semiconductor devices is reduced, and energy loss during the test process is also reduced.
[0006] To achieve the above objectives, this application provides the following solution.
[0007] In a first aspect, this application provides a test circuit suitable for continuous switching operation of power semiconductor devices. The test circuit includes: a capacitor, a switching transistor, a transformer, a first diode, a second diode, and a power semiconductor device under test (DUT). The capacitor, the switching transistor, the source-end inductor of the transformer, and the DUT form a charging circuit; the charging circuit is used to charge the source-end inductor of the transformer. The second diode, the source-end inductor of the transformer, and the DUT form a freewheeling circuit; the freewheeling circuit is used to provide freewheeling current to the source-end current of the transformer after the switching transistor is turned off. The capacitor, the first diode, and the negative-end inductor of the transformer form an energy circulation circuit; the energy circulation circuit is used to charge the capacitor after the DUT is turned off.
[0008] Secondly, this application also provides a test method for a test circuit applicable to continuous switching conditions of power semiconductor devices as described in the first aspect. The test method for continuous switching conditions of power semiconductor devices includes: turning on a switching transistor and the power semiconductor device under test, and charging the source inductor of a transformer using a capacitor; turning off the switching transistor, and using a freewheeling circuit to freewheel the source current of the transformer; turning off the power semiconductor device under test, and charging the capacitor using the induced current generated at the negative terminal of the transformer; repeating the above steps to perform continuous switching condition testing on the power semiconductor device under test.
[0009] Based on the specific embodiments provided in this application, the following technical effects are disclosed.
[0010] This application decouples voltage and current stress, eliminating the need for capacitors in the test circuit to simultaneously bear high voltage and current stress. This reduces the requirements for capacitors and also eliminates the need for the test circuit to have the capability to output high voltage and high current, thereby reducing the complexity and cost of the test circuit. Furthermore, this application utilizes the transformer's negative terminal inductor, the first diode, and the capacitor to form an energy circulation loop. When the transformer's source current is cut off, a current is induced in the transformer's negative terminal inductor, which charges the capacitor through the first diode, thus achieving energy circulation. Therefore, this application reduces both the complexity of continuous switching condition testing of power semiconductor devices and energy loss during the testing process. Attached Figure Description
[0011] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0012] Figure 1 This is a test circuit diagram applicable to the continuous switching condition of power semiconductor devices in the embodiments of this application.
[0013] Figure 2 This is a diagram showing the markings of the charging circuit in an embodiment of this application.
[0014] Figure 3 This is a diagram showing the markings of the freewheeling loop in the embodiments of this application.
[0015] Figure 4 This is a diagram illustrating the energy circulation loop in an embodiment of this application.
[0016] Figure 5 This is a flowchart of a test method applicable to continuous switching conditions of power semiconductor devices in the embodiments of this application.
[0017] Figure 6 This is a timing diagram of the control transistor in an embodiment of this application.
[0018] Figure 7 This is a control timing diagram of the power semiconductor device under test in an embodiment of this application.
[0019] Figure reference numerals: Capacitor - C, Switch - S1, Transformer - Tr, First Diode - D1, Second Diode - D2, Power Device Under Test - DUT. Detailed Implementation
[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0021] The purpose of this application is to provide a test circuit and test method suitable for continuous switching conditions of power semiconductor devices. By decoupling voltage and current stress, the complexity of continuous switching condition testing of power semiconductor devices is reduced, and energy loss during the test process is also reduced.
[0022] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0023] In one exemplary embodiment, such as Figure 1 As shown, a test circuit suitable for continuous switching operation of power semiconductor devices is provided. This test circuit includes: a capacitor C, a switching transistor S1, a transformer Tr, a first diode D1, a second diode D2, and a power semiconductor device under test (DUT). One end of the capacitor C is connected to the positive terminal of the second diode D2 and one end of the power semiconductor device under test (DUT); the other end of the capacitor C is connected to one end of the switching transistor S1 and the negative terminal of the first diode D1; the other end of the switching transistor S1 is connected to the negative terminal of the second diode D2 and one end of the source inductor of the transformer Tr; the other end of the source inductor of the transformer Tr is connected to the other end of the power semiconductor device under test (DUT); the positive terminal of the first diode D1 is connected to one end of the negative inductor of the transformer Tr; and the other end of the negative inductor of the transformer Tr is connected to one end of the power semiconductor device under test (DUT).
[0024] Specifically, the test circuit applicable to the continuous switching condition of power semiconductor devices includes three loops: a charging loop, a freewheeling loop, and an energy circulation loop.
[0025] like Figure 2 As shown, capacitor C, switching transistor S1, the source inductance of transformer Tr, and the power semiconductor device under test (DUT) form a charging circuit. This charging circuit charges the source inductance of transformer Tr. In the charging circuit: one end of the DUT is connected to one end of capacitor C; the other end of capacitor C is connected to one end of switching transistor S1; the other end of switching transistor S1 is connected to one end of the source inductance of transformer Tr; and the other end of the source inductance of transformer Tr is connected to the other end of the DUT.
[0026] In a preferred embodiment, the polarity of capacitor C is positive at the top and negative at the bottom in the initial state, and bipolar transistor is preferably selected as the switching transistor S1.
[0027] like Figure 3As shown, the second diode D2, the source inductance of the transformer Tr, and the power semiconductor device under test (DUT) form a freewheeling circuit. This freewheeling circuit is used to allow current to flow through the source of the transformer Tr after the switch S1 is turned off. In the freewheeling circuit: one end of the power semiconductor device DUT is connected to the anode of the second diode D2; the cathode of the second diode D2 is connected to one end of the source inductance of the transformer Tr; and the other end of the source inductance of the transformer Tr is connected to the other end of the power semiconductor device DUT.
[0028] like Figure 4 As shown, capacitor C, first diode D1, and the negative terminal inductor of transformer Tr form an energy circulation loop. This loop charges capacitor C after the power semiconductor device under test (DUT) is turned off. In the energy circulation loop: the positive terminal of first diode D1 is connected to one end of the negative terminal inductor of transformer Tr; the other end of the negative terminal inductor of transformer Tr is connected to one end of capacitor C; and the negative terminal of first diode D1 is connected to the other end of capacitor C.
[0029] Furthermore, as a preferred embodiment, the aforementioned test circuit suitable for continuous switching conditions of power semiconductor devices also includes an external power supply (not shown in the figure), which is used to initially charge capacitor C. Although the charging circuit uses capacitor C to charge the source-end inductor of transformer Tr, capacitor C is initially uncharged and needs to be charged by the external power supply. Charging stops once the set voltage is reached. Since the subsequent energy circulation circuit can recover the additional energy generated during the test process, i.e., charge capacitor C, there is no need to use the external power supply to charge capacitor C in subsequent processes.
[0030] In another exemplary embodiment, to better utilize the above-described test circuit for testing the power semiconductor device under test (DUT), this embodiment provides a test method suitable for continuous switching conditions of power semiconductor devices. For example... Figure 5 As shown, the test method applicable to the continuous switching condition of power semiconductor devices is as follows.
[0031] Step S1: Turn on the switching transistor S1 and the power semiconductor device under test (DUT), and use capacitor C to charge the source inductor coil of transformer Tr.
[0032] Initially, capacitor C is positive at the top and negative at the bottom. When the power device under test (DUT) changes from off to on, a changing current flows into the source inductor of transformer Tr, inducing a changing magnetic field in the core of transformer Tr. This changing magnetic field then induces a changing voltage in the negative inductor of transformer Tr. Because the polarities of the source and negative inductors of transformer Tr are opposite, the voltage at the source (positive at the top and negative at the bottom) will induce a voltage at the negative (negative at the top and positive at the bottom) at the negative terminal. Since the presence of diode D1, there is no current in the energy circulation loop at this time, so the loop can be considered non-existent. Therefore, the source inductor of transformer Tr can be considered an ordinary inductor. Thus, when the DUT changes from off to on, it is equivalent to capacitor C charging the source inductor of transformer Tr.
[0033] In addition, before the switch S1 and the power semiconductor device under test (DUT) are turned on for the first time, the capacitor C needs to be charged to the set voltage Us using an external power supply. This is because the energy circulation loop has not yet charged the capacitor C in the initial state. Only by using an external power supply to charge it for the first time can the energy circulation loop be used to charge the capacitor C once the cycle test begins. At this time, it is no longer necessary to use an external power supply to charge it.
[0034] Step S2: Turn off the switch S1 and use the freewheeling circuit to freewheel the source current of the transformer Tr.
[0035] After the switching transistor S1 is turned off, the source current of the transformer Tr will freewheel through the power semiconductor device under test (DUT) and the second diode D2.
[0036] Step S3: Turn off the power semiconductor device under test (DUT) and use the induced current generated at the negative terminal of the transformer to charge the capacitor C.
[0037] When the power semiconductor device under test (DUT) changes from being on to being off, the source current of the transformer Tr instantly becomes zero. Since the inductor current cannot change abruptly, a voltage with negative upper and positive lower is induced inside the source inductor coil of the transformer Tr. This induces a changing magnetic field in the iron core of the transformer Tr. The changing magnetic field then induces a voltage with positive upper and negative lower in the negative inductor coil of the transformer Tr. At this time, the energy circulation loop comes into play, and the induced current on the negative inductor coil flows through the first diode D1 to the capacitor C, which is equivalent to charging the capacitor C.
[0038] Repeat steps S1 to S3 above to complete the continuous switching test of the power semiconductor device under test (DUT). During the entire cyclic test, the timing control of the switching transistor S1 and the conduction state of the DUT is described in [reference needed]. Figure 6 and Figure 7 .
[0039] In summary, this application achieves decoupling of voltage and current stress, eliminating the need for the capacitor to simultaneously bear high voltage and current stress, thus reducing the requirements for the capacitor and significantly lowering experimental costs. Furthermore, this application incorporates an energy circulation loop in the test circuit. This loop reuses a portion of the energy generated by the voltage rise in the capacitor during the switching process of the power semiconductor device under test, achieving power circulation and improving the overall economy of the test circuit. It also reduces energy loss during the experiment, lowering the complexity and cost of the test circuit while maintaining test accuracy.
[0040] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0041] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A test circuit suitable for continuous switching conditions of power semiconductor devices, characterized in that, The test circuit applicable to the continuous switching condition of power semiconductor devices includes: a capacitor, a switching transistor, a transformer, a first diode, a second diode, and the power semiconductor device under test; The capacitor, the switching transistor, the source inductor of the transformer, and the power semiconductor device under test form a charging circuit; the charging circuit is used to charge the source inductor of the transformer. The second diode, the source inductor of the transformer, and the power semiconductor device under test form a freewheeling circuit; the freewheeling circuit is used to freewheel the source current of the transformer after the switching transistor is turned off. The capacitor, the first diode, and the negative terminal inductor of the transformer form an energy circulation loop; the energy circulation loop is used to charge the capacitor after the power semiconductor device under test is turned off.
2. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, One end of the capacitor is connected to the positive terminal of the second diode and one end of the power semiconductor device under test; the other end of the capacitor is connected to one end of the switching transistor and the negative terminal of the first diode; the other end of the switching transistor is connected to the negative terminal of the second diode and one end of the source inductor of the transformer; the other end of the source inductor of the transformer is connected to the other end of the power semiconductor device under test; the positive terminal of the first diode is connected to one end of the negative inductor of the transformer; the other end of the negative inductor of the transformer is connected to one end of the power semiconductor device under test.
3. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, In the charging circuit: One end of the power semiconductor device under test is connected to one end of the capacitor; the other end of the capacitor is connected to one end of the switching transistor; the other end of the switching transistor is connected to one end of the source inductor of the transformer; and the other end of the source inductor of the transformer is connected to the other end of the power semiconductor device under test.
4. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, In the freewheeling circuit: One end of the power semiconductor device under test is connected to the positive terminal of the second diode; the negative terminal of the second diode is connected to one end of the source inductor of the transformer; and the other end of the source inductor of the transformer is connected to the other end of the power semiconductor device under test.
5. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, In the energy cycle loop: The positive terminal of the first diode is connected to one end of the negative inductor coil of the transformer; the other end of the negative inductor coil of the transformer is connected to one end of the capacitor; and the negative terminal of the first diode is connected to the other end of the capacitor.
6. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, The test circuit applicable to continuous switching conditions of power semiconductor devices also includes an external power supply; the external power supply is used to perform the initial charge of the capacitor.
7. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, The switching transistor is a bipolar transistor.
8. The test circuit for continuous switching conditions of power semiconductor devices according to claim 1, characterized in that, In the initial state, the polarity of the capacitor is positive at the top and negative at the bottom.
9. A test method for a test circuit applicable to continuous switching conditions of power semiconductor devices as described in any one of claims 1-8, characterized in that, The test method applicable to continuous switching conditions of power semiconductor devices includes: The switching transistor and the power semiconductor device under test are turned on, and the capacitor is used to charge the source inductor of the transformer. Turn off the switching transistor and use the freewheeling circuit to freewheel the source current of the transformer; The power semiconductor device under test is turned off, and the capacitor is charged using the induced current generated at the negative terminal of the transformer. Repeat the above steps to perform continuous switching test on the power semiconductor device under test.
10. The test method for continuous switching conditions of power semiconductor devices according to claim 9, characterized in that, The test method applicable to continuous switching conditions of power semiconductor devices also includes: Before the switching transistor and the power semiconductor device under test are first turned on, the capacitor is charged to a set voltage using an external power supply.