Power module test circuit for suppressing self-heating effect and working method thereof

Abstract

A power module test circuit for inhibiting self-heating effect and a working method thereof, the power module test circuit comprising: a DC bus power supply; a first power module comprising: a first power switch tube to be tested and a first diode; a second power module comprising: a second power switch tube and a second diode; the second power switch tube and the first power switch tube are independently tested under the same test condition, and the drain current of the second power switch tube is smaller than that of the first power switch tube; a third power module comprising: a third power switch tube and a third diode; the third power switch tube and the first power switch tube are independently tested under the same test condition, and the drain current of the third power switch tube is smaller than that of the first power switch tube; a load inductance. The test accuracy of the power module test circuit is improved.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor device testing, specifically to a power module testing circuit and its operating method for suppressing self-heating effects. Background Technology

[0002] Dynamic characteristic testing of power modules mainly tests some key parameters during the turn-on and turn-off processes, including: turn-on delay td(on), turn-off delay td(off), current rise time tr, current fall time tf, turn-on loss Eon, and turn-off loss Eoff. These parameters are important indicators for evaluating the performance of power modules.

[0003] However, the existing power module test circuits have poor test accuracy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the problem of poor testing accuracy of power module test circuits in the prior art, thereby providing a power module test circuit and its working method that suppresses the self-heating effect.

[0005] To address the aforementioned technical problems, this invention provides a power module test circuit for suppressing self-heating effects, comprising: a DC bus power supply; a first power module, the first power module including: a first power switch to be tested and a first diode connected in reverse parallel with the first power switch; a second power module, the second power module including: a second power switch and a second diode connected in reverse parallel with the second power switch; independently testing the second power switch and the first power switch under the same test conditions, wherein the leakage current of the second power switch is less than the leakage current of the first power switch; and a third power module, the third power module including: a third power switch... A third diode is connected in reverse parallel with the third power switch. The third power switch and the first power switch are tested independently under the same test conditions. The leakage current of the third power switch is less than that of the first power switch. A load inductor is used. The collector of the first power switch, the emitter of the second power switch, and one end of the load inductor are connected. The emitter of the first power switch is electrically connected to the positive terminal of the DC bus power supply. The collectors of the second and third power switches are connected and electrically connected to the negative terminal of the DC bus power supply. The emitter of the third power switch is connected to the other end of the load inductor.

[0006] Optionally, the voltage rating of the second power switch is higher than that of the first power switch, and / or the temperature rating of the second power switch is higher than that of the first power switch.

[0007] Optionally, the voltage rating of the third power switch is higher than that of the first power switch, and / or the temperature rating of the third power switch is higher than that of the first power switch.

[0008] Optionally, the first power module further includes: a fourth power switch and a fourth diode connected in reverse parallel with the fourth power switch, wherein the emitter of the fourth power switch is connected to the collector of the first power switch, and the collector of the fourth power switch is floating; the second power module further includes: a fifth power switch and a fifth diode connected in reverse parallel with the fifth power switch, wherein the collector of the fifth power switch is connected to the emitter of the second power switch, and the emitter of the fifth power switch is floating.

[0009] Optionally, the collector of the first power switch and the emitter of the fourth power switch are connected as a first point, and the emitter of the second power switch and the collector of the fifth power switch are connected as a second point. The power module test circuit for suppressing self-heating effect further includes a connecting wire connecting the first point and the second point, wherein the length of the connecting wire is less than or equal to 1.5 times the length of the connecting wire between the center of the first power module and the center of the second power module.

[0010] Optionally, the third power module further includes: a sixth power switch and a sixth diode connected in reverse parallel with the sixth power switch, wherein the collector of the sixth power switch is connected to the emitter of the third power switch, and the emitter of the sixth power switch is floating.

[0011] Optionally, a capacitor is connected in parallel with the DC bus power supply; a current sensor is located in the path from the emitter of the first power switch to the positive terminal of the DC bus power supply.

[0012] This invention also provides a method for operating a power module test circuit that suppresses self-heating effects, comprising: heating a first power module to a predetermined test temperature using a heating stage; between a first time and a second time, the first power module, the second power module, and the third power module are all in an off state; between the second time and the third time, the first power module and the second power module are in an off state, and the third power switch is turned on; between the third time and the fourth time, the first power switch is turned on, the second power module is in an off state, the third power switch is turned on, and the current on the load inductor increases from 0 to a rated value; between the fourth time and the fifth time, the first power switch is turned off, the second power module is in an off state, the third power switch is turned on, and the dynamic characteristics related to the turn-off of the first power switch are measured.

[0013] Optionally, the time interval between the second and third time points is 1us-5us.

[0014] Optionally, between the fifth and sixth time points, the first power switch is turned on, the third power switch is turned on, and the second power module is turned off, and the dynamic characteristics related to the turn-on of the first power switch are measured.

[0015] Optionally, between the sixth and seventh time points, the first power switch is turned off, the second power module is in an off state, and the third power switch is turned on; after the seventh time point, the third power switch is turned off, the first power switch is turned off, and the second power module is in an off state.

[0016] Optionally, the time interval between the sixth and seventh time points is 48ms-52ms.

[0017] The present invention has the following advantages:

[0018] The present invention provides a method for operating a power module test circuit to suppress self-heating effects. The first moment is the start of the test. Between the first moment and the second moment, all power modules are in an off state; the first, second, and third power modules are all off. The DC bus power supply voltage is shared by the first and second power switches. Since the second and first power switches are tested independently under the same test conditions, the leakage current of the second power switch is less than that of the first power switch. Similarly, the leakage current of the third power switch is less than that of the first power switch when tested independently under the same test conditions. This ensures that both the second and third power switches have high blocking characteristics. The second and third power switches share most of the DC bus power supply voltage. The magnitude of the leakage current in the first power switch between the first and second moments is determined by the second and third power switches. The high blocking characteristics of the second and third power switches ensure that the leakage current in the first power switch is small between the first and second moments, thus preventing self-heating of the first power switch between these two moments. Between the second and third time points, the third power switch is turned on, and the DC bus power supply voltage is supplied by the first power switch. The first power switch exhibits a self-heating effect, but the time interval between the second and third time points can be controlled by adjusting the operating state of the third power switch, thus minimizing this time interval and suppressing the self-heating effect. Consequently, during the measurement of the turn-off-related dynamic characteristics of the first power switch between the fourth and fifth time points, the predetermined test temperature is less affected by the self-heating effect of the first power switch, resulting in higher stability of the predetermined test temperature and higher testing accuracy for the first power switch. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 The dynamic characteristic testing circuit is a dual-pulse circuit;

[0021] Figure 2 for Figure 1 Timing diagram of the dynamic characteristic test circuit;

[0022] Figure 3 This is a schematic diagram of a power module test circuit for suppressing self-heating effect according to an embodiment of the present invention;

[0023] Figure 4 This is a timing diagram provided for an embodiment of the present invention. Detailed Implementation

[0024] One type of dynamic characteristic testing circuit is a dual-pulse circuit, such as... Figure 1 As shown. Where, U DC ' is the high-voltage DC power supply, C' is the DC-side supporting capacitor, power switches T1' and T2' are IGBT units connected in series to form a half-bridge, D1' is a diode connected in anti-parallel to T1', and D2' is a diode connected in anti-parallel to T2'. T1' is the device under test (DUT), and L' is the load inductance. Power switch T2' remains off throughout the test. (Reference) Figure 2 VGE1' is a timing diagram of the drive voltage applied between the gate and collector of power switch T1', VCE1' is a timing diagram of the voltage between the emitter and collector of power switch T1', and IC1' is the current signal in power switch T1'. At time t1', VGE1' changes from low to high; between t1' and t2', power switch T1' is turned on, and the current in the load inductor L' increases from 0 until it reaches the rated value I at time t2. R The corresponding IC1' increases from 0 to I. RAt time t2', VGE1' changes from high to low. Between t2' and t3', power switch T1' is turned off, and the load current is freewheeled by diode D2'. The current on power switch T1' drops rapidly from IR to 0A. Time t2' is used to measure the dynamic characteristics related to the turn-off of power switch T1'. At time t3', VGE1' goes high again. Between t3' and t4', power switch T1' turns on, and the load current is rapidly transferred from diode D2' to power switch T1'. Time t3 is used to measure the dynamic characteristics related to the turn-on of power switch T1'. At time t4, VGE1' goes low, power switch T1' turns off, and the load current is freewheeled by diode D2', completing the test.

[0025] The dynamic characteristics of the power module are tested under defined operating conditions, such as U. DC The driving resistor R of D1 G Load current I L The junction temperature T of D1' J Under certain conditions, during the development phase of power devices, extreme tests should be conducted under the aforementioned operating conditions to assess the performance of the power module, such as testing under operating conditions with higher bus voltage and higher junction temperature of D1'.

[0026] During testing, the junction temperature of the power module is typically controlled by a heating platform to reach a set temperature. However, when a higher bus voltage or junction temperature is applied, due to the inherent characteristics of the power switch T1', a large leakage current is usually generated (leakage current is defined as the current flowing through the emitter when a voltage is applied across the collector and emitter of the power switch T1' when it is turned off; it is generally represented by ICES). This leakage current will generate significant power dissipation within the power switch T1' itself, creating a self-heating effect. This causes the junction temperature of the power switch T1' to be unable to be controlled to the given temperature. In severe cases, the temperature of the power switch T1' will continue to rise due to the self-heating effect, eventually leading to failure. The principle of the self-heating effect is as follows: the leakage current ICES flows through the load inductor L' and T1', while the voltage across T1' at this time is U. DC At this time, the leakage current power consumption of T1' is PL=U DC *ICES; During the period 0-t1, the bus voltage U DC The heat generated by the PL (Power Transistor PL) causes the junction temperature of the power switch T1' to exceed the set temperature. This makes dynamic performance testing impossible at the set temperature. In summary, the power module test circuit exhibits poor testing accuracy.

[0027] Based on this, embodiments of the present invention provide a power module test circuit for suppressing self-heating effects, referencing... Figure 3 ,include:

[0028] DC bus power supply U DC ;

[0029] A first power module A, comprising: a first power switch T1 to be tested and a first diode D1 connected in reverse parallel with the first power switch T1;

[0030] The second power module B includes: a second power switch T2 and a second diode D2 connected in reverse parallel with the second power switch T2; the second power switch T2 and the first power switch T1 are tested independently under the same test conditions, and the leakage current of the second power switch T2 is less than the leakage current of the first power switch T1.

[0031] The third power module C includes a third power switch T3 and a third diode D3 connected in reverse parallel with the third power switch T3; the third power switch T3 and the first power switch T1 are tested independently under the same test conditions, and the leakage current of the third power switch T3 is less than the leakage current of the first power switch T1.

[0032] Load inductance L;

[0033] The collector of the first power switch T1, the emitter of the second power switch T2, and one end of the load inductor L are connected. The emitter of the first power switch T1 is connected to the DC bus power supply U. DC The positive terminal is electrically connected, the collector of the second power switch T2 and the collector of the third power switch T3 are connected and connected to the DC bus power supply U. DC The negative terminal is electrically connected; the emitter of the third power switch T3 is connected to the other end of the load inductor L.

[0034] Under the same test conditions, the leakage current of the second power switch T2 is less than that of the first power switch T1 when the second power switch T2 and the first power switch T1 are tested independently. This means that when the first power module A and the second power module B are tested offline, the test conditions applied to the second power switch T2 are the same as those applied to the first power switch T1, and the leakage current of the second power switch T2 is less than that of the first power switch T1. During the offline test, the first power module A and the second power module B are tested independently of the power module test circuit.

[0035] The second power switch T2 has a higher voltage rating than the first power switch T1, and / or the second power switch T2 has a higher temperature rating than the first power switch T1. Specifically, in one embodiment, the second power switch T2 has a higher voltage rating than the first power switch T1, and the second power switch T2 has a lower than or equal to the temperature rating of the first power switch T1. In another embodiment, the second power switch T2 has a higher temperature rating than the first power switch T1, and the second power switch T2 has a lower than or equal to the voltage rating of the first power switch T1. In yet another embodiment, the second power switch T2 has a higher voltage rating than the first power switch T1, and the second power switch T2 has a higher temperature rating than the first power switch T1.

[0036] The fact that the withstand voltage rating of the second power switch T2 is higher than that of the first power switch T1 means that: when the second power switch T2 and the first power switch T1 are tested separately, the leakage current in the second power switch T2 is equal to the leakage current in the first power switch T1; and when the second power switch T2 and the first power switch T1 are operating at the same temperature, the driving voltage of the second power switch T2 is higher than that of the first power switch T1.

[0037] The higher temperature rating of the second power switch T2 compared to the first power switch T1 means that, under the condition that the leakage current of the second power switch T2 is equal to that of the first power switch T1, and the driving voltage of the second power switch T2 is equal to that of the first power switch T1, the second power switch T2 withstands a higher operating temperature than the first power switch T1. Under the same test conditions, the lower leakage current of the third power switch T3 compared to the first power switch T1 means that, when the first power module A and the third power module C are tested offline, the test conditions applied to the third power switch T3 are the same as those applied to the first power switch T1, and the offline test shows that the leakage current of the third power switch T3 is lower than that of the first power switch T1. During the offline test, the first power module A and the third power module C are tested independently of the power module test circuit.

[0038] The third power switch T3 has a higher voltage rating than the first power switch T1, and / or the third power switch T3 has a higher temperature rating than the first power switch T1. In one embodiment, the third power switch T3 has a higher voltage rating than the first power switch T1, and the third power switch T3 has a lower than or equal to the temperature rating of the first power switch T1. In another embodiment, the third power switch T3 has a higher temperature rating than the first power switch T1, and the third power switch T3 has a lower than or equal to the voltage rating of the first power switch T1. In yet another embodiment, the third power switch T3 has a higher voltage rating than the first power switch T1, and the third power switch T3 has a higher temperature rating than the first power switch T1.

[0039] The fact that the withstand voltage rating of the third power switch T3 is higher than that of the first power switch T1 means that: when the third power switch T3 and the first power switch T1 are tested separately, the leakage current in the third power switch T3 is equal to the leakage current in the first power switch T1; and when the third power switch T3 and the first power switch T1 are operating at the same temperature, the driving voltage of the third power switch T3 is higher than that of the first power switch T1.

[0040] The temperature rating of the third power switch T3 is higher than that of the first power switch T1. This means that, when the third power switch T3 and the first power switch T1 are tested separately, the leakage current in the third power switch T3 is equal to the leakage current in the first power switch T1, and the driving voltage of the third power switch T3 is equal to the driving voltage of the first power switch T1, the operating temperature that the third power switch T3 can withstand is higher than that that of the first power switch T1.

[0041] In this embodiment, the first power module A further includes: a fourth power switch T4 and a fourth diode D4 connected in reverse parallel to the fourth power switch T4. The emitter of the fourth power switch T4 is connected to the collector of the first power switch T1, and the collector of the fourth power switch T4 is floating, that is, the collector of the fourth power switch T4 is not connected to the DC bus power supply U. DCElectrical connection. The fourth power switch T4 does not participate in the operation of the power module test circuit. The reason for retaining the fourth power switch T4 and the fourth diode D4 in this embodiment is that the fourth power switch T4 and the fourth diode D4, and the first power switch T1 and the first diode D1 in the first power module A are packaged together as a half bridge and used as a whole. Therefore, the fourth power switch T4 and the fourth diode D4 are retained, but the collector of the fourth power switch T4 needs to be set to float.

[0042] It should be noted that in other embodiments, the first power module does not retain the fourth power switch and the fourth diode; the first power module only includes the first power switch and the first diode.

[0043] In this embodiment, the second power module B further includes: a fifth power switch T5 and a fifth diode D5 connected in reverse parallel to the fifth power switch T5. The collector of the fifth power switch T5 is connected to the emitter of the second power switch T2, and the emitter of the fifth power switch T5 is floating, that is, the emitter of the fifth power switch T5 is not connected to the DC bus power supply U. DC Electrical connection. The fifth power switch T5 does not participate in the operation of the power module test circuit. The reason for retaining the fifth power switch T5 and the fifth diode D5 in this embodiment is that the fifth power switch T5 and the fifth diode D5, the second power switch T2 and the second diode D2 in the second power module B are packaged together as a half bridge and used as a whole. Therefore, the fifth power switch T5 and the fifth diode D5 are retained, but the emitter of the fifth power switch T5 needs to be set to float.

[0044] It should be noted that in other embodiments, the second power module does not retain the fifth power switch and the fifth diode; the second power module only includes the second power switch and the second diode.

[0045] In this embodiment, the third power module C further includes a sixth power switch T6 and a sixth diode D6 connected in reverse parallel to the sixth power switch T6. The collector of the sixth power switch T6 is connected to the emitter of the third power switch T3, and the emitter of the sixth power switch T6 is floating, meaning that the emitter of the sixth power switch T6 is not electrically connected to the DC bus power supply UDC. The sixth power switch T6 does not participate in the operation of the power module test circuit. The reason for retaining the sixth power switch T6 and the sixth diode D6 in this embodiment is that the sixth power switch T6, the sixth diode D6, the third power switch T3, and the third diode D3 in the third power module C are packaged together as a half-bridge and used as a whole. Therefore, the sixth power switch T6 and the sixth diode D6 are retained, but the emitter of the sixth power switch T6 needs to be floating.

[0046] It should be noted that in other embodiments, the sixth power switch and the sixth diode are not retained in the third power module; the third power module only includes the third power switch and the third diode.

[0047] The third power switch T3 is used to either cut off the current in the load inductor L or turn on the current in the load inductor L.

[0048] In one embodiment, the collector of the first power switch T1 and the emitter of the fourth power switch T4 are connected to form a first point Q, and the emitter of the second power switch T2 and the collector of the fifth power switch T5 are connected to form a second point W. The power module test circuit for suppressing self-heating further includes a connecting wire connecting the first point Q and the second point W. The length of the connecting wire is less than or equal to 1.5 times the length of the connecting wire between the center of the first power module and the center of the second power module, for example, 1.1 times, 1.2 times, 1.3 times, 1.4 times, or 1.5 times. Because the length of the connecting wire is small, parasitic inductance can be suppressed.

[0049] The power module test circuit for suppressing self-heating effect also includes: capacitor C, connected to the DC bus power supply U. DC Parallel connection; current sensor, located between the emitter of the first power switch T1 and the DC bus power supply U. DC In the positive electrode path.

[0050] Another embodiment of the present invention also provides a method for operating a power module test circuit (as described above) to suppress self-heating effects, comprising:

[0051] The first power module A was heated to the predetermined test temperature using a heating stage;

[0052] Between the first time t1 and the second time t2, the first power module A, the second power module B and the third power module C are all in the disconnected state;

[0053] Between the second time t2 and the third time t3, the first power module A and the second power module B are in the off state, and the third power switch T3 is turned on.

[0054] Between time t3 and time t4, the first power switch T1 is turned on, the second power module B is turned off, and the third power switch T3 is turned on. The current in the load inductor L increases from 0 until it reaches the rated value I. R ;

[0055] From time t4 to time t5, the first power switch T1 is turned off, the second power module B is in the off state, and the third power switch T3 is turned on. The dynamic characteristics related to the turn-off of the first power switch T1 are measured.

[0056] Throughout the entire testing process of the power module test circuit, the second power switch T2 was in the off state.

[0057] The first time point t1 is the start time of the test. Between the first time point t1 and the second time point t2, all power modules are in the off state; the first power module A, the second power module B, and the third power module C are all in the off state. The DC bus power supply U... DC The voltage is shared by the first power switch T1 and the second power switch T2. Since the second power switch and the first power switch are tested independently under the same test conditions, the leakage current of the second power switch is less than that of the first power switch. Similarly, since the third power switch T3 and the first power switch are tested independently under the same test conditions, the leakage current of the third power switch is less than that of the first power switch. This results in both the second power switch T2 and the third power switch T3 having high blocking characteristics. The second power switch T2 and the third power switch T3 share the DC bus power supply U. DC For most of the voltage, the magnitude of the leakage current in the first power switch T1 from the first time t1 to the second time t2 is determined by the second power switch T2 and the third power switch T3. The high blocking characteristics of the second power switch T2 and the third power switch T3 can ensure that the leakage current in the first power switch T1 from the first time t1 to the second time t2 is small, thus avoiding the self-heating effect of the first power switch T1 between the first time t1 and the second time t2.

[0058] Between the second time t2 and the third time t3, the third power switch T3 is turned on, and the DC bus power supply U... DCThe voltage is borne by the first power switch T1, which has a self-heating effect. However, in this embodiment, the time interval from the second time t2 to the third time t3 can be controlled by controlling the working state of the third power switch T3, so that the time interval from the second time t2 to the third time t3 is smaller, thus suppressing the self-heating effect of the first power switch T1 from the second time t2 to the third time t3.

[0059] In one embodiment, the time interval between the second time t2 and the third time t3 is 1µs-5µs, for example, 1µs, 2µs, 3µs, 4µs, or 5µs. If the time interval between the second time t2 and the third time t3 is too short, it is difficult to control. If the time interval between the second time t2 and the third time t3 is greater than 5ms, the suppression of the self-heating effect of the first power switch T1 is weakened.

[0060] Between time t3 and time t4, the first power switch T1 and the third power switch T3 are turned on, and the current in the load inductor L increases from 0 until it reaches the rated value I. R .

[0061] In one embodiment, the rated value I R The required current for the test conditions can be set arbitrarily.

[0062] Between time t4 and time t5, the first power switch T1 is turned off, and the load current is freewheeled by the second diode D2. The current in the first power switch T1 is reduced from the rated value I. R The current rapidly drops to 0A. The current in the first power switch T1 decreases from the rated value I... R During the rapid drop to 0A, the turn-off related dynamic characteristics of the first power switch T1 are measured. The turn-off related dynamic characteristics of the first power switch T1 include turn-off delay, current fall time, and turn-off loss.

[0063] Since the self-heating effect of the first power switch T1 is suppressed, the predetermined test temperature is less affected by the self-heating effect of the first power switch T1 during the measurement of the turn-off related dynamic characteristics of the first power switch T1 from the fourth time t4 to the fifth time t5, resulting in higher stability of the predetermined test temperature and higher test accuracy of the first power switch T1.

[0064] Between the fifth time t5 and the sixth time t6, the first power switch T1 is turned on, the third power switch T3 is turned on, the second power module B is in the off state, the load current is rapidly transferred from the second diode D2 to the first power switch T1, the current in the first power switch T1 rapidly rises from 0A to I1, and then the current on the load inductor L increases from I1 to I2.

[0065] The turn-on related dynamic characteristics of the first power switch T1 are measured between the fifth time t5 and the sixth time t6. The turn-on related dynamic characteristics of the first power switch T1 include turn-on delay, current rise time, and turn-on loss. Specifically, the turn-on related dynamic characteristics of the first power switch T1 are measured as the current in the first power switch T1 rapidly rises from 0A to I1.

[0066] Between time t6 and time t7, the first power switch T1 is turned off, the second power module B is in the off state, the third power switch T3 is turned on, the load current is freewheeled by the second diode D2, and the current in the first power switch T1 rapidly drops to 0A. After time t7, the third power switch T3 is turned off, the first power switch T1 is turned off, the second power module B is in the off state, and the turning off of the third power switch T3 cuts off the current in the load inductor L.

[0067] In one embodiment, the time interval from the sixth time t6 to the seventh time t7 is greater than τ, where τ = Where L is the inductance of the load inductor L in the test circuit, and R is the parasitic resistance of the freewheeling circuit of the load inductor L and the second diode D2 in the test circuit. The advantage is that it avoids overvoltage failure caused by sudden interruption of the inductor current.

[0068] In one specific embodiment, the time interval between the sixth time t6 and the seventh time t7 is 48ms-52ms.

[0069] It should be noted that while heating the first power module, the heating platform can be used to heat the second power module or not. Since the first and second power modules are usually packaged together, in one embodiment, the first and second power modules are heated simultaneously.

[0070] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A power module test circuit for suppressing self-heating effect, characterized in that, include: DC bus power supply; A first power module, the first power module comprising: a first power switch transistor to be tested and a first diode connected in reverse parallel with the first power switch transistor; The second power module includes: a second power switch and a second diode connected in reverse parallel with the second power switch; the second power switch and the first power switch are tested independently under the same test conditions, and the leakage current of the second power switch is less than that of the first power switch. The third power module includes: a third power switch and a third diode connected in reverse parallel with the third power switch; the third power switch and the first power switch are tested independently under the same test conditions, and the leakage current of the third power switch is less than that of the first power switch. Load inductance; The collector of the first power switch, the emitter of the second power switch, and one end of the load inductor are connected. The emitter of the first power switch is electrically connected to the positive terminal of the DC bus power supply. The collectors of the second and third power switches are connected and electrically connected to the negative terminal of the DC bus power supply. The emitter of the third power switch is connected to the other end of the load inductor.

2. The power module test circuit for suppressing self-heating effect according to claim 1, characterized in that, The second power switch has a higher voltage rating than the first power switch, and / or the second power switch has a higher temperature rating than the first power switch.

3. The power module test circuit for suppressing self-heating effect according to claim 1, characterized in that, The third power switch has a higher voltage rating than the first power switch, and / or the third power switch has a higher temperature rating than the first power switch.

4. The power module test circuit for suppressing self-heating effect according to claim 1, characterized in that, The first power module further includes: a fourth power switch and a fourth diode connected in reverse parallel with the fourth power switch, wherein the emitter of the fourth power switch is connected to the collector of the first power switch, and the collector of the fourth power switch is floating. The second power module also includes: a fifth power switch and a fifth diode connected in reverse parallel to the fifth power switch, wherein the collector of the fifth power switch is connected to the emitter of the second power switch, and the emitter of the fifth power switch is floating.

5. The power module test circuit for suppressing self-heating effect according to claim 4, characterized in that, The collector of the first power switch and the emitter of the fourth power switch are connected to form a first point, and the emitter of the second power switch and the collector of the fifth power switch are connected to form a second point. The power module test circuit for suppressing self-heating effect further includes a connecting wire connecting the first point and the second point, wherein the length of the connecting wire is less than or equal to 1.5 times the length of the connecting wire between the center of the first power module and the center of the second power module.

6. The power module test circuit for suppressing self-heating effect according to claim 1, characterized in that, The third power module also includes: a sixth power switch and a sixth diode connected in reverse parallel to the sixth power switch, wherein the collector of the sixth power switch is connected to the emitter of the third power switch, and the emitter of the sixth power switch is floating.

7. The power module test circuit for suppressing self-heating effect according to claim 1, characterized in that, A capacitor is connected in parallel with the DC bus power supply; a current sensor is located in the path from the emitter of the first power switch to the positive terminal of the DC bus power supply.

8. A method for operating a power module test circuit for suppressing self-heating effect as described in any one of claims 1 to 7, characterized in that, include: The first power module is heated to a predetermined test temperature using a heating table. Between the first and second moments, the first, second, and third power modules are all in the off state. Between the second and third time points, the first and second power modules are in the off state, while the third power switch is turned on. Between the third and fourth moments, the first power switch is turned on, the second power module is in the off state, the third power switch is turned on, and the current on the load inductor increases from 0 to the rated value. From the fourth to the fifth time point, the first power switch is turned off, the second power module is in the off state, and the third power switch is turned on. The dynamic characteristics related to the turn-off of the first power switch are measured.

9. The operating method of the power module test circuit for suppressing self-heating effect according to claim 8, characterized in that, The time interval between the second and third moments is 1us-5us.

10. The operating method of the power module test circuit for suppressing self-heating effect according to claim 8, characterized in that, Between the fifth and sixth time points, the first power switch is turned on, the third power switch is turned on, and the second power module is turned off. The dynamic characteristics related to the turn-on of the first power switch are measured.

11. The operating method of the power module test circuit for suppressing self-heating effect according to claim 10, characterized in that, Between the sixth and seventh time points, the first power switch is turned off, the second power module is in the off state, and the third power switch is turned on; after the seventh time point, the third power switch is turned off, the first power switch is turned off, and the second power module is in the off state.

12. The operating method of the power module test circuit for suppressing self-heating effect according to claim 11, wherein the time interval between the sixth and seventh moments is 48ms-52ms.

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