Power device switching characteristic test circuit and test method thereof

Abstract

The embodiment of the invention discloses a power device switching characteristic test circuit and a test method thereof.The test circuit comprises a driving branch, a first voltage output branch, a second voltage output branch, a load branch and a sampling branch, the first voltage output branch is used for providing first voltage for a to-be-tested power device in the avalanche stress applying stage, and the second voltage output branch is used for providing second voltage for the to-be-tested power device in the avalanche stress applying stage; the driving branch is matched to apply avalanche stress to the to-be-tested power device; the second voltage output branch is used for providing a second voltage for the to-be-tested power device through the load branch in a first switch test stage before the avalanche stress application stage and a second switch test stage after the avalanche stress application stage so as to cooperate with the driving branch to carry out a switch characteristic test on the to-be-tested power device. According to the scheme, the switching characteristic test can be performed on the unrecovered power device to be tested within a short time after the power device to be tested is subjected to the avalanche stress, so that the influence of the power device to be tested after the power device to be tested is subjected to the avalanche stress can be tested more practically.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of electrical performance testing, and in particular to a testing circuit and a testing method for switching characteristics of a power device. Background Art

[0002] The switching characteristics of power devices are one of their most important performance indicators. The switching speed of the device determines the dynamic response capability of the system. Therefore, it is necessary to test the switching characteristics of power devices.

[0003] UIS (Unclamped Inductive Switching), also known as avalanche stress, is generally considered to be the most extreme stress condition that power devices are subjected to in power electronics applications. In the prior art, a station-to-station test method is usually used to test the changes in the switching characteristics of power devices before and after avalanche stress. However, the delay time of switching stations is long, which makes the test cycle longer. The long test switching process will cause the power devices to gradually recover from the avalanche stress state, and it is impossible to accurately characterize the changes in the switching characteristics of the power devices, resulting in an inability to judge the stability and reliability of the devices. Summary of the invention

[0004] The embodiment of the present invention provides a test circuit and a test method for the switching characteristics of a power device, so as to improve the test accuracy of the switching characteristics of the power device after being subjected to avalanche stress.

[0005] According to one aspect of the present invention, a circuit for testing switching characteristics of a power device is provided, comprising:

[0006] A driving branch, the driving branch being connected between a control electrode and a second electrode of the power device to be tested;

[0007] A first voltage output branch, the first voltage output branch is connected between the first pole and the second pole of the power device to be tested, and is used to provide a first voltage to the power device to be tested during the avalanche stress application stage, so as to cooperate with the driving branch to apply avalanche stress to the power device to be tested;

[0008] A second voltage output branch and a load branch, wherein the second voltage output branch and the load branch are connected in series between the first pole and the second pole of the power device to be tested, the second voltage output branch is used to provide a second voltage to the power device to be tested via the load branch in a first switch test phase before the avalanche stress application phase and a second switch test phase after the avalanche stress application phase, respectively, so as to cooperate with the drive branch to perform a switch characteristic test on the power device to be tested, and the load branch is used to adjust the output current of the second voltage output branch;

[0009] A sampling branch, the sampling branch is connected to the power device to be tested, and is used to collect the working waveform of the power device to be tested, and obtain the switching characteristics of the power device to be tested according to the working waveform.

[0010] Optionally, the first voltage output branch includes a first energy supply unit and a first switch unit;

[0011] The first end of the first energy supply unit is connected to the first end of the first switch unit, the second end of the first switch unit is connected to the first pole of the power device to be tested, and the second end of the first energy supply unit is connected to the second pole of the power device to be tested;

[0012] Wherein, the first energy supply unit includes a first voltage source, a first capacitor and a first inductor, the first switch unit includes a first switch, a first end of the first voltage source is connected to a first end of the first inductor, a second end of the first inductor is connected to a first end of the first switch, a second end of the first switch is connected to a first pole of the power device to be tested, a control end of the first switch is connected to a first signal source, a second end of the first voltage source is connected to a second pole of the power device to be tested, a first pole of the first capacitor is connected to a first end of the first voltage source, and a second pole of the first capacitor is connected to a second end of the first voltage source;

[0013] The first switch is a fast switch.

[0014] Optionally, the second voltage output branch includes a second energy supply unit and a second switch unit, the first end of the second energy supply unit is connected to the first end of the second switch unit, the second end of the second switch unit is connected to the first end of the load branch, the second end of the load branch is connected to the first pole of the power device to be tested, and the second end of the second energy supply unit is connected to the second pole of the power device to be tested;

[0015] Wherein, the second energy supply unit includes a second voltage source and a second capacitor, the second switch unit includes a second switch, a first end of the second voltage source is connected to a first end of the second switch, a second end of the second switch is connected to a first end of the load branch, a control end of the second switch is connected to a second signal source, a second end of the second voltage source is connected to a second pole of the power device to be tested, a first pole of the second capacitor is connected to a first end of the second switch, and a second pole of the second capacitor is connected to a second pole of the power device to be tested;

[0016] The load branch includes a resistor, a first end of the resistor is a first end of the load branch, and a second end of the resistor is a second end of the load branch;

[0017] Alternatively, the load branch includes a variable inductor and a freewheeling diode, the first end of the variable inductor is the first end of the load branch, the second end of the variable inductor is the second end of the load branch, and the freewheeling diode is connected in parallel with the variable inductor.

[0018] Optionally, the test circuit further includes a third switch unit, wherein the third switch unit is connected between the first pole and the second pole of the power device to be tested, and is used to provide an energy discharge circuit for the power device to be tested;

[0019] Wherein, the third switch unit comprises a third switch, a first end of the third switch is connected to the first pole of the power device to be tested, a second end of the third switch is connected to the second pole of the power device to be tested, and a control end of the third switch is connected to a third signal source;

[0020] The driving branch comprises a driving unit, a first end of the driving unit is connected to a driving signal, a second end of the driving unit is connected to a control electrode of the power device to be tested, and a third end of the driving unit is connected to a second electrode of the power device to be tested.

[0021] According to another aspect of the present invention, a method for testing a switching characteristic of a power device is provided, the method being performed by a testing circuit for the switching characteristic of a power device, the testing circuit for the switching characteristic of a power device comprising a driving branch, a first voltage output branch, a second voltage output branch, a load branch and a sampling branch;

[0022] The method for testing the switching characteristics of the power device includes:

[0023] In the first switch test phase, the second voltage output branch is controlled to provide the second voltage to the power device under test via the load branch, and the switching characteristic test of the power device under test is performed in cooperation with the driving branch, and the sampling branch is controlled to collect the working waveform of the power device under test to obtain the switching characteristic of the power device under test before being subjected to avalanche stress;

[0024] In the avalanche stress application stage, controlling the first voltage output branch to provide a first voltage to the power device under test, and cooperating with the driving branch to apply avalanche stress to the power device under test;

[0025] In the second switching test stage, the second voltage output branch is controlled to provide the second voltage to the power device under test via the load branch, and cooperates with the driving branch to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test to obtain the switching characteristics of the power device under test after being subjected to avalanche stress.

[0026] Optionally, the method for testing switching characteristics of a power device further includes:

[0027] Determine the change of the switching characteristic of the power device to be tested by respectively calculating the comparison values ​​of the same switching parameter of the power device to be tested before and after being subjected to the avalanche stress;

[0028] The switch parameter includes at least one of a rise time, a fall time, a turn-on delay time and a turn-off delay time of a current and / or a voltage.

[0029] Optionally, the first voltage output branch includes a first energy supply unit and a first switch unit, the first energy supply unit includes a first voltage source, a first capacitor and a first inductor, and the first switch unit includes a first switch; the second voltage output branch includes a second energy supply unit and a second switch unit, the second energy supply unit includes a second voltage source and a second capacitor, the second switch unit includes a second switch, and the test circuit further includes a third switch unit, and the third switch unit includes a third switch;

[0030] The first switch test phase includes a first sub-phase, a second sub-phase and a third sub-phase. In the first switch test phase, the method for testing the switching characteristics of the power device includes:

[0031] In the first sub-stage, the second switch is controlled to be turned on, and the second capacitor provides the second voltage to the power device under test via the load branch;

[0032] In the second sub-stage, the driving branch is controlled to turn on the power device to be tested, and the sampling branch is controlled to sample the gate-source voltage and the drain current of the power device to be tested in the on state;

[0033] In the third sub-stage, the driving branch is controlled to turn off the power device to be tested, and the sampling branch is controlled to sample the gate-source voltage and the drain current of the power device to be tested in the off state, and after the sampling is completed, the third switch is controlled to be turned on to discharge the source-drain voltage of the power device to be tested.

[0034] Optionally, the avalanche stress application stage includes a fourth sub-stage and a fifth sub-stage. In the avalanche stress application stage, the method for testing the switching characteristics of the power device includes:

[0035] In the fourth sub-stage, the first switch is controlled to be turned on, and the driving branch is controlled to turn on the power device to be tested, until the drain current of the power device to be tested reaches a preset current value, and then the driving branch is controlled to turn off the power device to be tested;

[0036] In the fifth sub-stage, the driving branch is controlled to turn off the power device to be tested, and when the source-drain voltage of the power device to be tested drops to a preset voltage value, the first switch is controlled to be quickly turned off.

[0037] Optionally, the first switch and / or the third switch is a fast switch.

[0038] Optionally, during the test process, a plurality of consecutive avalanche stress application stages are included, or a plurality of avalanche stress application stages and the second switch test stages are included, and the avalanche stress application stages and the second switch test stages are alternately arranged in sequence.

[0039] The technical solution provided by the embodiment of the present invention can realize the change of the switching characteristics of the power device under test before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, the switching characteristics of the unrecovered power device under test can be tested within a short time after the power device under test is subjected to avalanche stress, so that a more practical test can be obtained to determine the impact on the power device under test after being subjected to avalanche stress, and then the degradation of the dynamic switching characteristics of the power device under test can be characterized, which is beneficial to provide a real reference basis for the application of power devices.

[0040] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A schematic diagram of the structure of a circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of the structure of another test circuit for the switching characteristics of a power device provided by an embodiment of the present invention;

[0044] Figure 3 A schematic diagram of the structure of another circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of the structure of another circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention;

[0046] Figure 5 A flow chart of a method for testing switching characteristics of a power device provided by an embodiment of the present invention;

[0047] Figure 6 A flow chart of another method for testing switching characteristics of a power device provided by an embodiment of the present invention;

[0048] Figure 7 A flow chart of another method for testing switching characteristics of a power device provided by an embodiment of the present invention;

[0049] Figure 8 A schematic diagram of a sampling waveform provided by an embodiment of the present invention;

[0050] Fig. 9 A schematic diagram of switching parameters of a power device to be tested before and after being subjected to avalanche stress provided by an embodiment of the present invention;

[0051] Fig.10 Another sampling waveform schematic diagram provided by an embodiment of the present invention;

[0052] Fig.11 Another sampling waveform diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0055] In switching circuits, UIS (Unclamped Inductive Switching), also known as avalanche stress, is generally considered to be the most extreme stress condition that power devices are subjected to in power electronics applications. When a power device is subjected to avalanche stress, the switching characteristics may degrade, and the change in switching characteristics will directly affect the power device's loss and conversion efficiency, as well as the circuit's dynamic response and stability. Therefore, accurately characterizing the change in the switching characteristics of a power device is crucial to evaluating the stability and reliability of the power device.

[0056] At present, a station-to-station test method is usually used to test the changes in the switching characteristics of power devices before and after avalanche stress. However, the delay time of switching stations is in the ms or even s level. The long test switching process will cause the power devices to gradually recover from the avalanche stress state, and it is impossible to accurately characterize the changes in the switching characteristics of the power devices, resulting in an inability to judge the stability and reliability of the devices.

[0057] In view of the above problems, an embodiment of the present invention provides a test circuit for the switching characteristics of a power device to reduce the delay in the test switching process, which is conducive to accurately characterizing the changes in the switching characteristics of the power device, thereby improving the test effect. Figure 1 A schematic diagram of a circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 1 The test circuit for the switching characteristics of a power device provided in this embodiment includes:

[0058] A driving branch 11, the driving branch 11 is connected between a control electrode and a second electrode of the power device Q1 to be tested;

[0059] A first voltage output branch 12, the first voltage output branch 12 is connected between the first electrode and the second electrode of the power device Q1 to be tested, and is used to provide a first voltage to the power device Q1 to be tested during the avalanche stress application stage, so as to cooperate with the driving branch 11 to apply avalanche stress to the power device Q1 to be tested;

[0060] A second voltage output branch 13 and a load branch 14, the second voltage output branch 13 and the load branch 14 are connected in series between the first pole and the second pole of the power device Q1 to be tested, the second voltage output branch 13 is used to provide a second voltage to the power device Q1 to be tested via the load branch 14 in a first switch test phase before the avalanche stress application phase and a second switch test phase after the avalanche stress application phase, respectively, to cooperate with the drive branch 11 to perform a switch characteristic test on the power device Q1 to be tested, and the load branch 14 is used to adjust the output current of the second voltage output branch 13;

[0061] The sampling branch is connected to the power device Q1 to be tested, and is used to collect the working waveform of the power device Q1 to be tested, and obtain the switching characteristics of the power device Q1 to be tested according to the working waveform.

[0062] The power device Q1 to be tested is a silicon carbide power device or a gallium nitride power device, and may also be a silicon device, such as MOSFET, IGBT, triode, etc. The driving branch 11 is used to output a pulse signal to drive the power device Q1 to be tested. Taking the power device Q1 to be tested as a MOSFET as an example, the control electrode of the power device Q1 to be tested may be a gate, the first electrode may be a drain electrode D, and the second electrode may be a source electrode S.

[0063] Specifically, the first voltage output branch 12, the driving branch 11 and the power device to be tested Q1 together constitute an avalanche stress application circuit to achieve the application of avalanche stress to the power device to be tested Q1. The second voltage output branch 13, the load branch 14, the driving branch 11 and the power device to be tested Q1 together constitute a switch test circuit to achieve the switch characteristic test of the power device to be tested Q1. The sampling branch may include a first sampling branch SA1, a second sampling branch SA2 and a third sampling branch SA3, wherein the first sampling branch SA1 can be used to collect the voltage waveform (i.e., gate-source voltage) between the first pole and the control pole of the power device to be tested Q1, the second sampling branch SA2 can be used to collect the voltage waveform (i.e., source-drain voltage) between the first pole and the second pole of the power device to be tested Q1, and the third sampling branch SA3 can be used to collect the current (i.e., drain current) of the power device to be tested Q1.

[0064] by Figure 1 Taking the test circuit shown as an example, the specific working principle of the test circuit provided in this embodiment is as follows: in the first switch test stage, the first voltage output branch 12 is turned off, the second voltage output branch 13 is turned on, and the second voltage output branch 13 provides a second voltage to the power device Q1 to be tested via the load branch 14, and the on and off of the power device Q1 to be tested is controlled by the driving branch 11, and the voltage and current waveforms of the power device Q1 to be tested when it is turned on and off are respectively collected through the sampling branch to obtain the switching parameters of the power device Q1 to be tested, and then the switching characteristics of the power device Q1 to be tested before being subjected to avalanche stress are characterized.

[0065] In the avalanche stress application stage, the first voltage output branch 12 is turned on, the second voltage output branch 13 is turned off, and the first voltage output branch 12 provides the first voltage for the power device Q1 to be tested. After the first switch test stage is over, the power device Q1 to be tested is in the off state. Therefore, in the avalanche stress application stage, the power device Q1 to be tested needs to be turned on by the driving branch 11 first, so that the power device Q1 to be tested reaches a preset current value under the action of the first voltage, and then the power device Q1 to be tested is turned off by the driving branch 11. Under the action of the first voltage output branch 12, the voltage across the two ends of the power device Q1 to be tested is the maximum energy it can withstand before being seriously damaged, that is, the power device Q1 to be tested is subjected to avalanche stress.

[0066] In the second switch test phase, the first voltage output branch 12 is turned off, and the second voltage output branch 13 is turned on. The second voltage output branch 13 provides a second voltage to the power device Q1 to be tested via the load branch 14. The on and off of the power device Q1 to be tested is controlled by the driving branch 11, and the voltage and current waveforms of the power device Q1 to be tested when it is turned on and off are respectively collected through the sampling branch to obtain the switching parameters of the power device Q1 to be tested, and then the switching characteristics of the power device Q1 to be tested after being subjected to avalanche stress are characterized.

[0067] By comparing the changes of the same switch parameters in two tests, the dynamic changes of the switch characteristics of the power device Q1 to be tested after being subjected to avalanche stress can be obtained.

[0068] The technical solution provided by the embodiment of the present invention can realize the change of the switching characteristics of the power device Q1 to be tested before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, the switching characteristics of the unrecovered power device Q1 to be tested can be tested within a short time after the power device Q1 to be tested is subjected to avalanche stress, so that a more practical test can be obtained to determine the impact on the power device Q1 to be tested after being subjected to avalanche stress, and then the degradation of the dynamic switching characteristics of the power device Q1 to be tested can be characterized, which is beneficial to providing a real reference basis for the application of power devices.

[0069] Optionally, in one embodiment, the sampling branch may include an oscilloscope for collecting the voltage waveform and current waveform of the power device Q1 to be tested, and after collecting the waveforms of the gate-source voltage VGS, source-drain voltage VDS and drain current IDS of the power device Q1 to be tested, converting the waveforms into data for recording, so as to complete the test of the power device Q1 to be tested.

[0070] Figure 2 A schematic diagram of another circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 2On the basis of the above embodiment, optionally, the test circuit provided in this embodiment further includes a third switch unit 15, the third switch unit 15 is connected between the first pole and the second pole of the power device Q1 to be tested, and is used to provide an energy discharge circuit for the power device Q1 to be tested. The third switch unit 15 includes a third switch K3, a first end of the third switch K3 is connected to the first pole of the power device Q1 to be tested, a second end of the third switch K3 is connected to the second pole of the power device Q1 to be tested, and a control end of the third switch K3 is connected to a third signal source 23, and the third signal source 23 is used to provide a third control signal to the third switch K3 to control the on and off of the third switch K3.

[0071] In this embodiment, the third switch K3 is a fast switch with low switching loss, high switching speed and high voltage blocking capability. For example, the third switch K3 can be a fast switching transistor or a fast switching relay. The switching speed of the third switch K3 is in the ns level, and is used in conjunction with the third signal source 23. After the power device Q1 to be tested completes the switching characteristic test in the initial state, the power device Q1 to be tested can be quickly discharged by closing the third switch K3, reducing the discharge waiting time, thereby realizing the rapid switching of the stress of the power device Q1 to be tested, so that avalanche stress can be quickly applied to the power device Q1 to be tested through the first voltage output branch 12, thereby making the test result more accurate.

[0072] Figure 3 A schematic diagram of another circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 3 On the basis of the above embodiment, optionally, the first voltage output branch 12 includes a first energy supply unit and a first switch unit, the first end of the first energy supply unit is connected to the first end of the first switch unit, the second end of the first switch unit is connected to the first pole of the power device Q1 to be measured, the second end of the first energy supply unit is connected to the second pole of the power device Q1 to be measured, and the second pole of the power device Q1 to be measured is grounded.

[0073] Among them, the first energy supply unit includes a first voltage source U1, a first capacitor C1 and a first inductor L1, the first switch unit includes a first switch K1, the first end of the first voltage source U1 is connected to the first end of the first inductor L1, the second end of the first inductor L1 is connected to the first end of the first switch K1, the second end of the first switch K1 is connected to the first pole of the power device Q1 to be tested, the control end of the first switch K1 is connected to the first signal source 21, and is used to turn on or off in response to the first control signal output by the first signal source 21, the second end of the first voltage source U1 is connected to the second pole of the power device Q1 to be tested, the first pole of the first capacitor C1 is connected to the first end of the first voltage source U1, and the second pole of the first capacitor C1 is connected to the second end of the first voltage source U1.

[0074] Specifically, the first voltage source U1 is used to pre-charge the first capacitor C1 so that the avalanche stress application circuit can obtain a fast voltage output. The first switch K1 is a fast switch with low switching loss, high switching speed and high voltage blocking capability. For example, the first switch K1 can be a fast switching transistor or a fast switching relay. In this embodiment, the switching speed of the first switch K1 is in the ns level, and is used in conjunction with the first signal source 21 to control the test circuit to implement the application of avalanche stress to the power device Q1 to be tested. Among them, the first signal source 21 can be a digital signal source.

[0075] In the avalanche stress application stage, when the power device Q1 to be tested is turned on, all the energy output by the first voltage source U1 is stored in the first inductor L1, and when the power device Q1 to be tested is turned off, all the energy stored in the first inductor L1 is transferred to the power device Q1 to be tested, so UIS can reflect the maximum energy that the power device Q1 to be tested can withstand before being seriously damaged. Among them, since different power devices can withstand different avalanche stresses, the corresponding inductance values ​​of the first inductor L1 are also different. Therefore, here, the first inductor L1 is an adjustable inductor, and its inductance value can be designed according to the specific energy requirements of the power device Q1 to be tested, for example, its inductance value can be switched arbitrarily between uH level and mH level.

[0076] In this embodiment, after the first switch test phase is completed, the source-drain voltage VDS of the power device Q1 to be tested can be quickly released through the third switch K3, and combined with the rapid conduction of the first switch K1, avalanche stress can be quickly applied to the power device Q1 to be tested, which is conducive to improving the accuracy of the switch characteristic test. After the avalanche stress is applied to the power device Q1 to be tested, the avalanche stress application loop is cut off by quickly disconnecting the first switch K1, so that the delay time of the switch characteristic test of the power device Q1 to be tested after being subjected to the avalanche stress is controlled to the microsecond level, greatly reducing the recovery time of the power device Q1 to be tested, so as to accurately characterize the switch characteristic degradation phenomenon of the power device Q1 to be tested before and after the avalanche stress.

[0077] Continue to refer Figure 3 The second voltage output branch 13 includes a second energy supply unit and a second switch unit, the first end of the second energy supply unit is connected to the first end of the second switch unit, the second end of the second switch unit is connected to the first end of the load branch 14, the second end of the load branch 14 is connected to the first pole of the power device Q1 to be tested, and the second end of the second energy supply unit is connected to the second pole of the power device Q1 to be tested.

[0078] The second energy supply unit includes a second voltage source U2 and a second capacitor C2, the second switch unit includes a second switch K2, the first end of the second voltage source U2 is connected to the first end of the second switch K2, the second end of the second switch K2 is connected to the first end of the load branch 14, and the control end of the second switch K2 is connected to the second signal source 22, which is used to respond to the second control signal output by the second signal source 22 to turn on or off to control whether the second capacitor C2 provides voltage to the power device Q1 to be tested. The second end of the second voltage source U2 is connected to the second pole of the power device Q1 to be tested, the first pole of the second capacitor C2 is connected to the first end of the second switch K2, and the second pole of the second capacitor C2 is connected to the second pole of the power device Q1 to be tested. The second voltage source U2 is used to pre-charge the second capacitor C2 to obtain a voltage for rapid output.

[0079] Figure 4 A schematic diagram of another circuit for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 3 and Figure 4 , optionally, as Figure 3 As shown, the load branch 14 includes a resistor R1 (the resistor R1 may be an adjustable resistor or a replaceable fixed resistor), the first end of the resistor R1 is the first end of the load branch 14, and the second end of the resistor R1 is the second end of the load branch 14. Alternatively, Figure 4 As shown, the load branch 14 includes a variable inductor L2 and a freewheeling diode D1 , the first end of the variable inductor L2 is the first end of the load branch 14 , the second end of the variable inductor L2 is the second end of the load branch 14 , and the freewheeling diode D1 is connected in parallel with the variable inductor L2 .

[0080] Among them, by adjusting the resistance value of the resistor R1 or the inductance value of the variable inductor L2 (both can be adjusted to zero at the minimum), the adjustment of different current values ​​of the second voltage output branch 13 is realized, and the freewheeling diode D1 is used in conjunction with the variable inductor L2. When the branch is disconnected, the current in the variable inductor L2 is freewheeled by the freewheeling diode D1. Here, when the load branch 14 includes the resistor R1, the load branch 14 is a resistive load, and when the load branch 14 includes the variable inductor L2, the load branch 14 is an inductive load. The specific working process of this solution will be further explained later by taking the resistive load as an example.

[0081] Optionally, the driving branch 11 may include a driving unit (not shown in the figure), the first end of the driving unit is connected to the driving signal, the second end of the driving unit is connected to the control electrode of the power device Q1 to be tested, and the third end of the driving unit is connected to the second electrode of the power device Q1 to be tested. The driving signal may be a pulse signal, which may be provided by a digital signal source, and the driving unit provides a high-speed driving signal to the control electrode of the power device Q1 to be tested. Here, the driving unit is used in conjunction with the driving signal to realize constant voltage control, constant current control or multiple mixed mode control of the power device Q1 to be tested.

[0082] In other embodiments, the driving branch 11 may also include a current limiting unit (not shown in the figure), which is connected between the driving unit and the control electrode of the power device Q1 to be tested, and is used to realize constant current control of the power device Q1 to be tested. The test circuit for the switching characteristics of the power device provided by the embodiment of the present invention has a simple structure, and at least some control signals have a synchronous program control function. In the same set of circuits, by quickly disconnecting the avalanche stress application circuit and the switch characteristic test circuit, the switch characteristic test can be performed within the us level delay after the power device Q1 to be tested is subjected to avalanche stress, which greatly reduces the delay time, can be more in line with the influence of the power device in actual application after being subjected to avalanche stress, and is conducive to improving the test accuracy of the switch characteristic of the power device Q1 to be tested after being subjected to avalanche stress.

[0083] Optionally, an embodiment of the present invention further provides a method for testing the switching characteristics of a power device. The testing method can be performed by a testing circuit for the switching characteristics of a power device provided by any embodiment of the present invention. The structure of the testing circuit is as follows: Figures 1 to 4 shown.

[0084] Figure 5 A flow chart of a method for testing switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 5 The method for testing the switching characteristics of a power device provided in this embodiment includes:

[0085] S110. In the first switch test phase, the second voltage output branch is controlled to provide a second voltage to the power device under test via the load branch, and the driving branch is cooperated to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test, so as to obtain the switching characteristics of the power device under test before being subjected to avalanche stress.

[0086] S120. In the avalanche stress application stage, control the first voltage output branch to provide a first voltage to the power device to be tested, and cooperate with the driving branch to apply avalanche stress to the power device to be tested.

[0087] S130. In the second switch test phase, the second voltage output branch is controlled to provide a second voltage to the power device under test via the load branch, and the driving branch is cooperated to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test, so as to obtain the switching characteristics of the power device under test after being subjected to avalanche stress.

[0088] The technical solution provided by the embodiment of the present invention can realize the change of the switching characteristics of the power device Q1 to be tested before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, the switching characteristics of the unrecovered power device Q1 to be tested can be tested within a short time after the power device Q1 to be tested is subjected to avalanche stress, so that a more practical test can be obtained to determine the impact on the power device Q1 to be tested after being subjected to avalanche stress, and then the degradation of the dynamic characteristics of the power device Q1 to be tested can be characterized, which is beneficial to providing a real reference basis for the application of power devices.

[0089] Figure 6 A flowchart of another method for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 6 Based on the above embodiment, optionally, the method for testing the switching characteristics of a power device provided in this embodiment includes:

[0090] S110. In the first switch test phase, the second voltage output branch is controlled to provide a second voltage to the power device under test via the load branch, and the driving branch is cooperated to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test, so as to obtain the switching characteristics of the power device under test before being subjected to avalanche stress.

[0091] S120. In the avalanche stress application stage, control the first voltage output branch to provide a first voltage to the power device to be tested, and cooperate with the driving branch to apply avalanche stress to the power device to be tested.

[0092] S130. In the second switch test phase, the second voltage output branch is controlled to provide a second voltage to the power device under test via the load branch, and the driving branch is cooperated to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test, so as to obtain the switching characteristics of the power device under test after being subjected to avalanche stress.

[0093] S140 , determining a change in the switching characteristic of the power device to be tested by respectively calculating comparison values ​​of the same switching parameter of the power device to be tested before and after being subjected to avalanche stress.

[0094] After the sampling branch collects the voltage and current waveforms of the power device Q1 to be tested, it can convert the voltage and current waveforms into data for recording to obtain the corresponding switch parameters, and calculate the obtained switch parameters to obtain the change of the switch characteristics of the power device Q1 to be tested. The switch parameters include at least one of the rise time, fall time, turn-on delay time and turn-off delay time of the current and / or voltage. The comparison value of the same switch parameter can be a ratio or a difference. In other embodiments, the comparison value can also be other values ​​that can characterize the switch characteristics of the power device.

[0095] Figure 7 A flowchart of another method for testing the switching characteristics of a power device provided by an embodiment of the present invention, referring to Figure 7 and Figure 3 The first switch test phase includes a first sub-phase, a second sub-phase and a third sub-phase. In the first switch test phase, the avalanche stress application phase includes a fourth sub-phase and a fifth sub-phase. The second switch test phase includes a sixth sub-phase, a seventh sub-phase and an eighth sub-phase. The power device switch characteristic test method provided in this embodiment includes:

[0096] S1101 . In a first sub-phase, the second switch is controlled to be turned on, and the second capacitor provides a second voltage to the power device to be tested via a load branch.

[0097] S1102, in the second sub-phase, controlling the driving branch to turn on the power device to be tested, and controlling the sampling branch to sample the gate-source voltage and drain current of the power device to be tested in the on state.

[0098] S1103, in the third sub-stage, controlling the driving branch to turn off the power device to be tested, and controlling the sampling branch to sample the gate-source voltage and drain current of the power device to be tested in the off state, and controlling the third switch to be turned on after the sampling is completed to discharge the source-drain voltage of the power device to be tested.

[0099] S1201. In a fourth sub-stage, the first switch is controlled to be turned on, and the driving branch is controlled to turn on the power device to be tested, until the drain current of the power device to be tested reaches a preset current value, and then the driving branch is controlled to turn off the power device to be tested.

[0100] S1202 , in the fifth sub-stage, controlling the driving branch to turn off the power device to be tested, and when the source-drain voltage of the power device to be tested drops to a preset voltage value, controlling the first switch to be quickly turned off.

[0101] S1301, in the sixth sub-stage, the second switch is controlled to be turned on, and the second capacitor provides a second voltage to the power device to be tested via the load branch.

[0102] S1302 , in the seventh sub-stage, controlling the driving branch to turn on the power device to be tested, and controlling the sampling branch to sample the gate-source voltage and drain current of the power device to be tested in the on state.

[0103] S1303, in the eighth sub-stage, controlling the driving branch to turn off the power device to be tested, and controlling the sampling branch to sample the gate-source voltage and drain current of the power device to be tested in the off state, and controlling the third switch to be turned on after the sampling is completed to discharge the source-drain voltage of the power device to be tested.

[0104] Figure 8 A sampling waveform diagram provided by an embodiment of the present invention, combined with Figure 3 , Figure 7 and Figure 8 The specific working principle of the method for testing the switching characteristics of a power device provided in this embodiment is as follows:

[0105] Before time t0', the first capacitor C1 is pre-charged by the first voltage source U1, and the second capacitor C2 is pre-charged by the second voltage source U2.

[0106] In the first sub-phase (t0'-t0 time period), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, the third switch K3 is turned off in response to the third control signal output by the third signal source 23, and the driving branch 11 controls the power device Q1 to be tested to be turned off. The second capacitor C2 provides a second voltage for the power device Q1 to be tested. Since the power device Q1 to be tested is not turned on, the source-drain voltage VDS of the power device Q1 to be tested is at a high voltage. Among them, the second power supply U2 is a high voltage source.

[0107] In the second sub-stage (time period t0-t1), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, and the third switch K3 is turned off in response to the third control signal output by the third signal source 23. The driving branch 11 controls the power device Q1 to be tested to be turned on, and the drain current IDS of the power device Q1 to be tested is established. The waveform of the drain current IDS of the power device Q1 to be tested in the on state before being subjected to avalanche stress can be obtained through the third sampling branch SA3. At the same time, the gate-source voltage VGS of the power device Q1 to be tested in the on state before being subjected to avalanche stress is obtained through the first sampling branch SA1, and the waveform of the source-drain voltage VDS of the power device Q1 to be tested in the on state before being subjected to avalanche stress is obtained through the second sampling branch SA2.

[0108] In the third sub-stage (t1-t2' time period), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, the third switch K3 is turned off in response to the third control signal output by the third signal source 23, the driving branch 11 controls the power device Q1 to be turned off, the gate-source voltage VGS of the power device Q1 to be tested is 0V, the drain current IDS is 0A, and the source-drain voltage VDS is restored to the high voltage in the first sub-stage. The gate-source voltage VGS of the power device Q1 to be tested in the off state before being subjected to avalanche stress is obtained through the first sampling branch SA1, the source-drain voltage VDS waveform of the power device Q1 to be tested in the off state before being subjected to avalanche stress is obtained through the second sampling branch SA2, and the drain current IDS waveform of the power device Q1 to be tested in the off state before being subjected to avalanche stress can be obtained through the third sampling branch SA3.

[0109] At time t2', the second switch K2 is controlled to be turned off in response to the second control signal output by the second signal source 22, and the third switch K3 is turned on in response to the third control signal output by the third signal source 23, so that the source-drain voltage VDS of the power device Q1 to be tested is quickly reduced to 0V, and the switching characteristic test is completed. Each sampling branch converts the acquired waveform into data to obtain the switching characteristics of the power device Q1 to be tested before being subjected to avalanche stress.

[0110] In the fourth sub-stage (t2-t3 time period), the first switch K1 is turned on in response to the first control signal output by the first signal source 21, the second switch K2 is turned off in response to the second control signal output by the second signal source 22, the third switch K3 is turned off in response to the third control signal output by the third signal source 23, the driving branch 11 controls the power device Q1 to be tested to be turned on, and the drain current IDS continues to rise. In this process, all the energy output by the first voltage source U1 is stored in the first inductor L1. At t3, the drain current IDS rises to the preset current value, and the driving branch 11 controls the power device Q1 to be tested to be turned off.

[0111] In the fifth sub-stage (t3-t5' time period), the power device Q1 to be tested is in the off state, and the energy stored in the first inductor L1 is completely transferred to the power device Q1 to be tested. The power device Q1 to be tested is subjected to avalanche stress, and the source-drain voltage VDS of the power device Q1 to be tested is the avalanche voltage BVDSS. At time t4, when the third sampling branch SA3 obtains that the source-drain voltage VDS of the power device Q1 to be tested drops to a preset voltage value (e.g., 0V), the first switch K1 is quickly turned off to cut off the avalanche stress application circuit, thereby completing the avalanche stress application of the power device Q1 to be tested. Among them, the t2-t5' time period is the avalanche stress application time T-UIS.

[0112] In the sixth sub-phase (time period t5'-t5), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, the third switch K3 is turned off in response to the third control signal output by the third signal source 23, and the driving branch 11 controls the power device Q1 to be tested to be turned off. The second capacitor C2 provides a second voltage for the power device Q1 to be tested, and since the power device Q1 to be tested is not turned on, the source-drain voltage VDS of the power device Q1 to be tested is at a high voltage.

[0113] In the seventh sub-stage (time period t5-t6), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, and the third switch K3 is turned off in response to the third control signal output by the third signal source 23. The driving branch 11 controls the power device Q1 to be tested to be turned on, and the drain current IDS of the power device Q1 to be tested is established. The waveform of the drain current IDS of the power device Q1 to be tested in the on state after being subjected to avalanche stress can be obtained through the third sampling branch SA3. At the same time, the gate-source voltage VGS of the power device Q1 to be tested in the on state after being subjected to avalanche stress is obtained through the first sampling branch SA1, and the waveform of the source-drain voltage VDS of the power device Q1 to be tested in the on state after being subjected to avalanche stress is obtained through the second sampling branch SA2.

[0114] In the eighth sub-stage (after time t6), the first switch K1 is turned off in response to the first control signal output by the first signal source 21, the second switch K2 is turned on in response to the second control signal output by the second signal source 22, the third switch K3 is turned off in response to the third control signal output by the third signal source 23, the driving branch 11 controls the power device Q1 to be turned off, the gate-source voltage VGS of the power device Q1 to be tested is 0V, the drain current IDS is 0A, and the source-drain voltage VDS is restored to the high voltage in the sixth sub-stage. The gate-source voltage VGS of the power device Q1 to be tested in the off state after being subjected to avalanche stress is obtained through the first sampling branch SA1, the source-drain voltage VDS waveform of the power device Q1 to be tested in the off state after being subjected to avalanche stress is obtained through the second sampling branch SA2, and the drain current IDS waveform of the power device Q1 to be tested in the off state after being subjected to avalanche stress can be obtained through the third sampling branch SA3.

[0115] Each sampling branch converts the acquired waveform into data to obtain the switching characteristics of the power device Q1 under test after being subjected to avalanche stress. By comparing the same switching parameters of the power device Q1 under test before and after being subjected to avalanche stress, the change in the switching characteristics of the power device Q1 under test is obtained, thereby characterizing the degradation of the power device Q1 under test.

[0116] In this embodiment, the first switch K1 and the third switch K3 are both fast switches, and the delay when the two are switched alternately is of the order of us, which is conducive to reducing the delay time between different stages, thereby improving the accuracy of the switch characteristic test of the power device Q1 to be tested. Among them, at time t4, by quickly turning off the first switch K1, it can be ensured that the delay time of the time period t4-t5' is of the order of us, so as to ensure that the switch characteristic test of the unrecovered power device Q1 to be tested can be performed within the order of us after being subjected to avalanche stress, so as to obtain a more practical test of the influence on the switch characteristic of the power device Q1 to be tested after being subjected to avalanche stress.

[0117] Fig. 9 A schematic diagram of the switching parameters of a power device to be tested before and after being subjected to avalanche stress is provided in an embodiment of the present invention, with reference to Fig. 9 The switching parameters used to characterize the switching characteristics of the power device Q1 to be tested include one or more of the following parameters:

[0118] Current rise time Tr(i): the time interval between when the drain current IDS of the power device Q1 reaches 90% of the set current value and when the drain current IDS reaches 10% of the set current value. That is, the difference between the time corresponding to 90% IDS and the time corresponding to 10% IDS is the current rise time Tr(i).

[0119] Current turn-on delay time Tdon(i): The time interval between when the drain current IDS of the power device Q1 under test reaches 10% of the set current value and when the gate-source voltage VGS reaches 10% of the set voltage value. That is, the difference between the time corresponding to 10% IDS and the time corresponding to 10% VGS is the current turn-on delay time Tdon(i).

[0120] Current falling time Tf(i): the time interval between when the drain current IDS of the power device Q1 reaches 10% of the set current value and when the drain current IDS reaches 90% of the set current value. That is, the difference between the time corresponding to 10% IDS and the time corresponding to 90% IDS is the current falling time Tf(i).

[0121] Current turn-off delay time Tdoff(i): The time interval between when the drain current IDS of the power device Q1 under test reaches 90% of the set current value and when the gate-source voltage VGS reaches 90% of the set voltage value. That is, the difference between the time corresponding to 90% IDS and the time corresponding to 90% VGS is the current turn-off delay time Tdoff(i).

[0122] Of course, in other embodiments, the switch parameters may also include:

[0123] Current turn-on time Ton(i): The time interval between when the drain current IDS of the power device Q1 under test reaches 90% of the set current value and when the gate-source voltage VGS reaches 10% of the set voltage value. That is, the difference between the time corresponding to 90% IDS and the time corresponding to 10% VGS is the current turn-on time Ton(i).

[0124] Voltage turn-off delay time Tdoff(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 90% of the set voltage value and when the gate-source voltage VGS reaches 10% of the set voltage value. That is, the difference between the time corresponding to 90% VDS and the time corresponding to 10% VGS is the voltage turn-off delay time Tdoff(v).

[0125] Voltage off time Toff(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 10% of the set voltage value and when the gate-source voltage VGS reaches 10% of the set voltage value. That is, the difference between the time corresponding to 10% VDS and the time corresponding to 10% VGS is the voltage off time Toff(v).

[0126] Voltage drop time Tf(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 10% of the set voltage value and when the source-drain voltage VDS reaches 90% of the set voltage value. That is, the difference between the time corresponding to 10% VDS and the time corresponding to 90% VDS is the voltage drop time Tf(v).

[0127] Current off time Toff(i): The time interval between the drain current IDS of the power device Q1 under test reaching 10% of the set current value and the gate-source voltage VGS reaching 90% of the set voltage value. That is, the difference between the time corresponding to 10% IDS and the time corresponding to 90% VGS is the current off time Toff(i).

[0128] Voltage establishment delay time Tdon(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 10% of the set voltage value and when the gate-source voltage VGS reaches 90% of the set voltage value. That is, the difference between the time corresponding to 10% VDS and the time corresponding to 90% VGS is the voltage establishment delay time Tdon(v).

[0129] Voltage build-up time Ton(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 90% of the set voltage value and when the gate-source voltage VGS reaches 90% of the set voltage value. That is, the difference between the time corresponding to 90% VDS and the time corresponding to 90% VGS is the voltage build-up time Ton(v).

[0130] Voltage rise time Tr(v): The time interval between when the source-drain voltage VDS of the power device Q1 to be tested reaches 90% of the set voltage value and when the source-drain voltage VDS reaches 10% of the set voltage value. That is, the difference between the time corresponding to 90% VDS and the time corresponding to 10% VDS is the voltage rise time Tr(v).

[0131] The comparison values ​​of the same switch parameters of the power device Q1 to be tested before and after being subjected to avalanche stress are used to characterize the change of the switch characteristic, thereby detecting the stability and reliability of the power device Q1 to be tested.

[0132] Exemplarily, the change in the switching characteristic of the current turn-on delay time Tdon(i) of the power device Q1 under test is characterized by the ratio of the current turn-on delay time Tdon(i)2 after the power device Q1 under test is subjected to avalanche stress to the current turn-on delay time Tdon(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0133] The change in the switching characteristic of the current turn-on time Ton(i) of the power device Q1 under test is characterized by the ratio of the current turn-on time Ton(i)2 after the power device Q1 under test is subjected to avalanche stress to the current turn-on time Ton(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0134] The change of the switching characteristic of the current rise time Tr(i) of the power device Q1 under test is characterized by the ratio of the current rise time Tr(i)2 after the power device Q1 under test is subjected to avalanche stress to the current rise time Tr(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0135] The change in the switching characteristic of the voltage turn-off delay time Tdoff(v) of the power device Q1 under test is characterized by the ratio of the voltage turn-off delay time Tdoff(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage turn-off delay time Tdoff(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0136] The change in the switching characteristic of the voltage off time Toff(v) of the power device Q1 under test is characterized by the ratio of the voltage off time Toff(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage off time Toff(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0137] The change in the switching characteristic of the voltage drop time Tf(v) of the power device Q1 under test is characterized by the ratio of the voltage drop time Tf(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage drop time Tf(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0138] The change in the switching characteristic of the current turn-off delay time Tdoff(i) of the power device Q1 under test is characterized by the ratio of the current turn-off delay time Tdoff(i)2 after the power device Q1 under test is subjected to avalanche stress to the current turn-off delay time Tdoff(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0139] The change of the switching characteristic of the current off-time Toff(i) of the power device Q1 under test is characterized by the ratio of the current off-time Toff(i)2 after the power device Q1 under test is subjected to avalanche stress to the current off-time Toff(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0140] The change in the switching characteristic of the current fall time Tf(i) of the power device Q1 under test is characterized by the ratio of the current fall time Tf(i)2 after the power device Q1 under test is subjected to avalanche stress to the current fall time Tf(i)1 before the power device Q1 under test is subjected to avalanche stress.

[0141] The change in the switching characteristic of the voltage buildup delay time Tdon(v) of the power device Q1 under test is characterized by the ratio of the voltage buildup delay time Tdon(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage buildup delay time Tdon(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0142] The change in the switching characteristic of the voltage buildup time Ton(v) of the power device Q1 under test is characterized by the ratio of the voltage buildup time Ton(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage buildup time Ton(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0143] The change of the switching characteristic of the voltage rise time Tr(v) of the power device Q1 under test is characterized by the ratio of the voltage rise time Tr(v)2 after the power device Q1 under test is subjected to avalanche stress to the voltage rise time Tr(v)1 before the power device Q1 under test is subjected to avalanche stress.

[0144] Optionally, in other embodiments, other set voltage values ​​or current values ​​may be selected as sampling reference points, such as any sampling point where a certain switch parameter is between 0% and 100%.

[0145] The technical solution provided in this embodiment is to first initialize the switching characteristics of the power device Q1 to be tested, then apply avalanche stress to the power device Q1 to be tested, and test the switching characteristics of the power device Q1 to be tested again within the microseconds after the avalanche stress is applied, and calculate the switching parameters of the power device before and after the avalanche stress is applied, and use them to characterize the dynamic changes of the switching characteristics. The test method provided in this embodiment can screen out some power devices with defects in the process or problems in the manufacturing process.

[0146] Fig.10 Another sampling waveform diagram provided by the embodiment of the present invention is shown in FIG. Fig.10 On the basis of the above embodiments, optionally, the test process includes multiple continuous avalanche stress application stages. That is, after one avalanche stress application stage is completed, the next avalanche stress application stage is entered again, such as after the t2-t2_1 time period is completed, the t2_1-t5' time period is entered, and avalanche stress is applied to the power device Q1 under test again, so as to test the switching characteristics of the power device Q1 under test after being subjected to avalanche stress for multiple times, that is, after being subjected to avalanche stress for multiple times, the switching characteristics test is performed after the last avalanche stress is subjected to avalanche stress.

[0147] Fig.11 Another sampling waveform diagram provided by the embodiment of the present invention is shown in FIG. Fig.11 On the basis of the above embodiments, optionally, during the test process, multiple avalanche stress application stages and second switch test stages are included, and the avalanche stress application stages and the second switch test stages are alternately arranged in sequence. That is, after the avalanche stress application stage is completed, the second switch test stage is entered, and then the avalanche stress application stage and the second switch test stage are entered again, so as to realize continuous testing of the switch characteristics of the power device Q1 to be tested after multiple avalanche stresses, that is, each time after being subjected to avalanche stress, the corresponding switch characteristics are tested once. Among them, the working process of the test circuit at each moment between t2_1-t6_1 corresponds to the working process at the moment between t2-t6.

[0148] It should be noted that in Fig.10 and Fig.11 In the timing sequence, the process of t2-t2_1 or the process of t2'-t6 can be repeated multiple times, and the specific frequency can be set according to actual needs. In some implementations, in a single test process, the minimum delay between the turn-off moment of the first switch K1 and the turn-on moment of the second switch K2 can be less than or equal to 1us, so as to ensure that the switching characteristics of the unrecovered power device Q1 to be tested can be tested within the us level time after being subjected to avalanche stress.

[0149] in, Fig.10 and Fig.11 The working process of the test circuit corresponding to the timing can be referred to the relevant description in the above embodiment, which will not be repeated here.

[0150] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0151] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A test circuit for switching characteristics of a power device, characterized in that: include: A driving branch, wherein the driving branch is connected between a control electrode and a second electrode of the power device to be tested; A first voltage output branch, the first voltage output branch is connected between the first pole and the second pole of the power device to be tested, and is used to provide a first voltage to the power device to be tested during the avalanche stress application stage, so as to cooperate with the driving branch to apply avalanche stress to the power device to be tested; A second voltage output branch and a load branch, wherein the second voltage output branch and the load branch are connected in series between the first pole and the second pole of the power device to be tested, the second voltage output branch is used to provide a second voltage to the power device to be tested via the load branch in a first switch test phase before the avalanche stress application phase and a second switch test phase after the avalanche stress application phase, respectively, so as to cooperate with the drive branch to perform a switch characteristic test on the power device to be tested, and the load branch is used to adjust the output current of the second voltage output branch; A sampling branch, the sampling branch is connected to the power device to be tested, and is used to collect the working waveform of the power device to be tested, and obtain the switching characteristics of the power device to be tested according to the working waveform.

2. The test circuit for the switching characteristics of a power device according to claim 1, characterized in that: The test circuit further includes a third switch unit, which is connected between the first pole and the second pole of the power device to be tested and is used to provide an energy discharge circuit for the power device to be tested; Wherein, the third switch unit comprises a third switch, a first end of the third switch is connected to the first pole of the power device to be tested, a second end of the third switch is connected to the second pole of the power device to be tested, and a control end of the third switch is connected to a third signal source; The third switch is a fast switch.

3. The test circuit for the switching characteristics of a power device according to claim 1, characterized in that: The first voltage output branch includes a first energy supply unit and a first switch unit; The first end of the first energy supply unit is connected to the first end of the first switch unit, the second end of the first switch unit is connected to the first pole of the power device to be tested, and the second end of the first energy supply unit is connected to the second pole of the power device to be tested; Wherein, the first energy supply unit includes a first voltage source, a first capacitor and a first inductor, the first switch unit includes a first switch, a first end of the first voltage source is connected to a first end of the first inductor, a second end of the first inductor is connected to a first end of the first switch, a second end of the first switch is connected to a first pole of the power device to be tested, a control end of the first switch is connected to a first signal source, a second end of the first voltage source is connected to a second pole of the power device to be tested, a first pole of the first capacitor is connected to a first end of the first voltage source, and a second pole of the first capacitor is connected to a second end of the first voltage source; The first switch is a fast switch.

4. The test circuit for the switching characteristics of a power device according to claim 1, characterized in that: The second voltage output branch includes a second energy supply unit and a second switch unit, the first end of the second energy supply unit is connected to the first end of the second switch unit, the second end of the second switch unit is connected to the first end of the load branch, the second end of the load branch is connected to the first pole of the power device to be tested, and the second end of the second energy supply unit is connected to the second pole of the power device to be tested; Wherein, the second energy supply unit includes a second voltage source and a second capacitor, the second switch unit includes a second switch, a first end of the second voltage source is connected to a first end of the second switch, a second end of the second switch is connected to a first end of the load branch, a control end of the second switch is connected to a second signal source, a second end of the second voltage source is connected to a second pole of the power device to be tested, a first pole of the second capacitor is connected to a first end of the second switch, and a second pole of the second capacitor is connected to a second pole of the power device to be tested; The load branch includes a resistor, a first end of the resistor is a first end of the load branch, and a second end of the resistor is a second end of the load branch; Alternatively, the load branch includes a variable inductor and a freewheeling diode, the first end of the variable inductor is the first end of the load branch, the second end of the variable inductor is the second end of the load branch, and the freewheeling diode is connected in parallel with the variable inductor; The driving branch comprises a driving unit, a first end of the driving unit is connected to a driving signal, a second end of the driving unit is connected to a control electrode of the power device to be tested, and a third end of the driving unit is connected to a second electrode of the power device to be tested.

5. A method for testing switching characteristics of a power device, performed by a testing circuit for the switching characteristics of a power device, characterized in that: The test circuit for the switching characteristics of the power device comprises a driving branch, a first voltage output branch, a second voltage output branch, a load branch and a sampling branch; The method for testing the switching characteristics of the power device includes: In the first switch test phase, the second voltage output branch is controlled to provide the second voltage to the power device under test via the load branch, and the switching characteristic test of the power device under test is performed in cooperation with the driving branch, and the sampling branch is controlled to collect the working waveform of the power device under test to obtain the switching characteristic of the power device under test before being subjected to avalanche stress; In the avalanche stress application stage, controlling the first voltage output branch to provide a first voltage to the power device under test, and cooperating with the driving branch to apply avalanche stress to the power device under test; In the second switching test stage, the second voltage output branch is controlled to provide the second voltage to the power device under test via the load branch, and cooperates with the driving branch to perform a switching characteristic test on the power device under test, and the sampling branch is controlled to collect the working waveform of the power device under test to obtain the switching characteristics of the power device under test after being subjected to avalanche stress.

6. The method for testing the switching characteristics of a power device according to claim 5, characterized in that: Also includes: Determine the change of the switching characteristic of the power device to be tested by respectively calculating the comparison values ​​of the same switching parameter of the power device to be tested before and after being subjected to the avalanche stress; The switch parameter includes at least one of a rise time, a fall time, a turn-on delay time and a turn-off delay time of a current and / or a voltage.

7. The method for testing the switching characteristics of a power device according to claim 5, characterized in that: The first voltage output branch includes a first energy supply unit and a first switch unit, the first energy supply unit includes a first voltage source, a first capacitor and a first inductor, and the first switch unit includes a first switch; the second voltage output branch includes a second energy supply unit and a second switch unit, the second energy supply unit includes a second voltage source and a second capacitor, the second switch unit includes a second switch, and the test circuit also includes a third switch unit, and the third switch unit includes a third switch; The first switch test phase includes a first sub-phase, a second sub-phase and a third sub-phase. In the first switch test phase, the method for testing the switching characteristics of the power device includes: In the first sub-stage, the second switch is controlled to be turned on, and the second capacitor provides the second voltage to the power device under test via the load branch; In the second sub-stage, the driving branch is controlled to turn on the power device to be tested, and the sampling branch is controlled to sample the gate-source voltage and the drain current of the power device to be tested in the on state; In the third sub-stage, the driving branch is controlled to turn off the power device to be tested, and the sampling branch is controlled to sample the gate-source voltage and the drain current of the power device to be tested in the off state, and after the sampling is completed, the third switch is controlled to be turned on to discharge the source-drain voltage of the power device to be tested.

8. The method for testing the switching characteristics of a power device according to claim 7, characterized in that: The avalanche stress application stage includes a fourth sub-stage and a fifth sub-stage. In the avalanche stress application stage, the method for testing the switching characteristics of the power device includes: In the fourth sub-stage, the first switch is controlled to be turned on, and the driving branch is controlled to turn on the power device to be tested, until the drain current of the power device to be tested reaches a preset current value, and then the driving branch is controlled to turn off the power device to be tested; In the fifth sub-stage, the driving branch is controlled to turn off the power device to be tested, and when the source-drain voltage of the power device to be tested drops to a preset voltage value, the first switch is controlled to be quickly turned off.

9. The method for testing the switching characteristics of a power device according to claim 8, characterized in that: The first switch and / or the third switch is a fast switch.

10. The method for testing the switching characteristics of a power device according to claim 5, characterized in that: During the test process, it includes a plurality of continuous avalanche stress application stages, or includes a plurality of avalanche stress application stages and the second switch test stages, and the avalanche stress application stages and the second switch test stages are alternately arranged in sequence.

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