Test circuit and test method of power device

Abstract

The invention discloses a test circuit and a test method of a power device, and the test circuit of the power device comprises a charging branch, a current source branch, a first switch branch, a second switch branch, a third switch branch, a driving branch and a sampling branch. The first switch branch and the second switch branch are configured to transmit the current output by the current source branch to a tested power device in a first stage and a third stage; the charging branch and the third switch branch are connected between the first pole and the second pole of the tested power device, and the third switch branch is configured to control the charging branch to apply voltage between the first pole and the second pole of the tested power device in the second stage; and the driving branch is used for controlling the on-off of the tested power device in the second stage so as to apply avalanche stress to the tested power device through the charging branch. According to the scheme, the threshold voltage test can be carried out on the unrecovered tested power device within a short time after the tested power device is subjected to the avalanche stress, so that the stability of the tested power device is accurately detected.

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 a power device. Background Art

[0002] Power devices (such as MOSFET) are the core of power conversion and processing. Their robustness and reliability assessment and parameter degradation test are important bases for evaluating the reliability and efficiency of circuit systems. Among them, the threshold voltage of power devices is the basis for the device to work, and the stability of the threshold voltage can reflect the changes in device characteristics.

[0003] UIS (Unclamped Inductive Switching), also known as avalanche stress, is generally considered to be the most extreme stress condition that power devices suffer in power electronics applications. When a power device is subjected to avalanche stress, the threshold voltage may drift, thereby reducing the reliability of the power device and causing device degradation.

[0004] In the prior art, a station-to-station test method is usually used to test the change in threshold voltage of a power device before and after being subjected to avalanche stress. However, the delay time of switching stations is long, and it is impossible to accurately characterize the change in threshold voltage of the power device before and after being subjected to avalanche stress, thereby failing to judge the stability and reliability of the device well. Summary of the invention

[0005] The embodiments of the present invention provide a test circuit and a test method for a power device, which can test the change of the threshold voltage of the power device before and after being subjected to avalanche stress and improve the test accuracy of the power device.

[0006] According to one aspect of the present invention, there is provided a test circuit for a power device, comprising: a charging branch, a current source branch, a first switch branch, a second switch branch, a third switch branch, a driving branch and a sampling branch;

[0007] The first end of the current source branch is connected to the first end of the first switch branch, the second end of the first switch branch is respectively connected to the control electrode of the power device under test and the first end of the second switch branch, the second end of the second switch branch is connected to the first electrode of the power device under test, the second electrode of the power device under test is grounded, the second end of the current source branch is connected to the second electrode of the power device under test, and the first switch branch and the second switch branch are configured to transmit the current output by the current source branch to the power device under test in the first stage and the third stage;

[0008] The charging branch and the third switch branch are connected between the first pole and the second pole of the power device under test, and the third switch branch is configured to control the charging branch to apply a voltage between the first pole and the second pole of the power device under test in the second stage;

[0009] The driving branch is connected to the control electrode and the second electrode of the power device under test, and the driving branch is used to control the on and off of the power device under test in the second stage, so as to apply avalanche stress to the power device under test through the charging branch;

[0010] The sampling branch is connected between the first electrode and the second electrode of the power device under test, and the sampling branch is used to sample the threshold voltage of the power device under test in the first stage and the third stage respectively;

[0011] The first stage is located before the second stage, and the second stage is located before the third stage.

[0012] Optionally, the first switch branch includes a first switch, the second switch branch includes a second switch, and the current source branch includes a current source;

[0013] The first end of the current source is connected to the first end of the first switch, the second end of the first switch is connected to the control electrode of the power device under test, the first end of the second switch is connected to the control electrode of the power device under test, and the second end of the second switch is connected to the first electrode of the power device under test;

[0014] The control end of the first switch is connected to a first signal source, and the control end of the second switch is connected to a second signal source.

[0015] Optionally, the third switch branch includes a third switch, and the charging branch includes a voltage source, an energy storage capacitor and an energy storage inductor;

[0016] The first end of the voltage source is connected to the first end of the energy storage inductor, the second end of the energy storage inductor is connected to the first end of the third switch, the second end of the third switch is connected to the first electrode of the power device under test, the control end of the third switch is connected to the third signal source, and the second end of the voltage source is connected to the second electrode of the power device under test;

[0017] The first end of the energy storage capacitor is connected to the first end of the voltage source, and the second end of the energy storage capacitor is connected to the second end of the voltage source.

[0018] Optionally, the third switch is a fast switch.

[0019] Optionally, the driving branch includes a driving module and a fourth switch branch, the control end of the driving module is connected to a fourth signal source, the first output end of the driving module is connected to the first end of the fourth switch branch, the second output end of the driving module is connected to the second pole of the power device under test, and the second end of the fourth switch branch is connected to the control pole of the power device under test;

[0020] The fourth switch branch includes a fourth switch, a first end of the fourth switch is connected to the output end of the driving module, a second end of the fourth switch is connected to the control electrode of the power device under test, and a control end of the fourth switch is connected to a fifth signal source.

[0021] Optionally, the switch in each switch branch includes a power switch or a relay switch.

[0022] According to another aspect of the present invention, a power device testing method is provided, which is performed by a power device testing circuit, wherein the power device testing circuit includes a charging branch, a current source branch, a first switch branch, a second switch branch, a third switch branch, a driving branch, and a sampling branch; the power device testing method includes:

[0023] In the first stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first electrode and the second electrode of the power device under test to obtain the threshold voltage of the power device under test before being subjected to avalanche stress;

[0024] In the second stage, the third switch branch is controlled to transmit the output voltage of the charging branch to the first pole and the second pole of the power device under test, and the driving branch is controlled to drive the power device under test to be turned on and off, so as to apply avalanche stress to the power device under test through the charging branch;

[0025] In the third stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test after being subjected to avalanche stress.

[0026] Optionally, the power device testing method further includes:

[0027] The drift degree of the threshold voltage of the power device is determined according to the comparison value of the threshold voltage of the power device under test before and after being subjected to avalanche stress.

[0028] Optionally, the driving branch includes a driving module and a fourth switch branch, the first output end of the driving module is connected to the first end of the fourth switch branch, the second output end of the driving module is connected to the second pole of the power device under test, and the second end of the fourth switch branch is connected to the control pole of the power device under test;

[0029] The second stage includes a first sub-stage and a second sub-stage. In the second stage, the power device testing method includes:

[0030] In the first sub-stage, the fourth switch branch and the third switch branch are controlled to be turned on, and the driving module drives the power device under test to be turned on, until the driving current of the power device under test reaches a preset current value, and then the driving module is controlled to drive the power device under test to be turned off, so as to apply avalanche stress to the power device under test;

[0031] In the second sub-stage, when the voltage drop between the first electrode and the second electrode of the power device under test reaches a preset voltage value, the third switch branch is controlled to be quickly turned off.

[0032] Optionally, during the test process, a plurality of consecutive second stages are included, or a plurality of consecutive second stages and the third stage are included.

[0033] The technical solution provided by the embodiment of the present invention can measure the change of threshold voltage of different power devices before and after being subjected to avalanche stress by controlling the timing of turning on and off of the first switch branch, the second switch branch, the third switch branch and the driving branch, thereby characterizing the degradation of the power device. This solution can realize the change of threshold voltage of the tested power device before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, it is possible to perform threshold voltage testing on the unrecovered tested power device within a short period of time after being subjected to avalanche stress, thereby being able to obtain a more practical test of the impact of the tested power device after being subjected to avalanche stress, thereby accurately detecting the stability of the tested power device.

[0034] 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

[0035] 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.

[0036] Figure 1 A schematic diagram of the structure of a power device test circuit provided by an embodiment of the present invention;

[0037] Figure 2 A schematic structural diagram of another power device test circuit provided by an embodiment of the present invention;

[0038] Figure 3 A schematic structural diagram of another power device test circuit provided by an embodiment of the present invention;

[0039] Figure 4 A schematic structural diagram of another power device test circuit provided by an embodiment of the present invention;

[0040] Figure 5 A flow chart of a method for testing a power device provided by an embodiment of the present invention;

[0041] Figure 6 A flowchart of another power device testing method provided by an embodiment of the present invention;

[0042] Figure 7 A schematic diagram of a sampling waveform provided by an embodiment of the present invention;

[0043] Figure 8 Another sampling waveform schematic diagram provided by an embodiment of the present invention;

[0044] Fig. 9 Another sampling waveform diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0045] 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.

[0046] 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.

[0047] MOSFET is a metal oxide semiconductor field effect transistor, and the threshold voltage is an important parameter in power devices represented by MOSFET. Among them, the threshold voltage reflects the size of the gate voltage required when there is a specified current between the source and drain of the MOSFET. Therefore, the existence of the threshold voltage is the basis for the operation of MOSFET, and the MOSFET can only be turned on when the gate voltage reaches a certain value. In the switching circuit, UIS (Unclamped Inductive Switching), that is, avalanche stress, is generally considered to be the most extreme stress condition suffered by power devices in power electronics applications. When a power device is subjected to avalanche stress, the threshold voltage drift may occur, thereby reducing the reliability of the power device, causing the device to degrade, and increasing the application risk. Therefore, it is particularly important to be able to characterize this degradation phenomenon.

[0048] At present, a site-to-site test method is usually used to test the change in threshold voltage of power devices before and after avalanche stress. However, the delay time of switching sites is in the ms or even s level. Long-term test switching will cause the power devices to gradually recover from the avalanche stress state, and it is impossible to accurately characterize the parameter changes of the power devices, resulting in an inability to judge the stability and reliability of the devices.

[0049] In view of the above problems, an embodiment of the present invention provides a test circuit for a power device to improve the test effect of the power device so as to accurately characterize the parameter changes of the power device. Figure 1 A schematic diagram of a power device test circuit according to an embodiment of the present invention is provided. Figure 1 The power device test circuit provided in this embodiment includes: a charging branch 11, a current source branch 12, a first switch branch 13, a second switch branch 14, a third switch branch 15, a driving branch 16 and a sampling branch 17;

[0050] The first end of the current source branch 12 is connected to the first end of the first switch branch 13, the second end of the first switch branch 13 is respectively connected to the control electrode G of the power device under test Q1 and the first end of the second switch branch 14, the second end of the second switch branch 14 is connected to the first electrode D of the power device under test Q1, the second electrode S of the power device under test Q1 is grounded, the second end of the current source branch 12 is connected to the second electrode S of the power device under test Q1, and the first switch branch 13 and the second switch branch 14 are configured to transmit the current output by the current source branch 12 to the power device under test Q1 in the first stage and the third stage;

[0051] The charging branch 11 and the third switch branch 15 are connected between the first pole D and the second pole S of the power device Q1 under test, and the third switch branch 15 is configured to control the charging branch 11 to apply a voltage between the first pole D and the second pole S of the power device Q1 under test in the second stage;

[0052] The driving branch 16 is connected to the control electrode G and the second electrode S of the power device Q1 under test, and the driving branch 16 is used to control the on and off of the power device Q1 under test in the second stage, so as to apply avalanche stress to the power device Q1 under test through the charging branch 11;

[0053] The sampling branch 17 is connected between the first electrode D and the second electrode S of the power device Q1 under test. The sampling branch 17 is used to sample the threshold voltage V of the power device Q1 under test in the first stage and the third stage respectively. TH .

[0054] The power device Q1 under test may be a silicon carbide power device or a gallium nitride power device, or may be other power devices, and the embodiment of the present application is not limited thereto. The driving branch 16 is used to output a pulse signal to drive the power device Q1 under test. The control electrode of the power device Q1 under test may be a gate electrode, the first electrode D may be a drain electrode, and the second electrode S may be a source electrode.

[0055] In this embodiment, the charging branch 11, the third switch branch 15 and the power device under test Q1 together constitute an avalanche stress application loop, and the current source branch 12, the first switch branch 13, the second switch branch 14 and the power device under test Q1 together constitute a threshold voltage test loop. The test process of the power device under test Q1 may include a first stage, a second stage and a third stage, wherein the first stage is located before the second stage, and the second stage is located before the third stage.

[0056] In the first stage, the first switch branch 13 and the second switch branch 14 are turned on, and the current output by the current source branch 12 is transmitted to the first pole D, the control pole G and the second pole S of the power device under test Q1 through the first switch branch 13 and the second switch branch 14, wherein the first pole D and the control pole G are short-circuited, and the voltage between the first pole D and the second pole S of the power device under test Q1 is sampled through the sampling branch 17 to obtain the source-drain voltage VDS. Since the second switch branch 14 is turned on, the first pole D and the control pole G of the power device under test Q1 are short-circuited, and the gate-source voltage VGS between the control pole G and the second pole S of the power device under test Q1 is equal to the source-drain voltage VDS, that is, the voltage collected by the sampling branch 17 is the gate-source voltage VGS of the power device under test Q1, and the gate-source voltage VGS at this time is the threshold voltage of the power device under test Q1 before being subjected to avalanche stress, such as the first threshold voltage V TH1 .

[0057] In the second stage, the driving branch 16 and the third switch branch 15 are turned on, and the voltage output by the charging branch 11 is transmitted to the first pole D of the power device under test Q1 through the third switch branch 15, and a corresponding voltage is applied between the first pole D and the second pole S of the power device under test Q1. The driving branch 16 sends a driving signal to the control pole G of the power device under test Q1 to control the power device under test Q1 to turn on, and the driving current of the power device under test Q1 continues to increase. When the power device under test Q1 is turned off by the driving branch 16, the energy output by the charging branch 11 is completely transferred to the power device under test Q1, and avalanche stress appears between the first pole D and the second pole S of the power device under test Q1. The sampling branch 17 samples the source-drain voltage VDS of the power device under test Q1 to obtain the voltage that the power device under test Q1 is subjected to when it is subjected to avalanche stress.

[0058] When the sampling branch 17 collects the source-drain voltage VDS of the power device Q1 under test and drops to zero, in the third stage, the first switch branch 13 and the second switch branch 14 are controlled to be turned on again, and the current output by the current source branch 12 is transmitted to the first electrode D, the control electrode G and the second electrode S of the power device Q1 under test through the first switch branch 13 and the second switch branch 14, wherein the first electrode D and the control electrode G are short-circuited. Since the second switch branch 14 is turned on, the source-drain voltage VDS collected by the sampling branch 17 at this time is the threshold voltage of the power device Q1 under test after being subjected to avalanche stress, such as the second threshold voltage V TH2 By comparing the threshold voltages obtained from the two samplings, the degradation degree of the power device Q1 under test can be tested.

[0059] The technical solution provided by the embodiment of the present invention can measure the change of threshold voltage of different power devices before and after being subjected to avalanche stress by controlling the timing of turning on and off of the first switch branch 13, the second switch branch 14, the third switch branch 15 and the driving branch 16, thereby characterizing the degradation of the power device. This solution can realize the change of threshold voltage of the power device Q1 under test before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, it is possible to perform threshold voltage testing on the unrecovered power device Q1 under test within a short period of time after being subjected to avalanche stress, so as to obtain a more practical test of the influence of the power device Q1 under test after being subjected to avalanche stress, thereby accurately detecting the stability of the power device Q1 under test.

[0060] Optionally, in one embodiment, the sampling branch 17 may include an oscilloscope for collecting the voltage waveform and current waveform of the power device under test Q1, and after collecting the waveforms of the gate-source voltage VGS, source-drain voltage VDS and drive current IDS of the power device under test Q1, converting the waveforms into data for recording, so as to complete the test of the power device under test Q1.

[0061] Figure 2 A schematic diagram of another power device test circuit provided by an embodiment of the present invention, referring to Figure 2 On the basis of the above embodiment, optionally, the first switch branch 13 includes a first switch K1, the second switch branch 14 includes a second switch K2, and the current source branch 12 includes a current source 121; a first end of the current source 121 is connected to a first end of the first switch K1, a second end of the first switch K1 is connected to a control electrode G of the power device Q1 under test, a first end of the second switch K2 is connected to the control electrode G of the power device Q1 under test, and a second end of the second switch K2 is connected to a first electrode D of the power device Q1 under test.

[0062] Among them, the first switch K1 and the second switch K2 can be power switches, such as MOSFET, or relay switches, which are used to control the on and off of the loop. The control end of the first switch K1 is connected to the first signal source 21, and the first switch K1 is turned on or off in response to the first control signal output by the first signal source 21. The control end of the second switch K2 is connected to the second signal source 22, and the second switch K2 is turned on or off in response to the second control signal output by the second signal source 21. The first switch K1 cooperates with the first signal source 21, and the second switch K2 cooperates with the second signal source 22 to control the test circuit to realize the test of the threshold voltage of the power device Q1 under test. The current source 121 is used to provide current to the loop so that the loop can obtain a fast current output.

[0063] In this embodiment, both the first control signal and the second control signal have the function of synchronous programming. When the first switch K1 responds to the first control signal, the second switch K2 responds to the second control signal and is synchronously turned on. The current source 121 outputs current to provide corresponding current for the power device Q1 under test, so that the sampling branch 17 samples the threshold voltage of the power device Q1 under test.

[0064] Figure 3 A schematic diagram of another power device test circuit provided by an embodiment of the present invention, referring to Figure 3 On the basis of the above embodiments, optionally, the third switch branch 15 includes a third switch K3, the charging branch 11 includes a voltage source 111, an energy storage capacitor C1 and an energy storage inductor L1, a first end of the voltage source 111 is connected to a first end of the energy storage inductor L1, a second end of the energy storage inductor L1 is connected to a first end of the third switch K3, a second end of the third switch K3 is connected to a first pole D of the power device Q1 under test, a control end of the third switch K3 is connected to a third control signal DIO3, a second end of the voltage source 111 is connected to a second pole of the power device Q1 under test; a first end of the energy storage capacitor C1 is connected to a first end of the voltage source 111, and a second end of the energy storage capacitor C1 is connected to a second end of the voltage source 111.

[0065] Specifically, the voltage source 111 is used to precharge the energy storage capacitor C1 so that the loop can obtain a fast voltage output. The control end of the third switch K3 is connected to the third signal source 23, and is turned on or off in response to the third control signal output by the third signal source 23. The third signal source 23 is used in conjunction with the third switch K3 to control the test circuit to apply avalanche stress to the power device Q1 under test.

[0066] When the power device Q1 under test is in the on state, all the energy output by the voltage source 111 is stored in the energy storage inductor L1, and when the power device Q1 under test is in the off state, all the energy stored in the energy storage inductor L1 is transferred to the power device Q1 under test, which can reflect the maximum energy that the power device Q1 under test can withstand before being seriously damaged. Among them, the energy storage inductor L1 is an adjustable inductor, and its inductance value can be designed according to the specific needs of the power device Q1 under test. Different power devices can withstand different avalanche stresses, and the corresponding energy storage inductor L1 has different inductance values.

[0067] In this embodiment, the third switch K3 is a fast switch with low switching loss, high switching speed, and high voltage blocking capability, and the switching speed can reach ns level. The third switch K3 can specifically be a fast switching transistor, such as MOSFET, or a fast switching relay. The third switch K3 is used to control the on-off of the avalanche stress application circuit. After the power device Q1 under test is subjected to avalanche stress, the avalanche stress application circuit is cut off by quickly turning off the third switch K3, realizing fast stress switching, and quickly connecting the threshold voltage test circuit, thereby realizing the threshold voltage test with us level delay after the power device Q1 under test is subjected to avalanche stress.

[0068] Figure 4 A schematic diagram of another power device test circuit provided by an embodiment of the present invention, referring to Figure 4 On the basis of the above embodiments, optionally, the driving branch 16 includes a driving module 1601 and a fourth switch branch 1602, the control end of the driving module 1601 is connected to the fourth signal source 24, the driving module 1601 is turned on or off in response to the fourth control signal output by the fourth signal source 24, the first output end of the driving module 1601 is connected to the first end of the fourth switch branch 1602, the second output end of the driving module 1601 is connected to the second pole S of the power device Q1 under test, and the second end of the fourth switch branch 1602 is connected to the control pole G of the power device Q1 under test.

[0069] The fourth switch branch 1602 includes a fourth switch K4 , a first end of which is connected to the output end of the driving module 1602 , a second end of which is connected to the control electrode G of the power device Q1 under test, and a control end of which is connected to the fifth signal source 25 .

[0070] Specifically, the fourth signal source 24 controls the driving module 1601 to drive the power device Q1 under test, thereby controlling the power device Q1 under test to be turned on or off. The fourth switch K4 is used to respond to the fifth control signal output by the fifth signal source 25 to be turned on or off, thereby controlling the connection between the driving module 1601 and the control electrode G of the power device Q1 under test. Among them, the fourth control signal and the fifth control signal both have the function of synchronous program control.

[0071] In this embodiment, by setting the fourth switch K4, the on and off of the power device under test Q1 can be controlled more flexibly. The threshold voltage test process of the power device under test Q1 is realized by synchronous programming of the first control signal, the second control signal and the fifth control signal (the first switch K1 and the second switch K2 are turned on, and the fourth switch K4 is turned off). The process of applying avalanche stress to the power device under test Q1 is realized by synchronous programming of the third control signal, the fourth control signal and the fifth control signal (the fourth switch K4 and the third switch K3 are turned on).

[0072] The technical solution provided in this embodiment is that in the same circuit, the avalanche stress application circuit and the threshold voltage test circuit are quickly disconnected by the third switch K3, so that the threshold voltage test can be performed after the power device Q1 under test is subjected to avalanche stress with a delay of us level, which greatly reduces the delay time, is beneficial to improving the test accuracy of the threshold voltage after the power device Q1 under test is subjected to avalanche stress, and is beneficial to accurately characterizing the changes in the threshold voltage parameters.

[0073] Optionally, the first signal source 21 , the second signal source 22 , the third signal source 23 , the fourth signal source 24 and the fifth signal source 25 are all digital signal sources.

[0074] Optionally, an embodiment of the present invention further provides a method for testing a power device. The method can be performed by a test circuit for a power device provided by any embodiment of the present invention. The structure of the test circuit for the power device is as follows: Figure 1-Figure 4 shown.

[0075] Figure 5 A flowchart of a power device testing method provided by an embodiment of the present invention, referring to Figure 5 , the test method includes:

[0076] S110. In the first stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test before being subjected to avalanche stress.

[0077] S120. In the second stage, the third switch branch is controlled to transmit the output voltage of the charging branch to the first pole and the second pole of the power device under test, and the driving branch is controlled to drive the power device under test to be turned on and off, so as to apply avalanche stress to the power device under test through the charging branch.

[0078] S130. In the third stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test after being subjected to avalanche stress.

[0079] The technical solution provided by the embodiment of the present invention can measure the change of threshold voltage of different power devices before and after being subjected to avalanche stress by controlling the timing of turning on and off of the first switch branch, the second switch branch, the third switch branch and the driving branch, thereby characterizing the degradation of the power device. This solution can realize the change of threshold voltage of the power device under test before and after being subjected to avalanche stress through a set of test circuits without changing stations. Therefore, it is possible to perform threshold voltage test on the unrecovered power device under test within a short time after being subjected to avalanche stress, thereby being able to obtain a more practical test of the impact of the power device under test after being subjected to avalanche stress, thereby accurately detecting the stability of the power device under test.

[0080] Figure 6 A flowchart of another power device testing method provided by an embodiment of the present invention, combined with Figure 6 and Figure 4 The second stage includes a first sub-stage and a second sub-stage. The power device testing method provided in this embodiment includes:

[0081] S110. In the first stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test before being subjected to avalanche stress.

[0082] S1201. In the first sub-stage, the fourth switch branch and the third switch branch are controlled to be turned on, and the driving module drives the power device under test to be turned on. When the driving current of the power device under test reaches a preset current value, the driving module is controlled to drive the power device under test to be turned off, so as to apply avalanche stress to the power device under test.

[0083] S1202 . In the second sub-stage, when the voltage drop between the first electrode and the second electrode of the power device under test reaches a preset voltage value, the third switch branch is controlled to be quickly turned off.

[0084] S130. In the third stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test after being subjected to avalanche stress.

[0085] S140 , determining a threshold voltage drift degree of the power device according to a comparison value of the threshold voltage of the power device under test before and after being subjected to avalanche stress.

[0086] Figure 7 A sampling waveform diagram provided by an embodiment of the present invention, combined with Figure 4 , Figure 6 and Figure 7The specific working process of the power device testing method provided by the embodiment of the present invention is as follows:

[0087] Before time t0, the energy storage capacitor C1 is pre-charged through the voltage source 111, and the third switch K3 is turned off in response to the third control signal output by the third signal source 23. At this time, the fourth control signal output by the fourth signal source 24 is a shutdown signal (e.g., a low level), the driving module 1601 is turned off, and the power device Q1 under test is not turned on.

[0088] In the first stage (time period t0-t1), 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 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 fourth switch K4 is turned off in response to the fifth control signal output by the fifth signal source 25. The current output by the current source branch 12 is transmitted to the first electrode D, the control electrode G, and the second electrode S of the power device under test Q1 through the first switch K1 and the second switch K2, and the voltage between the first electrode D and the second electrode S of the power device under test Q1 is sampled through the sampling branch 17 to obtain the source-drain voltage VDS. Since the second switch K2 is turned on, the first electrode D and the control electrode G of the power device Q1 under test are short-circuited. Therefore, the gate-source voltage VGS between the control electrode G and the second electrode S of the power device Q1 under test is equal to the source-drain voltage VDS. The source-drain voltage VDS collected by the sampling branch 17 is the gate-source voltage VGS of the power device Q1 under test. The gate-source voltage VGS at this time is the threshold voltage of the power device Q1 under test before it is subjected to avalanche stress, that is, the first threshold voltage V TH1 At time t1, the first switch K1 is turned off in response to the first control signal, the second switch K2 is turned off in response to the second control signal, and the gate-source voltage VGS of the power device Q1 under test is 0V.

[0089] In the first sub-stage of the second stage (time period t2-t3), at time t2, the third switch K3 is turned on in response to the third control signal output by the third signal source 23, the fourth switch K4 is turned on in response to the fifth control signal output by the fifth signal source 25, the driving module 1601 is turned on in response to the fourth control signal output by the fourth signal source 24, the gate-source voltage VGS of the power device Q1 under test is greater than the threshold voltage, the power device Q1 under test is turned on, and the driving current IDS continues to increase. In this process, all the energy output by the voltage source 111 is stored in the energy storage inductor L1. At time t3, the driving current IDS increases to a preset current value, the driving module 1601 is turned off in response to the fourth control signal, and the power device Q1 under test is turned off to apply avalanche stress to the power device Q1 under test.

[0090] In the second sub-stage of the second stage (time period t3-t4), the power device Q1 under test is in the off state, and the energy stored in the energy storage inductor L1 is completely transferred to the power device Q1 under test. The power device Q1 under test is subjected to avalanche stress, and the source-drain voltage VDS of the power device Q1 under test is the avalanche voltage BVDSS. At time t4, when it is detected that the source-drain voltage VDS of the power device Q1 under test drops to a preset voltage value (e.g., 0V), the third switch K3 is quickly turned off to cut off the avalanche stress application circuit, thereby completing the application of avalanche stress to the power device Q1 under test.

[0091] In the third stage (time period t5-t6), at time t5, 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 on in response to the second control signal output by the second signal source 22, and the fourth switch K4 is turned off in response to the fifth control signal output by the fifth signal source 25. The current output by the current source branch 12 is transmitted to the first electrode D, the control electrode G, and the second electrode S of the power device under test Q1 through the first switch K1 and the second switch K2, and the voltage between the first electrode D and the second electrode S of the power device under test Q1 is sampled through the sampling branch 17. Since the second switch K2 is turned on, the first electrode D and the control electrode G of the power device under test Q1 are short-circuited. At this time, the source-drain voltage VDS collected by the sampling branch 17 is the threshold voltage of the power device under test Q1 after being subjected to avalanche stress, that is, the second threshold voltage V TH2 At time t6, the first switch K1 is turned off in response to the first control signal, and the second switch K2 is turned off in response to the second control signal. The gate-source voltage VDS of the power device Q1 under test is 0V, and the test is finished.

[0092] Among them, at time t4, by quickly turning off the third switch K3, the delay time of the t4-t5 time period can be guaranteed to be at the us level, so as to ensure that the threshold voltage test of the unrecovered power device Q1 under test can be performed within the us level time after being subjected to avalanche stress, so as to obtain a more practical test of the impact on the power device Q1 under test after being subjected to avalanche stress.

[0093] By comparing the threshold voltages obtained from the two samplings, the degradation degree of the power device Q1 under test can be tested. For example, the second threshold voltage V TH2 With the first threshold voltage V TH1 The ratio of is used to intuitively characterize the drift degree of the threshold voltage of the power device Q1 under test after being subjected to avalanche stress, so as to detect the stability of the power device Q1 under test through the drift of the threshold voltage.

[0094] Figure 8 Another sampling waveform diagram provided by the embodiment of the present invention is shown in FIG. Figure 8In the test process, multiple consecutive second stages are included. That is, after the second stage is completed, the second stage (i.e., the process of t2'-t4') is performed again, so as to detect the threshold voltage of the power device Q1 under test after it is subjected to avalanche stress for multiple times in a row, that is, after being subjected to avalanche stress for multiple times, the threshold voltage detection is performed after the last avalanche stress.

[0095] Fig. 9 Another sampling waveform diagram provided by the embodiment of the present invention is shown in FIG. Figure 8 , during the test process, multiple consecutive second and third stages are included. That is, after the third stage is completed, the second and third stage tests are performed again (i.e., the process of t2'-t6'), so as to realize the continuous detection of the threshold voltage of the power device Q1 under test after multiple avalanche stresses, that is, after each avalanche stress, the corresponding threshold voltage is detected once. For example, after the first avalanche stress is applied, the threshold voltage (such as the second threshold voltage V th2 ), after the avalanche stress is applied for the second time, the threshold voltage (such as the third threshold voltage V th3 ).

[0096] It should be noted that in Figure 8 and Fig. 9 In the timing sequence, the process from t2' to t4', or the process from t2' to t6' can be repeated multiple times, and the specific frequency can be set according to actual needs.

[0097] in, Figure 8 and Fig. 9 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.

[0098] 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.

[0099] 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 a power device, characterized in that: include: A charging branch, a current source branch, a first switch branch, a second switch branch, a third switch branch, a driving branch and a sampling branch; The first end of the current source branch is connected to the first end of the first switch branch, the second end of the first switch branch is respectively connected to the control electrode of the power device under test and the first end of the second switch branch, the second end of the second switch branch is connected to the first electrode of the power device under test, the second electrode of the power device under test is grounded, the second end of the current source branch is connected to the second electrode of the power device under test, and the first switch branch and the second switch branch are configured to transmit the current output by the current source branch to the power device under test in the first stage and the third stage; The charging branch and the third switch branch are connected between the first pole and the second pole of the power device under test, and the third switch branch is configured to control the charging branch to apply a voltage between the first pole and the second pole of the power device under test in the second stage; The driving branch is connected to the control electrode and the second electrode of the power device under test, and the driving branch is used to control the on and off of the power device under test in the second stage, so as to apply avalanche stress to the power device under test through the charging branch; The sampling branch is connected between the first electrode and the second electrode of the power device under test, and the sampling branch is used to sample the threshold voltage of the power device under test in the first stage and the third stage respectively; The first stage is located before the second stage, and the second stage is located before the third stage.

2. The power device test circuit according to claim 1, characterized in that: The first switch branch includes a first switch, the second switch branch includes a second switch, and the current source branch includes a current source; The first end of the current source is connected to the first end of the first switch, the second end of the first switch is connected to the control electrode of the power device under test, the first end of the second switch is connected to the control electrode of the power device under test, and the second end of the second switch is connected to the first electrode of the power device under test; The control end of the first switch is connected to a first signal source, and the control end of the second switch is connected to a second signal source.

3. The power device test circuit according to claim 1, characterized in that: The third switch branch includes a third switch, and the charging branch includes a voltage source, an energy storage capacitor and an energy storage inductor; The first end of the voltage source is connected to the first end of the energy storage inductor, the second end of the energy storage inductor is connected to the first end of the third switch, the second end of the third switch is connected to the first electrode of the power device under test, the control end of the third switch is connected to the third signal source, and the second end of the voltage source is connected to the second electrode of the power device under test; The first end of the energy storage capacitor is connected to the first end of the voltage source, and the second end of the energy storage capacitor is connected to the second end of the voltage source.

4. The power device test circuit according to claim 3, characterized in that: The third switch is a fast switch.

5. The power device test circuit according to claim 1, characterized in that: The driving branch includes a driving module and a fourth switch branch, the control end of the driving module is connected to a fourth signal source, the first output end of the driving module is connected to the first end of the fourth switch branch, the second output end of the driving module is connected to the second pole of the power device under test, and the second end of the fourth switch branch is connected to the control pole of the power device under test; The fourth switch branch includes a fourth switch, a first end of the fourth switch is connected to the output end of the driving module, a second end of the fourth switch is connected to the control electrode of the power device under test, and a control end of the fourth switch is connected to a fifth signal source.

6. The power device test circuit according to any one of claims 2 to 5, characterized in that: The switch in each switch branch includes a power switch or a relay switch.

7. A method for testing a power device, characterized in that: The test circuit of the power device is executed by the test circuit of the power device, wherein the test circuit of the power device includes a charging branch, a current source branch, a first switch branch, a second switch branch, a third switch branch, a driving branch and a sampling branch; The power device testing method comprises: In the first stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first electrode and the second electrode of the power device under test to obtain the threshold voltage of the power device under test before being subjected to avalanche stress; In the second stage, the third switch branch is controlled to transmit the output voltage of the charging branch to the first pole and the second pole of the power device under test, and the driving branch is controlled to drive the power device under test to be turned on and off, so as to apply avalanche stress to the power device under test through the charging branch; In the third stage, the first switch branch and the second switch branch are controlled to transmit the current output by the current source branch to the power device under test, and the sampling branch is controlled to sample the voltage between the first pole and the second pole of the power device under test to obtain the threshold voltage of the power device under test after being subjected to avalanche stress.

8. The power device testing method according to claim 7, characterized in that: The power device testing method further includes: The drift degree of the threshold voltage of the power device is determined according to the comparison value of the threshold voltage of the power device under test before and after being subjected to avalanche stress.

9. The method for testing a power device according to claim 7, characterized in that: The driving branch comprises a driving module and a fourth switch branch, wherein a first output end of the driving module is connected to a first end of the fourth switch branch, a second output end of the driving module is connected to a second electrode of the power device under test, and a second end of the fourth switch branch is connected to a control electrode of the power device under test; The second stage includes a first sub-stage and a second sub-stage. In the second stage, the power device testing method includes: In the first sub-stage, the fourth switch branch and the third switch branch are controlled to be turned on, and the driving module drives the power device under test to be turned on, until the driving current of the power device under test reaches a preset current value, and then the driving module is controlled to drive the power device under test to be turned off, so as to apply avalanche stress to the power device under test; In the second sub-stage, when the voltage drop between the first electrode and the second electrode of the power device under test reaches a preset voltage value, the third switch branch is controlled to be quickly turned off.

10. The method for testing a power device according to claim 7, characterized in that: During the test, a plurality of consecutive second stages are included, or a plurality of consecutive second stages and the third stage are included.

Images