Online power device aging test circuit, comprehensive test analysis method and system for vehicle working conditions

Abstract

This application provides an online power device aging test circuit, a comprehensive test and analysis method, and a system for automotive applications. The aging test circuit includes a three-phase six-arm bridge circuit composed of the power devices under test, a temperature-sensitive electrical parameter measurement circuit, an arm switching circuit, and a spare arm circuit. The temperature-sensitive electrical parameter measurement circuit measures the time-varying characteristics of the temperature-sensitive electrical parameters of the connected power devices under test. The arm switching circuit connects the power devices under test to either the three-phase six-arm bridge circuit or the temperature-sensitive electrical parameter measurement circuit. The spare arm circuit replaces any arm circuit containing the power device connected to the temperature-sensitive electrical parameter measurement circuit, forming a spare three-phase six-arm bridge circuit. The online power device aging test circuit provided in this application can perform online detection of the aging status of automotive inverter power devices under power cycling conditions.

Description

Technical Field

[0001] This application belongs to the field of new energy vehicle technology and relates to the performance testing technology of vehicle electric drive power devices. Specifically, it provides an online power device aging test circuit, comprehensive test and analysis method and system for vehicle operating conditions. Background Technology

[0002] As new energy vehicles develop towards higher power density and longer driving range, power devices (such as IGBTs and SiC MOSFETs) have become core components of electric drive systems. Under complex automotive operating conditions (such as frequent start-stop and high-current charging and discharging), power devices are subjected to severe junction temperature fluctuations over a long period, which can lead to failures such as bond wire detachment and solder layer fatigue. How to accurately assess the aging state of devices has become a key technical challenge for improving vehicle reliability.

[0003] Power cycling tests, which simulate the temperature stress of power devices in the on / off state, are widely used to evaluate the aging, reliability and service life of power devices. Although traditional DC power cycling can accelerate the thermal fatigue process, its constant current loading mode is difficult to reproduce the real composite stress that power devices are subjected to in real automotive operating conditions. In contrast, AC power cycling, by applying alternating current load, can more realistically reflect the aging mechanism of devices in scenarios such as motor drives and inverters.

[0004] However, existing AC power cycling tests generally employ offline thermal resistance measurement methods, which require interrupting the power cycle and switching the device under test (DUT) to a thermal resistance testing circuit for temperature-sensitive parameter acquisition. This method has limitations in two aspects: First, the downtime is lengthy, causing interruptions in the cycling process and changes in the temperature field. If the device needs to be disassembled for thermal resistance measurement, frequent clamping can lead to fluctuations in the device's heat dissipation conditions, affecting the accuracy of aging tests. Second, frequent start-stop cycles extend the test cycle; for life assessment experiments requiring thousands of cycles, the impact of offline measurement on the test cycle is significant. Therefore, current AC power cycling tests can only use lower-frequency thermal resistance monitoring to avoid significantly impacting the power cycle. Summary of the Invention

[0005] The purpose of this application is to solve the problems of existing AC power cycle testing schemes, and to enable online measurement of the temperature-sensitive electrical parameters of the power device under test without interrupting the power cycle, and to accurately analyze the aging condition of each part, for actual automotive operating conditions.

[0006] The first aspect of this application provides an online power device aging test circuit for automotive applications. This test circuit includes a three-phase six-arm bridge circuit composed of the power device under test; and further includes:

[0007] Thermosensitive electrical parameter measurement circuit, used to measure the time-varying characteristics of the thermosensitive electrical parameters of the connected power device under test;

[0008] The bridge arm switching circuit includes a source switching switch and a drain switching switch corresponding to each power device under test, used to connect the corresponding power device under test to the three-phase six-bridge arm circuit under test, or to the temperature-sensitive electrical parameter measurement circuit.

[0009] The backup bridge arm circuit includes two backup power devices connected in series, and a backup coil led out from the connection point of the two backup power devices, used to replace the bridge arm circuit where any of the power devices under test connected to the temperature-sensitive electrical parameter measurement circuit are located, so as to form a backup three-phase six-bridge arm circuit.

[0010] The second aspect of this application provides a comprehensive test and analysis method that uses the aforementioned online power device aging test circuit for automotive applications to analyze the aging condition of the power device under test without interrupting the power device aging test based on AC power cycling. The method includes the following operations:

[0011] Operation 1: Maintain the three-phase six-bridge-arm circuit under test in the power cycle state corresponding to the operating conditions of the vehicle under test;

[0012] Operation 2: By switching the state of the bridge arm switching circuit, connect the power device under test that needs to be analyzed for aging to the temperature-sensitive electrical parameter measurement circuit, and at the same time turn off the power device on the same bridge arm, or connect the power device on the same bridge arm to another temperature-sensitive electrical parameter measurement circuit.

[0013] Operation 3: Use the spare bridge arm circuit to replace the bridge arm circuit where the power device under test is located in the temperature-sensitive electrical parameter measurement circuit, so as to form a spare three-phase six-bridge arm circuit and put it in the power cycle state corresponding to the working condition of the vehicle under test.

[0014] Operation 4: Measure the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit and analyze its aging status.

[0015] Operation 5: After completing the measurement of the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test, turn off the backup power device. By switching the state of the bridge arm switching circuit, use the bridge arm circuit where the power device under test is connected to the temperature-sensitive electrical parameter measurement circuit to replace the backup bridge arm circuit, so as to reconstruct the three-phase six-bridge arm circuit under test and put it in the power cycle state corresponding to the operating condition of the vehicle under test.

[0016] A third aspect of this application provides a comprehensive test and analysis system, comprising:

[0017] The aforementioned online power device aging test circuit for automotive applications;

[0018] The control unit controls the AC power cycling state of the tested three-phase six-arm circuit or the standby three-phase six-arm circuit according to the preset vehicle operating conditions.

[0019] The switching unit is used to switch the tested three-phase six-arm circuit to a standby three-phase six-arm circuit, or to switch the standby three-phase six-arm circuit to the tested three-phase six-arm circuit.

[0020] The analysis unit analyzes the aging status of various locations of the power device under test based on the measurement results of the time-varying characteristics of the temperature-sensitive electrical parameters connected to the temperature-sensitive electrical parameter measurement circuit.

[0021] The online power device aging test circuit for automotive applications provided in this application constructs a three-phase six-arm bridge circuit using the power device under test, and simultaneously constructs a one-phase spare bridge arm circuit using a spare power device. Furthermore, a bridge arm switching circuit enables the switching of the power device under test between the power cycling circuit and the temperature-sensitive electrical parameter measurement circuit. The spare bridge arm circuit replaces the power device performing thermal resistance measurement to maintain the power cycling. Through this design, the power cycling operation can be maintained without interrupting the measurement of the temperature-sensitive electrical parameters of any power device. This ensures that other power devices under test that are not undergoing temperature-sensitive electrical parameter measurement remain under the power cycling condition for aging testing, avoiding the impact of measuring and analyzing the aging state parameters of the power device under test on the normal aging tests of other power devices. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of the AC power cycling section in an online power device aging test circuit for automotive applications provided according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of the temperature-sensitive electrical parameter measurement circuit in an online power device aging test circuit for automotive applications provided according to an embodiment of this application.

[0024] Figure 3 This is a schematic diagram of a closed-loop control strategy for driving the AC power cycling section to perform power device aging tests in some embodiments.

[0025] Figure 4 A simulation diagram of phase current for AC power cyclic switching using a bridge arm switching strategy;

[0026] Figure 5 A flowchart illustrating a bridge arm switching strategy provided according to an embodiment of this application;

[0027] Figure 6 This is a simulation diagram of the phase current for AC power cyclic switching according to the bridge arm switching strategy provided in the embodiments of this application;

[0028] Figure 7 The measured phase current results for AC power cyclic switching based on the arm switching strategy provided in the embodiments of this application;

[0029] Figure 8 This is a flowchart of the comprehensive test and analysis method provided according to the embodiments of this application;

[0030] Figure 9 This is a flowchart illustrating the measurement of the time-varying characteristics of temperature-sensitive electrical parameters of a power device under test in one specific embodiment.

[0031] Figure 10 A physical image of the junction temperature calibration experimental platform;

[0032] Figure 11 This is a schematic diagram of the junction temperature calibration results;

[0033] Figure 12 This is a schematic diagram illustrating the analysis results of the aging condition of various parts of the power device under test in one embodiment.

[0034] Figure 13 This is a schematic diagram of the framework structure of the comprehensive test and analysis system provided according to the embodiments of this application;

[0035] Figure 14 A physical diagram of the comprehensive testing and analysis experimental platform provided according to the embodiments of this application;

[0036] Figure 15 This is a schematic diagram of the structure function of the device under test before and after aging, obtained through online measurement and analysis.

[0037] Figure 16 This is a schematic diagram showing the on-state voltage drop of the power device under test during the online measurement of the heating process before and after aging. Detailed Implementation

[0038] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0039] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, in the description of this application, in order to distinguish different units, the terms "first," "second," etc. are used in this specification, but these are not limited by the manufacturing order, nor should they be construed as indicating or implying relative importance. Their names may differ in the detailed description and claims of this application.

[0040] The vocabulary used in this specification is for illustrative purposes and is not intended to limit the scope of this application. It should also be noted that, unless otherwise expressly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection via an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of these terms in this application.

[0041] This application provides an online power device aging test circuit for automotive applications through embodiments. This aging test circuit can perform online temperature-sensitive electrical parameter measurements on power devices under test that require aging analysis during the continuous AC power cycle-based aging test of multiple power devices under test.

[0042] Specifically, the aging test circuit consists of an AC power circulation section, a thermal resistance measurement section, and a switching section. Figure 1 and Figure 2 Schematic diagrams of the AC power cycling section and the temperature-sensitive electrical parameter measurement circuit of the aging test circuit are shown in some embodiments, while the switching section is also shown. Figure 1 and Figure 2 .

[0043] <AC Power Cycling Section>

[0044] The AC power cycling section simulates actual automotive operating conditions, continuously subjecting at least one power device under test to AC power loading for aging tests. This assesses how the device ages gradually over time under different automotive operating conditions. (Reference) Figure 1 The AC power circulation section is mainly composed of the three-phase six-bridge-arm circuit under test.

[0045] The three-phase six-bridge-arm circuit under test is a circuit for performing AC cyclic loading aging tests on the power device under test. In the embodiments of this application, the power device under test can be an IGBT (Insulated Gate Bipolar Transistor), a SiC MOSFET (Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistor), or other devices with similar structures that can perform switching actions under the control of a regulating signal to regulate current and voltage. In the fields of new energy vehicles, the above-mentioned power devices are widely used in electric drive systems, on-board charging systems, etc., for example, as core components to form inverters to convert the DC power from the battery into AC power to drive the motor.

[0046] During use, the aforementioned power devices need to face complex automotive operating conditions, such as frequent start-stop and high-current charging and discharging. Under these conditions, the power devices are subjected to severe junction temperature fluctuations over a long period of time, which can lead to failure problems such as bond wire detachment and solder layer fatigue. Studies have shown that power devices are the components with the highest failure rate in converter systems, accounting for about 34%. Therefore, the three-phase six-bridge arm circuit under test is constructed using the same topology as the three-phase inverter. Through closed-loop modulation control, it can be made to cycle AC power under various preset automotive operating conditions, thereby conducting continuous aging tests on each power device under test.

[0047] Specifically, refer to Figure 1 The tested three-phase six-arm bridge circuit adopts a three-phase inverter topology known to those skilled in the art: Phase A arm circuit is formed by power devices P1 and P4 connected in series, where the source of P1 is connected to the drain of P4, and an A-phase line is led out from the connection point to connect to the A-phase coil; Phase B arm circuit is formed by power devices P2 and P5 connected in series, where the source of P2 is connected to the drain of P5, and a B-phase line is led out from the connection point to connect to the B-phase coil; Phase C arm circuit is formed by power devices P3 and P6 connected in series, where the source of P3 is connected to the drain of P6, and a C-phase line is led out from the connection point to connect to the C-phase coil; the drains of P1, P2, and P3 are connected to the positive terminal of the DC power supply; the sources of P4, P5, and P6 are connected to the negative terminal of the DC power supply; the A-phase, B-phase, and C-phase coils are connected in a star configuration. The gates (G) of these six power devices... A1 G A2 G B1 G B2 G C1 G C2Based on the received gate drive signal, the drain and source of the power supply are turned on or off, thereby converting the DC power output from the DC power supply into AC power.

[0048] In the embodiments of this application, the aforementioned portion is referred to as the three-phase six-arm circuit under test, which refers to the circuit that needs to be continuously subjected to AC power according to various operating conditions of the vehicle under test, and the aging condition of at least one power device is measured and analyzed by the temperature-sensitive electrical parameter measurement circuit described later. Accordingly, in the embodiments of this application, the power device that needs to be measured and analyzed for aging condition is referred to as the power device under test. For example, in Figure 1 In the illustrated embodiment, when it is necessary to measure and analyze the aging condition of power devices P1 to P6, all six power devices are referred to as the power devices under test; if it is only necessary to measure the aging condition of power device P1, then only power device P1 can be referred to as the power device under test.

[0049] The AC power loading of the tested three-phase six-arm bridge circuit can be performed using various closed-loop modulation control strategies known to those skilled in the art, for example, as follows: Figure 3 As shown, the target iq, id, and electrical angular velocity are determined according to the required vehicle operating conditions (such as low-speed heavy-load conditions, high-speed light-load conditions, etc.). Simultaneously, the actual three-phase current I is acquired through a current sensor. A I B I C Then, Clark and Park transformations are performed to transform the current i in a two-phase resolver coordinate system. q i d . Target i q i d and actual i q i d The difference is taken and fed into a proportional-integral (PI) controller to calculate the voltage U in the two-phase rotating coordinate system. q U d Then, through Clark and Park inverse transformations, the three-phase voltage U is obtained. A U B U C The three-phase voltage is modulated by the SVPWM algorithm to obtain the gate control signal of the six-arm three-phase bridge under test, which controls the switching of six power devices to realize the output of sinusoidal three-phase current.

[0050] In some specific embodiments, the devices implementing the above-mentioned closed-loop modulation control include, but are not limited to, digital signal processors (DSPs), microcontroller units (MCUs), field-programmable gate arrays (FPGAs), and embedded systems based on Linux or RTOS. These devices utilize high-precision analog-to-digital converters (ADCs) to acquire three-phase current data from current sensors in real time. They then use built-in closed-loop modulation control algorithms or modules to generate gate control signals for each power device, which are converted into analog signals by digital-to-analog converters (DACs) or directly output as digital signals. Furthermore, an interactive interface can be provided for the above-mentioned closed-loop modulation control device to monitor the system's operating status in real time, adjust control parameters, and perform fault diagnosis.

[0051] <Temperature-Sensitive Electrical Parameter Measurement Circuit>

[0052] After the power device under test is subjected to continuous AC power cycling (i.e., continuous aging test), various parts of the device will age, and the degree of aging of each part will show different trends as the aging test continues. Therefore, it is necessary to analyze the degree of aging of each power device under test at preset time intervals during the aging test.

[0053] Since temperature is a major cause of failure in power devices, the aging degree of the tested power device can be analyzed by using temperature stress parameters. Considering that direct temperature measurement would damage the packaging structure of the power device, the junction temperature of power devices is generally measured indirectly. This involves measuring the temperature-sensitive electrical parameters related to the junction temperature of the power device, and then using the mapping relationship between the pre-calibrated temperature-sensitive electrical parameters and the junction temperature to obtain the junction temperature change caused by aging of the power device, so as to analyze its aging condition.

[0054] Currently, commonly used temperature-sensitive electrical parameters include the on-resistance, threshold voltage, and body diode voltage drop of power devices. Among these, the threshold voltage and on-resistance are easily affected by the trap charge at the gate oxide interface of the power device, causing threshold voltage drift and resulting in changes in on-resistance, thus affecting the accuracy of junction temperature measurement. The body diode voltage drop, however, is relatively stable during device aging and is considered the most suitable temperature-sensitive parameter, exhibiting good linearity and sensitivity. Therefore, in the embodiments of this application, the temperature-sensitive electrical parameter of the power device under test (preferably, the body diode voltage drop) is selected as the measurement target. By connecting the power device under test to the temperature-sensitive electrical parameter measurement circuit at different stages of the aging test, the time-varying characteristics of its temperature-sensitive electrical parameter can be obtained. In the comprehensive test and analysis method described later, the correspondence between the temperature-sensitive electrical parameter and the junction temperature can be used to further obtain the thermal resistance and thermal capacitance characteristics of various parts of the power device under test, thereby enabling precise analysis of the different aging trends exhibited by various locations of the power device under test under actual automotive operating conditions.

[0055] refer to Figure 2 In the embodiments of this application, the temperature-sensitive electrical parameter measurement circuit includes a heating module, a current measuring source, and a voltage drop measurement module. The heating module, the current measuring source, and the voltage drop measurement module are connected in parallel to the drain and source of the power device under test.

[0056] The heating module includes a heating current I0 H The heating current source and the switch S that controls the heating I When it is necessary to heat the power device under test connected to the measurement circuit, switch S I Turn on, and simultaneously control V GS The turn-on voltage is reached, enabling a stable turn-on current I to be formed between the heating current source and the power device under test. H (Preferred, I) H (greater than 10A), under the action of the conduction current, the power device is continuously heated until its junction temperature is heated to a preset target. The preset target can be that the junction temperature of the power device reaches a preset temperature and remains stably at that temperature, or it can be a set heating current I. H The heating time set for the power device under test.

[0057] It should be known that Figure 2 The heating current source shown is only one optional heating method for the power device under test. Those skilled in the art can also use other optional heating methods to construct a heating module to heat the junction temperature of the power device under test to a preset target.

[0058] Once the power device under test is heated to the preset target, the heating process can be ended, and V can be switched off. GS Set the turn-off voltage to completely turn off the power device under test, and then inject a stable measurement current I into its body diode. M (Preferred, I) M The voltage drop of the body diode was measured as it ranged from 80mA to 120mA, and the change of its voltage drop over time was measured.

[0059] In embodiments of this application, a measurement current I is injected into the body diode. M The voltage drop across the body diode is measured via a current source and a voltage drop measurement module. The current source is connected to the source and drain of the power device under test (DUT) connected to the measurement circuit, respectively. When the DUT is in the off state, it generates a measurement current I flowing through the body diode of the DUT. MThe two measuring terminals of the voltage drop measurement module are connected to the source and drain of the power device under test connected to the measurement circuit, respectively. They are used to measure the body diode voltage drop of the power device under test caused by the measuring current when the power device under test connected to the measurement circuit is in the off state.

[0060] In some specific embodiments, the current source and voltage drop measurement module can be configured by selecting a current source and voltmeter with appropriate range and accuracy according to the test requirements of the power device under test.

[0061] The specific implementation method for analyzing the aging condition of the power device under test by obtaining the time-varying characteristics of the temperature-sensitive electrical parameters based on the measurement results will be described in detail in the section on comprehensive test and analysis methods later.

[0062] <Switching section and its switching strategy>

[0063] As analyzed above, during the aging test of the three-phase six-arm bridge circuit under test, which involves continuous AC power cyclic loading, it is necessary to repeatedly evaluate the aging trend of each power device under test at certain time intervals. Each measurement of the time-varying characteristics of the temperature-sensitive parameters includes both heating and cooling phases, each typically lasting around 200 seconds. If an offline measurement method is used, i.e., interrupting the AC power cycle of the aging test and switching the power device under test to the measurement circuit for temperature-sensitive parameter acquisition, the following problems arise: First, the shutdown process is lengthy, causing interruptions in the cyclic operation and changes in the temperature field. If the device needs to be disassembled for thermal resistance measurement, frequent clamping will also lead to fluctuations in the device's heat dissipation conditions, affecting the accuracy of the aging test. Second, frequent start-stop cycles extend the test cycle. For life assessment experiments requiring thousands of cycles, the impact of offline measurement on the test cycle cannot be ignored.

[0064] To address the aforementioned issues, this application utilizes a bridge arm switching circuit and a spare bridge arm circuit to form a switching section. This allows for the measurement of temperature-sensitive electrical parameters of a specific power device under test without interrupting the aging test process under AC power loading. The bridge arm switching circuit includes a source switching switch and a drain switching switch corresponding to each power device under test, used to connect the corresponding power device to the three-phase six-bridge arm circuit under test, or to the temperature-sensitive electrical parameter measurement circuit. The spare bridge arm circuit includes two spare power devices connected in series, and a spare coil drawn from the connection point of the two spare power devices. This coil replaces any bridge arm circuit containing a power device connected to the temperature-sensitive electrical parameter measurement circuit, thus forming a spare three-phase six-bridge arm circuit.

[0065] Specifically, in Figure 1 and Figure 2In the embodiment shown, the bridge arm switching circuit includes a total of six source switching switches S. S1 S S2 S S3 S S4 S S5 S S6 and six drain switching switches S D1 S D2 S D3 S D4 S D5 S D6 .

[0066] S S1 and S D1 Corresponding to the power device under test P1, S on phase A bridge arm circuit S1 It includes a common input terminal connected to the source of P1, and two switchable output terminals, one of which is connected to the bridge arm circuit where P1 is located (i.e., Figure 1 One is connected to the connection point between P1 and P4, and the other is connected to a measuring terminal of the temperature-sensitive electrical parameter measuring circuit. Figure 2 (The measuring terminal above the voltmeter). Similarly, S D1 It includes a common input terminal connected to the drain of P1, and two switchable output terminals, one of which is connected to the bridge arm circuit where P1 is located (i.e., Figure 1 The location of the drain electrode in the Chinese circuit is one, while the other is connected to another measuring terminal of the temperature-sensitive electrical parameter measuring circuit. Figure 2 (The measuring terminal below the voltmeter).

[0067] The power device under test, which is in the same A-phase bridge arm circuit as P1, is P4, and its corresponding source switching switch is S. S4 The drain switching switch is S. D4 S S2 It includes a common input terminal connected to the source of P4, and two switchable output terminals, one of which is connected to the bridge arm circuit containing P4 (i.e., Figure 1 The other is connected to a measuring terminal of the temperature-sensitive electrical parameter measuring circuit. Figure 2 (The measuring terminal above the voltmeter). Similarly, S D4 It includes a common input terminal connected to the drain of P4, and two switchable output terminals, one of which is connected to the bridge arm circuit containing P4 (i.e., Figure 1 The connection point between P1 and P4 is one of the terminals, and the other is connected to another measuring terminal of the temperature-sensitive electrical parameter measuring circuit. Figure 2 (The measuring terminal below the voltmeter).

[0068] The above describes the connection method of the source switching switch and drain switching switch for the A-phase bridge arm circuit where P1 and P4 are located. For the power devices under test P2 and P5 in the B-phase bridge arm circuit, and the power devices under test P3 and P6 in the C-phase bridge arm circuit, their corresponding source switching switches and drain switching switches can adopt the same connection method, which will not be repeated here.

[0069] Each source switching switch and drain switching switch can be switched by switching signals (e.g., high and low level signals) sent by the switching device. Referring to the aforementioned closed-loop modulation control device, the control of the bridge arm switching circuit can also be implemented by devices such as digital signal processors (DSPs), microcontroller units (MCUs), field-programmable gate arrays (FPGAs), and embedded systems based on Linux or RTOS. Obviously, for any power device under test, the switching actions of its corresponding source switching switch and drain switching switch need to be kept synchronized.

[0070] Source and drain switching devices can be constructed using circuit switching devices with single-pole double-throw (SPDT) characteristics. For example, a SPDT electromagnetic relay can be used. This relay includes a common contact (COM), a normally open contact (NO), and a normally closed contact (NC). When an input signal (such as a high-level signal or the flow of current through the electromagnetic coil) is received, an electromagnetic force is generated in the electromagnet core, attracting the armature and connecting the common contact to the normally open contact. When another input signal (such as a low-level signal or the cancellation of current flow through the electromagnetic coil) is received, the electromagnetic force in the electromagnet core disappears, and the common contact connects to the normally closed contact. By switching the input signal to the electromagnetic relay, the connection state of the source / drain of each power device with the two measuring terminals of the three-phase six-arm circuit under test or the temperature-sensitive electrical parameter measurement circuit can be switched. This allows selective connection of the corresponding power device under test to the three-phase six-arm circuit under test or to the temperature-sensitive electrical parameter measurement circuit.

[0071] Figure 2 The embodiment shown includes only one temperature-sensitive electrical parameter measurement circuit; therefore, all source switching switches S S1 ~S S6 One of the switchable output terminals is connected to a measuring terminal of the temperature-sensitive electrical parameter measuring circuit, and all drain switching switches S D1 ~S D6 One of the switchable output terminals is connected to the other measurement terminal of the temperature-sensitive electrical parameter measurement circuit. Obviously, at any given time, the temperature-sensitive electrical parameter measurement circuit can only connect to one power device under test.

[0072] In some alternative embodiments, the number of temperature-sensitive electrical parameter measurement circuits can be increased. For example, two temperature-sensitive electrical parameter measurement circuits can be set up. One circuit is used to measure the temperature-sensitive electrical parameters of the three power devices P1, P2, and P3 in the upper half of each phase bridge arm circuit, and the other circuit is used to measure the temperature-sensitive electrical parameters of the three power devices P4, P5, and P6 in the lower half of each phase bridge arm circuit. At any given time, it is necessary to ensure that the power devices connected to each temperature-sensitive electrical parameter measurement circuit come from the same bridge arm circuit. For example, the temperature-sensitive electrical parameters of P1 and P4 can be measured simultaneously by the two temperature-sensitive electrical parameter measurement circuits, or the temperature-sensitive electrical parameters of P2 and P5 can be measured simultaneously, or the temperature-sensitive electrical parameters of P3 and P6 can be measured simultaneously. However, the temperature-sensitive electrical parameters of P1 and P2, or P1 and P3, or P1 and P5, or P1 and P6 cannot be measured simultaneously, because this measurement method will not be able to maintain the operation of AC power cycling.

[0073] After a device under test (DUT) is connected to the temperature-sensitive electrical parameter measurement circuit via a bridge arm switching circuit, in order to maintain the aging test of other DUTs, the bridge arm containing the DUT needs to be replaced by a spare bridge arm circuit to ensure the continuous AC power cycle. This is used when any DUT is connected to the temperature-sensitive electrical parameter measurement circuit, such as... Figure 1 As shown, the spare bridge arm circuit includes two spare power devices P7 and P8 connected in series, and a spare coil led out from the connection point of P7 and P8. The model of P7 and P8 is preferably the same as that of each power device under test, and they are connected to the three-phase six-bridge arm circuit under test using the same topology as the bridge arm circuit of phases A, B, and C. In the embodiments of this application, this phase bridge arm circuit can be called the D-phase bridge arm circuit, and its spare coil, namely the D-phase coil, is connected to the A, B, and C phase coils in a star configuration.

[0074] The gates of P7 and P8 can also receive gate control signals from the aforementioned closed-loop modulation control devices, and in conjunction with the switching action of the bridge arm switching circuit, switch from the tested three-phase six-bridge arm circuit to the standby three-phase six-bridge arm circuit, or switch from the standby three-phase six-bridge arm circuit to the tested three-phase six-bridge arm circuit.

[0075] For example, when the three-phase six-arm bridge circuit under test is in normal AC power cycling mode, the closed-loop modulation control device controls the standby power devices P7 and P8 to be in the off state. When it is necessary to connect the power device P1 under test on the A-phase bridge arm circuit to the temperature-sensitive electrical parameter measurement circuit, the switching device switches the device to the source via the source switching switch S. S1 and drain switching switch S D1The corresponding switching signal is sent to connect it to the temperature-sensitive electrical parameter measurement circuit. At the same time, the closed-loop modulation control device turns it off by controlling the gate of P4, or the switching device turns it off by switching the source switch S. S4 and drain switching switch S D4 Send the corresponding switching signal to connect P4 to another temperature-sensitive electrical parameter measurement circuit; simultaneously, the closed-loop modulation control device sends a signal to the gates G of P7 and P8. D1 G D2 The gate control signal originally sent to P1 and P4 is sent, causing the D-phase bridge arm circuit to replace the A-phase bridge arm circuit. This switches the tested three-phase six-bridge arm circuit to a standby three-phase six-bridge arm circuit and maintains AC power circulation, thereby ensuring the continuous aging test of the tested power devices P3 to P6. When the temperature-sensitive electrical parameter measurement of P1 (or the temperature-sensitive electrical parameter measurement of P1 and P4) ends, the closed-loop modulation control device controls P7 and P8 to turn off, and simultaneously the switching device switches to the source switching switch S. S1 and drain switching switch S D1 Send the corresponding switching signal, and switch the source to the switching switch S. S4 and drain switching switch S D4 Send the corresponding switching signal to reconnect the A-phase bridge arm circuit where P1 and P4 are located to the AC power cycle. Then, the closed-loop modulation control device sends the gate control signal to P1 and P4 again, so that the standby three-phase six-bridge arm circuit is switched back to the three-phase six-bridge arm circuit under test.

[0076] Because each phase coil has inductive characteristics, the current flowing through each coil cannot change abruptly. Therefore, if the timing of the switching between the tested bridge arm circuit and the standby bridge arm circuit is not properly chosen, the energy stored in the inductor can cause fluctuations in the three-phase current. Figure 4 The simulation example shown illustrates the changes in current in each phase under a bridge arm switching strategy. In this example, the temperature-sensitive electrical parameters of the power device P3 on the C-phase bridge need to be measured, and the C-phase bridge arm circuit is switched to the D-phase bridge arm circuit when the C-phase circuit is at its peak. Obviously, during the switching process, the D-phase current needs to track the original C-phase current from 0, which makes it impossible to transition smoothly, and also causes fluctuations in the A-phase and B-phase currents.

[0077] It is evident that the timing of the switching will affect the smooth operation of the AC power cycle. Therefore, in some preferred embodiments, the following bridge arm switching strategy is adopted to control the switching between the tested three-phase six-bridge arm circuit and the standby three-phase six-bridge arm circuit:

[0078] (1) When the phase current of the bridge arm circuit where the power device under test is located is zero, the backup bridge arm circuit replaces the bridge arm circuit where the power device under test is located, thereby switching the three-phase six-bridge arm circuit under test to the backup three-phase six-bridge arm circuit.

[0079] (2) When the phase current of the standby bridge arm circuit is zero, the bridge arm circuit where the power device under test is connected to the temperature-sensitive electrical parameter measurement circuit is located is replaced by the standby bridge arm circuit, thereby switching the standby three-phase six-bridge arm circuit to the three-phase six-bridge arm circuit under test.

[0080] Figure 5 The illustrated embodiment demonstrates the specific process of switching bridge arm circuits using the above strategy, such as... Figure 5 As shown, during the aging test of the three-phase six-arm bridge circuit under test to maintain AC power cycling, when it is necessary to measure the temperature-sensitive electrical parameters of the power device under test, the phase current of the bridge arm circuit where the power device under test is located is monitored. When the phase current is zero, switching is performed. At this time, the power device under test performs temperature-sensitive electrical parameter measurement operation, and the standby three-phase six-arm bridge circuit maintains AC power cycling. After the temperature-sensitive electrical parameter measurement is completed, the phase current of the standby bridge arm circuit is monitored. When the phase current is zero, switching is performed again.

[0081] Figure 6 The simulation example illustrates the changes in phase currents when using the above-described bridge arm switching strategy. Figure 7 The actual experimental results are shown, through Figure 6 , Figure 7 It can be seen that by using the above-mentioned preferred bridge arm switching strategy, current oscillations caused by inductor freewheeling can be effectively avoided, ensuring the stable operation of aging tests.

[0082] Some embodiments of this application also provide a comprehensive test and analysis method. This method uses the aforementioned online power device aging test circuit for automotive applications to analyze the aging condition of the power device under test without interrupting the power device aging test based on AC power cycling. Figure 8 As shown, the method includes the following operations:

[0083] Operation 1: Maintain the three-phase six-bridge-arm circuit under test in the power cycle state corresponding to the operating conditions of the vehicle under test;

[0084] Operation 2: By switching the state of the bridge arm switching circuit, connect the power device under test that needs to be analyzed for aging to the temperature-sensitive electrical parameter measurement circuit, and at the same time turn off the power device on the same bridge arm, or connect the power device on the same bridge arm to another temperature-sensitive electrical parameter measurement circuit.

[0085] Operation 3: Use the spare bridge arm circuit to replace the bridge arm circuit where the power device under test is located in the temperature-sensitive electrical parameter measurement circuit, so as to form a spare three-phase six-bridge arm circuit and put it in the power cycle state corresponding to the working condition of the vehicle under test.

[0086] Operation 4: Measure the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit and analyze its aging status.

[0087] Operation 5: After completing the measurement of the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test, turn off the backup power device. By switching the state of the bridge arm switching circuit, use the bridge arm circuit where the power device under test is connected to the temperature-sensitive electrical parameter measurement circuit to replace the backup bridge arm circuit, so as to reconstruct the three-phase six-bridge arm circuit under test and put it in the power cycle state corresponding to the operating condition of the vehicle under test.

[0088] Because the aging test of the power device under test can last for hundreds or even thousands of hours, therefore, Figure 8 As shown, for any power device under test that needs to be analyzed for aging, operations two to five above can be executed cyclically at preset time intervals.

[0089] Furthermore, since the aging of power devices may accelerate as aging tests proceed, and greater attention is generally needed to monitor aging after prolonged operation, it is preferable that the aforementioned time interval be continuously shortened as aging tests continue. For example, at the beginning of the aging test, the time-varying characteristics of temperature-sensitive electrical parameters and aging analysis are performed on each tested power device at 30-hour intervals. After 300 hours of continuous aging tests, the time-varying characteristics of temperature-sensitive electrical parameters and aging analysis are performed on each tested power device at 20-hour intervals. After 500 hours of continuous aging tests, the time-varying characteristics of temperature-sensitive electrical parameters and aging analysis are performed on each tested power device at 10-hour intervals.

[0090] <Analysis of Power Device Aging Based on Time-Varying Characteristics of Thermosensitive Electrical Parameters>

[0091] In the above operations, operation four is used to measure the time-varying characteristics of the temperature-sensitive electrical parameters of the device under test, and to analyze the aging condition of various parts of the power device under test based on the measurement results. In some specific embodiments, this operation includes the following steps:

[0092] The first step is to heat the junction temperature of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit to the preset target, then stop heating and measure the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test.

[0093] The second step is to analyze the aging status of various locations of the power device under test based on the time-varying characteristics of the temperature-sensitive electrical parameters.

[0094] The specific implementation method of the first step has been described in detail in the introduction of the temperature-sensitive electrical parameter measurement circuit above. The analysis process of the second step will be described in detail below with reference to the accompanying drawings.

[0095] Figure 9 This illustrates a specific embodiment for analyzing the aging condition of a power device under test based on the time-varying characteristics of its temperature-sensitive electrical parameters. (Refer to...) Figure 9 The analysis process includes the following steps:

[0096] Step a: Based on the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test, determine its transient thermal response curve through a pre-calibrated bulk diode voltage drop-junction temperature relationship model.

[0097] Referring to the previous text, by continuously collecting the body diode voltage drop of the power device under test during the cooling process using a voltage drop measurement block, the characteristics of the temperature-sensitive electrical parameter (i.e., body diode voltage drop) changing over time can be obtained. Using a pre-calibrated body diode voltage drop-junction temperature relationship model, the curve of junction temperature changing over time can be obtained.

[0098] The calibration methods for the voltage drop-junction temperature relationship of a body diode are well known to those skilled in the art; for example, they can be used... Figure 10 The junction temperature calibration experimental platform shown uses a temperature chamber to maintain the power device (DUT) used for calibration at a set junction temperature, and then measures the body diode voltage drop corresponding to each junction temperature. Figure 11 The calibration results for three power devices of the same model from the same batch are shown. It can be seen that there is a negative correlation between the body diode voltage drop and the junction temperature, indicating high sensitivity and a good linear relationship, making it suitable for monitoring changes in device junction temperature. Figure 11 In the illustrated embodiment, averaging the results from the three samples yields the following relationship between junction temperature and bulk diode voltage drop: T j = -356.4V F +999.2, obviously, for other types of power devices, a similar form of body diode voltage drop-junction temperature relationship model can be obtained.

[0099] Using the pre-calibrated bulk diode voltage drop-junction temperature relationship model, the measured time-varying characteristics of the bulk diode can be converted into a curve of junction temperature changing with time. Then, the transient thermal impedance a(t) can be calculated from the junction temperature change using the following formula.

[0100]

[0101] Among them, T j The junction temperature varies with time, T0 is the initial value of the junction temperature, and ΔP is the change in heating power of the device under test during the experiment.

[0102] After obtaining the thermal impedance curve a(t), it can be plotted on a logarithmic time axis to obtain the transient thermal response curve, the expression of which is:

[0103]

[0104] Where z = lnt, ζ = lnτ, a(z) is the thermal impedance, and R(ζ) is the thermal resistance.

[0105] Step b: Determine the time constant spectrum based on the transient thermal response curve.

[0106] Specifically, the time constant spectrum can be obtained by differentiating a(z) with respect to z and then performing a deconvolution operation, as shown in the following equation:

[0107]

[0108] in, The term "deconvolution" indicates a deconvolution operation. In some specific embodiments, the above operation can be implemented using Bayesian deconvolution, inverse Fourier filtering, or other methods known to those skilled in the art.

[0109] Step c: Discretize the time constant spectrum to obtain the FOSTER model.

[0110] Step d: Convert the FOSTER model into a CAUER model to obtain the thermal resistance-thermal capacity structure function of the power device under test.

[0111] Given the time constant spectrum R(z), a thermal network model can be obtained. The theoretical basis of the thermal network model is that when the effective area of ​​the heat source is close to the top surface of the device, the thermal model of the device can be regarded as one-dimensional heat conduction. Thermoelectric analogy theory is typically used to describe the thermal network model of the device using a circuit composed of thermal resistance and thermal capacitance. Typical examples are the FOSTER model and the CAUER model.

[0112] The time constant spectrum function is an extension of the continuous case of the FOSTER model. Discretization of the time constant spectrum yields the expression for the FOSTER model as shown in the following equation:

[0113]

[0114] in, Let R represent the local thermal resistance and local thermal capacity in the FOSTER model. Since the FOSTER model lacks practical physical meaning, it needs to be transformed into the CAUER model, which reflects the device's stack-up structure, to obtain the local thermal resistance R in the CAUER model. n and local heat capacity C n .

[0115] By accumulating the local thermal resistance and local heat capacity, we can obtain the accumulated thermal resistance-accumulated heat capacity structure function as shown in the following equation:

[0116]

[0117] Alternatively, only the local heat capacity can be accumulated to obtain a local structure function that reflects the relationship between local thermal resistance and accumulated heat capacity. In the embodiments of this application, the above structure function can be referred to as the thermal resistance-heat capacity structure function.

[0118] Step e: Analyze the aging status of each location of the power device under test based on the thermal resistance-thermal capacity structure function.

[0119] For example, the cumulative thermal resistance R of a power device from the junction to the case direction can be... ∑ The x-axis represents the cumulative heat capacity C. ∑ Using the vertical axis, we can obtain the following: Figure 12 The cumulative structure function curve shown above can accurately reflect the aging status of various parts of the power device under test during the time period of temperature-sensitive electrical parameter measurement.

[0120] Some embodiments of this application also provide a comprehensive test and analysis system, such as... Figure 13 As shown, the system includes:

[0121] An online power device aging test circuit, control unit, switching unit, and analysis unit designed for automotive applications.

[0122] The online power device aging test circuit for automotive applications is used to perform continuous AC power loading aging tests on the power devices under test, and to measure the time-varying characteristics of the temperature-sensitive electrical parameters of each power device under test online during the process. The control unit controls the AC power cycling state of the tested three-phase six-bridge-arm circuit or the standby three-phase six-bridge-arm circuit according to the preset automotive operating conditions. The switching unit is used to switch the tested three-phase six-bridge-arm circuit to the standby three-phase six-bridge-arm circuit, or the standby three-phase six-bridge-arm circuit to the tested three-phase six-bridge-arm circuit. The analysis unit analyzes the aging status of each location of the power devices under test based on the measurement results of the time-varying characteristics of the temperature-sensitive electrical parameters of the power devices connected to the temperature-sensitive electrical parameter measurement circuit.

[0123] The specific implementation methods of the above-mentioned circuits and units have been described in detail above, and will not be repeated here.

[0124] <Specific Implementation Example 1>

[0125] This embodiment adopts Figure 13 The framework structure shown illustrates a comprehensive testing and analysis experimental platform. Figure 14 This is a physical image of the experimental platform.

[0126] In this experimental platform, the power device under test is a discrete SiC MOSFET, model C3M0120065K, with a maximum voltage of 650V and a maximum current of 25A, close to the voltage and current requirements of automotive inverters. The load inductance is 2mH. The temperature-sensitive electrical parameter measurement circuit is equipped with a 30A / 10V heating power supply, a temperature measuring power supply with an error within 3mA, and a differential voltmeter with an error within 1.5mV, with a temperature resolution of 0.02℃. The single-pole double-throw switch is a 380VAC / 20A electromagnetic relay (J107F1CS205VDC.45), and the phase current is acquired using a LEM CAS25-NP current sensor. The experimental platform is monitored and controlled via an ACT200 FPGA board.

[0127] The power cycle aging test process is conducted by alternating between high-speed light-load and low-speed heavy-load vehicle operating conditions: under low-speed heavy-load conditions, i q For 20A, i d The current is 0A, the mechanical speed is 1500 Rpm, the device switching frequency is 20kHz, and the operating conditions are under high-speed, light-load conditions. q For 4A, i d The current is 0A, the mechanical speed is 7000 Rpm, and the device switching frequency is 20kHz.

[0128] The bridge arm circuit switching strategy, verified by online measurements during normal power cycling, has been shown in the following figures. Figure 7 ,Depend on Figure 7 As can be seen, when switching between the C-phase bridge arm and the D-phase spare bridge arm, the three-phase current did not fluctuate significantly, proving that the zero-current switching strategy can achieve a smooth and reliable switching.

[0129] After 650 hours of AC power cycling test aging, the structure function of the device under test obtained through online measurement and analysis is as follows: Figure 15 As shown, the structure function shifts to the left after aging, while the typical solder layer aging structure curve should shift to the right. Combined with... Figure 16 Analysis of the on-state voltage drop during the heating process of the power device under test shows that after the device has aged, the on-state voltage drop increases significantly when the device is heated with a current of 13A. Therefore, it is inferred that the bond wire of the power device under test has aged. It can be seen that the comprehensive test and analysis method and system provided in this application can accurately analyze and locate the aging of each part of the power device under test.

[0130] The specific embodiments of this application have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A comprehensive test and analysis method, using an online power device aging test circuit designed for automotive applications, analyzes the aging status of the power device under test without interrupting the power device aging test based on AC power cycling. The online power device aging test circuit for automotive applications includes a three-phase six-bridge-arm circuit composed of the power devices under test, and a temperature-sensitive electrical parameter measurement circuit for measuring the time-varying characteristics of the temperature-sensitive electrical parameters of the connected power devices under test; a bridge-arm switching circuit including a source switching switch and a drain switching switch corresponding to each power device under test, for connecting the corresponding power device under test to the three-phase six-bridge-arm circuit under test, or to the temperature-sensitive electrical parameter measurement circuit; a spare bridge-arm circuit including two spare power devices connected in series, and a spare coil led out from the connection point of the two spare power devices, for replacing any bridge-arm circuit containing a power device under test connected to the temperature-sensitive electrical parameter measurement circuit, to form a spare three-phase six-bridge-arm circuit; characterized in that… Includes the following operations: Operation 1: Maintain the three-phase six-bridge-arm circuit under test in the power cycle state corresponding to the operating conditions of the vehicle under test; Operation 2: By switching the state of the bridge arm switching circuit, connect the power device under test that needs to be analyzed for aging to the temperature-sensitive electrical parameter measurement circuit, and at the same time turn off the power device on the same bridge arm, or connect the power device on the same bridge arm to another temperature-sensitive electrical parameter measurement circuit. Operation 3: Use the spare bridge arm circuit to replace the bridge arm circuit where the power device under test is located in the temperature-sensitive electrical parameter measurement circuit, so as to form a spare three-phase six-bridge arm circuit and put it in the power cycle state corresponding to the working condition of the vehicle under test. Operation 4: Measure the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit and analyze its aging status. Operation 5: After completing the measurement of the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test, turn off the backup power device. By switching the state of the bridge arm switching circuit, use the bridge arm circuit where the power device under test is connected to the temperature-sensitive electrical parameter measurement circuit to replace the backup bridge arm circuit, so as to reconstruct the three-phase six-bridge arm circuit under test and put it in the power cycle state corresponding to the operating condition of the vehicle under test.

2. The comprehensive test and analysis method according to claim 1, characterized in that, For any power device under test that needs to be analyzed for aging, operations two through five are executed cyclically at preset time intervals.

3. The comprehensive test and analysis method according to claim 1, characterized in that, Operation four includes the following steps: After heating the junction temperature of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit to the preset target, the heating is stopped and the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test are measured. Based on the time-varying characteristics of the temperature-sensitive electrical parameters, the aging status of various locations of the power device under test is analyzed.

4. The comprehensive test and analysis method according to claim 3, characterized in that, The temperature-sensitive electrical parameter is the body diode voltage drop caused by a stable measuring current when the power device is in the off state. The aging condition of various locations of the power device under test is analyzed through the following steps: Based on the time-varying characteristics of the temperature-sensitive electrical parameters of the power device under test, its transient thermal response curve is determined by using a pre-calibrated bulk diode voltage drop-junction temperature relationship model. The time constant spectrum is determined based on the transient thermal response curve; The time constant spectrum is discretized to obtain the FOSTER model; The FOSTER model is transformed into the CAUER model to obtain the thermal resistance-thermal capacity structure function of the power device under test; The aging status of the power device under test at various locations is analyzed based on the aforementioned thermal resistance-thermal capacity structure function.

5. The comprehensive test and analysis method according to claim 1, characterized in that, The switching between the tested three-phase six-arm circuit and the standby three-phase six-arm circuit is controlled based on the following bridge arm switching strategy: When the phase current of the bridge arm circuit where the power device under test is located, which needs to be connected to the temperature-sensitive electrical parameter measurement circuit, is zero, the spare bridge arm circuit replaces the bridge arm circuit where the power device under test is located, thereby switching the three-phase six-bridge arm circuit under test to the spare three-phase six-bridge arm circuit. When the phase current of the standby bridge arm circuit is zero, the bridge arm circuit where the power device under test is located, which is connected to the temperature-sensitive electrical parameter measurement circuit, replaces the standby bridge arm circuit, thereby switching the standby three-phase six-bridge arm circuit to the three-phase six-bridge arm circuit under test.

6. The comprehensive test and analysis method according to claim 1, characterized in that, The spare bridge arm circuit is connected to the three-phase six-bridge arm circuit under test with the same topology as the bridge arm circuit where the power device under test is located, and the spare coil is connected to the three-phase coil of the three-phase six-bridge arm circuit under test in a star connection manner.

7. The comprehensive test and analysis method according to claim 1, characterized in that, Each of the source switching switches is used to switch the connection status between the source of its corresponding power device and the three-phase six-bridge circuit under test or a measuring terminal of the temperature-sensitive electrical parameter measuring circuit; Each of the drain switching switches is used to switch the connection status between the drain of its corresponding power device and the three-phase six-bridge circuit under test or with another measuring terminal of the temperature-sensitive electrical parameter measuring circuit.

8. The comprehensive test and analysis method according to claim 7, characterized in that, The source switching switch includes a common input terminal connected to the source of the corresponding power device under test, and two switchable output terminals connected to a measuring terminal of the bridge arm circuit where the corresponding power device under test is located and the temperature-sensitive electrical parameter measuring circuit, respectively. The drain switching switch includes a common input terminal connected to the drain of the corresponding power device under test, and two switchable output terminals connected to the bridge arm circuit where the corresponding power device under test is located and another measuring terminal of the temperature-sensitive electrical parameter measuring circuit, respectively.

9. The comprehensive test and analysis method according to claim 1, characterized in that, For any power device under test, the switching actions of its corresponding source switching switch and drain switching switch remain synchronized.

10. The comprehensive test and analysis method according to claim 1, characterized in that, The temperature-sensitive electrical parameter is the body diode voltage drop caused by a stable measuring current when the power device is in the off state. The temperature-sensitive electrical parameter measurement circuit includes: The heating module is used to heat the junction temperature of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit to a preset target. A measuring current source, whose two ends are respectively connected to the source and drain of the power device under test, is used to generate a measuring current flowing through the body diode of the power device under test when the power device under test connected to the temperature-sensitive electrical parameter measuring circuit is in the off state. The voltage drop measurement module has two measurement terminals connected to the source and drain of the power device under test connected to the temperature-sensitive electrical parameter measurement circuit, respectively. It is used to measure the body diode voltage drop of the power device under test caused by the measurement current when the power device under test connected to the temperature-sensitive electrical parameter measurement circuit is in the off state.

11. The comprehensive test and analysis method according to claim 1, characterized in that, The number of the temperature-sensitive electrical parameter measurement circuit is greater than or equal to one; At any given time, the number of power devices under test connected to any temperature-sensitive electrical parameter measurement circuit shall not exceed one, and the number of bridge arm circuits in which the power devices under test connected to the temperature-sensitive electrical parameter measurement circuit are located shall not exceed one.

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