Double pulse test system and method

Abstract

The present disclosure relates to double pulse testing systems and methods. Methods and systems for correcting for inductive loads when testing high voltage devices are described. The high voltage device is a device under test (DUT) in a double pulse test, which may require an inductive load. The method may include estimating a range of inductor current contributions after the device under test connected to an inductive load having an air core inductor is turned on during a period of low current and high voltage. The method subtracts the estimated inductor current contribution from the collector current of the device under test to output a corrected collector current. This allows the double pulse test to be performed using an air core inductor. The vehicle may use the device under test in a traction power application.

Description

Technical Field

[0001] The present disclosure relates to testing power semiconductor devices, and more particularly to systems and methods for double pulse testing of devices (eg, vehicle power electronics). Background Art

[0002] Double pulse testing can be used to determine the operating characteristics of power semiconductor devices. A typical inductor with a magnetic core is used as a current source for a power semiconductor device. Magnetic core inductors can easily achieve high inductance; however, magnetic core inductors have some disadvantages, such as (1) the inductance of magnetic core inductors varies with current level; (2) magnetic core inductors can even saturate at higher currents. Switching loss evaluation using double pulse testing generally requires a wide current level range (e.g., 1A to 1000A), so inductors with magnetic cores are not ideal candidates for such applications. Summary of the invention

[0003] A double pulse test method and system are described that provide correction of sensed current by correcting for the contribution of an inductor. In an example of a low current high voltage time period, after a device under test connected to an inductive load having an air core inductor is turned on, a range of inductor current contribution is estimated. The estimated inductor current contribution is then subtracted from the collector current of the device under test to output a corrected collector current.

[0004] In an example embodiment, the method includes estimating the inductor current, the step of estimating the inductor current including sensing a first voltage across a power supply capacitor, sensing a second voltage across the device under test, and using the first voltage and the second voltage to estimate a current change of the inductor.

[0005] In an example embodiment, the method includes estimating a change in current flowing through the inductive load, the step of estimating a change in current flowing through the inductive load includes calculating using the following equation:

[0006]

[0007] Among them, v C is the first voltage, v ce is the second voltage, L is the inductance of the load inductor, and dt is the change in time.

[0008] In an exemplary embodiment, the step of estimating the inductor current includes setting a first voltage to a constant to represent a power supply voltage or extracting a high level portion of a sensed second voltage, sensing a second voltage across the device under test, and using the first voltage and the second voltage to estimate a current change of the inductor.

[0009] According to the present invention, a double pulse test method is provided, the method comprising: a processor performing the following operations: operating a device under test (DUT) according to a double pulse test arrangement, the DUT being connected to an inductive load defined by an air-core inductor; outputting a corrected collector current, the corrected collector current being derived from a difference between a collector current of the DUT measured after the DUT is turned on and an inductor current obtained after the DUT is turned on.

[0010] According to an embodiment of the present invention, the inductance is approximately 10 μH to 80 μH.

[0011] According to an embodiment of the present invention, the inductive load has an inductance of about 1 μH to 1 mH.

[0012] A vehicle may use a device under test. The vehicle will include a high voltage traction battery, a power control circuit connected to the high voltage traction battery and a motor. A power integrated circuit is provided, the performance of which can be measured by the following operations: estimating the range of inductor current contribution after the device under test connected to an inductive load having an air core inductor is turned on during a low current and high voltage period, and subtracting the estimated inductor current contribution from the collector current of the device under test to output a corrected collector current. The vehicle may also have a controller for estimating the power in the high voltage traction battery.

[0013] In an example embodiment of a vehicle, estimating the inductor current includes sensing a first voltage across a power supply capacitor, sensing a second voltage across the device under test, and using the first voltage and the second voltage to estimate a current change in the inductor.

[0014] In an example embodiment, the inductor is an air core inductor in any of the above example embodiments.

[0015] In an exemplary embodiment, the inductor used in any one of the exemplary embodiments described above has an inductance of about 1 μH to 1 mH or an inductance of about 10 μH to 20 μH.

[0016] According to the present invention, there is provided a vehicle, the vehicle comprising: a traction battery; a power control circuit connected to the traction battery and a motor and comprising a power integrated circuit, the performance of the power integrated circuit being measured by: estimating a range of inductor current contribution after a device under test connected to an inductive load having an air-core inductor is turned on during a low-current high-voltage period, and subtracting the estimated inductor current contribution from a collector current of the device under test to output a corrected collector current; and a controller for estimating power in the traction battery.

[0017] According to an embodiment of the present invention, the corrected collector current is based on a first sensed voltage across a power supply capacitor and a second sensed voltage across the device under test.

[0018] According to one embodiment of the present invention, the change of the current flowing through the inductive load is L , the first sensing voltage v dc and the second sensing voltage v ce are related according to the following equation:

[0019]

[0020] Wherein, L is the inductance of the inductive load.

[0021] According to an embodiment of the present invention, the inductive load has an inductance of about 1 μH to 1 mH.

[0022] According to an embodiment of the present invention, the inductance is 10 μH to 20 μH.

[0023] According to one embodiment of the present invention, the inductor current is based on a first voltage set as a constant to represent a power supply voltage and a second voltage across the device under test, and the controller is further configured to derive a current change of the inductor based on the first voltage and the second voltage.

[0024] According to one embodiment of the present invention, the change of the current flowing through the inductive load is L , the first voltage v dc and the second voltage v ce are related according to the following equation:

[0025]

[0026] Wherein, L is the inductance of the inductive load.

[0027] According to an embodiment of the present invention, the inductive load has an inductance of 1 μH to 1 mH.

[0028] According to the present invention, there is provided a vehicle comprising: a traction battery; a power control circuit connected to the traction battery and an electric machine and comprising a power integrated circuit having switching losses, wherein the power integrated circuit has switching losses estimated by a double pulse test when the power integrated circuit is connected to an air core inductor acting as an inductive load with devices of the power integrated circuit in an on state; and a controller configured to estimate a remaining charge of the traction battery based on the switching losses, the switching losses being corrected using a corrected collector current estimate from the double pulse test.

[0029] According to an embodiment of the invention, the power integrated circuit is a switch controllably connecting the traction battery to the motor, and wherein the double pulse test is operated to output a corrected collector current derived from a difference between a collector current of the device obtained after the device is turned on and an inductor current obtained after the device is turned on.

[0030] According to one embodiment of the present invention, the change of the current flowing through the inductive load is L , the first voltage v dc and the second voltage v ce are related according to the following equation:

[0031]

[0032] Wherein, L is the inductance of the inductive load.

[0033] According to an embodiment of the present invention, the inductive load has an inductance of 1 μH to 1 mH or an inductance of 10 μH to 20 μH. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1A is a schematic diagram of a testing system according to an example embodiment.

[0035] Figure 1B is a schematic diagram of a testing system according to an example embodiment.

[0036] Figure 2 is a graph of the test waveform.

[0037] Figure 3 is a graph of a test waveform after correction according to an example embodiment.

[0038] Figure 4 is a schematic diagram of an electric vehicle according to an example embodiment.

[0039] Figure 5 is a schematic diagram of an electrical system for a vehicle according to an example embodiment.

[0040] Figure 6 is a flow chart of a method for double pulse testing according to an example embodiment. DETAILED DESCRIPTION

[0041] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present invention, which may be implemented in various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present invention in various ways.

[0042] Double pulse testing provides a method and system for testing the gate drive and dynamic behavior of power electronic components under various conditions using almost negligible power. The method and system described herein can be used to test the power circuit and power circuit elements of electric vehicles or hybrid vehicles. The power electronic components switch to provide a voltage of 100 volts or more from the traction battery. Double pulse testing can perform testing on the device under test using a test signal with double pulses. In double pulse testing of the device under test (DUT), the test device usually includes a large magnetic inductor with a magnetic core to provide a load that approximates the current source fed to the DUT. This large inductor will be used to ensure that the current is almost flat in steady state during switching transients in the DUT. However, such an inductor introduces disadvantages during testing, for example, the inductance of such an inductor varies with the current level, and such an inductor can be saturated at higher currents. Switching loss evaluation of a DUT using double pulse testing usually requires a wide current level range (e.g., 1A to 1000A), and therefore, an inductor with a magnetic core is not an ideal candidate for such an application. Therefore, air core inductors can be used in systems for testing. Air core inductors can provide various benefits. Air core inductors have a substantially constant inductance over a wide range of current levels. In various examples, the inductance can be about 10.0 μH (+ / - 0.5 μH or + / - 1.0 μH). In an example, the inductance is up to about 20 μH (+ / - 0.5 μH or + / - 1.0 μH). In an example, the inductance is up to about 80 μH (+ / - 0.5 μH or + / - 1.0 μH). In an example, the inductance can be about 1 μH to 1 mH (with a deviation of + / - 5% or + / - 10%). The inductor can provide an inductance in the range of about 10 μH to about 20 μH (with a deviation of + / - 10%). The inductor may provide an inductance in the range of about 10 μH to about 40 μH (with a deviation of + / - 10%) or an inductance in the range of about 10 μH to about 80 μH (with a deviation of + / - 10%). Air core inductors do not have saturation problems because air core inductors do not have a magnetic core. However, air core inductors introduce the disadvantage of low energy density resulting in large size and low inductance.

[0043] In order to ensure that the current is almost constant during switching transients during the test, the load inductance is very high to meet the requirements of the low current, high voltage operating point. As a result, the volume of the inductor is large, and therefore the electrical energy stored in the inductor is also large. However, this results in a long time to ramp up the current at the high current and low voltage operating point. This also requires a large amount of voltage compensation lost during the charging of the inductor. In order to address the shortcomings of air-core inductors, different air-core inductors (each air-core inductor has a different inductance) are used for different operating conditions. For example, a small inductor is selected for low current situations, while a large inductor is selected for high current situations. The inventors of the present application have found a need for a test system with a single air-core inductor that results in a compact test device. However, a single air-core inductor is a non-ideal current source. The inventors of the present application have also found a need to correct the behavior of the non-ideal current source of a single air-core inductor.

[0044] Figure 1A A schematic diagram of a double pulse test system 100 is shown including a device under test (DUT) 101 connected to an inductive load 103. A high voltage DC power supply 105 provides the main power for the test. A drive circuit 107 receives a switch signal from a processor 110 and provides a gate signal to the device under test 101. The inductive load 103 includes a single relatively small air core inductor with minimal parasitic capacitance.

[0045] The double pulse test can be performed in a half-bridge topology, and the behavior of the device under test 101 (e.g., an insulated gate bipolar transistor (IGBT)) is tested under different load conditions using diodes in the corresponding half-bridge. The double pulse test can test the gate drive and dynamic behavior of the power electronic components under various conditions using almost negligible power. The double pulse test can test the device behavior at different temperature levels, short circuit behavior, short circuit shutdown, gate drive behavior, RG ON and RG OFF Adjustment of the diodes, overvoltage behavior at cutoff, current distribution in parallel connection, diode recovery, measurement of switching energy and other tests.

[0046] Figure 1B A double pulse test circuit 120 is shown for testing a DUT 101. The voltage across the DUT is measured as v ce The inductor 123 is connected in parallel with the upper device 127 of the half bridge. The voltage across the inductor is v L Inductor 123 may be a single relatively small air core inductor with minimal parasitic capacitance. The current flowing through inductor 123 is i LThe upper device 127 of the half bridge may include a high voltage switch (e.g., an IGBT with a reverse mounted diode connected across it or just a diode). The power supply is shown as a capacitor 125. The voltage across capacitor 125 is v dc The first positive node 128 is connected to the positive terminal of the inductor 123, the positive terminal of the capacitor 125, and the positive terminal of the half-bridge upper device 127. The negative terminal of the DUT 101 is connected to the negative terminal of the capacitor 125. The processor 110 may include circuits for calculating the electrical properties of the DUT or other electrical signals in the system 100.

[0047] Inductor 123 may be an air core inductor for double pulse testing. Inductor 123 includes an inductance that is approximately constant over a wide range of current levels (e.g., 1A to 1000A) during testing. Since inductor 123 does not have a magnetic core, inductor 123 does not have the saturation problem of magnetic core inductors. However, air core inductors have their own disadvantages, which are low energy density resulting in large volume and small inductance. In order to ensure that the current is almost constant during switching transients, the load inductance at inductor 123 is very high in order to meet the requirements at low current, high voltage operating points. As a result, the inductor volume is large and the energy stored in the inductor is also large. However, this results in a long time to ramp up the current at high current, low voltage operating points, and requires a large amount of voltage compensation lost during inductor charging. To solve this problem, different air core inductors (each air core inductor has a different inductance) are used for different operating conditions. In other words, a small inductance is selected for low current situations, while a large inductance is selected for high current situations.

[0048] Figure 2 A graph 200 of the resulting waveform from a double pulse test system is shown without correction using a single relatively small air core inductor with minimal parasitic capacitance. For extreme cases (such as low current, high voltage cases), the DUT 101 turn-on collector current may have a very steep slope after the DUT reverse recovery current peak due to the low inductance selected for the inductor 123. The steep slope may represent the high level portion of the sensed electrical signal that causes the current to rise over time. The DUT turns on at time t1 when the collector current begins to rise rapidly. After the current reaches the load current, the current does not level off but overshoots beyond the load current due to the reverse recovery current of the upper device of the half bridge. However, after the current overshoot / reverse recovery current, between time t2 and t3 (Δt), the load current continues to rise when it should be constant.

[0049] Figure 3Graph 300 shows the resulting waveform from a double pulse test system with load current correction. That is, the current is substantially flat between times t2 and t3 (Δt). The flat portion of the sensed waveform shown in graph 300 is Figure 3 The flat portion of the sensed waveform shown in Figure 300 is relative to Figure 2 The uncorrected similar region of is flat. The contribution of the inductor to the current can be estimated using the following equation. The change in current through the inductive load during Δt can be subtracted from the current through the DUT during Δt. L , to change waveform 200 so that waveform 200 is converted to waveform 300. The value of the inductor is L. The time is t. If v dc If it is not measured or cannot be measured, then v ce Come to v dc Approximate calculation.

[0050]

[0051] The inductor current can be estimated using the voltage value measured in the test system 100. In operation, the first voltage is set to a constant to represent the power supply voltage. In various examples, the first voltage can be set to the high level portion of the extracted sensed second voltage. Here, v ce The high level portion can be used as the voltage v dc .v ce The high level portion of occurs before the DUT is turned on, for example, before time t1 in graphs 200 and 300. That is, the voltage can be associated with the value during the current increase (e.g., the slope of graph 200). In another example, a second voltage across the device under test can be measured. These two voltages can be used to estimate the current change of the inductor (e.g., the current change shown in graph 200), and the current change of the inductor can be subtracted to output a modified graph 300.

[0052] Figure 4A plug-in hybrid electric vehicle or electric vehicle 412 is shown that may include one or more motors 414 mechanically connected to a hybrid transmission 416. The motor 414 can operate as a motor or a generator. For a hybrid vehicle, the transmission 416 is mechanically connected to an internal combustion engine 418. The transmission 416 is also mechanically connected to a drive shaft 420, wherein the drive shaft 420 is mechanically connected to wheels 422. The motor 414 can provide propulsion and deceleration capabilities when the engine 418 is turned on or off. The motor 414 also acts as a generator and can provide fuel economy benefits by recovering energy that is usually lost as heat in the friction braking system. Under certain conditions, the motor 414 can also reduce vehicle emissions by allowing the engine 418 to operate at a more efficient speed and allowing the hybrid electric vehicle 412 to operate in an electric mode when the engine 418 is turned off. Similar advantages can be obtained for electric vehicles that do not include an internal combustion engine 418.

[0053] The traction battery or battery pack 424 stores energy that can be used by the motor 414. The vehicle battery pack 424 generally provides a high voltage DC output. The traction battery 424 is electrically connected to one or more power electronics modules. One or more contactors (not shown) can isolate the traction battery 424 from other components when disconnected, and can connect the traction battery 424 to other components when closed. The power electronics module 426 is also electrically connected to the motor 414 and provides the ability to transfer electrical energy bidirectionally between the traction battery 424 and the motor 414. For example, a typical traction battery 424 can provide a DC voltage, and the motor 414 can require a three-phase AC current to operate. The power electronics module 426 can convert the DC voltage into the three-phase AC current required by the motor 414. In the regenerative mode, the power electronics module 426 can convert the three-phase AC current from the motor 414 used as a generator into the DC voltage required by the traction battery 424. The description here is also applicable to pure electric vehicles. For pure electric vehicles, the hybrid transmission 416 can be a gearbox connected to the motor 414, and as previously described, the engine 418 can be omitted. The power electronics module 426 may include a plurality of power integrated circuits (eg, IGBTs) that are tested according to the systems and methods described herein.

[0054] The traction battery 424 can provide energy for other vehicle electrical systems in addition to providing energy for propulsion. A typical system may include a DC / DC converter module 428, wherein the DC / DC converter module 428 converts the high voltage DC output of the traction battery 424 to a low voltage DC supply compatible with other vehicle loads. Other high voltage loads (such as compressors and electric cabin or component heaters) can be connected directly to the high voltage without using the DC / DC converter module 428. The low voltage system can be electrically connected to an auxiliary battery 430 (e.g., a 12V battery or a 24V battery).

[0055] Embodiments of the present disclosure may include a vehicle such as a vehicle 412, which may be a hybrid vehicle, a range-extended hybrid vehicle, an electric vehicle, or a plug-in hybrid vehicle that can recharge a traction battery 424 via an external power source 436. The external power source 436 may be connected to an electrical outlet. The external power source 436 may be electrically connected to an electric vehicle supply equipment (EVSE) 438. The EVSE 438 may provide circuitry and controls for regulating and managing energy transfer between the power source 436 and the vehicle 412. The external power source 436 may provide DC power or AC power to the EVSE 438. The EVSE 438 may have a charging connector 440 for plugging into a charging port 434 of the vehicle 412. The charging port 434 may be any type of port configured to transfer power from the EVSE 438 to the vehicle 412. The charging port 434 may be electrically connected to a charger or an onboard power conversion module 432. The power conversion module 432 may condition the power supplied from the EVSE 438 to provide the appropriate voltage level and current level to the traction battery 424. The power conversion module 432 may interface with the EVSE 438 to coordinate the transfer of power to the vehicle 412. The EVSE charging connector 440 may have pins that mate with corresponding recesses of the charging port 434. Alternatively, the various components described as being electrically connected may transfer power using wireless inductive coupling. The power conversion module 432 may include power solid-state circuits (e.g., IGBTs) that may be tested according to the systems and methods described herein.

[0056] The various components shown in FIG. 1 may have one or more associated controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus (e.g., a controller area network (CAN)) or via discrete conductors. One or more controllers may also operate in an independent manner without communicating with one or more other controllers. For example, one of the controllers may be implemented by a battery energy control module (BECM) 446 to control various charging and discharging functions and battery cell charge balancing. The BECM 446 may be disposed in the traction battery pack 424 and may be connected to one or more sensor modules to sense the voltage across the ultracapacitor.

[0057] Vehicle traction battery packs can be constructed from a variety of chemistries. Typical battery pack chemistries include lead-acid, nickel-metal hydride (NIMH), or lithium-ion (Li-Ion). Other traction battery chemistries may also be used.

[0058] Figure 5 An electrical system for a hybrid vehicle or electric vehicle is shown. A low voltage auxiliary battery 430 can provide electrical energy to a controller 501 via a low voltage power supply 510. A high voltage battery 424 is a traction battery and provides electrical energy for driving a vehicle 412. A DC-link capacitor 511 smoothes the electrical signal from the high voltage battery 424 to a switch stage 515. The switch stage 515 can act as an inverter for supplying an electrical drive signal to a motor 414 that provides power to the vehicle 412. The switch stage 515 can include a power integrated circuit (e.g., an IGBT). The switch stage 515 should be designed to minimize switching losses and maximize thermal efficiency. The inverter 515 not only drives the electric motor 414, but also captures energy released by regenerative braking and feeds the energy back to the high voltage battery 424. The switch stage 515 and its individual components can be tested using the systems and methods described herein to minimize switching losses. The phase current and phase voltage measurement stage 503 measures the electrical signals output from the switching stage 515 and outputs the results to the controller 501. The controller 501 may use the measurements from the measurement stage 503 to output control signals to the drive stage 505, which in turn controls the operation of the switching stage 515. The controller 501 may also use the phase current measurements and / or phase voltage measurements from the measurement stage 503 to control the drive stage 505.

[0059] The vehicle 412 may include a connected power control circuit that includes a device under test (DUT) as described herein. The DUT may include an electronic power device (e.g., a switch, an IGBT, a FET, etc.). Using the system and structure for double pulse testing described herein, the switching losses of the electronic power device may be estimated. The double pulse test may be performed using an air core inductor acting as an inductive load to correct for the collector current estimate or other losses of the DUT in the on state. The controller (e.g., BECM 446 or other vehicle processing circuit) may use the losses estimated by the double pulse test to estimate the remaining charge of the traction battery. More accurate estimates of the losses (e.g., by knowing the exact behavior of the DUT or the exact behavior of each DUT in the vehicle) may result in more accurate estimates of the SOC, charging reminders, or remaining mileage. These are desired by the vehicle operator.

[0060] Figure 6 A method 600 is shown for double pulse testing with a test system having only a single relatively small air core inductor with minimal parasitic capacitance used as a load. At 601, a double pulse test is initiated. At 602, a voltage v across a power supply capacitor may be performed. dc At 603, the voltage v across the DUT is measured. ce At 604, the current i flowing through the DUT is measured. c At 605, the current change across the inductive load is calculated using the above formula. At 606, a corrected current is obtained by subtracting the calculated current change from the sensed current. At 607, the final corrected current is output (e.g., to a display on an electrical device connected to a computer). The display may show the same Figure 3 and Figure 4 Although method 600 may be performed in sequential steps, some steps (eg, steps 602 to 604) may be performed in any order or simultaneously.

[0061] The focus of this description is on DUT on operation. It will be appreciated that this similar procedure can be performed for DUT off. Similar calculations can be performed to correct for changes in the current across the DUT.

[0062] Such compensation is not required for the operation of the diode during on or off periods, since the voltage across the inductor during diode conduction is as small as the diode conduction voltage, which is a few volts. Therefore, the change in current Δi during diode conduction is very small.

[0063] It is believed that the use of a single small air core inductor (which occupies only a small volume and is lightweight) can be used for a variety of operating conditions without changing the inductor. By compensating for the inductor rise current, the highest accuracy in the calculation of switching losses can be ensured. The inductor can provide an inductance of about 10 μH to about 20 μH or an inductance in the range of 1 μH to 1 mH or other inductance values.

[0064] The double pulse test described herein can be used to determine various properties of the device under test. The properties may include device behavior at different temperature levels, short circuit behavior and short circuit cutoff, gate drive behavior, gate resistance on or gate resistance off adjustment, overvoltage behavior when the device is off (e.g., adjustment of active clamping), current distribution when connected in parallel, diode recovery or switching energy measurement. The double pulse test described herein can be used with power electronic devices (e.g., IGBT) or with other electronic devices (e.g., MOSFET).

[0065] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the present invention. Specifically, the words used in the specification are descriptive words rather than restrictive words, and it should be understood that various changes can be made without departing from the spirit and scope of the present invention. In addition, the features of the various embodiments of implementation can be combined to form further embodiments of the present invention.

Claims

1. A double pulse test method, comprising: The following operations are performed by the processor: operating the device under test according to a double pulse test arrangement, the device under test being connected to an inductive load defined by an air core inductor; outputting a corrected collector current of the device under test, the corrected collector current being derived from a difference between the collector current of the device under test measured after the device under test is turned on and a change in the current flowing through the inductive load, The change in current is based on a first sensed voltage across a power supply capacitor and a second sensed voltage across the device under test.

2. The double pulse test method according to claim 1, wherein: The change of the current di L , the first sensing voltage v dc and the second sensing voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

3. The double pulse test method according to claim 1 or 2, wherein: The inductive load has an inductance of approximately 10 μH to 20 μH.

4. A double pulse test method, comprising: The following operations are performed by the processor: operating the device under test according to a double pulse test arrangement, the device under test being connected to an inductive load defined by an air core inductor; outputting a corrected collector current of the device under test, the corrected collector current being derived from a difference between the collector current of the device under test measured after the device under test is turned on and a change in the current flowing through the inductive load, The change in the current is based on a first voltage set as a constant to represent a power supply voltage and a second voltage across the device under test.

5. The double pulse test method as claimed in claim 4, wherein: A second voltage across the device under test is sensed, and the first voltage and the second voltage are used to estimate the change in the current.

6. The double pulse test method as claimed in claim 5, wherein: The change of the current di L , the first voltage v dc and the second voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

7. The double pulse test method according to any one of claims 4 to 6, wherein: The inductive load has an inductance of approximately 10 μH to 20 μH.

8. The double pulse test method according to claim 4, wherein: The first voltage is set to a high level portion extracted from the sensed second voltage.

9. A vehicle comprising: Traction batteries; a power control circuit connected to the traction battery and the motor and including a power integrated circuit having a device under test electrically connected to an inductive load defined by an air core inductor; a controller configured to operate the device under test according to a double pulse test arrangement and output a corrected collector current of the device under test, the corrected collector current being derived from a difference between the collector current of the device under test obtained after the device under test is turned on and a change in a current flowing through the inductive load, The change in current is based on a first sensed voltage across a power supply capacitor and a second sensed voltage across the device under test.

10. The vehicle of claim 9, wherein: The change of the current di L , the first sensing voltage v dc and the second sensing voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

11. The vehicle of claim 9, wherein: The device under test has switching losses estimated by double pulse testing, and an air core inductor is used as an inductive load to correct the collector current estimate of the device under test in the on state; The controller is further configured to use the switching loss to estimate a remaining charge of a traction battery.

12. The vehicle of claim 11, wherein: The power integrated circuit is a switch that controllably connects the traction battery to the electric machine.

13. The vehicle of claim 12, wherein: The change of the current di L , the first sensing voltage v dc and the second sensing voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

14. A vehicle as claimed in any one of claims 9 to 13, wherein: The inductive load has an inductance of 10 μH to 20 μH.

15. A vehicle comprising: Traction batteries; a power control circuit connected to the traction battery and the motor and including a power integrated circuit having a device under test electrically connected to an inductive load defined by an air core inductor; a controller configured to operate the device under test according to a double pulse test arrangement and output a corrected collector current of the device under test, the corrected collector current being derived from a difference between the collector current of the device under test obtained after the device under test is turned on and a change in a current flowing through the inductive load, The change in current is based on a first voltage set as a constant to represent a power supply voltage and a second voltage across the device under test, wherein the controller is further configured to derive the change in current based on the first voltage and the second voltage.

16. The vehicle of claim 15, wherein: The change of the current di L , the first voltage v dc and the second voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

17. The vehicle of claim 15, wherein: The device under test has switching losses estimated by double pulse testing, and an air core inductor is used as an inductive load to correct the collector current estimate of the device under test in the on state; The controller is further configured to use the switching loss to estimate a remaining charge of a traction battery.

18. The vehicle of claim 17, wherein: The power integrated circuit is a switch that controllably connects the traction battery to the electric machine.

19. The vehicle of claim 18, wherein: The change of the current di L , the first voltage v dc and the second voltage v ce are related according to the following equation: Wherein, L is the inductance of the inductive load.

20. A vehicle as claimed in any one of claims 15 to 19, wherein: The inductive load has an inductance of 10 μH to 20 μH.

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