System and method for gate threshold voltage measurement

Abstract

To provide a measurement circuit for predicting a potential future failure of a power transistor.SOLUTION: The measurement circuit 290 includes a current source 312 that supplies a current to the drain terminal 231 of the transistor 230, a voltage measurement circuit 320 that measures a drain-source voltage of the transistor 230, and a regulator circuit 330. The regulator circuit receives a voltage measurement signal VDS_MEAS indicative of a drain-source voltage of the transistor from the voltage measurement circuit and adjusts a gate-source voltage of the transistor based on the drain-source voltage of the transistor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates generally to integrated circuit technology, and more particularly to measuring the threshold voltage of a transistor. [Background technology]

[0002] Power transistors may be utilized in a variety of power electronics applications, such as drivers for electric motors. In such applications, the continuous thermal cycling associated with repeatedly turning the power transistor on and off can lead to degradation of the power transistor. For example, continuous thermal cycling of the power transistor can degrade the gate oxide of the power transistor, ultimately leading to failure.

[0003] The inventors of embodiments of the present disclosure have recognized that certain electrical characteristics of power transistors, such as gate threshold voltage, can indicate device degradation and thus predict potential future failures. The inventors of embodiments of the present disclosure have also recognized that the ability to monitor certain electrical characteristics of power transistors while still coupled within a high-level application circuit can be limited. Embodiments of the present disclosure may address one or more of these challenges. [Brief explanation of the drawings]

[0004] A more complete understanding of the present embodiments can be obtained by reference to the following description in conjunction with the accompanying drawings, in which like reference numerals indicate like features and in which: [Figure 1] 1 shows a schematic diagram of a gate threshold test circuit according to an embodiment of the present disclosure. [Figure 2] 1 shows a schematic diagram of a motor drive circuit according to an example embodiment of the present disclosure. [Figure 3] 1 illustrates a block diagram of a measurement circuit according to an example embodiment of the present disclosure. [Figure 4] 1 shows a schematic diagram of a measurement circuit according to an example embodiment of the present disclosure. [Figure 5]1 illustrates operation of a method for measuring a gate threshold voltage of a transistor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] The details of one or more embodiments are set forth in the following description and the accompanying drawings. Other features will be apparent from the description and drawings, and from the claims.

[0006] 1 shows a schematic diagram of a gate threshold test circuit 100 according to an embodiment of the present disclosure. The gate threshold test circuit 100 may include a current source 110 and a transistor 120. The current source 110 generates a test current I with a value of, for example, 1 mA, 10 mA, 50 mA, 100 mA, 150 mA, 200 mA, 250 mA, or more. test The transistor 120 may include a drain terminal 121, a source terminal 122, and a gate terminal 123. To test the gate threshold voltage of the transistor 120, the current source 110 may be configured to provide a test current I test may be coupled to provide a drain terminal 121 of transistor 120, a gate terminal 123 may be coupled to drain terminal 121, and a source terminal 122 may be coupled to ground GND. By coupling gate terminal 123 to drain terminal 121, a test current I from current source 110 is generated. test A bias voltage sufficient to drive transistor 120 at a level sufficient to sink the test current I can be generated at gate terminal 123. test The level of bias voltage required at gate terminal 123 to drive transistor 120 to sink a given value of V may be referred to as the gate threshold voltage VGTH of transistor 120.

[0007] The gate threshold voltage VGTH of a transistor can change over the lifetime of the transistor. For example, during repeated use in high-power applications, the gate oxide of a transistor such as transistor 120 can degrade over time. Gate oxide degradation can increase the gate threshold voltage VGTH of a transistor such as transistor 120. The inventors of embodiments of the present disclosure have recognized that it is beneficial to test the gate threshold voltage VGTH of a transistor such as transistor 120 over the lifetime of the transistor when included in a high-power application.

[0008] FIG. 2 shows a schematic diagram of a motor drive circuit 200 according to an embodiment of the present disclosure. The motor drive circuit 200 may include a DC voltage source 202, an inverter circuit 204, and a motor 206. The motor 206 may be an electric motor. The DC voltage source 202 may provide a DC voltage of, for example, 400 V, 800 V, or more across a positive supply rail VDC+ and a negative supply rail VDC−. The inverter circuit 204 may include multiple transistors configured to drive the motor 206. For example, the inverter circuit 204 may include transistors 230, 240, 250, 260, 270, and 280. As shown in FIG. 2, the inverter circuit 204 may be configured as a three-phase inverter. For example, transistors 230 and 240 may be coupled in series between VDC+ and VDC− to form a first half-bridge that drives motor 206, transistors 250 and 260 may be coupled in series between VDC+ and VDC− to form a second half-bridge that drives motor 206, and transistors 270 and 280 may be coupled in series between VDC+ and VDC− to form a third half-bridge that drives motor 206.

[0009] The inverter circuit 204 may also include a gate drive circuit 220. The gate drive circuit 220 may include a plurality of gate drivers 221 and 222 and a plurality of corresponding switches 226 and 227. The plurality of gate drivers 221 and 222 may be configured to respectively drive a plurality of transistors during an operation phase of the inverter circuit 204. For example, the gate drive circuit 220 may include a gate driver 221a coupled to drive the gate of transistor 230 via a switch 226a, a gate driver 221b coupled to drive the gate of transistor 250 via a switch 226b, and a gate driver 221c coupled to drive the gate of transistor 270 via a switch 226c. In the present disclosure, each of the gate drivers 221a-c may also be referred to as a high-side gate driver. Further, gate drive circuit 220 may include gate driver 222a coupled to drive the gate of transistor 240 via switch 227a, gate driver 222b coupled to drive the gate of transistor 260 via switch 227b, and gate driver 222c coupled to drive the gate of transistor 280 via switch 227c. In this disclosure, each of gate drivers 222a-c may also be referred to as a low-side gate driver. During an operation phase of inverter circuit 204, switches 226a-c and 227a-c may be enabled such that switches 226a-c and 227a-c, respectively, are in an on state, thereby enabling gate drivers 221a-c and gate drivers 222a-c to drive their respective transistors. For example, during the operating phase of inverter circuit 204, gate drivers 221a-c and gate drivers 222a-c may drive their respective transistors, including transistors 230, 250, and 270, and transistors 240, 260, and 280, on and off in a coordinated, repetitive manner to provide three-phase drive to motor 206.Although switches 226a-c and 227a-c are shown as being included within gate drive circuit 220 in the exemplary embodiment shown in FIG. 2, switches 226a-c and 227a-c may also be implemented separately from gate drive circuit 220 in some embodiments.

[0010] Inverter circuit 204 may also include a plurality of measurement circuits 290a, 290b, 290c, 290d, 290e, and 290f (collectively, measurement circuits 290). In some embodiments, each of measurement circuits 290 may be configured to measure the gate threshold voltage of a respective one of a plurality of transistors, including transistors 230, 240, 250, 260, 270, and 280, during an initialization phase of inverter circuit 204. For example, as shown in FIG. 2, measurement circuit 290a may be configured to measure the gate threshold voltage of transistor 230, measurement circuit 290b may be configured to measure the gate threshold voltage of transistor 250, measurement circuit 290c may be configured to measure the gate threshold voltage of transistor 270, measurement circuit 290d may be configured to measure the gate threshold voltage of transistor 240, measurement circuit 290e may be configured to measure the gate threshold voltage of transistor 260, and measurement circuit 290f may be configured to measure the gate threshold voltage of transistor 280.

[0011] Prior to the inverter circuit 204 operating phase in which the inverter circuit 204 drives the motor 206, the inverter circuit 204 may undergo an initialization phase. During this initialization phase, the gate thresholds of one or more of the transistors 230, 240, 250, 260, 270, and 280 may be measured. For example, the gate thresholds of the transistors 230, 240, 250, 260, 270, and 280 may be measured one at a time. When the gate threshold voltage of one transistor is being measured, the other transistors may be held in an off state so as not to interfere with the measurement of the other transistor. Additionally, the gate driver corresponding to the switch under test may be disabled to prevent the corresponding gate driver from interfering with the gate threshold voltage measurement. For example, when the gate threshold voltage of transistor 230 is being measured during the initialization phase of inverter circuit 204, switch 226a may be placed in an off state to effectively disable gate driver 221a, thereby preventing gate driver 221a from interfering with measurement circuit 290a's measurement of the gate threshold voltage of transistor 230. Additionally, transistors 240, 250, 260, 270, and 280 may each be held in an off state by their respective gate drivers so as not to interfere with the measurement of transistor 230's gate threshold voltage.

[0012] In some embodiments, the gate threshold voltage of each of transistors 230, 240, 250, 260, 270, and 280 may be measured one by one during an initialization phase of inverter circuit 204 and reported to a processing unit (not shown in FIG. 2). Each gate threshold measurement may be compared to an expected value. A gate threshold voltage value that is greater than expected may indicate, for example, degradation and potential future failure of the measured transistor.

[0013] After the initialization phase, inverter circuit 204 may proceed to an operation phase. During the operation phase, gate drivers 221a-c and 222a-c of gate drive circuit 220 may repeatedly turn transistors 230, 240, 250, 260, 270, and 280 on and off in a coordinated manner to provide three-phase drive to motor 206. As described in further detail below with reference to FIG. 3 , each measurement circuit 290 may measure the on-state drain-source voltages of transistors 230, 240, 250, 260, 270, and 280 during the operation phase of inverter circuit 204, in addition to measuring the gate threshold voltages of transistors 230, 240, 250, 260, 270, and 280 during the initialization phase of inverter circuit 204. The drain-source voltages of transistors 230, 240, 250, 260, 270, and 280 may be reported to a processing unit (not shown in FIG. 2 ). Similar to the measured gate threshold voltage, a measured on-state drain-source voltage that differs from the expected on-state drain-source voltage can indicate degradation and potential future failure of the measured transistor.

[0014] In some embodiments, the transistors of inverter circuit 204, including transistors 230, 240, 250, 260, 270, and 280, may each comprise a metal-oxide-semiconductor field-effect transistor (MOSFET). Transistors 230, 240, 250, 260, 270, and 280 may each comprise, for example, a silicon carbide (SiC) MOSFET. In other embodiments, the transistors of inverter circuit 204, including transistors 230, 240, 250, 260, 270, and 280, may each comprise a silicon insulated gate bipolar transistor (IGBT). IGBTs are sometimes referred to as having gate, collector, and emitter terminals, as opposed to the respective gate, drain, and source terminals of MOSFETs. However, the principles of embodiments of the present disclosure may apply equally whether transistors 230, 240, 250, 260, 270, and 280 are implemented as MOSFETs or IGBTs. Therefore, in this disclosure, the term "drain" or "drain terminal" may refer to either the drain or drain terminal of a MOSFET or the collector or collector terminal of an IGBT. Furthermore, in this disclosure, the term "source" or "source terminal" may refer to either the source or source terminal of a MOSFET or the emitter or emitter terminal of an IGBT. For example, in this disclosure, a term such as the "drain-source" voltage of a transistor may refer to either the drain-source voltage of a MOSFET or the collector-emitter voltage of an IGBT. Similarly, in this disclosure, a term such as the "gate-source" voltage of a transistor may refer to either the gate-source voltage of a MOSFET or the gate-emitter voltage of an IGBT.

[0015] In some embodiments, one or more instances of measurement circuit 290 may be implemented either on a separate semiconductor die or on the same monolithic semiconductor die as one or more gate drivers, such as high-side gate drivers 221a-c and low-side gate drivers 222a-c of gate drive circuit 220. In embodiments in which one or more instances of measurement circuit 290 may be implemented on a separate semiconductor die from the respective one or more gate drivers, one or more instances of measurement circuit 290 may be packaged with one or more respective gate drivers within the same multi-die integrated circuit package. Additionally, one or more instances of measurement circuit 290 and the corresponding gate drivers may be further co-packaged within one or more transistors, such as transistors 230, 240, 250, 260, 270, and 280, within a multi-die integrated circuit package, whether implemented on the same monolithic semiconductor die or on separate semiconductor dies.

[0016] 3 shows a block diagram of an instance of measurement circuit 290 according to an embodiment of the present disclosure. For simplicity, a single instance of measurement circuit 290 is shown in FIG. 3. However, as described above with reference to FIG. 2, separate instances of measurement circuit 290 may be utilized to measure the gate threshold voltages of each of transistors 230, 240, 250, 260, 270, and 280. Furthermore, although measurement circuit 290 may be described herein as measuring the gate threshold voltages (and on-state drain-source voltages) of transistors such as transistors 230, 240, 250, 260, 270, and 280 included within inverter circuit 204, measurement circuit 290 may also be utilized to measure the gate threshold voltages of transistors included in other forms of power electronics, such as transistors used in half-bridge or full-bridge power converter topologies or other motor driver topologies.

[0017] Measurement circuit 290 may be implemented in any suitable manner in accordance with the operations described in this disclosure. In some embodiments, measurement circuit 290 may include a current source 312, a diode 314, a voltage measurement circuit 320, and a regulator circuit 330. In some embodiments, measurement circuit 290 may also include an analog-to-digital converter 340.

[0018] The current source 312 may provide a test current I with a value of, for example, 1 mA, 10 mA, 50 mA, 100 mA, 150 mA, 200 mA, 250 mA, or more. test 3, current source 312 may be coupled in series with diode 314, which may in turn be coupled to drain terminal 231 of transistor 230. Thus, when enabled by the ENABLE signal, current source 312 provides a test current I test may be provided to drain terminal 231. Although current source 312 and diode 314 are shown in FIG. 3 as separate from voltage measurement circuit 320, current source 312 and diode 314 may also be considered part of voltage measurement circuit 320. Voltage measurement circuit 320 may be coupled across transistor 230, with a first terminal coupled to drain terminal 231 of transistor 230 and a second terminal coupled to source terminal 232 of transistor 230. Voltage measurement circuit 320 may measure the drain-source voltage of transistor 230 and provide a voltage measurement signal VDS_MEAS. As described above with reference to FIG. 2, when the gate threshold voltage of transistor 230 is being measured, the other transistors of inverter circuit 204, including transistors 240, 250, 260, 270, and 280, may be held in an off state. Thus, the electrical node connected to the source terminal 232 of the transistor 230 may serve as a floating ground for the voltage measurement circuit 320 and other components within the instance of the measurement circuit 290 coupled to the transistor 230 .

[0019] Regulator circuit 330 may include a reference input 331, a feedback input 332, and a gate drive output 333. Regulator circuit 330 may also include an enable input and may be configured to adjust the gate-source voltage of transistor 230 based on the drain-source voltage of transistor 230 in response to an ENABLE signal received at the enable input. When enabled, regulator circuit 330 may be configured to drive gate terminal 233 of transistor 230 based on a comparison of reference input 331 and feedback input 332. For example, regulator circuit 330 may be configured to receive a voltage measurement signal VDS_MEAS indicative of the drain-source voltage of transistor 230 from voltage measurement circuit 320. Specifically, regulator circuit 330 may receive voltage measurement signal VDS_MEAS at reference input 331, such that voltage measurement signal VDS_MEAS can function as a reference voltage for adjusting the gate-source voltage of transistor 230. Gate drive output 333 may be coupled to gate terminal 233 of transistor 230. Feedback input 332 may also be coupled to gate terminal 233 of transistor 230. Based on a comparison of the feedback received at feedback input 332 with the voltage measurement signal VDS_MEAS received at reference input 331, regulator circuit 330 may drive gate terminal 233 of transistor 230 to have the same value as VDS_MEAS. Specifically, regulator circuit 330, in some embodiments, may adjust the gate-source voltage of transistor 230 to be equal to the drain-source voltage of transistor 230, represented by VDS_MEAS. With the gate-source voltage adjusted to be equal to the drain-source voltage, gate terminal 233 of transistor 230 drives test current I received at drain terminal 231. test can be driven to a voltage level sufficient to sink

[0020] By adjusting the gate-source voltage of transistor 230 to be equal to the drain-source voltage of transistor 230, the measured drain-source voltage VDS_MEAS is adjusted to the test current I test 2. The measurement circuit 290 may also represent a measurement of the gate threshold voltage of the transistor 230 at a given value of . Thus, the measurement circuit 290 may be utilized to measure the gate threshold voltage of the transistor 230 when the transistor 230 is included among other devices in a power application, such as the inverter circuit 204.

[0021] In some embodiments, measurement circuit 290 may also include an analog-to-digital converter 340. As shown in FIG. 3, analog-to-digital converter 340 may be coupled to voltage measurement circuit 320. Analog-to-digital converter 340 may be configured to receive voltage measurement signal VDS_MEAS and output a digital signal V_MEAS corresponding to the analog value of voltage measurement signal VDS_MEAS. Thus, digital signal V_MEAS may represent the gate threshold voltage of transistor 230 when current source 312 and regulator circuit 330 are enabled. As described above with reference to FIG. 2, this gate threshold voltage may be measured during an initialization phase of inverter circuit 204 and reported upstream to a processing unit for comparison with an expected gate threshold voltage value.

[0022] In some embodiments, the voltage measurement circuit 320 may also be utilized to measure the on-state drain-source voltage of the transistor 230 during the operation phase of the inverter circuit 204. For example, during the operation phase of the inverter circuit 204, the ENABLE signal may be deasserted to disable the current source 312 and the regulator circuit 330. During the operation phase, the transistor 230 may be repeatedly switched on and off by the gate driver 221a of the gate drive circuit 220, as described above with reference to FIG. 2 . During the on-state of the transistor 230, the voltage measurement circuit 320 may measure the drain-source voltage of the transistor 230. Thus, during this on-state, the voltage measurement signal VDS_MEAS may represent the on-state drain-source voltage of the transistor 230. The analog-to-digital converter 340 may continue to receive the voltage measurement signal VDS_MEAS and provide a digital signal V_MEAS corresponding to the analog value of VDS_MEAS. Thus, during the operation phase of the inverter circuit 204, the digital signal V_MEAS may represent the on-state drain-source voltage of the transistor 230. Also, as discussed above with reference to FIG. 2, this on-state drain-source voltage can be measured during the operation phase of inverter circuit 204 and reported to an upstream processing unit for comparison with an expected on-state drain-source voltage value.

[0023] Thus, measurement circuit 290 can provide a single circuit that can measure and report both the gate threshold voltage of transistor 230 and the on-state drain-source voltage of transistor 230. For example, voltage measurement signal VDS_MEAS can correspond to the gate threshold voltage of transistor 230 when regulator circuit 330 is enabled. Additionally, voltage measurement signal VDS_MEAS can correspond to the on-state drain-source voltage of transistor 230 when transistor 230 is driven by gate driver 221a in the on-state and regulator circuit 330 is disabled.

[0024] FIG. 4 illustrates a schematic diagram of an instance of a measurement circuit 490 according to an embodiment of the present disclosure. The measurement circuit 490 may function as one embodiment of the measurement circuit 290 described above with reference to FIGS. 2 and 3. For simplicity, a single instance of a schematic diagram of the measurement circuit 490 is shown in FIG. 4. However, similar to the description above with reference to FIG. 2, separate instances of a measurement circuit, such as the measurement circuit 490, may be utilized to measure the gate threshold voltages of each of the transistors 230, 240, 250, 260, 270, and 280. Furthermore, although the measurement circuit 490 may be described herein as measuring the gate threshold voltages (and on-state drain-source voltages) of transistors, such as the transistors 230, 240, 250, 260, 270, and 280, included within the inverter circuit 204, the measurement circuit 490 may also be utilized to measure the gate threshold voltages (and on-state drain-source voltages) of transistors included in other forms of power electronics, such as transistors used in half-bridge or full-bridge power converter topologies or other motor driver topologies.

[0025] Measurement circuit 490 may be implemented in any suitable manner consistent with the operations described in this disclosure. In some embodiments, measurement circuit 490 may include voltage measurement circuit 420 and regulator circuit 430. In some embodiments, measurement circuit 490 may also include analog-to-digital converter 340.

[0026] Voltage measurement circuit 420 may function as an embodiment of voltage measurement circuit 320 described above with reference to Figure 3. Voltage measurement circuit 420 may be implemented in any suitable manner consistent with the operation described in this disclosure. In some embodiments, voltage measurement circuit 420 may include current source 402, diode 404, diode 406, amplifier 408, resistor 410, and resistor 412.

[0027] The current source 402 may provide a test current I with a value of, for example, 1 mA, 10 mA, 50 mA, 100 mA, 150 mA, 200 mA, 250 mA, or more. test4, current source 402 may be coupled in series with diode 404 and diode 406, which may then be coupled to drain terminal 231 of transistor 230. Thus, when enabled by an ENABLE signal, current source 402 provides test current I to drain terminal 231 through diode 404 and diode 406. test , can be provided. An amplifier 408 can be utilized to measure the drain-source voltage of transistor 230. For example, amplifier 408 can have a positive input terminal coupled to node 405 between diode 404 and diode 406. Amplifier 408 can also have a negative input terminal coupled to node 403 between current source 402 and diode 404 through resistor 410. Resistor 412 can be coupled between the output terminal of amplifier 408 and the negative input terminal of amplifier 408. Amplifier 408 can compare the voltages at its positive and negative input terminals and provide an output voltage that causes its negative input terminal to equal its positive input terminal. Thus, the voltage across resistor 410 can be equal to the voltage drop across diode 404. Furthermore, resistor 412 can have the same resistance value as resistor 410, and diode 406 can be configured to have the same voltage drop as diode 404. Thus, the feedback network formed by resistors 410 and 412 can cancel the forward voltage drop of diodes 404 and 406. Thus, the output of amplifier 408 can provide a voltage measurement signal VDS_MEAS that is equal to the drain-source voltage of transistor 230.

[0028] 2, when the gate threshold voltage of transistor 230 is being measured, the other transistors of inverter circuit 204, including transistors 240, 250, 260, 270, and 280, may be held in an off state. Thus, the electrical node coupled to source terminal 232 of transistor 230 may serve as a floating ground for voltage measurement circuit 420 and other components within the instance of measurement circuit 490 coupled to transistor 230.

[0029] Regulator circuit 430 may function as one embodiment of regulator circuit 330 described above with reference to FIG. 3. Regulator circuit 430 may be implemented in any suitable manner consistent with the operation described in this disclosure. In some embodiments, regulator circuit 430 may include a reference input 431, a feedback input 432, and a gate drive output 433. Regulator circuit 430 may also include resistor 440, resistor 442, amplifier 444, resistor 446, resistor 448, switch 450, resistor 452, resistor 454, transistor 460, diode 462, and resistor 464.

[0030] Reference input 431 may be coupled to receive voltage measurement signal VDS_MEAS from voltage measurement circuit 420. Resistor 440 and resistor 442 may be coupled in series between reference input 431 and a floating ground coupled to source terminal 232 of transistor 230. Amplifier 444 may have a positive input terminal connected to intermediate node 441 between resistors 440 and 442 and may therefore receive a divided voltage proportional to VDS_MEAS. Feedback input 432 may be coupled to receive a gate voltage applied to gate terminal 233 of transistor 230. Resistors 446 and 448 may be coupled in series between feedback input 432 and a floating ground coupled to source terminal 232 of transistor 230. Amplifier 444 may have a negative input terminal connected to intermediate node 447 between resistors 446 and 448 and therefore may receive a divided voltage proportional to the gate-source voltage of transistor 230. Amplifier 444 may compare the voltages at its positive and negative input terminals and provide the amplifier output voltage to transistor 460 via switch 450 and resistor 454 .

[0031] 4, the output of amplifier 444 may be coupled to the base of transistor 460 via switch 450 and resistor 454. When regulator circuit 430 is enabled by an ENABLE signal, switch 450 may pass the amplifier output to the base of transistor 460 via resistor 454. As shown in FIG. 4, resistor 452 may be coupled between voltage source VCC, and resistor 454 may be coupled between switch 450 and the base of transistor 460. In some embodiments, transistor 460 may be a P-type bipolar junction transistor (P-type BJT or PNP transistor). Transistor 460 may have an emitter coupled to voltage source VCC, a base coupled to the output of amplifier 444 via switch 450 and resistor 452, and a collector coupled to gate drive output 433 via diode 462 and resistor 464. Thus, when regulator circuit 430 is enabled by the ENABLE signal, transistor 460 can drive gate drive output 433 according to the amplifier output voltage of amplifier 444 .

[0032] In some embodiments, a first ratio of the resistance values ​​of resistor 440 to resistor 442 may be equal to a second ratio of the resistance values ​​of resistor 446 to resistor 448. Thus, the voltage division provided by resistors 440 and 442 to the positive input terminal of amplifier 444 may be equal to the voltage division provided by resistors 446 and 448 to the negative input terminal of amplifier 444. Thus, the gate drive voltage provided by regulator circuit 430 at gate drive output 433 (and fed back to amplifier 444 via feedback input 432 and resistors 446 and 448) may be equal to the voltage of voltage measurement signal VDS_MEAS. As shown in FIG. 4 , gate drive output 433 may be coupled to gate terminal 233 of transistor 230. Thus, regulator circuit 430 may adjust the gate-source voltage of transistor 230 to be equal to the drain-source voltage of transistor 230 when regulator circuit 430 is enabled by the ENABLE signal.

[0033] By adjusting the gate-source voltage of transistor 230 to be equal to the drain-source voltage of transistor 230, the measured drain-source voltage VDS_MEAS is adjusted to the test current I test 2. The measurement circuit 490 may also represent a measurement of the gate threshold voltage of the transistor 230 at a given value of . Thus, the measurement circuit 490 may be utilized to measure the gate threshold voltage of the transistor 230 when the transistor 230 is included among other devices in a power application, such as the inverter circuit 204.

[0034] In some embodiments, the measurement circuit 490 may also include an analog-to-digital converter 340. As shown in FIG. 4, the analog-to-digital converter 340 may be coupled to the voltage measurement circuit 420. The analog-to-digital converter 340 may be configured to receive the voltage measurement signal VDS_MEAS and output a digital signal V_MEAS corresponding to the analog value of the voltage measurement signal VDS_MEAS. Thus, the digital signal V_MEAS may represent the gate threshold voltage of the transistor 230 when the regulator circuit 430 is enabled. As described above with reference to FIG. 2, this gate threshold voltage may be measured during an initialization phase of the inverter circuit 204 and may be reported upstream to a processing unit for comparison with an expected gate threshold voltage value.

[0035] In some embodiments, the voltage measurement circuit 420 can also be utilized to measure the on-state drain-source voltage of the transistor 230 during the operation phase of the inverter circuit 204. For example, during the operation phase of the inverter circuit 204, the ENABLE signal may be deasserted to disable the regulator circuit 430. During the operation phase, the transistor 230 may be repeatedly switched on and off by the gate driver 220a of the gate drive circuit 221, as described above with reference to FIG. 2 . During the on-state of the transistor 230, the voltage measurement circuit 420 can measure the drain-source voltage of the transistor 230. Thus, during this on-state, the voltage measurement signal VDS_MEAS can represent the on-state drain-source voltage of the transistor 230. The analog-to-digital converter 340 can continue to receive the voltage measurement signal VDS_MEAS and provide a digital signal V_MEAS corresponding to the analog value of VDS_MEAS. Thus, during the operation phase of the inverter circuit 204, the digital signal V_MEAS can represent the on-state drain-source voltage of the transistor 230. Also, as described above with reference to FIG. 2, this on-state drain-source voltage may be measured during the operation phase of inverter circuit 204 and reported to an upstream processing unit for comparison with an expected on-state drain-source voltage value.

[0036] Thus, measurement circuit 490 can provide a single circuit that can measure and report both the gate threshold voltage of transistor 230 and the on-state drain-source voltage of transistor 230. For example, voltage measurement signal VDS_MEAS may correspond to the gate threshold voltage of transistor 230 when regulator circuit 430 is enabled. Additionally, voltage measurement signal VDS_MEAS may correspond to the on-state drain-source voltage of transistor 230 when transistor 230 is driven by gate driver 221a in the on-state and regulator circuit 330 is disabled.

[0037] FIG. 5 illustrates operation of a method 500 for measuring the gate threshold voltage of a transistor according to an embodiment of the present disclosure. Method 500 may be performed by any suitable mechanism, such as measurement circuit 290, measurement circuit 490, or any combination of their components. Method 500 may be performed with fewer or more steps than shown in FIG. 5. Additionally, steps of method 500 may be omitted, repeated, performed in parallel, performed in a different order than shown in FIG. 5, or performed recursively. One or more steps of method 500, while shown sequentially, may be performed simultaneously or reordered.

[0038] Step 502 may include providing a current to the drain terminal of the transistor. For example, as described above with reference to FIG. 3, current source 312 may provide a test current I to transistor 230 through diode 314. test As another example, as described above with reference to FIG. 4, current source 402 may provide a test current I to transistor 230 through diode 404 and diode 406. test may be supplied.

[0039] Step 504 may include measuring the drain-source voltage of the transistor. For example, as described above with reference to FIG. 3, voltage measurement circuit 320 may measure the drain-source voltage of transistor 230. Voltage measurement circuit 320 may further perform the step of generating a voltage measurement signal VDS_MEAS based on the measured drain-source voltage of transistor 230. As another example, as described above with reference to FIG. 4, voltage measurement circuit 420 may measure the drain-source voltage of transistor 230. Voltage measurement circuit 420 may further perform the step of generating a voltage measurement signal VDS_MEAS based on the measured drain-source voltage of transistor 230.

[0040] Step 506 may include adjusting the gate-source voltage of the transistor based on the drain-source voltage of the transistor. For example, as described above with reference to FIG. 3, regulator circuit 330 may adjust the gate-source voltage of transistor 230 to be equal to the drain-source voltage of transistor 230 represented by voltage measurement signal VDS_MEAS from voltage measurement circuit 320. Specifically, regulator circuit 330 may perform the operation of driving gate terminal 233 of transistor 230 based on a comparison of the gate voltage received at feedback input 332 and voltage measurement signal VDS_MEAS received at reference input 331. As another example, as described above with reference to FIG. 4, regulator circuit 430 may adjust the gate-source voltage of transistor 230 based on the drain-source voltage of transistor 230 represented by voltage measurement signal VDS_MEAS from voltage measurement circuit 420.

[0041] Step 508 may include determining a gate threshold voltage of the transistor based on the measured drain-source voltage of the transistor. For example, by adjusting the gate-source voltage of transistor 230 to be equal to the drain-source voltage of 230, as described above with reference to Figures 3 and 4, the voltage measurement signal VDS_MEAS, which indicates the drain-source voltage, may also represent the gate threshold voltage of transistor 230.

[0042] Step 510 may include converting the analog value of the voltage measurement signal to a digital signal. For example, as described above with reference to Figures 3 and 4, the analog-to-digital converter 340 may generate the digital signal V_MEAS based on the analog value of the voltage measurement signal VDS_MEAS.

[0043] Embodiments herein may include a measurement circuit. The measurement circuit includes a current source configured to supply a current to a drain terminal of the transistor. The measurement circuit further includes a voltage measurement circuit configured to measure a drain-source voltage of the transistor. The measurement circuit further includes a regulator circuit configured to receive a voltage measurement signal indicative of the drain-source voltage of the transistor from the voltage measurement circuit and to adjust a gate-source voltage of the transistor based on the drain-source voltage of the transistor. The regulator circuit may include one or more of the following additional elements in any combination: Element 1: The regulator circuit is configured to adjust the gate-source voltage of the transistor to be equal to the drain-source voltage of the transistor. Element 2: The regulator circuit includes an enable input and is configured to adjust the gate-source voltage of the transistor based on the drain-source voltage of the transistor in response to an enable signal received at the enable input. Element 3: The voltage measurement signal corresponds to a gate threshold voltage of the transistor when the regulator circuit is enabled. Element 4: The voltage measurement signal corresponds to an on-state drain-source voltage of the transistor when the transistor is operating in an on-state and the regulator circuit is disabled. Element 5: The regulator circuit comprises a reference input coupled to receive the voltage measurement signal, a gate drive output coupled to the gate terminal of the transistor, and a feedback input coupled to the gate terminal of the transistor, the regulator circuit configured to drive the gate terminal of the transistor based on a comparison of the reference input and the feedback input. Element 6: The measurement circuit further comprises an analog-to-digital converter coupled to the voltage measurement circuit and configured to output a digital signal corresponding to an analog value of the voltage measurement signal.

[0044] Embodiments herein may include an inverter circuit. The inverter circuit includes a plurality of transistors configured to drive an electric motor. The inverter circuit further includes a gate drive circuit including a plurality of gate drivers configured to respectively drive the plurality of transistors during an operation phase of the inverter circuit. Additionally, the inverter circuit includes a measurement circuit configured to measure a gate threshold voltage of a transistor among the plurality of transistors during an initialization phase of the inverter circuit. The measurement circuit includes a current source configured to supply a current to a drain terminal of the transistor, a voltage measurement circuit configured to measure a drain-source voltage of the transistor, and a regulator circuit. The regulator circuit is configured to receive a voltage measurement signal indicative of the drain-source voltage of the transistor from the voltage measurement circuit and adjust the gate-source voltage of the transistor based on the drain-source voltage of the transistor. The inverter circuit may include one or more of the following additional elements in any combination: Element 1: The inverter circuit includes a plurality of measurement circuits, each of the plurality of measurement circuits configured to measure a gate threshold voltage of a respective one of the plurality of transistors during an initialization phase of the inverter circuit. Element 2: Each transistor of the plurality of transistors includes a silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET). Element 3: Each transistor of the plurality of transistors comprises a silicon insulated gate bipolar transistor (IGBT). Element 4: The regulator circuit comprises an enable input and is configured to adjust a gate-source voltage of the transistor based on a drain-source voltage of the transistor in response to an enable signal received at the enable input. Element 5: The voltage measurement signal corresponds to a gate threshold voltage of the transistor when the regulator circuit is enabled. Element 6: The voltage measurement signal corresponds to an on-state drain-source voltage of the transistor when the transistor is driven in an on-state and the regulator circuit is disabled.Element 7: The regulator circuit comprises a reference input coupled to receive the voltage measurement signal, a gate drive output coupled to the gate terminal of the transistor, and a feedback input coupled to the gate terminal of the transistor, the regulator circuit configured to drive the gate terminal of the transistor based on a comparison of the reference input and the feedback input. Element 8: The inverter circuit further comprises an analog-to-digital converter coupled to the voltage measurement circuit and configured to output a digital signal corresponding to the analog value of the voltage measurement signal.

[0045] Embodiments herein may include a method including the steps of providing a current to a drain terminal of a transistor, measuring a drain-source voltage of the transistor, adjusting a gate-source voltage of the transistor based on the drain-source voltage of the transistor, and determining a gate threshold voltage of the transistor based on the measured drain-source voltage of the transistor. The method may include one or more of the following additional elements or steps in any combination and in any suitable order: Element 1: generating a voltage measurement signal based on the drain-source voltage of the transistor; Element 2: adjusting the gate-source voltage includes driving a gate terminal of the transistor based on a comparison of the gate voltage and the voltage measurement signal; Element 3: converting an analog value of the voltage measurement signal into a digital signal.

[0046] Although examples have been described above, other modifications and variations may be made from this disclosure without departing from the spirit and scope of these examples. The above description of various embodiments illustrates the principles of the present invention. Numerous variations and modifications will be apparent to those skilled in the art based on the above disclosure. It is intended that the following claims be interpreted to encompass all such variations and modifications.

Claims

1. A measurement circuit comprising: a current source configured to provide a current to a drain terminal of the transistor; a voltage measurement circuit configured to measure the drain-source voltage of the transistor; 1. A regulator circuit, comprising: receiving a voltage measurement signal from the voltage measurement circuit indicative of the drain-source voltage of the transistor; a regulator circuit configured to adjust a gate-source voltage of the transistor based on the drain-source voltage of the transistor.

2. 2. The measurement circuit of claim 1, wherein the regulator circuit is configured to adjust the gate-source voltage of the transistor to be equal to the drain-source voltage of the transistor.

3. 2. The measurement circuit of claim 1, wherein the regulator circuit comprises an enable input and is configured to adjust the gate-source voltage of the transistor based on the drain-source voltage of the transistor in response to an enable signal received at the enable input.

4. The regulator circuit a reference input coupled to receive the voltage measurement signal; a gate drive output coupled to a gate terminal of the transistor; a feedback input coupled to the gate terminal of the transistor; The measurement circuit of claim 1 , wherein the regulator circuit is configured to drive the gate terminal of the transistor based on a comparison of the reference input and the feedback input.

5. The measurement circuit of claim 1 , further comprising an analog-to-digital converter coupled to the voltage measurement circuit and configured to output a digital signal corresponding to an analog value of the voltage measurement signal.

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