Patent Description:
A gate driver is an integrated circuit configured to convert a low voltage (LV) switching signal into a high voltage (HV) signal suitable for driving a power transistor ON/OFF. Some systems (e.g., automotive systems) require the power transistor to be monitored in order to protect against faults, such as a short circuit, that could lead to damage.

<CIT> discloses a saturation edge detection circuit for testing a saturation level in an IGBT. It includes a first input operable to receive an on signal, a second input coupled to an IGBT driver circuit, and an output coupled to a control electrode of the IGBT. The output indicates a change in a state of a saturation voltage associated with the IGBT during operation of the IGBT.

It is the object of the invention to provide a power system capable of generating detailed system analysis information.

The above object is accomplished by the features of independent claims <NUM> and <NUM>.

A power system has the features of claim <NUM>. It includes a power transistor that is configurable in an ON condition or an OFF condition corresponding to a signal at a gate of the power transistor; a desaturation sense circuit coupled to a terminal of the power transistor; the desaturation sense circuit including a blanking capacitor configured to be charged to a voltage corresponding to a desaturation condition of the power transistor; a gate driver including: a driver circuit configured to generate the signal at the gate of the power transistor according to an input signal at an input terminal of the gate driver; and a desaturation fault detection circuit that is configured receive the voltage of the blanking capacitor and generate a fault signal when the voltage of the blanking capacitor exceeds a threshold; and a control module configured to perform a test of the power system, the test including: transmitting a test signal to a test terminal of the gate driver to configure the power transistor in the OFF condition and to configure the desaturation fault detection circuit to receive the voltage of the blanking capacitor, the voltage of the blanking capacitor charged by the desaturation fault detection circuit during the test.

In some aspects, the techniques described herein relate to a power system, wherein the test further includes: not receiving the fault signal in response to the test signal; failing the test; and determining from the test that failed: the desaturation fault detection circuit did not generate the fault signal; the blanking capacitor was not charged; or the power transistor was short circuited. In some aspects, the techniques described herein relate to a power system, wherein the test further includes: receiving the fault signal in response to the test signal; passing the test; and determining from the test that passed: the desaturation fault detection circuit and the blanking capacitor are operating properly to detect the desaturation condition of the power transistor; and the power transistor is not short circuited.

The test is a first test, the test signal is a first test signal, and the fault signal is a first fault signal. The control module is further configured to perform a second test of the power system after the first test is passed, the second test including: transmitting a second test signal to the input terminal of the gate driver to configure the power transistor in the ON condition and to configure the desaturation fault detection circuit to receive the voltage of the blanking capacitor, the voltage of the blanking capacitor charged by the power transistor in the ON condition.

In some aspects, the techniques described herein relate to a power system, wherein the gate driver further includes: an isolation barrier between a low-voltage side and a high-voltage side, and a multiplexer configured to communicate the second test signal at the input terminal of the gate driver and the first test signal at the test terminal of the gate driver across the isolation barrier over a shared communication channel.

In some aspects, the techniques described herein relate to a power system, wherein the second test further includes: receiving the fault signal in response to the second test signal; failing the second test; and determining from the second test that failed: the gate of the power transistor did not receive the signal from the driver circuit to configure the power transistor in the ON condition; the blanking capacitor was not charged by the power transistor in the ON condition; or the power transistor was open circuited.

In some aspects, the techniques described herein relate to a power system, wherein the second test further includes: receiving no fault signal in response to the second test signal;
passing the second test; and determining from the second test that passed: the driver circuit is operating properly to transmit the signal to the gate of the power transistor to configure the power transistor in the ON condition; the desaturation sense circuit is operating properly to charge the power transistor according to a desaturation voltage at the terminal of the power transistor; and the power transistor is not open circuited.

In some aspects, the techniques described herein relate to a power system, wherein the power transistor is an insulated gate bipolar transistor (IGBT) coupled at the gate to the driver circuit, coupled at a collector to the desaturation sense circuit, and coupled at an emitter to a ground.

In some aspects, the techniques described herein relate to a power system, wherein the desaturation sense circuit includes: a resistor coupled to a desaturation terminal of the gate driver; and a diode coupled between the resistor and the collector of the insulated gate bipolar transistor, wherein an anode of the diode is coupled to the resistor and a cathode of the diode is coupled to the collector of the insulated gate bipolar transistor, wherein the blanking capacitor is coupled between the desaturation terminal and the ground so that the voltage of the blanking capacitor corresponds to a collector-emitter voltage of the IGBT when the IGBT is in the ON condition.

In some aspects, the techniques described herein relate to a power system, wherein the desaturation fault detection circuit includes: a current source coupled between a power source and the desaturation terminal of the gate driver; a desaturation switch coupled between the desaturation terminal and the ground, the desaturation switch configurable to clear the voltage of the blanking capacitor; and a comparator coupled at a first terminal to the desaturation terminal of the gate driver to receive the voltage of the blanking capacitor and coupled at a second terminal to a threshold voltage corresponding to the threshold.

In some aspects, the techniques described herein relate to a method for testing a power system as defined in claim <NUM>, the method including: receiving a first test signal at a test terminal of a gate driver to begin a test; configuring a power transistor in an OFF condition; charging, by a desaturation fault detection circuit of the gate driver, a blanking capacitor, the blanking capacitor coupled externally to the gate driver at a desaturation terminal of the gate driver; comparing, by the desaturation fault detection circuit, the voltage of the blanking capacitor to a threshold; and transmitting, by the desaturation fault detection circuit, a first fault signal to a fault terminal of the gate driver when the voltage of the blanking capacitor exceeds the threshold. The method further includes receiving a second test signal at an input terminal of the gate driver to begin a second test after the first test has passed; configurating the power transistor in an ON condition; configurating the desaturation fault detection circuit of the gate driver to receive the voltage of the blanking capacitor, the voltage of the blanking capacitor charged by the power transistor in the ON condition; comparing, by the desaturation fault detection circuit, the voltage of the blanking capacitor to the threshold; and transmitting, by the desaturation fault detection circuit, a second fault signal to the fault terminal of the gate driver when the voltage of the blanking capacitor exceeds the threshold.

In some aspects, the techniques described herein relate to a method, further including: not receiving the fault signal at the fault terminal in response to the test signal at the test terminal; failing the test; and determining from the test that failed: the desaturation fault detection circuit did not generate the fault signal; the blanking capacitor was not charged; or the power transistor was short circuited.

In some aspects, the techniques described herein relate to a method, further including: receiving the fault signal at the fault terminal in response to the test signal at the test terminal; passing the test; and determining from the test that passed: the desaturation fault detection circuit and the blanking capacitor are operating properly to detect a desaturation condition of the power transistor; and the power transistor is not short circuited.

In some aspects, the techniques described herein relate to a method, wherein the gate driver further includes an isolation barrier between a low-voltage side and a high-voltage side of the gate driver, the method further including: communicating the second test signal at the input terminal or the first test signal at the test terminal across the isolation barrier over a shared communication channel.

In some aspects, the techniques described herein relate to a method, further including: not receiving the second fault signal at the fault terminal in response to the second test signal at the input terminal; passing the second test; and determining from the second test that passed: a driver circuit of the gate driver is operating properly to transmit an ON signal to a gate of the power transistor to configure the power transistor in the ON condition; a desaturation sense circuit is operating properly to couple the blanking capacitor to a collector of the power transistor; and the power transistor is not open circuited.

In some aspects, the techniques described herein relate to a method, further including: receiving the second fault signal at the fault terminal in response to the second test signal at the input terminal; failing the second test; and determining from the second test that failed: a gate of the power transistor did not receive an ON signal from a driver circuit of the gate driver to configure the power transistor in the ON condition; the blanking capacitor was not coupled to a collector of the power transistor; or the power transistor was open circuited.

In some aspects, the techniques described herein relate to a method, wherein the power transistor is an insulated gate bipolar transistor (IGBT) coupled at a gate to a driver circuit of the gate driver, coupled at a collector to a desaturation sense circuit of the gate driver, and coupled at an emitter to a ground.

In some aspects, the techniques described herein relate to a gate driver including: a driver circuit configured to generate an output signal at an output terminal of the gate driver to control an ON/OFF condition of a power transistor according to an input signal at an input terminal of the gate driver; and a desaturation fault detection circuit configured, upon receiving a test signal at a test terminal of the gate driver, to: disable a desaturation switch coupled between a desaturation terminal of the gate driver and a ground so that a current source of the desaturation fault detection circuit can charge a voltage of a blanking capacitor that is coupled externally to the gate driver at the desaturation terminal; receive the voltage of the blanking capacitor at a first input of a comparator coupled to the desaturation terminal, the comparator having a second input coupled to a threshold voltage; and transmit a fault signal to a fault terminal of the gate driver when the voltage of the blanking capacitor exceeds the threshold voltage, the fault signal indicating that the desaturation fault detection circuit is functioning properly.

In some aspects, the techniques described herein relate to a gate driver, wherein the gate driver further includes: an isolation barrier between a low-voltage side and a high-voltage side; and a multiplexer configured to communicate the input signal at the input terminal of the gate driver and the test signal at the test terminal of across the isolation barrier over a shared communication channel.

The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the disclosure, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings.

The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views.

Switching large currents can be accomplished using a power transistor. The power transistor may be a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). The power transistor may be fabricated using silicon (Si) or silicon carbide (SiC) processes. The power transistor may be configured in an ON condition to conduct current or an OFF condition to block current by a gate driver coupled to a controlling terminal (e.g., gate terminal) of the power transistor.

High current levels switched by the power transistor can be damaging or dangerous when a malfunction (i.e., fault) in the operation of the power transistor occurs. For example, excessive heat or fire may be generated by a power transistor in an over-current (e.g., short-circuit) condition. Accordingly, the gate driver may be configured with a fault detection circuit to monitor a condition of the power transistor and generate a fault signal when a high-current condition (e.g., over-current condition) occurs. In one possible implementation, the fault detection circuit may be configured to sense a desaturation condition of the power device to detect the high-current condition. In another possible implementation, the fault detection circuit may be configured to sense the current of the power device directly to detect the high-current condition. In either case, the fault detection circuits can be considered so vital to safety, that industries (e.g., automotive industries) may require that a power system occasionally test the function (i.e., action) of the protection circuits before beginning, or resuming, normal operation of the power system. The periodic testing of the fault detection circuitry can protect against a fault that occurs but fails to be detected by the fault detection circuit (i.e., a false-negative fault detection).

A false-negative fault detection can occur when a component of the fault detection circuit internal to the gate driver fails or operates not as specified, but a false-negative fault detection can also occur when another circuit or component in the power system external to the gate driver fails or operates not as specified. A problem with existing testing methods and circuitry is that they may be configured to test only the test circuit internal to the gate driver. The circuits and methods disclosed herein can expand the testing capability to include circuitry external to the gate driver. The disclosed circuits and methods use a shared communication channel for test signals and normal operation signals so that the additional testing can be accomplished without significantly increasing the complexity of the gate driver. The disclosed approach may have the technical effects of improving safety of a power system and providing more diagnostic information when a fault in the protection occurs, which can help troubleshooting, repair, or replacement.

<FIG> illustrates a power system according to a first possible implementation of the present disclosure. The power system <NUM> includes a power transistor <NUM>. As shown, the power transistor <NUM> may be implemented as an IGBT having a collector terminal <NUM>, a gate terminal <NUM>, and an emitter terminal <NUM>. The power transistor is configurable in an ON condition (i.e., conducting) or an OFF condition (i.e., resisting) based on a signal at the gate terminal <NUM>. The signal is generated at an output terminal <NUM> (OUT) of a gate driver <NUM> and coupled to the gate terminal <NUM> via a gate resistor <NUM>. A fault (e.g., defect) in a gate resistor <NUM> can prevent the signal from the gate driver from reaching the power transistor <NUM>. The emitter terminal <NUM> of the power transistor and a ground terminal <NUM> (GND) of the gate driver may be coupled to a ground <NUM>.

An IGBT is typically in the saturation region while it is in the ON condition but can become desaturated when it is shorted or is conducting too much current. Accordingly, the power system <NUM> may include a desaturation sense circuit that is configured to sense a saturation state of the power transistor <NUM>, while the gate driver transmits an ON signal to the power transistor <NUM> (e.g., while the power transistor is in the ON condition). The desaturation sense circuit can include a desaturation resistor <NUM> coupled to a desaturation terminal <NUM> (DESAT) of the gate driver. The desaturation sensor circuit can further include a blanking capacitor <NUM> coupled between the desaturation terminal <NUM> and the ground <NUM>. The desaturation sense circuit can further include a diode <NUM>. The diode is coupled between the desaturation resistor <NUM> and the collector terminal <NUM> of the power transistor <NUM>. The diode <NUM> is oriented so that the anode of the diode is coupled to the desaturation resistor <NUM> and the cathode of the diode <NUM> is coupled to the collector terminal <NUM>.

The desaturation sense circuit is configured to generate a voltage on the blanking capacitor <NUM> according to the voltage at the collector terminal <NUM>. In other words, the voltage of the blanking capacitor can correspond to the collector-emitter voltage (i.e., forward voltage) of the power transistor <NUM>. When the power transistor turns ON, a current source in the gate driver charges the blanking capacitor <NUM> and the diode <NUM> conducts. During normal operation the voltage of the blanking capacitor <NUM> is clamped (i.e., by the diode that is conducting) to the voltage at the collector of the power transistor <NUM> (i.e., the collector-emitter voltage). When the IGBT is shorted, the clamping is effectively removed so that the voltage of the blanking capacitor <NUM> is charged to a higher voltage. As will be discussed, the gate driver can monitor the voltage of the blanking capacitor <NUM> and generate a fault if this voltage rises too high. A fault (defect) in the blanking capacitor <NUM>, the desaturation resistor <NUM>, and/or the diode <NUM> can create a false-negative fault detection. For example, if the blanking capacitor <NUM> cannot be charged (e.g., is shorted) then the voltage at the desaturation terminal <NUM> (DESAT) may remain grounded regardless of the desaturation condition of the power transistor <NUM>.

The gate driver <NUM> is an isolated gate driver that includes an isolation barrier <NUM> between a low-voltage side <NUM> and a high-voltage side <NUM>. The isolation barrier can provide galvanic isolation between the sides while allowing signals to be inductively coupled (e.g., using a transformer) or electrically coupled (e.g., using a capacitor) between sides.

The high-voltage side <NUM> of the gate driver <NUM> includes a desaturation terminal <NUM> (DESAT) configured to transmit a current from a current source and receive a voltage of the blanking capacitor <NUM>. The high-voltage side <NUM> further includes an output terminal <NUM> configured to transit an output signal to control an ON/OFF condition of the power transistor <NUM>. The high-voltage side <NUM> further includes a ground terminal <NUM> (GND).

The low-voltage side <NUM> of the gate driver <NUM> includes an input terminal <NUM> (IN) configured to receive an input signal from a control module <NUM> having levels corresponding to the ON/OFF conditions of the power transistor <NUM>. In other words, the gate driver <NUM> is configured to convert a low-voltage input signal to a high-voltage output signal to control the power transistor <NUM>, and to protect (i.e., shield, isolate) the control module <NUM> from the high-voltages of the power transistor <NUM>. The low-voltage side <NUM> further includes a test terminal <NUM> (TEST) configured to receive a test signal from the control module. The test signal can configure the gate driver to perform a test of its ability to detect a fault (i.e., its protection capabilities). The low-voltage side <NUM> further includes a fault terminal <NUM> (FLT) configured to transmit a fault signal to the control module, when a fault is detected.

The control module <NUM> may be a processor or controller that is configured by instructions to control the modes of the gate driver (e.g., test mode, normal mode, fault mode). For example, the control module <NUM> may transmit input signals to the gate driver <NUM> (i.e., normal mode) until it receives a fault signal from the gate driver. In response, the gate driver <NUM> may cease transmitting input signals to the gate driver (i.e., fault mode). Occasionally (e.g., at startup), the control module <NUM> may transmit test signals (i.e., test mode) intended to generate a fault. A fault received by the control module <NUM> in response to the test signals, can verify the operation of fault detection circuits of the gate driver <NUM>. Further, the fault can further verify the operation of the desaturation sense circuit (e.g., blanking capacitor <NUM>) and the power transistor <NUM> (e.g., not short circuited).

The operating protocols and test protocols for the power system <NUM> may be stored as instructions (e.g., software instructions) on a memory (e.g., non-transitory computer readable memory) accessible by the control module <NUM>. For example, a method (i.e., computer implemented process) for testing the power system may be stored as computer readable instructions that, when recalled, can configured the control module <NUM> to transmit signals corresponding to a test of the fault protection capabilities of the power system <NUM>. Further, the control module <NUM> may be configured to interpret the received signals and to generate a corresponding response.

In a possible implementation, the control module <NUM> may be configured to pass or fail a test based on the signals received in response to a test. Further, failing the test may include analyzing the signals from the test to determine the possible sources of failure. In other words, the disclosed approach includes diagnostics of the function of the fault (e.g., short-circuit) protection for the gate driver. The disclosed approach can use two tests to better diagnose a source of a failure.

<FIG> is a flow chart illustrating desaturation fault-detection testing for the power system of <FIG>. The testing includes a two-test protocol <NUM> including a first test <NUM> (i.e., TEST_1) and a second test <NUM> (i.e., TEST_2) to test the fault detection capability (i.e., action) of the gate driver. The two-test protocol <NUM> may be executed (i) after startup <NUM> or (ii) after a fault <NUM> is detected during normal operation <NUM>.

The first test <NUM> includes placing the power transistor <NUM> in the OFF condition (i.e., turning the power transistor OFF) and charging the blanking capacitor <NUM> so a voltage of the blanking capacitor at the desaturation terminal <NUM> (DESAT) can exceed a threshold during a period of the first test (i.e., first period). The threshold can be a fixed voltage that corresponds to a desaturation condition of the power transistor <NUM>. The voltage on the blanking capacitor <NUM> is charged during the first test <NUM> to simulate a desaturation condition when it exceeds the threshold. It is not an actual desaturation condition (i.e., over current condition) because the power transistor <NUM> is in the OFF condition. The gate driver <NUM> is configured to monitor a fault terminal <NUM> (i.e., FLT) during the first period corresponding to the first test for a fault signal.

The first test <NUM> fails when no fault signal is received by the control module <NUM> during the first period. In the first-test failed state <NUM> (i.e., FAIL_1), some conclusions may be made about the operation of the power system <NUM>. For example, not receiving the fault signal could indicate that the blanking capacitor <NUM> was not charged during the first period and may be evidence that the blanking capacitor is damaged (e.g., is short circuited). Not receiving the fault signal could also indicate that the power transistor <NUM> was not turned OFF during the first period and may be evidence that the power transistor <NUM> is short circuited. Not receiving the fault signal could also indicate that the blanking capacitor was properly charged, but the gate driver <NUM> did not generate a fault signal in response to the blanking capacitor <NUM> voltage being at or above the threshold, which could be evidence that desaturation fault detection circuitry in the gate driver is not operating properly.

The first test <NUM> passes when a fault signal is received by the control module <NUM> during the first period. In the first-test passed state <NUM> (i.e., PASS_1), some conclusions may be made about the operation of the power system <NUM>. For example, the fault signal indicates that the blanking capacitor <NUM> was charged to a voltage exceeding the threshold, which would not be possible if the blanking capacitor <NUM> was damaged (e.g., short circuited) or the power transistor <NUM> was not OFF (e.g., short circuited). The fault signal further indicates that the gate driver <NUM> was operating properly to generate the fault signal in response to the blanking capacitor <NUM> voltage being at or above the threshold.

After the first test <NUM> passes, a second test <NUM> (i.e., TEST_2) may be performed. The second test <NUM> includes placing the power transistor <NUM> in the ON condition (i.e., turning the power transistor ON). In this condition, the blanking capacitor <NUM> is charged to a voltage corresponding to a desaturation condition of the power transistor <NUM>, which corresponds to a level of the current conducted by the power transistor <NUM>. In other words, the voltage on the blanking capacitor <NUM> is charged during the second test <NUM> according to the actual desaturation condition of the power transistor <NUM>. When the blanking capacitor <NUM> voltage exceeds the threshold during a second period corresponding to the second test, the current in the power transistor <NUM> is too high and a fault exists. The gate driver <NUM> is configured to monitor a fault terminal <NUM> (i.e., FLT) during the second period corresponding to the second test for a fault signal.

The second test <NUM> fails when a fault signal is received by the control module <NUM> during the second period. In the second-test failed state <NUM> (i.e., FAIL_2), some conclusions may be made about the operation of the power system <NUM>. For example, receiving the fault signal could indicate that the desaturation resistor <NUM> or diode <NUM> is damaged (e.g., open circuited) so that the blanking capacitor <NUM> was not coupled to the collector terminal <NUM> of the power transistor <NUM>. Receiving the fault signal could also indicate that the power transistor <NUM> is not capable of being turned ON (e.g., is open circuited). Not receiving the fault signal could also indicate that the gate driver <NUM> did not properly configure the power transistor <NUM> in the ON condition. For example, the output terminal <NUM> of the gate driver and/or the gate resistor <NUM> prevented an ON signal from being applied to the gate terminal <NUM> of the power transistor <NUM>.

The second test <NUM> passes when no fault signal is received by the control module <NUM> during the second period. In the second-test passed state <NUM> (i.e., PASS_2), some conclusions may be made about the operation of the power system <NUM>. For example, not receiving the fault signal indicates that the power transistor was turned ON and the desaturation resistor <NUM> and the diode <NUM> coupled the blanking capacitor <NUM> to the collector terminal <NUM>.

After the first test <NUM> and the second test <NUM> have passed, then the gate driver <NUM> and the control module <NUM> may operate normally. Normal operation <NUM> may include the control module <NUM> transmitting ON/OFF input signals to the input terminal <NUM> of the gate driver <NUM>. The gate driver <NUM> continues to monitor the desaturation condition (i.e., current condition) of the power transistor <NUM> during normal operation <NUM>. A high current in the power transistor <NUM> (e.g., due to a short circuit) may cause the gate driver <NUM> to generate a fault signal at the fault terminal <NUM> that is received by the control module <NUM>. This fault <NUM> during normal operation may trigger the two-test protocol <NUM> to be repeated in order to help diagnose the problem with the power system <NUM>.

The control module <NUM> may be configured to shutdown operation of the power system <NUM> in the event of a fault. Further, the controller may be configured to generate messages or signals to indicate a type of failure based on the results of the two-test protocol <NUM>. The type may correspond to a component, or components, likely responsible for the failure. One technical advantage of the present approach is that more components are tested in the two-test protocol <NUM> than in other approaches, and the tested components include components external to the gate driver <NUM>.

<FIG> is a block diagram that schematically illustrates a gate driver according to a possible implementation of the present disclosure. As discussed previously, the gate driver <NUM> includes a low-voltage side <NUM> and a high-voltage side <NUM> isolated (e.g., galvanic isolation) by an isolation barrier <NUM>. Signals can be communicated across the isolation barrier <NUM> from the low-voltage side <NUM> to the high-voltage side <NUM> using a forward communication channel <NUM>. Signals can be communicated across the isolation barrier <NUM> from the high-voltage side <NUM> to the low-voltage side <NUM> using a feedback communication channel <NUM>.

The gate driver <NUM> may be configured to receive input (e.g., from the control module) on the low-voltage side <NUM> at an input terminal <NUM> (i.e., IN+), a test terminal <NUM> (i.e., DSCHK) and transmit a fault signal (e.g., to the control module) at a fault terminal <NUM> (i.e., /DSFLT). Additionally, a reset signal or enable signal may be received at a reset terminal <NUM> (i.e., /RST/EN). For example, a reset signal can be transmitted to the reset terminal <NUM> in order to clear (i.e., change states of) a fault signal at the fault terminal <NUM>.

The gate driver <NUM> includes a driver circuit to generate signals to control the power transistor to an ON/OFF condition. The driver circuit can include an output terminal <NUM> that includes a high output (i.e., OUTH) and a low output (i.e., OUTL) coupled to a gate resistor network <NUM>. The driver circuit may further include a high-side transistor <NUM> and a low-side transistor <NUM>. The driver circuit can be controlled by an input signal at the input terminal <NUM> communicated over the forward communication channel <NUM>. The high-side transistor <NUM>, the low-side transistor <NUM>, and the gate resistor network <NUM> may be considered part of an output stage (i.e., OUT STAGE) of the driver circuit.

To turn ON the power transistor <NUM>, the high-side transistor <NUM> may be configured in an ON condition to couple an upper high-voltage rail (VDD2) to the gate terminal of the power transistor <NUM> via a first gate resistor (Rg(on)) of a gate resistor network <NUM> while a low-side transistor <NUM> is in an OFF condition. To turn OFF the power transistor <NUM>, the low-side transistor <NUM> may be configured in an ON condition to couple a lower high-voltage rail (VEE2) to the gate terminal of the power transistor <NUM> via a second gate resistor (Rg(off)) of a gate resistor network <NUM>, while a high-side transistor <NUM> is in an OFF condition. In a possible implementation, the driver further includes a shutdown circuit <NUM> configured to turn the power transistor <NUM> OFF if a fault is detected.

The gate driver <NUM> includes a desaturation fault detection circuit <NUM>, that when enabled, is configured to receive a voltage from a desaturation sense circuit <NUM> coupled at the desaturation terminal <NUM> of the gate driver. As discussed, the desaturation sense circuit <NUM> includes a desaturation resistor <NUM> (RDESAT) and a diode <NUM> (DDESAT). The desaturation resistor and the diode can be configured to couple a blanking capacitor <NUM> (CB) to a terminal (e.g., collector terminal) of the power transistor <NUM>. The voltage received by the desaturation fault detection circuit <NUM> is the voltage of the blanking capacitor <NUM>.

The desaturation fault detection circuit <NUM> includes a comparator <NUM> and can be enabled to compare the voltage of the blanking capacitor <NUM> to a desaturation fault detection voltage (i.e., threshold voltage <NUM>) using a desaturation switch <NUM> (i.e., DESAT SW) coupled between the desaturation terminal <NUM> and the ground <NUM>. For example, the desaturation switch <NUM> may be turned ON to ground the desaturation terminal <NUM> (i.e., clear the voltage of the blanking capacitor) in order to disable the desaturation fault detection circuit <NUM>. Alternatively, the desaturation fault detection circuit <NUM> may be enabled when the desaturation switch <NUM> is OFF. The signal to enable the desaturation fault detection circuit <NUM> can be triggered by the power transistor <NUM> being ON (i.e., conducting). Additionally, the desaturation fault detection circuit <NUM> can be enabled by a test signal when the power transistor <NUM> is OFF in order to test the desaturation fault detection circuit <NUM>.

The desaturation fault detection circuit <NUM> includes a current source <NUM> coupled between a power source (VDD2) and the desaturation terminal <NUM>. The current source <NUM> is configured to charge the blanking capacitor <NUM> to a voltage. When the power transistor <NUM> is ON, this voltage is clamped to the collector voltage (i.e., desaturation voltage) of the power transistor <NUM> and represents the current level in the power transistor <NUM>. When the power transistor is OFF and the desaturation fault detection circuit <NUM> is enabled (i.e., TEST_1), this voltage can be charged to a level that is higher than the threshold voltage <NUM>. When the voltage of the blanking capacitor <NUM> is greater than or equal to the threshold voltage <NUM>, then the comparator <NUM> may output a fault signal that can be communicated over the feedback communication channel <NUM> to the fault terminal <NUM>.

The desaturation fault detection circuit <NUM> can be enabled by a test signal at the test terminal <NUM> or a test signal at an input terminal <NUM>. The test signals are communicated over a shared communication channel. In particular, the desaturation fault detection circuit <NUM> may be enabled while the power transistor <NUM> is configured in the OFF condition for the first test <NUM> by a first test signal received at the test terminal <NUM> of the gate driver <NUM>. Also, the desaturation fault detection circuit <NUM> may be enabled while the power transistor <NUM> is configured in the ON condition for the second test <NUM> by a second test signal received at the input terminal <NUM> of the gate driver <NUM>. The shared communication channel may enable a two-test protocol <NUM> without a significant increase in the complexity of the gate driver <NUM>.

<FIG> illustrates a shared communication channel for a gate driver according to a possible implementation of the present disclosure. As mentioned, the forward communication channel <NUM> is a shared communication channel configured to transmit signals from the input terminal <NUM> or the test terminal <NUM> across the isolation barrier <NUM>. The isolation barrier can be crossed using electrical coupling or magnetic coupling. For the implementation shown in <FIG>, magnetic (i.e., inductive) coupling is achieved using a transformer <NUM> between the low-voltage side <NUM> and the high-voltage side <NUM> of the gate driver. The gate driver includes a multiplexer <NUM> that is configured to couple the input signal (IN+) at the input terminal to a low-voltage transmitter <NUM> (LV TX). When a test signal is received at the test terminal, the multiplexer <NUM> is configured to couple a modulated version of the test signal (i.e., DSCHK_PULSE) to the low-voltage transmitter <NUM> (LV TX). The gate driver includes a pulse generator <NUM> that is configured to generate a series of pulses corresponding to the test signal. For example, the pulse generator <NUM> may start generating a series of pulses (i.e., pulse train) when the test signal begins and may stop when the test signal ends, where the period between the start and the stop corresponds to the test period. The pulse train is coupled by the transformer <NUM> to a high-voltage receiver <NUM> (HV RX). The gate driver further includes a deglitch filter <NUM> (e.g., low pass filter) coupled between the high-voltage receiver <NUM> and the driver circuit. The deglitch filter <NUM> is configured to block the pulse train during the first test and to pass an input signal (IN+) of sufficient duration to activate the second test. The gate driver further includes a charge pump <NUM> configured to output a signal (DSCHK_EN) that can enable the desaturation fault detection circuit <NUM>. For example, the output of the charge pump can control the desaturation switch <NUM>. The output of the charge pump is cleared by a clear signal (DSCHK_CLR) so that the desaturation fault detection circuit <NUM> is disabled (e.g., desaturation switch <NUM> is turned ON) whenever the power transistor <NUM> is ON and/or after the test has concluded (i.e., after the test period).

Input signals for the power transistor <NUM> are passed by the deglitch filter <NUM> to the output stage (OUT STAGE) of the gate driver. The input signals do not reach the desaturation switch <NUM> because, in this condition, the charge pump <NUM> is disabled and the power transistor <NUM> is turned ON. Test signals for the desaturation fault detection circuit <NUM> are blocked by the deglitch filter <NUM>. In this condition, the charge pump is enabled, and its output controls the desaturation switch <NUM> to enable the desaturation fault detection circuit <NUM>. As a result, the input signal at the input terminal and the test signal at the test terminal can be communicated across the isolation barrier over a shared communication channel including the low-voltage transmitter <NUM>, the transformer <NUM>, and the high-voltage receiver <NUM>.

In the following figures, signals at various locations in the power system <NUM> will be shown for a few possible test and operating scenarios. These timing diagrams (graphs) will help further explain the operation of the power system; however, the invention is not limited to these examples. Descriptions of the graphed signals are provided in TABLE <NUM> below.

<FIG> illustrates signals of a power system during a first desaturation test (i.e., DESAT CHECK TEST_1) that lead to a first-test failed state (i.e., FAIL_1) according to a first possible implementation of the present disclosure. In the first test (i.e., TEST_1), the power transistor can be maintained in an OFF state by output signals (i.e., OUT H/L) that are LOW in response to an input signal (i.e., IN+) that is LOW. The first test can be triggered by a HIGH desaturation check signal (i.e., DSCHK) at the test terminal. The first test signal can be communicated across the isolation barrier to generate a corresponding desaturation check enable signal (i.e., DSCHK_EN) for the at the desaturation switch of the desaturation fault detection circuit.

The desaturation check enable signal (i.e., DSHK_EN) can result from the following process. A HIGH DSCHK signal received at the test terminal can be applied to a filter to generate a desaturation check filter signal (i.e., DSCHK_FILT), which is a delayed version of the first test signal. The DSCHK_FILT signal can then be applied to a pulse generator to generate a desaturation check pulse signal (i.e., DSCHK_PULSE). The DSCHK_PULSE signal can be communicated over the shared communication channel and received by a charge pump circuit that generates a desaturation check charge pump signal (i.e., DSCHK_CP) from the series of pulses. The DSCHK_CP signal can then be applied to check demodulation logic to generate the desaturation check enable signal (i.e., DSCHK_EN), which can enable the desaturation fault detection circuit when at a HIGH level.

After being enabled, the desaturation fault detection circuit can charge the blanking capacitor to generate a desaturation signal (i.e., DESAT). In the graphs shown, the first test fails because a desaturation fault signal (i.e., /DSFLT) fails to indicate a FAULT (i.e., fails to go LOW), as expected for the first test. The source of this failure is the comparator, which outputs a desaturation output signal (i.e., DESAT_OUT) that remains in a low condition (i.e., NO FAULT) despite the DESAT signal being larger than the threshold. In proper operation, the DESAT_OUT signal would transition when the DESAT voltage becomes greater than or equal to the threshold, and the transition to the DESAT_OUT signal would cause a corresponding transition in the /DSFLT signal. Accordingly, <FIG> illustrates a first test that fails for the reason of a comparator error.

<FIG> illustrates signals of a power system during a first test (i.e., DESAT CHECK TEST_1) that lead to a first-test failed state (i.e., FAIL_1) according to a second possible implementation of the present disclosure. As shown, the first test fails because the /DSFLT signal fails to indicate a FAULT (i.e., fails to go LOW), as expected for the first test. The failure results because the DESAT signal fails to increase during the first test. This failure to increase can result from a short circuited (i.e., shorted) power transistor (e.g., IGBT) and/or a short circuited blanking capacitor (CB). In proper operation, the blanking capacitor would be charged by the desaturation fault detection circuit to a voltage that is greater than or equal to the threshold (i.e., VDESAT-THR) so that the DESAT_OUT signal would transition and trigger the /DSFLT signal to transition to a LOW level (i.e., FAULT). Accordingly, <FIG> illustrates a first test that fails because the power transistor and/or the blanking capacitor was short circuited.

<FIG> illustrates signals of a power system during a second test (i.e., DESAT CHECK TEST_2) that lead to a second-test failed state (i.e., FAIL_2) according to a first possible implementation of the present disclosure. As shown, the first test (i.e., DESAT CHECK TEST_1) passes because the /DSFLT signal transitions LOW (i.e., indicates a fault) as expected in response to the DESAT signal being greater than or equal to the threshold. As a result, it can be concluded that the power transistor is not shorted, the blanking capacitor can be charged (e.g., is not shorted), and the comparator is functioning properly. Accordingly, the two-test protocol can proceed to the second test after a reset signal (i.e., /RST/EN) resets the /DSFLT signal to the NO FAULT condition (i.e., HIGH).

The second test can be activated (i.e., triggered) by a HIGH input signal (i.e., IN+) at the input terminal. The IN+ signal can be communicated across the isolation barrier to generate output signals (i.e., OUT H/L) that configure the power transistor in an ON condition. The charge pump and demodulation logic used in the first test are disable by the DSCHK_CLR signal that is HIGH during the second test. The DESAT signal increases as the blanking capacitor is charged by the current source of the desaturation fault detection circuit to a voltage corresponding to a terminal of the power transistor. As shown, the second test fails because the DESAT signal increases to a level that is greater than or equal to the desaturation threshold voltage (VDESAT-THR). From the signals, it can be concluded that the voltage on the blanking capacitor was not clamped by the collector of the power transistor, despite the OUTH/L signals being HIGH to turn ON the power transistor. As a result, the desaturation fault detection circuit transitions its output signal (i.e., DESAT_OUT) to trigger the /DSFLT signal to go LOW (i.e., FAULT). From this failure, it can be concluded that the voltage on the blanking capacitor was not clamped by the collector of the power transistor. This can occur when the blanking capacitor is not properly coupled to the collector of the power transistor, which can result from a fault in the desaturation resistor (RDESAT) or desaturation diode (DDESAT). Alternatively, this failure to clamp the blanking capacitor voltage can result from the power transistor being open circuited.

<FIG> illustrates signals of a power system during a second test (i.e., DESAT CHECK TEST_2) that lead to a second-test failed state (i.e., FAIL_2) according to a second possible implementation of the present disclosure. As shown, the second test fails because the DESAT signal increases to a level that is greater than or equal to the desaturation threshold voltage (VDESAT-THR). As a result, the desaturation fault detection circuit transitions its output signal (i.e., DESAT_OUT) to trigger /DSFLT signal to go LOW (i.e., FAULT). From this failure, it can be concluded that the voltage on the blanking capacitor was not clamped by the collector of the power transistor. This can occur when the gate of the power transistor did not receive the ON signal from the driver circuit (i.e., was OFF during the test), which can result from a fault in the driver circuit (e.g., high-side transistor or low-side transistor) or the gate resistor network.

<FIG> is a flow chart of a method for testing a power system according to a first possible implementation of the present disclosure. The method <NUM> includes a first test <NUM> and a second test <NUM>. The second test <NUM> is performed when the first test <NUM> is passed (i.e., PASS_1), otherwise the second test <NUM> is not performed.

The first test <NUM> includes receiving <NUM> a test signal at a test terminal of the gate driver. The first test further includes configuring <NUM> a power transistor, coupled to the gate driver, in an OFF condition. The first test <NUM> further includes charging <NUM> a voltage of a blanking capacitor using a desaturation fault detection circuit of the gate driver. The blanking capacitor is externally coupled to the gate driver at a desaturation terminal. The first test <NUM> further includes comparing <NUM> the voltage of the blanking capacitor to a threshold using the desaturation fault detection circuit of the gate driver. A fault terminal of the gate driver can be monitored for a fault. If a fault is output <NUM> as a result of the charging, then the first test passes (PASS_1), otherwise no fault is generated, and the first test fails (FAIL_1).

In a possible implementation, the first test <NUM> may further include determining likely sources of the failure. For example, if the voltage of the blanking capacitor (i.e., DESAT signal) exceeded the threshold during the first test but no fault was generated, then the first test likely failed due to a faulty comparator. In another example, if the voltage of the blanking capacitor (i.e., DESAT signal) does not increase during the first test (e.g., is approximately ground), then the first test likely failed due to a short in either (or both) of the power transistor (e.g., IGBT) or the blanking capacitor (i.e., CB).

The second test <NUM> includes receiving <NUM> a test signal at a test terminal of the gate driver. The second test <NUM> further includes configuring <NUM> a power transistor, coupled to the gate driver, in an ON condition. The second test <NUM> further includes charging <NUM> a voltage of a blanking capacitor using a desaturation fault detection circuit of the gate driver. The blanking capacitor is externally coupled to the gate driver at a desaturation terminal. The second test <NUM> further includes comparing <NUM> the voltage of the blanking capacitor to the threshold using the desaturation fault detection circuit of the gate driver. A fault terminal of the gate driver can be monitored for a fault. If no fault is output <NUM> as a result of the charging, then the second test passes (PASS_2), otherwise a fault is generated, and the second test fails (FAIL_2).

In a possible implementation, the second test <NUM> may further include determining likely sources of the failure. For example, if the output of the gate driver (i.e., OUTH/L signal) is HIGH to turn on the power transistor and the voltage of the blanking capacitor exceeded the threshold, then the second test likely failed due to the power transistor (e.g., IGBT) and/or the desaturation sense circuit being open circuited. In another example, if the output of the gate driver (i.e., OUTH/L signal) is LOW so that the power transistor remains OFF then the second test likely failed due to a faulty driver circuit (e.g., high-side transistor, low-side transistor) or a faulty (e.g., open) gate resistor.

Thus far, the fault protection circuitry tested was for sensing a desaturation (i.e., DESAT) condition as an indicator of high current in the power transistor. A high current condition in a power transistor may also be sensed by sensing the current conducted by the power transistor using a sensor (e.g., resistor) in series with the power transistor in what is called a current sense (CS) approach.

<FIG> illustrates a power system according to a second possible implementation of the present disclosure. The power system 1000A includes a power transistor <NUM>. As shown, the power transistor <NUM> may be implemented as a three terminal IGBT including a collector terminal <NUM>, a gate terminal <NUM>, and an emitter terminal <NUM>. The power transistor is configurable in an ON condition (i.e., conducting) or an OFF condition (i.e., resisting) based on a signal at the gate terminal <NUM>. The signal is generated at an output terminal (OUT) of a gate driver <NUM> and coupled to the gate terminal <NUM> via a gate resistor <NUM>. The emitter terminal <NUM> of the power transistor <NUM> and a ground <NUM> are coupled to a ground terminal (GND) of the gate driver <NUM>.

The gate driver <NUM> includes a current sense (CS) terminal that is coupled to a current sense circuit. The current sense circuit (i.e., CS circuit) includes a current-sense resistor <NUM> (RSENSE) configured to convert a current flowing through the power transistor <NUM> into a voltage. The current-sense resistor <NUM> is coupled between the emitter terminal <NUM> of the power transistor <NUM> and the ground <NUM>. The emitter terminal <NUM> of the power transistor <NUM> is coupled to the CS terminal of the gate driver <NUM> via a current-sense filter (e.g., lowpass filter). The current-sense filter includes a filter resistor <NUM> (i.e., RF) coupled between the emitter terminal <NUM> and the CS terminal of the gate driver and a filter capacitor <NUM> (i.e., CF) coupled between the CS terminal of the gate driver <NUM> and the ground terminal (GND) of the gate driver (i.e., ground <NUM>).

<FIG> illustrates a power system according to a third possible implementation of the present disclosure. The power system 1000B is substantially the same as the implementation shown in <FIG> with the exception of the power transistor <NUM>. As shown, the power transistor <NUM> may be implemented as a four terminal IGBT including a collector terminal <NUM>, a gate terminal <NUM>, a first emitter terminal <NUM> (i.e., power emitter), and a second emitter terminal <NUM> (i.e., Kelvin emitter). In one possible implementation, the first emitter terminal <NUM> is coupled directly to ground <NUM> while the second emitter terminal <NUM> is coupled to the same ground <NUM> through the current-sense resistor <NUM>. In another possible implementation, the first emitter terminal <NUM> is coupled directly to a first ground (i.e., power ground) and the second emitter terminal <NUM> is coupled to a second ground (i.e., signal ground) through the current-sense resistor <NUM>. In either case the voltage at the second emitter terminal <NUM> is filtered by the current sense filter, including the filter resistor 1031and the filter capacitor <NUM>, before being transmitted to the current sense terminal (CS) of the gate driver <NUM>.

<FIG> is a block diagram that schematically illustrates a gate driver configured for current sensing according to a possible implementation of the present disclosure. As discussed previously, the gate driver <NUM> includes a low-voltage side <NUM> and a high-voltage side <NUM> isolated (e.g., galvanic isolation) by an isolation barrier <NUM>. Signals can be communicated across the isolation barrier <NUM> from the low-voltage side <NUM> to the high-voltage side <NUM> using a forward communication channel <NUM>. Signals can be communicated across the isolation barrier <NUM> from the high-voltage side <NUM> to the low-voltage side <NUM> using a feedback communication channel <NUM>.

The gate driver <NUM> may be configured to receive input (e.g., from the control module) on the low-voltage side <NUM> at an input terminal <NUM> (i.e., IN+), a CS-test terminal <NUM> (i.e., CSCHK) and transmit a fault signal (e.g., to the control module) at a CS-fault terminal <NUM> (i.e., /CSFLT). Additionally, a reset signal or enable signal may be received at a reset terminal <NUM> (i.e., /RST/EN). For example, a reset signal can be transmitted to the reset terminal <NUM> in order to clear (i.e., change states of) a fault signal at the CS-fault terminal <NUM>.

The gate driver <NUM> includes a driver circuit to generate signals to control the power transistor <NUM> to an ON/OFF condition. The driver circuit can include an output terminal <NUM> that includes a high output (i.e., OUTH) and a low output (i.e., OUTL) coupled to a gate resistor network <NUM>. The driver circuit may further include a high-side transistor <NUM> and a low-side transistor <NUM>. The driver circuit can be controlled by an input signal at the input terminal <NUM> communicated over the forward communication channel <NUM>. The high-side transistor <NUM>, the low-side transistor <NUM>, and the gate resistor network <NUM> may be considered part of an output stage (i.e., OUT STAGE) of the driver circuit.

The gate driver <NUM> includes a current-sense fault detection circuit <NUM>, that when enabled, is configured to receive a voltage from the current-sense filter <NUM> coupled at the current sense terminal <NUM> (CS) of the gate driver. As discussed, a current-sense resistor <NUM> (RSENSE) is configured to sense the current condition of the power transistor <NUM> as a voltage. This voltage can charge the filter capacitor <NUM> of the current-sense filter <NUM> so the voltage received by the current-sense fault detection circuit <NUM> is the voltage of the filter capacitor <NUM> (CF) while the power transistor <NUM> is ON.

The current-sense fault detection circuit <NUM> includes a comparator <NUM>. The comparator <NUM> is configured to compare a voltage at a first input to a current-sense fault detection voltage (i.e., threshold voltage <NUM>) and output a CS fault when the voltage is greater than or equal to the threshold. The first input of the comparator <NUM> is coupled to the current sense terminal <NUM> by a current sense switch <NUM> (i.e., CS SW). The current sense switch <NUM> can be turned ON (i.e., closed) when the power transistor <NUM> is ON so that the voltage at the current sense terminal <NUM> is the voltage of the filter capacitor <NUM>. The current sense switch may be OFF while the power transistor <NUM> is OFF during a test of the current-sense fault detection circuit <NUM>.

The current-sense fault detection circuit <NUM> includes a CS test switch <NUM> coupled between a test voltage and the first input of the comparator <NUM>. During a test of the current-sense fault detection circuit <NUM>, the current sense switch <NUM> may be turned OFF (opened) to decouple the current sense terminal <NUM> from the first input of the comparator <NUM>. Additionally, the CS test switch <NUM> may be turned ON to couple the test voltage to the first input of the comparator <NUM>. The test voltage coupled to the first input of the comparator may be greater than the threshold voltage <NUM> so that the comparator generates a CS-fault. This CS-fault may be communicated over the feedback communication channel <NUM> to a transistor <NUM> at the CS-fault terminal <NUM> in order to transition the /CSFLT signal at the CS-fault terminal <NUM>, thereby indicating a CS-fault. If no CS-fault appears at the CS-fault terminal <NUM>, then it may be concluded that there is a fault in the comparator <NUM> or the transistor <NUM>.

<FIG> is a flow chart illustrating current-sense fault-detection testing for the power system of <FIG>. The testing includes a one-test protocol <NUM> including a first test <NUM> (i.e., TEST_1) to test the fault detection capability (i.e., action) of the current-sense fault detection circuit <NUM>. The one-test protocol <NUM> may be executed (i) after startup <NUM> or (ii) after a fault <NUM> is detected during normal operation <NUM>.

The first test <NUM> includes placing the power transistor <NUM> in the OFF condition (i.e., turning the power transistor OFF) and coupling a test voltage to an input of the comparator <NUM> that exceeds the threshold voltage <NUM>. The reference voltage can be a fixed voltage that corresponds to an over-current condition of the power transistor <NUM>. The test voltage coupled to the input of the comparator simulates the over-current condition. It is not an actual over-current condition because the power transistor <NUM> is in the OFF condition during the test. A control module is configured to monitor a CS-fault terminal <NUM> (i.e., /CSFLT) during a first period corresponding to the first test <NUM> for a fault signal. When the gate driver is operating correctly, a fault signal will be received.

The first test <NUM> fails when no fault signal is received by the control module <NUM> during the first period. In the first-test failed state <NUM> (i.e., FAIL_1), some conclusions may be made about the operation of the gate driver <NUM>. For example, not receiving the fault signal could indicate that (i) the comparator <NUM> did not output a fault signal in response to the test or (ii) the transistor <NUM> did not respond to the fault signal.

The first test <NUM> passes when a fault signal is received by the control module <NUM> during the first period. In the first-test passed state <NUM> (i.e., PASS_1), some conclusions may be made about the operation of the power system <NUM>. For example, the fault signal indicates that the comparator <NUM> and the transistor <NUM> are operating as expected.

<FIG> is a flow chart of a method for testing a power system according to a second possible implementation of the present disclosure. The method <NUM> includes a first test <NUM>. The first test <NUM> includes receiving <NUM> a test signal at a test terminal of the gate driver. The first test further includes configuring <NUM> a power transistor, coupled to the gate driver, in an OFF condition. The first test <NUM> further includes decoupling <NUM> the CS terminal of the gate driver from the comparator of the current-sense fault detection circuit. The first test <NUM> further includes coupling <NUM> a test voltage to the comparator. The first test <NUM> further includes comparing <NUM> the test voltage to a threshold using the comparator. A fault terminal of the gate driver can be monitored for a fault. If a fault is output <NUM>, then the first test passes (PASS_1), otherwise no fault is generated, and the first test fails (FAIL_1).

In a possible implementation, the first test <NUM> may further include determining likely sources of the failure. For example, if the test voltage exceeded the threshold during the first test but no fault was generated, then the first test may have failed due to a faulty comparator or a faulty transistor at the fault terminal.

In the specification and/or figures, typical embodiments have been disclosed. The present disclosure is not limited to such exemplary embodiments. The use of the term "and/or" includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. As used in the specification, and in the appended claims, the singular forms "a," "an," "the" include plural referents unless the context clearly dictates otherwise. The term "comprising" and variations thereof as used herein is used synonymously with the term "including" and variations thereof and are open, non-limiting terms. The terms "optional" or "optionally" used herein mean that the subsequently described feature, event or circumstance may or may not occur, and that the description includes instances where said feature, event or circumstance occurs and instances where it does not. When such a range is expressed, an aspect includes from the one particular value and/or to the other particular value.

Some implementations may be implemented using various semiconductor processing and/or packaging techniques. Some implementations may be implemented using various types of semiconductor processing techniques associated with semiconductor substrates including, but not limited to, for example, Silicon (Si), Gallium Arsenide (GaAs), Gallium Nitride (GaN), Silicon Carbide (SiC) and/or so forth.

It will be understood that, in the foregoing description, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled to another element, it may be directly on, connected or coupled to the other element, or one or more intervening elements may be present. In contrast, when an element is referred to as being directly on, directly connected to or directly coupled to another element, there are no intervening elements present. Although the terms directly on, directly connected to, or directly coupled to may not be used throughout the detailed description, elements that are shown as being directly on, directly connected or directly coupled can be referred to as such. The claims of the application, if any, may be amended to recite exemplary relationships described in the specification or shown in the figures.

Claim 1:
A power system (<NUM>) comprising:
a power transistor (<NUM>) that is configurable in an ON condition or an OFF condition corresponding to a signal at a gate (<NUM>) of the power transistor (<NUM>);
a desaturation sense circuit (<NUM>) coupled to a terminal of the power transistor (<NUM>) and including a blanking capacitor (<NUM>) configured to be charged to a voltage corresponding to a desaturation condition of the power transistor (<NUM>);
a gate driver (<NUM>) including:
a driver circuit configured to generate the signal at the gate (<NUM>) of the power transistor (<NUM>) according to an input signal at an input terminal of the gate driver (<NUM>); and
a desaturation fault detection circuit (<NUM>) that is configured to receive the voltage of the blanking capacitor (<NUM>) and to generate a fault signal when the voltage of the blanking capacitor (<NUM>) exceeds a threshold; and
a control module (<NUM>) configured to perform a test of the power system (<NUM>) and comprises:
means for transmitting a test signal to a test terminal of the gate driver (<NUM>) to configure the power transistor (<NUM>) in the OFF condition and
means for configuring the desaturation fault detection circuit (<NUM>) to receive the voltage of the blanking capacitor (<NUM>),
wherein the desaturation fault detection circuit (<NUM>) comprises means for charging the blanking capacitor (<NUM>) during the test,
wherein the test is a first test, the test signal is a first test signal, and the fault signal is a first fault signal; wherein the control module (<NUM>) is further configured to perform a second test of the power system (<NUM>) after the first test is passed and further comprises:
means for transmitting a second test signal to the input terminal of the gate driver (<NUM>) to configure the power transistor (<NUM>) in the ON condition and
means for configuring the desaturation fault detection circuit (<NUM>) to receive the voltage of the blanking capacitor (<NUM>), wherein the blanking capacitor (<NUM>) is charged by the power transistor (<NUM>) in the ON condition.