Apparatus and method to achieve fast-fault detection on power semiconductor devices

A fault-detection circuit for a power transistor, the fault-detection circuit comprising:

• a protection comparator having a comparator input and a comparator output, wherein the comparator input is configured to detect a collector-to-emitter voltage of the power transistor;
• a gate sense terminal configured to measure a gate voltage of the power transistor;
• a switch coupled between the comparator output and a reference voltage, the switch controlled to be closed when the power transistor transitions from an off state to an on state until the gate voltage crosses a pre-determined threshold, wherein
• the fault-detection circuit is configured to generate an output signal at the comparator output indicative of a fault based on the measured collector-to-emitter voltage.

A method for detecting fault condition for a power transistor having a gate, a first terminal and a second terminal, the method comprising:

• turning on the power transistor from an off state;
• determining whether a gate voltage of the power transistor crosses a pre-determined threshold;
• in response to a determination that the gate voltage crosses the pre-determined threshold, coupling a sense input terminal to a voltage node that is connected to the first terminal by closing a switch coupled between the sense input terminal and the voltage node;
• determining whether a collector-to-emitter voltage of the power transistor at the sense input terminal crosses a pre-determined threshold;
• and
• in response to a determination that the measured collector-to-emitter voltage crosses the pre-determined threshold, determining a fault.