A High-Speed Protection Circuit for IGBTs Subjected to Hard-Switching Faults

This paper describes a high-speed protection circuit for insulated-gate bipolar transistors (IGBTs) subjected to hard-switching faults (HSFs). The reverse transfer capacitance depends on the collector-emitter voltage, and it produces a significant effect on the switching behavior not only under normal conditions but also under HSF conditions. A gate charge characteristic under HSF conditions differs from that under normal turn-on conditions. Hence, an HSF can be detected by monitoring both the gate-emitter voltage and the amount of gate charge during the turn-on transient period. IGBTs can be rapidly protected from destruction by using this method because a blanking time is unnecessary. Simulation and experiment verify the validity of the proposed high-speed protection circuit.