A high-speed protection circuit for IGBTs subjected to hard-switching faults

This paper describes a high-speed protection circuit for IGBTs subjected to hard-switching faults (HSF). The reverse transfer capacitance depends on a collector-emitter voltage and it produces a significant effect on a 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, a hard-switching fault can be detected by monitoring both a gate-emitter voltage and an amount of gate charge during the turn-on transient period. IGBTs can be rapidly protected from destruction because a blanking time is unnecessary. Simulation and experiment verify the validity of the proposed high-speed protection circuit.