A short circuit protection method based on a gate charge characteristic

This paper describes a high-speed circuit to protect IGBTs against short-circuit faults. The reverse transfer capacitance depends on a collector-emitter voltage and it produces a significant effect on a switching behavior under short-circuit fault conditions as well as under normal conditions. A gate charge characteristic under short-circuit fault conditions differs from that under normal turn-on conditions. Hence, hard-switching fault (HSF) can be detected by monitoring both a gate-emitter voltage and an amount of gate charge. IGBTs can be rapidly protected from destruction because the protection circuit based on a gate charge characteristic does not require any blanking time. Fault under load can be also detected by almost the same circuit configuration. Simulation and experiment verify the validity of the novel protection circuit based on a gate charge characteristic.