A High Speed Short-Circuit Protection Circuit with Current Limitation and Soft Turn-Off for High Power IGBTs

This paper presents a high speed protection circuit to avoid IGBT failure caused by the short-circuit conditions such as hard switching fault (HSF) and fault under load (FUL). When a short circuit occurs, fast fault detection and protection circuits are necessary to limit the short-circuit current and a soft turn-off function is required to control the collector voltage overshoot during the IGBT turn-off transient. The proposed short-circuit fault detection is achieved by the integration of the collector current slew rate di/dt which can be sampled by the voltage across the parasitic inductance between the IGBT Kelvin emitter and power emitter. The di/dt is also applied to the proposed voltage controlled current source circuits VCCS1 and VCCS2 to regulate the gate drive current. The VCCS1 can control the di/dt under HSF and reduce the protection time under both HSF and FUL, resulting in short-circuit current limitation. The VCCS2 can control the collector voltage overshoot under various short-circuit current levels when the IGBT is shut down, achieving soft turn-off. The experimental results verify the good performance of the proposed short-circuit protection circuit.