Enhancing Short Circuit Capability of 1.2-kV Si IGBT Using a Gate-Source Shorted Si Depletion Mode MOSFET in Series With the Emitter

Short-circuit (SC) capability is a critical requirement for power switches in modern power electronics applications. A tradeoff between on-state voltage drop, switching loss, and SC capability of insulated gate bipolar transistors (IGBTs) is performed by manufacturers. In general, IGBTs optimized with low on-state voltage have poor SC capability compared with those with good SC capability. In this report, a novel method is described to improve the SC capability of IGBTs optimized with low on-state voltage drop by using a gate-source-shorted Si depletion-mode (DM) mosfet connected in series with the emitter. A seven-fold increase in the SC capability of commercially available 1.2-kV IGBTs was achieved at high dc bus voltages with minimal impact on on-state and switching loss performance. The proposed method also provides a sensing voltage signal at the drain of the Si DM-mosfet, which can be used to monitor the on-state current magnitude and to detect SC fault conditions.