Enhancing Short Circuit Ruggedness of 1.7 kV IGBTs using a Gate-Source-Shorted Depletion-Mode MOSFET in Series with the Emitter

Abstract

Commercial IGBTs optimized with low on-state voltage drop (V CE,SAT ) have poor short circuit ruggedness (t SC ). This paper demonstrates a new concept to enhance t SC for commercially available 1.7 kV IGBTs designed with low V CE,SAT using a gate-source-shorted (GSS) Si depletion-mode (DM) MOSFET in series. A five-fold improvement in t SC to over 25 μs was achieved at a DC bus voltage of 1100 V with only 15% increase in V CE,SAT and no change in total switching loss. The new concept also provides a sense voltage to monitor collector current during normal circuit operation and to detect SC events.