Switching behaviour of high voltage IGBTs and its dependence on gate-drive

Simulation results on high voltage 5.5 kV IGBTs are presented for both IGBTs with triangular shaped electrical field (Type A) and nearly rectangular electrical field distribution (Type B) under blocking voltage conditions. Measurement results of a 3.5 kV IGBT are compared with respective simulations. With unchanged gate-control, for high voltage B-type IGBTs a dramatic increase in switching speed is observed compared with A-type IGBTs, which may lead to destruction of the IGBT and the corresponding freewheeling diode. A study on the influence of the gate drive on the switching behaviour of the IGBT and the diode in the circuit is presented. Fundamental aspects of the switching of IGBT and diode, which are of general interest and apply also to power-MOSFETS, are revealed and are explained by a simple model. Remedies to avoid device failure caused by the increased switching speed of the B-type IGBT are shown.