Modeling the turn-off characteristics of insulated-gate bipolar transistor

In this paper, a more accurate model for obtaining the turn-off current of insulated-gate bipolar transistors (IGBT) is proposed which shows that the turn-off current is overestimated in the previous models. Since the IGBT is regarded as a bipolar junction transistor (BIT) in series with a metal-oxide-semiconductor field-effect transistor (MOSFET), the turn-off I-V formula for IGBT was obtained by combining the turn-off formulae of each component device in the previous model. However, the coupling effect between the MOSFET and BIT during the turn-off process was not taken into consideration. In order to improve the accuracy of turn-off modeling, the drift hole current associated with the MOSFET electron current is assumed to decay in proportion to the electron current as the gate voltage is turned off. and the electron current injected into the pnp-BJT emitter is also taken into consideration when calculating the excess hole concentration in the base. The accuracy of this turn-off model is verified by both the simulated results and the measured data.