Theoretical investigations on IGBT snubberless, self-clamped drain voltage switching-off operation under a large inductive load

The authors describe the results of numerical investigations of IGBT (insulated-gate bipolar transistor) snubberless switching-off operation under a large inductive load (the so-called sustaining mode operation). A simulation of this kind has not previously been performed because it involves severe convergence problems. However, the authors have successfully analyzed this phenomenon by using a device simulator TONADDE2C which implements a rapid device/circuit solving algorithm. All of the electron current is found to be supplied by impact ionization during the sustaining mode; the drain voltage is self-clamped at the sustaining voltage by electrons, owing to impact ionization. The sustaining voltage is considered to be a function of the p-n-p transistor part of the common-base current drain and the structure parameters, and it can be controlled by the carrier lifetime through the former