Analytical model for the inductive turn-off process of GCT with dynamic avalanche

摘要

Dynamic avalanche injection during the turn-off of the gate commutated thyristors (GCTs) can slow down the removal of the remaining carriers, thereby affecting the turn-off characteristics. In addition, it is also a key factor inducing the turn-off failure of the device. However, the analytical model for the turn-off process considering dynamic avalanche effect has been not developed so far. In this paper, the turn-off process is divided into two phases, without dynamic avalanche and with dynamic avalanche, to be analyzed while assuming the appearance of the electron current in the space charge region of the P base/N- drift junction as the initial condition of occurrence of dynamic avalanche. As a result, a one-dimensional (1-D) physics-based analytical model is derived based on the basic principles of semiconductor and it gives insight into the details of internal physical mechanisms of the GCTs when dynamic avalanche occurs. And the analytically calculated results obtain a good agreement with the numerical simulations on the whole. It is also revealed that the avalanche-generated current filament is the main reason causing the difference between the 1-D analytical model and the two-dimensional (2D) numerical simulation.