A Voltage Model of p-i-n Diodes at Reverse Recovery Under Short-Time Freewheeling

Fast switching and large capacity in modern power converters generate large-voltage peak during the diode's reverse-recovery process. Being different from the steady-state reverse recovery, short-time freewheeling of diodes at higher speed switching may generate higher reverse-recovery voltage peak. In this paper, the reverse recovery of p-i-n diodes under short-time freewheeling in a typical power converter circuit is studied with considerations of different initial current of the related IGBTs. By establishing the boundary connections between the turn-on and the turn-off transient stages, a mixed model of the diode's reverse-recovery voltage peak under short-time freewheeling is finally obtained, which combines the physics-based model with the behavior model. Model parameters were then extracted through measurements and circuit extraction methods to relax the complexity. Experiments were performed in a half-bridge inverter unit with 1200-V/50-A IGBTs and p-i-n freewheeling diodes at different short freewheeling time. The accuracy of the proposed model is verified by comparing the simulated waveforms with the measured data. The influence of different initial current on the voltage peak at short-time freewheeling was also evaluated using the proposed model.