Minimization of reverse recovery effects in hard-switched inverters using CoolMOS power switches

CoolMOS power switches offer appealingly low forward voltage drops in switching power converter applications up to 800 V, but the poor reverse recovery characteristics of their internal body diodes makes them difficult to use in hard-switching applications. A new technique based on synchronous rectification concepts, referred to as active channel freewheeling, is introduced as a promising approach for minimizing the diode reverse recovery effects. According to this approach, the reverse-conducting MOSFET channel is used to shunt the freewheeling current away from the body diode by gating the CoolMOS switches throughout their freewheeling intervals. Both simulation and experimental results are provided to explore the beneficial impact of this approach on the inverter's turn-on switching losses and peak device currents. The impacts of device terminal characteristics, temperature, and gating dead time on technique effectiveness are also examined.