A novel load adaptive zero voltage switching utilizing diode reverse recovery current for soft-switching choppers

Diode reverse recovery normally increases switching losses and produces noise in power electronics circuits. Over the past few decades, device manufacturers put a lot of effort into improving the reverse recovery speed and softness by sacrificing the conduction losses. This paper, however, introduces a novel concept that utilizes diode reverse recovery current as a resonant inductor boosting current to achieve zero voltage operation with load adaptively. Analytical results demonstrate the load adaptive capability of the proposed scheme. Simulation results further verified the effectiveness of the proposed method. IGBT and CoolMos/sup TM/ based chopper experimental results shows the capability of load current adaptivity level depends on the characteristics of body diode and resonant tank. The body diodes of the CoolMos/sup TM/ under test are very slow thus the proposed scheme can achieve true ZVT at all load current range. However, for the tested IGBT have a "fast recovery" diode. Thus it can only achieve true zero voltage switching under certain load range. Even beyond this range, the device still can be turned on at a very Low voltage. However, by using external slow diode, the zero voltage switching still can be achieved by fixed timing control at all load range. The proposed design method can also be implemented for other types of zero-voltage transition schemes such as auxiliary resonant commutated pole (ARCP), resonant snubber inverter (RSI), and coupled inductor schemes as well.