ZVT Circuit applied for Wide Input Range Isolated Converters

This paper proposed an isolated zero voltage transition (ZVT) circuit for wide input range applications, which can achieve zero voltage switching (ZVS) for primary switches and zero current switching (ZCS) for secondary synchronous rectifiers in full input and load range. Compared with traditional ZVT circuits, the auxiliary inductor can be automatically fast reset, thus the auxiliary switch can also be turned off with ZCS and the rms value of auxiliary current is reduced accordingly. Besides, the auxiliary current can be further reduced by coupling to main inductor and the extra losses of auxiliary circuit are minimized. Finally, based on an existing full bridge topology, a standard 1/4 brick -48V bus converter prototype was built for verification. A peak efficiency up to 97.13% and maximum output power up to 1000W is achieved.