A Nonisolated ZVS Asymmetrical Buck Voltage Regulator Module With Direct Energy Transfer

This paper presents a new nonisolated asymmetrical buck voltage regulator module. A transformer is used to extend the extremely low duty cycle of a conventional buck converter. Turn-off losses can be significantly reduced due to the extension of duty cycle, and there are no turn-on losses owing to the zero-voltage turn-on condition. At the same time, the voltage stress over the synchronous rectifier MOSFETs is also reduced. Therefore, the reverse-recovery losses of the body diode can be reduced. Furthermore, the MOSFETs with lower voltage rating and lower RDS(on) can be used to reduce the conduction losses. In order to reduce the turn-off losses above the switching frequency of 1 MHz further, a new current-source driver is also proposed, which is suitable to this new topology. A 12-V input prototype with the switching frequency of 1 MHz was implemented. Simulation and experimental results verify the functionality and benefits of the proposed topology.