A novel non-isolated ZVS asymmetrical buck converter for 12 V voltage regulators

This paper presents a new non-isolated asymmetrical buck converter. The transformer is used to extend the extremely low duty-cycle of a conventional buck converter. The turn-off loss can be significantly reduced due to the extension of duty-cycle and there is no turn-on loss owing to zero-voltage turn-on condition. At the same time, the voltage stress over the synchronous rectifier (SR) MOSFETs is also reduced. Therefore, the reverse recovery losses of the body diode can also be reduced. Furthermore, MOSFETs with the lower voltage rating and lower R_ds(on) can be used to reduce the conduction loss further. To further reduce the turn-off loss above the switching frequency of 1MHz, current-source gate driver can be also applied to this topology. A prototype at switching frequency of 1MHz was implemented and the preliminary experimental results verify the functionality of the new circuit.