ZVS synchronous buck converter with improved light load efficiency and ripple-free current

Abstract

A zero-voltage-switching (ZVS) synchronous buck converter with improved light load efficiency and ripple-free current is proposed in this paper. An auxiliary circuit is added to a conventional buck converter. The auxiliary circuit provides a ripple-free current and ZVS feature. Due to the ZVS feature, the switching loss is significantly reduced. However, the conduction loss due to the auxiliary circuit increases. Especially at light loads, the conduction loss is much larger than the switching loss. Therefore, by disabling the synchronous switch at light loads, the circulating current in the auxiliary circuit is reduced and the efficiency at light loads is improved. The operation principle and steady-state analysis of the proposed converter are provided. A prototype of the proposed converter is developed, and its experimental results are presented for validation. © Springer-Verlag Berlin Heidelberg 2011.