Topology Derivation and Generalized Analysis of Zero-Voltage-Switching Synchronous DC-DC Converters With Coupled Inductors

In conventional dc-dc converters with synchronous rectifiers, hard-switching operation of the main switch and reverse-recovery problem of the synchronous switch result in degraded performance. In order to avoid these two undesired shortcomings, employing a coupled inductor is a simple yet effective solution. Apart from the improved soft-switching characteristic, low component count is also achieved since only a coupled winding and a series auxiliary diode are added. In this paper, a general zero-voltage-switching (ZVS) topology with a coupled inductor is proposed and based on which, a family of ZVS synchronous buck, boost, and buck-boost converters is readily obtained. For each fundamental dc-dc converter, several viable ZVS topologies evolve, among which an optimum topology can be chosen according to the different requirement in practical engineering applications. To help the topology selection, generalized analysis and individual comparison are also undertaken. In addition, design consideration is illustrated and experiment results are provided to validate converter effectiveness. Furthermore, thanks to its generality, the topology derivation and generalized analysis can be easily extended to various synchronous dc-dc converters.