An Adaptive ZVS Full-Bridge DC–DC Converter With Reduced Conduction Losses and Frequency Variation Range

This paper presents a description and analysis of a full-bridge converter with a novel passive and robust auxiliary circuit for zero-voltage-switching (ZVS) operation. A generalized time-domain state-space analysis is provided to describe the steady-state behavior of the auxiliary circuit. Complete comparison between the well-known single-inductor auxiliary circuit, and the proposed one is presented. For a similar peak current in the auxiliary branch, needed for ZVS, a minimum of 20% reduction in rms current is achieved to decrease the conduction losses in the power switches and in the auxiliary circuit. Also, 65% reduction in switching frequency variation is obtained. This narrower frequency range reduces the need for very high-frequency operation and the associated gate driver losses as well as the difficulty of electromagnetic interference (EMI) filter design. All the theoretical results are experimentally verified.