Analysis and Design of Full-Bridge Converter With a Simple Passive Auxiliary Circuit Achieving Adaptive Peak Current for ZVS and Low Circulating Current

This article presents the analysis and design considerations of a phase shift full-bridge converter with a new simple and reliable passive auxiliary circuit for zero-voltage switching (ZVS) operation. The steady-state behavior of the converter is analyzed in detail. The contribution of the energy stored to both auxiliary circuit and leakage inductance is considered in the analysis of ZVS condition, the auxiliary current adjustment ability and the rms circulating current of the auxiliary circuit are described, and the impacts of narrow frequency variation on the converter are analyzed. The design procedures based on analytical models considering phase shift angle and input voltage variation are presented, which gives basic parameter configurations for the converter operating at a fixed frequency. The function model between the switching frequency and phase shift angle is established, which is helpful to design and optimize the converter operating at an adaptive frequency to reduce circulating current. In the proposed converter, the auxiliary current is adaptively controlled and has a sharp peak current, so the circulating current and conduction loss are greatly reduced. An experimental prototype is implemented to confirm the predicted results.