Asymmetrical Half-Bridge Converter With Zero DC-offset Current in Transformer Using New Rectifier Structure

Abstract

A conventional asymmetrical half-bridge (AHB) converter is a good candidate for low power applications such as TV and LED driver. It has small number of components and all switching devices have soft swtiching capability. However, when the AHB converter is designed with wide input voltage range, it has a large offset current in transformer which increases size of the transformer and core loss. Also, DC-offset current worsens ZVS condition of one of the half-bridge switches resulting in low efficiency in light load condition. To overcome above problems, a new asymmetrical half-bridge converter with coupled inductor rectifier (CIR) is proposed in this paper. Since two capacitors of the new rectifier equalize an average current flowing through secondary rectifier, the proposed converter doesn’t have DC-offset current. Therefore, the proposed converter reduces size of the transformer and can increase efficiency. Experiment is implemented with a 250V-400V input voltage variation and 50V/200W output specifications.