Circulating Current-less Phase-Shifted Full-Bridge Converter With New Rectifier Structure

A conventional phase-shifted full bridge (PSFB) converter has several advantages for high power applications since it has full-bridge structure and all switching devices can achieve soft switching. However, it has large circulating current in primary side when it operates with small duty-ratio resulting in large conduction loss at primary switches. Also, since rectifier diodes have a voltage ringing between parasitic components, it has large voltage stress. To overcome above problems, a new PSFB converter which eliminates the circulating current and voltage ringing using coupled output inductor is proposed in this paper. As a result, the proposed converter reduces a conduction loss at primary side and can use small voltage rating diode in secondary rectifier. To verify the effect and feasibility, prototype converters are experimented with a 320-400V input voltage and 56V/12.8A output specification.