A Four-Phase Current-Fed DC-DC Converter for Wide Voltage Range Applications

High power isolated bidirectional dc-dc converters with wide voltage range are attracting increasing attention in many applications. The bidirectional current-fed DC-DC converters are known to be suitable for wide voltage range application, compared to DAB based converters, due to reduced circulating current and current ripple. However, for wider voltage range application where the duty cycle becomes lower than 0.33 or higher than 0.66, power transfer capability of the existed three-phase current-fed converters is limited due to increased circulating current. In this paper, a four-phase current-fed push-pull DC-DC converter is proposed for wide voltage range applications, the duty cycle range can widely varies from 0.25 to 0.75 without increasing the circulating current. Also, the proposed converter reduces the current ripple and size of filter inductor, and current stress of the switch. Further, the concept of combined four-phase transformer is proposed for eliminating the DC-flux offset caused by DC current through each phase. Experimental results from a 15kW prototype of four-phase push-pull are provided to validate the proposed converter.