Dual-bridge DC/DC converter with wide-range ZVS and zero circulating current

This paper presents a new DC/DC converter topology, which consists of two bridge inverters, a full-wave rectification circuit and a current-doubler output filter. Each inverter operates at 50% duty cycle and generates a symmetrical and isolated square output voltage. Phase-shift control is employed to control phase offset between the two bridge inverters. By shifting one bridge inverter´s phase, the converter changes the two inverter output voltages´ overlapping areas applying to the output filter to regulate its output voltage. One typical circuit configuration discussed in this paper is a dual half-bridge DC/DC converter. Each half-bridge inverter, like an open-loop Bus Converter, always operates at 50% duty cycle to achieve wide-range Zero Voltage Switching (ZVS) and maximum efficiency, while the converter itself operates in a phase-shifted ZVS full-bridge mode with zero circulating current. For low output voltage regulation and converter startup, Pulse Width Modulation (PWM) control is used. The topology can also optimally utilize magnetic components and reduces semiconductor stress. A 1KW 385V/48V dual half-bridge DC/DC converter was designed to validate the concept of this new topology. Test results show the topology can achieve 96+% efficiency and maintain soft switching over a wide load range.