A Three-Leg-Based Full-Bridge Converter With Wide Input Voltage Range

Abstract

Traditional phase-shift full-bridge converters are popular in industrial applications due to the advantages of simple design, fixed-frequency control and soft switching. However, a large duty cycle variation range is required in applications with a wide input voltage range, which can cause loss of soft switching range, excessive circulating currents and output current ripple. This article introduces a three-leg converter that is a hybrid combination of two full-bridges. The current and power of the two transformers in the converter are shared automatically by adopting the symmetrical structure and modulation, and output current ripple is suppressed by the superposition of the two transformer voltages. The circulating current is minimized in the proposed converter that the conduction loss is reduced. By adding two auxiliary switches on the secondary side, zero-voltage switching and zero-current switching of all switches can be achieved to maintain high efficiency in a wide range. An experimental prototype rated at 1 kW is designed to convert 220–460 V input to 100 V output. The experimental results show that the proposed converter can achieve high efficiency over a wide input voltage and load range.