Simulation and Design of an Improved Phase-Shifted Full-Bridge DC-DC Converter with Lower RMS Current and Voltage Stresses

In this paper, an improved phase-shifted full-bridge (PSFB) dc-dc converter with coupled inductors and a current doubler rectifier (CDR) for battery charger applications in electric vehicles (EVs) is proposed. By using two coupled inductors as opposed to traditional output filter inductors, the RMS currents, the circulating current, and the voltage stresses on the secondary side are decreased. Besides, the zero-voltage-switching (ZVS) operation range is lengthened. Therefore, higher efficiencies are achieved. The two recursive inductors in the primary side have small and negligible values compared to the output inductors and, consequently, neither complex control systems nor extra components (like auxiliary circuits and active clamps) are needed. Thus, by using the proposed topology a simple structure with a simple control system will be obtained. Utilizing the proposed converter leads to reduce the RMS currents, the circulating current, and the voltage stresses on the secondary side. Besides, the cost and size of the system are not changed compared to the traditional one, as well. Moreover, the required energy for ZVS operation of power MOSFETs will be decreased which leads to higher efficiencies over a more extended operation range. Finally, the proposed and traditional converters have been simulated under the following conditions: the input voltage (150-250 V), switching frequency (200 kHz), the output voltage (75-85 V), and the output current (1.85-18.5 A). The simulation results validate the major benefits of the proposed phase-shifted full-bridge dc-dc converter over the traditional one.