A ZVS phase-shift full-bridge DC/DC converter with optimized reactive current used for electric vehicles

This paper presents a Zero Voltage Switching (ZVS) phase-shift DC/DC converter, which is able to optimize the amount of reactive current required to guarantee ZVS for the power MOSFETs. The intended application for the proposed DC/DC converter is automotive, in particular a battery charger for an electric vehicle. Since a very wide range of load/line variations is expected in this application, the converter should be able to sustain ZVS under different conditions in order to demonstrate a reliable and efficient performance. The converter utilizes coupled inductors to provide the reactive current for soft-switching. The coupled inductor in conjunction with the specific control system is able to generate the optimal amount of reactive current produced by the auxiliary circuit. This leads to minimized conduction losses in the power MOSFETs, as well as the losses in the coupled inductors. In the proposed approach, the peak value of the reactive current is controlled by the phase-shift between the leading leg and lagging leg of the full-bridge converter to optimize the load impact. In addition, the peak current value is controlled by the switching frequency in order to compensate for the input voltage variations. Experimental results for a 2kW prototype are presented. The results show a significant improvement in efficiency and enhanced performance of the converter particularly for heavy loads.