A load/line adaptive zero voltage switching DC/DC converter used in electric vehicles

This paper presents a load/line adaptive Zero Voltage Switching (ZVS) full-bridge converter, which is able to optimize the amount of reactive current required to guarantee ZVS of the power MOSFETs. The proposed DC/DC converter is used as a battery charger for an electric vehicle. Since this application demands a wide range of load/line variations, the converter should be able to sustain ZVS under different conditions. The converter employs coupled inductors to provide the reactive current for the full-bridge semiconductor switches, which ensures ZVS at turn-on times. The coupled inductor along with the specific control system is able to generate the optimum value of the reactive current injected by the auxiliary circuit in order to minimize extra 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. Also, the reactive current is controlled by the switching frequency in order to compensate for the input voltage variations. Experimental results for a 2kW DC/DC converter are presented. The results show an improvement in efficiency and better performance of the converter particularly for heavy loads.