Implementation and Design Steps for Resonant DC-DC Converter in Vehicular Applications

In this paper, frequency selection methodology for inductor-inductor-capacitor (LLC) based resonant circuit for an on-board charger of a electric vehicle (EV) is presented. A battery load is a variable load and non-linear in nature unlike passive resistive load applications. Based on nature of the battery and the LLC resonant converter frequency selection and design steps for the LLC converter is proposed. The soft-switching is identified for full-load range for all the switches of the converter. The worst operating point of the converter is identified as light-load condition to design the LLC converter configuration. Finally, the design is validated on 600W, 145kHz laboratory prototype.