Simple-Structure Fixed-Frequency Isolated Resonant Converter for EV Battery Charger Applications With CC–CV Charge Method

This article presents a simple fixed-frequency reconfigurable resonant converter (RC) with constant-current (CC)—constant-voltage (CV) charge for electric vehicle batteries. The CC–CV charge is implemented using the LCC converter inherent CC characteristic and the series LC converter inherent CV characteristic when operating at the resonant frequency. The proposed battery charger operating modes from CC to CV is performed by a dual resonant network, which is reconfigured by an auxiliary switch resulting in the battery charging time reduction and efficiency improvement. The output current variation of the conventional method in CC mode is minimized using the auxiliary switch to block the feed-forward path, while it provides better efficiency by operating as a synchronous rectifier (SR) in CV mode. The proposed converter operation and performance is analyzed in detail. An 180 W experimental prototype generating a 50–90 V output voltage and 0.2–2 A output current from a 340 V input voltage is designed and implemented to confirm the theoretical analysis. The maximum efficiency of 98.8% is achieved due to the structure simplicity, using the SR at CV mode, operating at the resonance frequency, zero voltage switching operation of the switches, and zero current switching operation of the diodes.