A Novel Quasi-Resonant Battery Charger for Photovoltaic Applications

This work presents the analysis, design, PCB implementation and testing of a quasi-resonant low-voltage battery charger intended to be supplied by a photovoltaic (PV) module. The proposed battery charger exploits the Discontinuous Voltage Mode operation to transfer to the load a controlled and discrete amount of energy, alternately stored and released by two half-bridge capacitors. A small resonant inductance is added to assist the soft commutation of all the converter MOSFETs. The mathematical description of the operating principle and the main design equations of the converter are reported. Based on experiments, a 100 W prototype of the proposed battery charger achieves a flat conversion efficiency higher than 92 % over the wide 20 W - 95 W power range, with a peak of nearly 94 % at 40W.