High-Efficiency ZCS Buck Converter for Rechargeable Batteries

To obtain zero-current-switching (ZCS) operation, this paper develops a novel soft-switching approach for rechargeable batteries. By inserting an auxiliary switch in series with a resonant capacitor, the proposed topology can obtain a novel ZCS buck dc-dc battery charger and significantly decrease the switching losses in active power switches. The proposed ZCS dc-dc battery charger has a straightforward structure, low cost, easy control, and high efficiency. The operating principles and design procedure of the proposed charger are thoroughly analyzed. The optimal values of the resonant components are computed by applying the characteristic curve and electric functions derived from the circuit configuration. Finally, a prototype charger circuit designed for a 12-V 48-Ah lead acid battery is constructed and tested to confirm the theoretical predictions. The maximum charging efficiency of the proposed topology during the overall charging period is 90.3%. Satisfactory performance is obtained from the experimental results.