Abstract - This paper applies a buck zero-current-switching pulse-width-modulated converter in battery chargers to achieve low switching losses, high charging efficiency and small circuit volume. The developed novel battery charger circuit has the advantages of the hard-switching and resonant converters with constant-frequency control, lowered resonant time and the operation of all switching components under the zero-current-switching condition. Practical experimental results demonstrate the theoretical effectiveness of the developed charging circuit. A practical mean charging efficiency of over 90% is attained and the developed circuit is awfully fit for high-frequency operations.