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A new step-down converter is presented. It is composed of an auxiliary switch, a diode, and a coupled winding to the buck inductor in the conventional buck converter. By transferring the buck-inductor current to the coupled winding in a very short period, the negatively built-up leakage inductor current of the buck winding guarantees the zero-voltage switching (ZVS) operation of the buck switch in all load conditions. Furthermore, since the negatively built-up leakage inductor current is minimized after the zero voltage of the buck switch is achieved, the unnecessary current build-up and the conduction loss are minimized. Therefore, efficient ZVS operation with load variation is achieved. The operation principle, ZVS analysis, design, and experimental results of the proposed converter are presented.