This paper proposes the interleaved buck converter using a soft switching auxiliary circuit. In this scheme, an auxiliary circuit is added to the conventional interleaved buck converter and used to achieve soft-switching conditions for both the main switch and freewheeling diode. In addition, the switch in the auxiliary circuit operates under soft-switching conditions. Also, according to the input to output conditions, the main switch achieved zero-current-transition(ZCT) or zero-current & zero-voltage-transition(ZCZVT) at turn on. Thus, the proposed interleaved buck converter provides a higher efficiency. The basic operations, in this paper, are discussed and design guidelines are presented. The usefulness of the proposed converter is verified on a 200kHz, 180W prototype converter.