This article suggested a new interleaved high step-down converter that consists of just one auxiliary switch to establish zero-voltage transition for all main and auxiliary switches. Because of the paralleled structure, the reliability of the designed converter has increased, and output current ripple is decreased. Also by using coupled inductors, the high current gain is achieved. In this converter, zero-voltage switching (ZCS) condition is established for all diodes, thus reverse recovery problems in these diodes do not exist. The proposed converter is fully described and analyzed, and to acknowledge the theoretical analysis, a 200 W prototype has been implemented. The proposed converter efficiency is about 96% at full load, and a decrease about 9 dB/μV is obtained in electromagnetic interferences (EMI) measurement of the proposed converter in comparison with hard-switched counterpart.