A New High Step-down Converter with Low Ripple Current and High Efficiency

This paper introduces a new high step-down converter that achieves zero voltage switching in both primary and auxiliary switches without relying on coupled inductors, thus ensuring low ripple in input and output currents. The auxiliary circuit is optimized with the fewest possible components, facilitating zero voltage switching for the main and auxiliary switches and solving the reverse recovery issue of freewheeling diodes through zero current switching conditions. Additionally, this design reduces voltage stress on the switches, allowing the use of MOSFETs with lower drain-source resistance. A key advantage of this converter is that it avoids using coupled inductors, which eliminates issues related to leakage inductance and potential increases in the converter's size and weight. This enhances the converter's efficiency and practicality. The auxiliary circuit design can also be extended to multiple phases, making it adaptable for various applications. The control mechanism is simple because the auxiliary switch operates in complementary with the main switch, simplifying the overall circuit design and integration. The proposed converter's design and operational principles have been validated through PSpice simulations, and a 90W prototype has been constructed. Experimental results demonstrate an impressive 95 percent efficiency at full load.