High-Efficiency Nonisolated Converter with Very High Step-Down Conversion Ratio

This paper introduces a new nonisolated converter topology with very high step-down conversion ratio and high efficiency for high current low voltage point-of-load voltage regulator modules. Compared to a conventional two-phase buck converter, the new converter triples the effective duty-ratio and lowers the voltage stress of the transistors, significantly reducing the overall volume of the converter while maintaining high efficiency. The new converter is capable of delivering high current to the output by two interleaved phases and further features an inherent current sharing to balance the load between the phases. The use of lower voltage stress transistors allows operation at high switching frequencies that translates into fast dynamic response to load perturbations. The operation of the topology is verified on a 30 W, 48 V-to-1 V prototype, demonstrating peak efficiency of 91.5% and above 88% for most of the load range.