Analysis and Implementation of a Transformerless Interleaved ZVS High-Step-Down DC-DC Converter

High step-down dc-dc converters are widely utilized with the rapid development of big data and cloud computing. Conventional buck converter cannot provide satisfactory performance due to super small duty-cycle. In this article, the double step-down benefit of SC-buck converter and the capacitors soft charging and discharging benefit of resonant dual-path hybrid buck converter are combined together to propose a new nonisolated dc-dc topology: interleaved series-capacitor resonant hybrid buck converter, which is suitable for the high-step-down and high-current-output applications. The introduction of resonant tank in the hybrid structure not only realizes the soft switching of all switches, but also eliminates the current spike generated by capacitor hard discharging. Combined with the circuit modification of SC-buck converter, the proposed converter can eliminate the problem of high switch-voltage stress of the existing converter encountered during start-up. Other strengths of this topology are automatic current sharing between two interleaved modules, lower switching loss, lower conduction loss, and reduced inductor loss due to more current paths provided by the hybrid structure. The validity of theoretical analysis and converter operation is confirmed by the implementation of a 160 W prototype at 48 V input voltage and 4 V output voltage. The maximum efficiency of the prototype is 96.26% and the efficiency is 93.86% in full-load condition.