Where is the Inductor: A Review and Comparison of the Hybrid DC-DC Buck Topologies

There is an ever-increasing voltage gap between the power buses and the advanced digital loads, driving substantial demand for efficient and compact DC-DC step-down conversion topologies. This paper reviews the switched-capacitor-inductor (SCI) hybrid DC-DC buck converters, categorizing them into five groups based on the location of the power inductor: inductor-last, inductor-first, inductor-ground, inductor-parallel, and inductor-middle. Then, this paper analyzes two critical performance metrics and proposes a unified pre-design figure-of-merit (FoM) for evaluating various hybrid converters.