Modeling and Comparison of Passive Component Volume of Hybrid Resonant Switched-Capacitor Converters

Abstract

Hybrid and resonant switched-capacitor (SC) convertersenable efficient utilization of both active and passive components, and have the potential to achieve higher efficiency and higher power density than conventional SC and magnetic-based converters. One or more added inductors offer an additional degree of freedom in the design space. It is of great interest to understand the tradeoffsbetween capacitor and inductor size and volume allocation. In this article, we analyze the reactive energy processed by the passive components and use it to calculate the total passive component volume. It is shown that the total passive component volume of resonant SC (ReSC) converters can be expressed as a function of flying capacitor voltage ripple, and the optimized capacitor voltage ripple that minimizes the total volume is dependent on topology specific parameters and the relative energy density ratio between capacitors and inductors. Moreover, we also demonstrate through theoretical analysis and experimentation that ReSC converters use significantly less passive component volume than conventional SC and buck converters for the same amount of power converted. Next, to compare different ReSC topologies, a normalized passive volume parameter is proposed for simple and fair comparison. This can be used along with a normalized switch stress parameter (based on switch VA ratings) to create a framework to showcase the relative performance of different topologies. This framework can be used to visualize and compare the passive and active component utilization among different topologies. Additionally, the proposed reactive power analysis is extended to hybrid converters with regulation capability.