High-Frequency Resonant Switched-Capacitor Converters with Multi-Winding Current Ballasting: Analysis and Optimization

This work explores analysis and optimization of multi-winding current-ballasting in high-frequency coupled mag-netic structures for direct-conversion resonant switched-capacitor (ReSC) DC-DC converters, a technique that can mitigate AC con-duction losses, improving efficiency at high frequency. While past work has explored merged-LC resonators which combine capacitance and inductance into a single structure, here we show similar benefits can be achieved with separately lumped capacitors in di-rect-conversion ReSC topologies. We develop a state-space model to determine optimum per-winding current density profiles and show that such profiles can be achieved by presenting a unique (flying) capacitance to each winding in a multiphase ReSC archi-tecture. A hardware prototype with planar air-core test structures is used for validation and also to explore practical limitations.