Extending Conversion Ratio of a Series-Capacitor Buck Topology by Adding N Capacitor Cells

Abstract

This paper introduces an extension methodology for modular multi-phase series-capacitor buck converter that enables scaling to an arbitrary number of capacitor cells, with minimum operation states and minimum topological subcircuits. By distributing the voltage conversion across multiple capacitive stages, the new design reduces device voltage stress and improves overall efficiency. The converter extension using a basic capacitor cell enables a highly modular architecture with a minimal component count and distinguished subcircuits while supporting high conversion ratios. The interaction between the capacitor and the inductor results in a soft charging operation, which reduces the losses of the converter, and contributes to higher efficiency. Additional features of the new converter include a significantly extended effective duty ratio, reduced inductor and output current ripple, high output current capability, and architecture-inherent output current sharing that balances the loading between the phases. Simulation and experimental results obtained from a modular, interleaved-two-phase, three-capacitor-cell prototype validate the developed methodology and demonstrate strong agreement with the theoretical analyses.