Modulation Improvements for High Phase-Count Series-Capacitor Buck Converters

Abstract

This paper presents various phase activation sequences which raise the maximum input-to-output voltage conversion ratio of an N-inductor, N-phase Series-Capacitor (SerC) Buck Converter beyond the traditional limit of $1/N^{2}$. Phase counts up to 16 are analysed with conversion ratios increasing by a factor of up to 7. This paper additionally introduces a modulation technique that effectively increases the DPWM output voltage resolution by a factor of N by employing a novel method of minor duty increments (MDI). An experimental discrete prototype of an 11-phase, 48V–1.0VSerC Buck was fabricated to validate both the increase in the output voltage ceiling and DPWM resolution, as well as to evaluate the MDI-DPWM output voltage linearity.