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Modified Split-Phase Switching with Improved Fly Capacitor Utilization in a 48V-to-POL Dual Inductor Hybrid-Dickson Converter


This work demonstrates a modified split-phase switching scheme which maintains complete soft-charging operation when applied to a dual inductor hybrid-Dickson (DIH) switched-capacitor converter, while simultaneously greatly increasing the allowable fly capacitor voltage ripple and subsequent passive component utilization. Dissimilar to previous DIH split-phase demonstrations which sequentially introduce capacitive elements as a switching phase progresses, here all fly capacitors are inserted upon initialization of each phase, with select capacitors being disengaged before each phase's conclusion. As a result no switches experience a periodic reverse bias. This work includes analysis directing this insight along with a hardware prototype that achieves a peak efficiency of 93.8% (87.5%) at 750kHz switching frequency, for 48V-to-3V (1V) conversion. Effective capacitor utilization and complete soft-charging is verified experimentally, and a power density of 54.4 kW/liter (892W/inch ) at 3V output is recorded despite the use of stable Class I (C0G/NP0) dielectric capacitors and oversized inductors with minimal current ripple for simplified analysis.

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