Voltage and Current Balancing Control for 48-V Two-Stage Hybrid-Switched-Capacitor Converter

The paper presents a novel control strategy for balancing the flying capacitor voltage and output inductor current of a 48-V-to-1-V two-stage hybrid-switched-capacitor converter. The first stage is a 3-to-1 Dickson converter with two flying capacitors and the second stage is formed by four parallel two-phase series-capacitor buck converters for regulation and high output current. To reduce the charge redistribution, the decoupling capacitor between two stages is designed to be smaller than two flying capacitors. The duty ratio of the Dickson converter is designed to keep the charge balancing of two flying capacitors. With small decoupling capacitors, the bus voltage ripple becomes larger and a phase rotation control is proposed for the current balancing of the second stage. The operational principle of the balance control is introduced, and a 48-V-to-1-V/240A two-stage prototype is built to verify the effectiveness of the balancing control.