Merged-Two-Stage Resonant and PWM Soft-Charging of Hybrid-Switched-Capacitor DC-DC Converters

The efficiency and power density of switched-capacitor dc-dc converters are usually limited by the charge sharing loss of capacitors. In a merged-two-stage hybrid-switched-capacitor design, soft-charging can be achieved by merging a magnetic-based converter with a switched-capacitor-based converter. The magnetic-based converter functions as a current source to charge and discharge the switched capacitors without charge sharing loss. This paper investigates the output impedance of two types of merged-two-stage hybrid-switched-capacitor dc-dc converters with 1) resonant soft-charging, in which the switched-capacitors are soft-charged by sinusoidal current waveforms and 2) PWM soft-charging, in which the switched-capacitors are soft-charged by PWM current waveforms. A few circuit topologies leveraging the merged-two-stage soft charging mechanism are discussed. The effectiveness of the output impedance analysis is verified by SPICE simulations.