The cascaded resonant switched-capacitor converter is an energy-efficient and power-dense solution to unregulated 48-to-12-V power conversion. This work explores approaches to achieve output voltage regulation with this topology while maintaining high efficiency and high power density. The two switch nodes at the second stage are merged into one for the automatic balancing of capacitor voltages. A hybrid resonant-PWM control method is presented to realize soft charging of the middle capacitor and flying capacitors. A hardware prototype is designed and built to verify the performance of the proposed converter. At 12-V fixed output voltage, it achieves a power density of 1835 W/in3, a peak efficiency of 98.8% with 48-V input and 98.3% with 54-V input (including gate drive loss), both of which are among the best in the state-of-the-art regulated 48-to-12-V solutions.
