A Regulated Cascaded Hybrid Switched-Capacitor Converter with Soft-Charging and Zero Voltage Switching for 48-to-12-V Applications

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. At 12-V fixed output voltage, it achieves a power density of 3115 $\mathrm{W}/\text{in}^{3}$, a peak efficiency of 99.0% with 48-V input and 98.6% 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.