This work explores hybrid Series-Parallel (SP) switched capacitor (SC) DC-DC converter architectures designed for high-voltage, high-conversion-ratio applications that use inductor current ripple frequency multiplication, a property previously reported for Flying Capacitor Multilevel (FCML) converters. The design is realized using a single high-voltage GaN switch and low-voltage Si switches for the SP and PWM stages. Due to the better passive utilization of SP over other architectures, a lower switching frequency is achieved while meeting the same ripple requirements with superior flying capacitor voltage balancing. The SC stage is used to reduce COSS loss at the GaN switching node via a pseudo-soft charging process. A simple voltage-mode active balancing scheme provides single-cycle flying capacitor voltage regulation. The design achieves 48V: 3V and 60V: 3.75V step down with over 91% efficiency and peak input voltage of 170V with 92% efficiency at 64W output power.
