A High Conversion-Ratio Hybrid Series-Parallel DC-DC Converter with Pseudo-Soft-Charging and Inductor Current Frequency Multiplication

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 C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OSS</inf> 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.