A High Performance 48-to-6 V Multi-Resonant Cascaded Series-Parallel (CaSP) Switched-Capacitor Converter

Switched-capacitor (SC) converter topologies can achieve high efficiency and high power density due to their efficient switch utilization and use of high energy density capacitors. The use of resonant inductors can further improve efficiency by enabling soft-charging and soft-switching operations. However, the number of components (switches and capacitors) increases proportionally with the conversion ratio, increasing circuit complexity and potentially reducing performance. Because of this, SC converters with multiple operating states per switching cycle are attractive for high-step down applications as they can achieve the same conversion ratio as two-phase SC converters with fewer components. This work proposes and explores a new multi-phase resonant cascaded series-parallel (CaSP) topology, comprising a cascaded 2-to-1 SC stage with a 4-to-1 series-parallel stage. A 48-to-6 V prototype design for data center applications was built and tested, and achieved 98.6% peak efficiency (98.1% including gate drive loss), 95.3% full-load efficiency (95.2% including gate drive loss) at 70 A output, and 2140 W/in(3) power density by box volume.