A Resonant Cockcroft-Walton Switched-Capacitor Converter Achieving Full ZCS and >10kW/inch³ Power Density

Hybrid LC switched-capacitor converter architectures have demonstrated high power density while retaining efficiency at high conversion ratios. This work presents a resonant Cockcroft-Walton (CW) converter that achieves full zero-current switching (ZCS) on all switches using a single inductor and requiring only one current sensor. To do so, an N-phase clocking scheme is employed, eliminating the parallel paths that typically introduce transient shorting losses in a conventional 2-phase CW converter. The reduced voltage stress on the CW's fly capacitors results in a dramatic reduction in volume when using common MLCC capacitors. A discrete 1:5 CW prototype using silicon FETs and a spiral trace inductor was assembled on two commonly available PCB processes: 0.8 mm FR4 with 2 oz. Cu, and 0.127 mm polyimide film with 0.75 oz. Cu. The latter achieved a peak efficiency of 95% and a maximum power density of 0.686 W/mm ³ (11.2 kW/inch ³ ) in a volume of 44.5 mm ³ (0.00271 inch ³ ), excluding level-shifting and clock generation circuits.