D24.7 - 48-V/1-MHz Hybrid Switched-Capacitor Converter Achieving Load-Independent Zero-Voltage Switching

This paper presents a hybrid switched-capacitor (HSC) converter capable of zero-voltage switching (ZVS). To validate the approach, a 48-V to 1-V, 1-MHz prototype was developed. The converter employs three switched-capacitor (SC) stages that first divide the 48-V input into three equal parts and then perform a 2:1 step-down conversion to 8 V. Each SC stage drives a two-phase interleaved Buck converter, which further steps down the voltage to 1 V. ZVS is achieved by incorporating external inductors and capacitors into the circuit—a method also applicable to other HSC converters with similar topologies. The external inductors are connected to the bridge midpoints, where they charge and discharge the switch parasitic output capacitance during the dead time of the SC stage, thereby enabling ZVS. Experimental results indicate that the proposed ZVS method improves efficiency by approximately 3.1\% near the peak-efficiency point and by about 1.7\% at full load, compared with zero-current switching (ZCS).