Split-phase control: Achieving complete soft-charging operation of a dickson switched-capacitor converter

Switched-capacitor (SC) converters are gaining popularity due to their high power density and suitability for on-chip integration. Soft-charging techniques can be used to eliminate the current transient during the phase switching instances, and improve the power density and efficiency of SC converters. In this paper, we propose a split-phase control scheme that enables the Dickson converter to achieve complete soft-charging operation, which is not possible using the conventional two-phase control. An analytical method is extended to understand and design split-phase controlled Dickson converters. The proposed technique and analysis are verified by both simulation and experimental results. An 8-to-1 step-down Dickson converter is built to demonstrate the reduction in output impedance and improvement in efficiency as a result of the split-phase controlled soft-charging operation.