Power- & area-efficiency enhancement techniques of switched-capacitor power converters for low-power applications

Abstract

Switched-capacitor (SC) power converters that use capacitors as energy storage elements offer much better power density than switched-inductor counterparts and are thus attractive in low-power area-constrained applications. This paper first reviews the importance of having auto-reconfigurable conversion ratios in the SC power stage in order to enable the regulator to maintain high power efficiency under unstable input voltages. To minimize the required capacitors and power switches in SC power converters, multiple-output SC power regulators can share capacitors and power switches in the power stage for generating multiple regulated outputs and thus improving the converter area efficiency. To simultaneously illustrate above concepts, an auto-reconfigurable dual-output SC power regulator is developed to generate two outputs while saving 1 flying capacitor and 3 power switches compared with using two independent single-output doubler and tripler. The proposed regulator has minimal cross regulation between outputs and achieves a maximum power efficiency of 88% via auto-reconfiguration when the input voltage varies from 1.1V to 1.6V.