Development of a multistage current-controlled switched-capacitor step-down DC/DC converter with continuous input current

Abstract

This paper presents the design and analysis of a low-profile multistage current-controlled switched-capacitor (SC) step-down dc/dc converter. The converter not only exhibits all advantages of classical SC converters, but also features good regulation capability and continuous input current waveform, resulting in low conducted electromagnetic interference with the supply network. The concept of energy transfer is achieved by paralleling the input and output of two step-down converter cells and operating them in antiphase. The voltage conversion ratio is determined by controlling the charging trajectories of the capacitors in each cell. As the circuit is unnecessary to use any inductive elements, possibilities of integrated circuit fabrication and high power density are promising. By applying the state-space averaging technique, a third-order state-space model for an n-stage converter is derived. Static and small-signal dynamic behaviors of the converter are investigated. A 70-W 48-V/12 V converter is implemented. Analytical predictions are verified with experimental measurements.