A digitally-controlled 2-/3-phase 6-ratio switched- capacitor DC-DC converter with adaptive ripple reduction and efficiency improvements

Abstract

A digitally controlled 2-/3-phase 6-ratio switched-capacitor (SC) DC-DC converter with low output voltage ripple and high efficiency is presented. Operating with a wide input voltage range of 1.6V to 3.3V, this SC converter can deliver a maximum power of 250mW to an output of 0.5V to 3V. Six voltage conversion ratios (VCRs) can be generated with only 2 flying capacitors by using 2- or 3-phase operation. Compared with a 2-phase SC converter, the maximum efficiency improvement is 20%. An adaptive ripple reduction scheme is proposed to achieve 4 times reduction in the output voltage ripple. Complexity of controller design is reduced by using digital synthesis and the technique is scalable. Fast loop response is achieved by synchronized hysteretic control. The converter achieves a peak efficiency of 91%.