Synthesis and Analysis of a Series-Connected Switched-Capacitor DC-DC converter

Abstract

series-connected SC (Switched Capacitor) DC-DC converter is introduced. Aiming at an IC implementation of a stepped-down converter for mobile devices, we synthesize the series-connected DC-DC converter by using a family of the charge-averaging type converter. Different from conventional converters, the proposed converter provides only Q/P(P { 2 ,3,...,N} and Q {1,2,...,N - 1}) stepped-down voltages. However, the number of power switches for the proposed converter is less than 75 % of that for the conventional converters.Furthermore, the characteristics concerning efficiency and ripple factor are clarified by theoretical analyses since the theoretical analyses concerning the series connected SC power converters have not been performed as far as authors know. The analysis results provide the limitation values of the characteristics of designed circuits. The validity of the circuit designand the theoretical analysis is confirmed by SPICE simulations. Under the condition that the output load RL = 5 ­, the simulations show that 1. the power efficiency is more than 90 %, 2. the electrical power is about 440 mW, and 3. the ripple factor is less than 0.05.