Design of a step-up/step-down SC DC-DC converter with series-connected capacitors

A step-up/step-down switched-capacitor (SC) DC-DC converter with series-connected capacitors is proposed in this paper. The circuit can provide more various types of output-voltages than conventional converters, because the series-connected capacitors in a ring-connection enable us to convert an input voltage at short step-up/step-down interval. Furthermore, high efficiency can be achieved by using the power-switches with novel bootstrap circuits. Via maximum circuits constructed with diodes, maximum voltage of the power converter is charged to a capacitor in the bootstrap circuit. By connecting the charged-capacitor between the gate terminals of power-switches and the output terminal of the maximum circuit, the bootstrap circuits reduce the on-resistance of the power-switches. The simulations show that 1) the proposed circuit can realize shorter step-up/step-down interval than the conventional ring-type power converter and 2) the efficiency is more than 95% when the output load R_o=100 Ω.