Design Optimization for Low-Power Reconfigurable Switched-Capacitor DC-DC Voltage Converter

Abstract

Low-power circuits often employ dynamic voltage scaling and energy harvesting. Such circuits need a power management unit that can convert the voltage source to a wide range of target voltages with high efficiency. Targeting such a power management unit, this paper presents a reconfigurable architecture of switched capacitor (SC) voltage converter. It introduces a design optimization methodology that can determine trade-off among design parameters to meet the goal. The proposed converter employs a reconfigurable topology with four capacitors. It provides 11 conversion ratios: 6 step-down and 5 step-up ratios supporting wide input/output voltage range. An analytical model for the output impedance of the proposed reconfigurable SC topology is presented. Using the model, the proposed optimization methodology can minimize the total power dissipation. To validate the proposed architecture and optimization methodology, the converter has been implemented in a 130-nm CMOS process using integrated capacitors of total size 2.2 nF. Simulation results show that the optimized converter circuit achieves an efficiency range from 83.41% to 74.69% for a load current of $100~\mu \text{A}$ .