PWM switched capacitor voltage divider with high step-down ratio

Novel PWM switched capacitor voltage dividers (SCVDs) are proposed for high step-down voltage conversion applications. The proposed PWM-SCVDs achieve greater stepdown voltage conversion at a given duty cycle than do conventional PWM buck converters, which suffer from extremely low duty cycle for high step-down applications. Fundamental operation analysis was performed to compare the proposed PWM-SCVDs with a traditional PWM buck converter in terms of step-down ratio and normalized inductor ripple current. Two 30-W prototypes of PWM-SCVDs were built and their power conversion efficiencies were measured at step-down ratios of 0.214 and 0.125 for an output voltage of 6.0 V. Efficiencies higher than 86% and 83%, respectively, were achieved in an output power range higher than 10 W. Measured duty cycles were about 0.4, demonstrating that the proposed PWM-SCVDs achieve high step-down voltage conversion without operation at extremely low duty cycle.