Duty ratio control of resonant switched capacitor DC-DC converter

Resonant switched capacitor (RSC) converter has the advantage of zero-current switching, however, its output power range is narrow and its voltage conversion ration is predetermined by its topology. In this paper, a new duty ratio control method for RSC converter was presented. In the proposed method, the discharging time was fixed and the charging time was variable. By adjusting the ratio of charging time, good output voltage regulation for large changes in input voltage and/or load values could be obtained. Most of the switching devices were still zero-current switching. The advantage of low switching current and low EMI in RSC converter was still kept in the proposed duty ratio control scheme. A step-down RSC converter was used as an example in this paper. The circuit operation principle and steady-state characteristics were described in detail. A step-down RSC prototype with the proposed method has been implemented and tested; theoretical prediction of its regulation is verified experimentally