A Multiple Input Variable Output Switched Capacitor DC–DC Converter for Harnessing Renewable Energy and Powering LEDs

This paper presents the design, operation and testing of a multiple input variable output voltage conversion ratio switched capacitor (SC) converter topology capable of powering a string of LEDs. Eleven gain modes of operation are achieved by the circuit operating with only 9 switches, 2 flying capacitors and one filter capacitor. The paper develops and presents a mathematical analysis of how to model and predict the efficiency of the SC converter using the differential charge analysis technique when operating in the fast switching limit (FSL). Experimental results validated with all the simulated output voltage values in PSIM software ensuring the feasibility of the proposed converter topology. Further, the converter was experimentally tested with commercially available switches and capacitors in a laboratory environment to power a LED string at 18 V delivering 240 mA current with one source as a battery and the second as a solar source to harness maximum renewable energy. The converter efficiency has been found to be greater than 80% with an acceptable regulation in open loop mode. The tested converter has potential for application involving LEDs for general lighting or for any applications involving dual source at the input with buck, boost or unity gain modes available at the output with minimum electronic components, PCB area and an inductorless topology.