A large DC-gain highly efficient hybrid switched-capacitor-boost converter for renewable energy systems

A new hybrid switched-capacitor-boost converter in which the energy is processed only once is proposed: the input ports of a switched-capacitor (SC) circuit and a boost power stage are connected in parallel whereas their output ports are connected in series. The SC converter is formed by two sub-stages which are operated with interleaving. It is unregulated. Its capacitors are charged till almost saturation, the difference between the voltages across the capacitors at the end of the charging interval and end of the discharging interval is very small, resulting in a very high efficiency of the capacitors charging process. The purpose of the SC stage is to give most of the voltage step-up gain. It processes most of the energy. Only a small portion of the energy is processed by a PWM boost converter. Its purpose is to assure overall regulation. As the role of this stage is not to step-up the voltage, it can work with a small duty-cycle value, chosen to get the highest possible efficiency. The sub-stages of the SC circuit are interleaved with the boost stage to minimize the input current ripple. As a result, a converter with high efficiency, large voltage step-up, and small input current ripple is obtained. The line and load regulation ability of the new configuration is proved analytically and confirmed experimentally. A 200 W prototype was built to step-up an input voltage of 14 V to 98 V. The measured efficiency is 87%.