Study on different input connections' effect of step-up switched capacitor AC-AC converters

Effects of different input connections on step-up switched capacitor AC-AC converters are a neglected field in previous references. Two kinds of step-up switched-capacitor converter (SCC) with different input connections are studied in this paper: balanced SCC and unbalanced SCC. The transient working processes and equivalent resistance of two converters concerning equivalent series resistance of capacitors are discussed. Derivation of equivalent resistance of the balanced SCC is also proposed in this paper. Voltage gains of two SCCs are compared in different duty cycle and switching frequency to determine the optimal duty cycle and the appropriate switching frequency. Then a 1 kW prototype is built. By comparing the voltage gains and conversion efficiencies of two kinds of SCC under the condition of 50% duty cycle and optimal switching frequency theoretically and experimentally, the highest efficiencies of two kinds SCC are obtained. The relevant theoretical and experimental results show that the balanced SCC presents better performance.