Comparative analysis of two compact and highly efficient resonant switched capacitor converters

Abstract

In this paper we compare two resonant switched capacitor converters in which the resonant inductor can be placed in series with a resonant capacitor (AC side), conducting a sinusoidal current, or it can be placed in series with the input source (DC side), conducting rectified sinusoidal current. Both resonant converters have the same voltage gain, and although the change in the position of the resonant inductor is, at first glance, of minor importance, the analysis and results show that it has huge impact on the capability to achieve ZVS transitions at low output power and on the inductor design and power losses. The experimental results show that for circuit with the resonant inductor in the AC side, the ZVS transitions produce an effective switching frequency significantly higher than the resonant frequency which forces the implementation of cycle skipping at light loads. The difference between the power losses in these two approaches is between 3W and 5W. The prototype implemented for the experiments provides up to 4.5kW with 33.3W power loss (99.3% efficiency). In the case of light load (1.5kW) power losses are only 8.25W (η=99.45%). Its power density is higher than 65kW/dm3.