Non‐resonant soft‐switching technique with linear current on switching cycle time‐scale for switched‐capacitor DC‐DC converters

Abstract

The switched-capacitor DC-DC converters have been widely applied to convert energy from low voltage to DC bus for the power generation systems with fuel cells, photovoltaic array, and so on. However, the large capacitance is generally selected to eliminate the high current spike of switched-capacitors in the hard-switching switched-capacitor (SC) DC-DC converters, which will lead to the large volume and weight of capacitors and of converters. To solve this problem, a non-resonant soft-switching (NRSS) technique with linear current on switching cycle time-scale for switched-capacitor DC-DC converters is first proposed in this paper, which achieves zero-current-switching (ZCS) turn-on of switches and ZCS turn-off of diodes with linear current on switching cycle time-scale. In detail, the NRSS technique is proposed based on the idea that the current of an auxiliary inductor on switching cycle time-scale is considered as the linear parts for the resonant current of the auxiliary inductor on resonant cycle time-scale. The proposed NRSS technique is utilized into SC DC-DC converter and the current spikes of switches can be reduced to two third by using the same capacitance compared with the hard-switching SC DC-DC converters and be reduced to a third compared with the resonant soft-switching SC DC-DC converters. Further, nine new soft-switching SC DC-DC converters, with single switch and double switches, are built based on the proposed non-resonant soft-switching technique. Finally, the non-resonant soft-switching technique is verified theoretically and experimentally by three of the nine proposed SC DC-DC converters. This paper provides a new way to realize soft-switching during the non-resonant interval on switching cycle time-scale and a new method to significantly reduce the required capacitance in SC DC-DC converters.