Article ID: 24006436
Voltages of powertrains and lithium-ion batteries (LIBs) of electric vehicles are increasing to 600–800 V, whereas ordinary fast chargers are designed for 400-V systems. An additional on-board or internal voltage conversion stage is necessary to accommodate traditional chargers to high-voltage powertrains. This paper proposes a resonant switched capacitor converter (RSCC) with a conversion ratio of either 1.5 or 2.0 to bridge the voltage gap between 400-V chargers and 600- or 800-V systems. The proposed RSCC contains a 3-level flying capacitor circuit that realizes the changeable conversion ratio between 1.5 and 2.0. Furthermore, a zero-voltage switching (ZVS) cell, which consists of a tiny inductor and capacitor, is added to eliminate losses due to parasitic capacitances of MOSFETs and diodes. Experimental tests using a 1-kW prototype demonstrated power conversion efficiencies in both the 1.5x and 2.0x conversion modes were higher than 98% in medium- and heavy-load regions.
