High efficiency multilevel switched-capacitor DC-DC converters for interfacing DC-buses with separate ground

Switched-capacitor multilevel DC-DC converters for interfacing DC-buses with separate grounds have been proposed recently. Including a very small inductor in series with the low-voltage DC-bus or source, significantly reduces semiconductor switching losses. However, past investigations have not tried to establish how converter performance depends on the sizes of both clamping and voltage-divider capacitors. This paper will show that in these types of SC converters, the size of C
_vd
has a dominant influence on performance. Very significant improvements in overall performance are achieved by proper sizing of C
_vd
even in the absence of L
_r
. Further, asymmetrical connection of loads or sources in 4-level converters leads to operation with higher voltage conversion ratios.