Compact energy efficient switched-capacitor multilevel DC-DC converters for interfacing DC-buses with common ground

Multilevel switched-capacitor DC-DC converters have been proposed for applications that require interfacing two DC-buses or sources. High-voltage DC-bus in general is specified to be an integer multiple that of the low-voltage side. Low efficiency, bulky capacitor banks and unequal voltage sharing have been identified as some of the shortcomings of these converter topologies. This paper will show how to overcome the above mentioned shortcomings even when relatively small capacitor banks are employed. It will be shown that connecting a very small inductor (parasitic cable inductance is adequate) in series with clamping capacitors leads to very significant improvements in performance. For a given performance, the size of clamping capacitor can be greatly reduced when L
_r
is included. This makes it possible to build more compact and efficient converters.