Method and apparatus for zero-current switching control in switched-capacitor converters

A method of operating a switched-capacitor converter that includes an input, an output, a rectifier at the output, and a plurality of legs coupled between the input and the rectifier, each leg comprising a capacitor, a first group of the legs being coupled to a first branch of the rectifier and a second group of the legs being coupled to a second branch of the rectifier, and a switch device connected to each leg, the method comprising:

• alternately switching the switch devices connected to the first and the second groups of legs to transfer energy from the input to the output;
• and
• modifying the switching based on zero-crossing information which indicates, for each leg of the first group of legs, when current through the switch device connected to said each leg crosses or nearly crosses zero, so that each switch device connected to a leg within the first group of legs is turned off when the current through said each switch device crosses or nearly crosses zero and remains off until all switch devices connected to legs within the first group of legs have been turned off for a predetermined amount of time,
• wherein the modified switching turns on at least two switch devices connected to legs within the first group of legs for partially overlapping time intervals within a switching cycle, the partially overlapping time intervals having different time durations.