US Patent 10536094 Efficient switching for converter circuit

An apparatus includes a first switch leg connected between a first input terminal and a first output terminal, the first switch leg comprising serially connected switches. The apparatus also includes a second switch leg connected between a second input terminal and the first output terminal, the second switch leg comprising serially connected switches. The apparatus further includes a third switch leg connected between an input voltage midpoint and the first output terminal. A controller controls the first switch leg, the second switch leg and the third switch leg, wherein the controller is configured to disable the second switch leg for a first time period and alternately enable the first switch leg and the third switch leg during the first time period, and to disable the first switch leg for a second time period and to alternately enable the second leg and the third leg during the second time period.