Method and apparatus for converting a DC voltage to an AC voltage

Embodiments of the present invention are directed to an uninterruptible power supply for providing AC power to a load. In embodiments of the present invention, the uninterruptible power supply includes an input to receive AC power from an AC power source, an output that provides AC power, a DC voltage source that provides DC power, the DC voltage source having an energy storage device, an inverter (200) operatively coupled to the DC voltage source to receive DC power and to provide AC power. The inverter includes first and second output nodes to provide AC power to the load (126), first and second input nodes to receive DC power from the DC voltage source (18a), a resonant element (140) having a first terminal and a second terminal, the second terminal being electrically coupled to the first output node, a first switch (134) electrically coupled between the first terminal of the resonant element and the first input node, and a set of switches (106, 112, 118, 124) operatively coupled between the first and second output nodes and the first and second input nodes and controlled to generate AC power from the DC power. The uninterruptible power supply further includes a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply.