Methods and apparatus for providing uninterruptible power are provided by aspects of the invention. One aspect is more particularly directed to an uninterruptible power supply for providing power to a load. The uninterruptible power supply includes a first input to receive input power from an input power source, an output to provide output power, a bypass input to receive bypass power from a bypass power source, wherein the bypass input is selectively coupled to the output to provide output power from the bypass power source, an input power circuit coupled to the first input and having a DC output that provides DC power having a first DC voltage level, a back-up power source coupled to the input power circuit to provide DC power at the DC output in a back-up mode of operation, and an inverter circuit having an output coupled to the DC output of the input power circuit and having an output coupled to the output of the uninterruptible power supply to provide the output power derived from at least one of the input power source and the back-up power source. The uninterruptible power supply is constructed and arranged in a bypass mode of operation to control the inverter circuit to convert AC power from the bypass power source at the output of the inverter circuit to DC power at the input of the inverter circuit.