Patent ID: 7432615

Claim:
A system for providing power to a load, the system comprising: a first input to receive AC power from a first AC power source; a second input to receive AC power from a second AC power source; a third input to receive DC power from a first DC power source; an output that provides output AC power to the load; converter circuitry, coupled to the first, second and third inputs and the output, and controllable to select from the first AC power source, the second AC power source and the first DC power source to provide input power and derive the output AC power from the input power; a first bypass device coupled to the first input and the output and controllable to operate in a bypass mode to couple the first input to the output to provide AC power from the first AC power source directly to the output, bypassing the converter circuitry; and a second bypass device coupled to the second input and the output and controllable to operate in a bypass mode to couple the second input to the output to provide AC power from the second AC power source directly to the output, bypassing the converter circuitry; wherein the converter circuitry includes a plurality of controllable switches, each of the controllable switches being coupled to one of the first, second and third inputs to control current draw by the converter circuitry from the first AC power source, the second AC power source and the first DC power source; wherein, in a first power source transition mode, the converter circuitry is adapted to detect an input AC voltage waveform period of the first AC power source and to control the controllable switches such that the converter circuitry draws current from the first AC power source during a first portion of the waveform period and the converter circuitry draws current from the first DC power source during a second portion of the waveform period for multiple waveform periods; wherein, in a second power source transition mode, the converter circuitry is adapted to detect an input AC voltage waveform period of the second AC power source and to control the controllable switches such that the converter circuitry draws current from the second AC power source during a first portion of the waveform period and the converter circuitry draws current from the first DC power source during a second portion of the waveform period for multiple waveform periods; further comprising a fourth input to receive DC power from a second DC power source, and wherein the converter circuitry is coupled to the fourth input through a controllable switch that is controlled in the first transition mode to draw current from the second DC power source during the first portion of the waveform period for multiple waveform periods.