Patent ID: 8878389

Claim:
An uninterruptible power supply comprising: a first input having an input line connection and an input neutral connection to receive a first input voltage from a first voltage source; a second input having a positive input connection and a negative input connection to receive a second input voltage from a second voltage source; a boost circuit configured to provide a positive output DC voltage with respect to the input neutral connection and a negative output DC voltage with respect to the input neutral connection in both a line mode of operation and a backup mode of operation, the boost circuit including a first switching device having a first end and a second end with the second end coupled to the negative input connection and the boost circuit including a second switching device having a first end and a second end; a first connection circuit configured to couple the first input to the boost circuit in the line mode of operation, and configured to couple the second input to the boost circuit in the backup mode of operation; and a second connection circuit configured to couple the first end of the second switching device to the input neutral connection in the line mode of operation and to couple the first end of the second switching device to the positive input connection in battery mode of operation.