Method and apparatus for providing uninterruptible power

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 battery;
• a second input to receive a second input voltage from the battery;
• 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;
• a first connection circuit to couple the first input to the boost circuit in the line mode of operation;
• and
• a second connection circuit to couple the second input to the boost circuit in the backup mode of operation;
• wherein the uninterruptible power supply is constructed and arranged to isolate the battery from the input neutral connection in the line mode of operation;
• wherein the boost circuit has a positive input, a negative input and a neutral input, wherein the neutral input is coupled to the input neutral connection, and wherein the second connection circuit includes a first diode coupled between a positive terminal of the battery and the positive input and a second diode coupled between a negative terminal of the battery and the negative input;
• and
• wherein the power supply is constructed and arranged to simultaneously draw current from both the first voltage source and the battery in a combined mode of operation.

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 backup voltage source;
• a second input to receive a second input voltage from the backup 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;
• and
• means for coupling the second input to the boost circuit in the backup mode of operation and for isolating the backup voltage source from the input neutral connection in the line mode of operation, wherein the means includes a first isolation device coupled to a positive terminal of the backup voltage source and a second isolation device coupled to a negative terminal of the backup voltage source;
• wherein the uninterruptible power supply is configured to operate with an AC voltage source at the first input having a peak AC voltage that is less than the positive output DC voltage, and wherein the battery has a battery voltage that is less than the positive output DC voltage and greater than the peak AC voltage.

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 backup voltage source;
• a second input to receive a second input voltage from the backup 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;
• means for coupling the second input to the boost circuit in the backup mode of operation and for isolating the backup voltage source from the input neutral connection in the line mode of operation, wherein the means includes a first isolation device coupled to a positive terminal of the backup voltage source and a second isolation device coupled to a negative terminal of the backup voltage source;
• and
• means for simultaneously drawing current from both the first voltage source and the backup voltage source in a combined mode of operation.

A method of providing power to a load, the method comprising:

• receiving input power at a line connection and a neutral connection from a first voltage source;
• rectifying the input power to produce a first rectified voltage at a first node during a positive portion of an input voltage wave and a second rectified voltage at a second node during a negative portion of the input voltage wave;
• in a line mode of operation, producing a positive DC voltage with respect to the neutral connection from the first rectified voltage and a negative DC voltage with respect to the neutral connection from the second rectified voltage;
• coupling a second voltage source to the first node and the second node using a connection circuit that is configured to isolate the second voltage source from the neutral connection in the line mode of operation, wherein coupling a second voltage source includes coupling a first isolation device between the second voltage source and the first node and coupling a second isolation device between the second voltage source and the second node;
• and
• simultaneously drawing current from both the first voltage source and the second voltage source in a combined mode of operation.