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

• US 6,404,658 B1
• Filed: 05/13/1999
• Issued: 06/11/2002
• Est. Priority Date: 05/13/1999
• Status: Expired due to Term

• Current Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: Reilly, David E.
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/311,043
• Time in Patent Office: 1,125 Days
• Field of Search: 363/125, 363/37, 363/40, 363/41, 363/43, 363/132, 363/21, 323/258, 323/222
• US Class Current: 363/125
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 7/53832 in a push-pull arrangement
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

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 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, first and second input nodes to receive DC power from the DC voltage source, a resonant element having a first terminal and a second terminal, the second terminal being electrically coupled to the first output node, a first switch electrically coupled between the first terminal of the resonant element and the first input node, and a set of switches 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.

Claims

1. An uninterruptible power supply for providing AC power to a load, the uninterruptible power supply comprising:

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 operatively coupled to the DC voltage source to receive DC power and to provide AC power, the inverter including;

first and second output nodes to provide AC power to the load;

first and second input nodes to receive DC power from the DC voltage source;

a resonant element having a first terminal and a second terminal, the second terminal being electrically coupled to the first output node;

a first switch electrically coupled between the first terminal of the resonant element and the first input node, the first switch being controlled to cause the DC power to bypass the resonant element at regular intervals; and

a set of switches 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; and

a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source; and

a transfer switch operatively 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.

2. The uninterruptible power supply of claim 1, wherein the set of switches includes:

a second switch electrically coupled between the second output node and the second input node;

a third switch electrically coupled between the second output node and the first input node;

a fourth switch electrically coupled between the first output node and the first input node; and

a fifth switch electrically coupled between the first output node and the second input node.

3. The uninterruptible power supply of claim 2, wherein the inverter further includes:

a sixth switch electrically coupled between the first terminal of the resonant element and the second input node.

4. The uninterruptible power supply of claim 3, wherein the resonant element includes an inductor.

5. The uninterruptible power supply of claim 4, wherein each of the switches includes a transistor.

6. The uninterruptible power supply of claim 5, wherein the energy storage device includes a battery.

7. The uninterruptible power supply of claim 6, wherein the transfer switch is constructed and arranged to receive the AC power from the input and to receive the AC power from the inverter and to provide one of the AC power from the input and the AC power from the inverter to the load.

8. The uninterruptible power supply of claim 1, wherein the resonant element includes an inductor.

9. The uninterruptible power supply of claim 1, wherein each of the switches includes a transistor.

10. The uninterruptible power supply of claim 1, wherein the energy storage device includes a battery.

11. The uninterruptible power supply of claim 1, wherein the transfer switch is constructed and arranged to receive the AC power from the input and to receive the AC power from the inverter and to provide one of the AC power from the input and the AC power from the output of the inverter to the load.

12. An uninterruptible power supply for providing AC power to a load having a capacitive element, the uninterruptible power supply comprising:

an input to receive AC power from an AC power source;

an output that provides AC power;

a voltage source that provides DC power, the voltage source having an energy storage device;

an inverter operatively coupled to the voltage source to receive DC power and having an output to provide AC power, the inverter including;

means for charging the capacitive element by supplying electrical current from the voltage source through the inverter to the load through a resonant element;

means for supplying load current from the voltage source through the inverter, bypassing the resonant element, after the capacitive element has been charged to a predetermined voltage;

means for discharging the capacitive element through the resonant element; and

means for transferring energy from the resonant element to the energy storage device; and

a transfer switch constructed and arranged to select one of the AC power source and the voltage source as an output power source for the uninterruptible power supply.

13. The uninterruptible power supply of claim 12, wherein the energy storage device includes a battery.

14. The uninterruptible power supply of claim 13, wherein the resonant element includes an inductor.

15. The uninterruptible power supply of claim 14, wherein the transfer switch is constructed and arranged to receive the AC power from the input and to receive the AC power from the output of the inverter and to provide one of the AC power from the input and the AC power from the output of the inverter to the load.

16. The uninterruptible power supply of claim 12, wherein the resonant element includes an inductor.

17. The uninterruptible power supply of claim 12, wherein the transfer switch is constructed and arranged to receive the AC power from the input and to receive the AC power from the output of the inverter and to provide one of the AC power from the input and the AC power from the output of the inverter to the load.

18. A method of supplying an uninterruptible AC voltage to a load having a capacitive element using an uninterruptible power supply having a DC voltage source with an energy storage device, the method comprising steps of:

charging the capacitive element by supplying electrical current from the DC voltage source to the load through a resonant element in the uninterruptible power supply;

supplying load current from the DC voltage source to the load, bypassing the resonant element, after the capacitive element has been charged to a predetermined voltage;

discharging the capacitive element through the resonant element; and

transferring energy from the resonant element to the energy storage device in the DC voltage source.

19. The method of claim 18, further comprising steps of:

receiving an AC voltage from an AC power source;

selecting one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply.

20. The method of claim 18, wherein the resonant element includes an inductor.

21. An uninterruptible power supply for providing AC power to a load, the uninterruptible power supply comprising:

an input to receive AC power from an AC power source;

an output that provides output AC power having a waveform that is substantially rectangular in shape;

a DC voltage source that provides DC power, the DC voltage source having an energy storage device;

an inverter operatively coupled to the DC voltage source to receive DC power and to provide the output AC power, the inverter including;

first and second output nodes to provide AC power to the load;

first and second input nodes to receive DC power from the DC voltage source;

a resonant element having a first connection point and a second connection point, the second connection point being electrically coupled to the first output node;

a first switch electrically coupled between the first connection point of the resonant element and the first input node, the first switch being controlled to electrically couple the resonant element between the first input node and the first output node at regular intervals of the output AC power waveform; and

a set of switches operatively coupled between the first and second output nodes and the first and second input nodes and controlled to generate the output AC power from the DC power.

22. The uninterruptible power supply of claim 21, wherein the inverter further includes a second switch coupled between the first connection point of the resonant element and the second input node, the second switch being controlled to electrically couple the resonant element between the second input node and the first output node at regular intervals of the output AC power waveform.

23. The uninterruptible power supply of claim 22, wherein the output AC power waveform has a positive portion having a first edge and a second edge, and a negative portion having a first edge and a second edge, and wherein the first switch is controlled to couple the resonant element between the first input node and the first output node during the first edge of the positive portion and the second edge of the negative portion, and wherein the second switch is controlled to couple the resonant element between the second input node and the first output node during the second edge of the positive portion and the first edge of the negative portion.