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

• US 6,400,591 B2
• Filed: 03/19/2001
• Issued: 06/04/2002
• 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: Landsman, Emanual E., Reilly, David E., Curtis, Jeffrey
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/811,974
• Publication Number:
  US 20010033505A1
• Time in Patent Office: 442 Days
• Field of Search: 363/125, 363/37, 363/17, 363/56.01, 363/56.02, 363/56.03, 307/64, 307/66
• 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, wherein during a first time period, the first switch is controlled to allow an electrical current path to connect the resonant element to the capacitive element, an electrical current of the path storing energy in the resonant element and charging the capacitive element to a first voltage level, and during a second time period, the first switch is controlled to block the current path to cause the stored energy in the resonant element to further charge the capacitive element to a second voltage level during the second time period. 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 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 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 having the capacitive element;

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, wherein during a first time period, the first switch is selected to enable an electrical current path from the resonant element to the capacitive element, an electrical current of the path storing energy in the resonant element and charging the capacitive element to a first voltage level, and during a second time period, the first switch is selected to block the electrical current path to cause the stored energy in the resonant element to further charge the capacitive element to a second voltage level during the second time period;

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 for the uninterruptible power supply.

2. The uninterruptible power supply of claim 1, wherein the first voltage level is a portion of a voltage source and the second voltage level is substantially the voltage source.

3. 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.

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

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

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

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

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

8. The uninterruptible power supply of claim 7, 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.

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

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

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

12. 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.

13. 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 to a first voltage level by creating an electrical current path from the inverter to the load through a resonant element, wherein the resonant element stores energy from an electrical current of the path;

means for blocking the electrical current path after the capacitive element has been charged to the first voltage level to cause energy from the resonant element to be transferred to the capacitive element to further charge the capacitive element to a second voltage level; 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.

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

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

16. The uninterruptible power supply of claim 15, 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.

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

18. The uninterruptible power supply of claim 13, 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.

19. 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 to a first voltage level by supplying electrical current from the DC voltage source to the load through a resonant element in the uninterruptible power supply,

storing energy in the resonant element from the electrical current;

blocking the electrical current from the DC voltage source to the load through the resonant element after the capacitive element has been charged to the first voltage level; and

transferring the stored energy from the resonant element to the capacitive element to further charge the capacitive element to a second voltage level.

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

supplying load current from the DC voltage source to the load after the capacitive element has been charged to the second voltage level;

blocking the load current from the DC voltage to the load after a predetermined period;

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.

21. The method of claim 19, 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.

22. The method of claim 19, wherein the resonant element includes an inductor.