Charger

• US 6,121,756 A
• Filed: 10/25/1999
• Issued: 09/19/2000
• Est. Priority Date: 11/25/1997
• Status: Expired due to Fees

• Current Assignee: Powerware Corporation (Eaton Corporation PLC.)
• Original Assignee: Powerware Corporation (Eaton Corporation PLC.)
• Inventors: Johnson, Robert William Jr., Gucyski, Jeff, Widener, Steven R., Paulakonis, Joseph C.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/426,347
• Time in Patent Office: 330 Days
• Field of Search: 320/128, 320/137, 320/140, 320/143, 320/163, 320/FOR 148, 320/FOR 150, 320/FOR 153, 320/FOR 156, 363/24, 363/25, 363/131, 363/132, 363/133, 307/48, 307/66, 307/151
• US Class Current: 320/140
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

An uninterruptible power supply (UPS) comprises a low voltage converter (02); a coupled inductor (60) comprising a first inductor (63) coupled to the battery, a second inductor (61) coupled to a first output terminal of a rectifier, and a third inductor (62) coupled to a second output terminal of the rectifier; a snubber circuit; and a high voltage inverter (01).

Claims

1. An uninterruptible power supply (UPS), comprising:

(a) a transformer having a primary winding and a secondary winding;

(b) a low voltage converter (02) comprising a battery providing a DC voltage operatively coupled to a primary winding of said transformer, whereby a first AC voltage differential is generated across the secondary winding of said transformer;

(c) a high voltage inverter (01) comprising first and second load terminals adapted to be coupled across a load in an emergency situation;

a transistor Q1 and another transistor Q2, wherein said transistors Q1 and Q2 are switchable from conducting to non-conducting states and vice versa so as to produce an output voltage waveform across said load terminals when a load is coupled thereto, said output voltage being characterized by an amplitude that varies between a positive peak (V) and a negative peak (-V); and

(d) coupled inductor means (60) comprising a first winding (63) operatively coupled to said battery, and at least a second winding (61,

     62) operatively coupled to said high voltage inverter, wherein said first and second windings are wound around a common core.

2. An uninterruptible power supply as recited in claim 1, further comprising a snubber circuit operatively coupled to said second and third inductors.

3. An uninterruptible power supply as recited in claim 1, wherein a transistor Q3, another transistor Q4, and first drive means (41, 42) for driving said transistors Q3 and Q4 from a conducting state to a non-conducting state and vice versa;

wherein Q3 is operatively coupled to a first terminal of said primary winding of said transformer, Q4 is operatively coupled to a second terminal of said primary winding, and said battery is operatively coupled to a third terminal of said primary winding.

4. An uninterruptible power supply as recited in claim 1, further comprising a rectifier, having first and second output terminals (12, 14), for converting said first AC voltage across the secondary winding to a first high DC voltage (V) at said first output terminal and a second high DC voltage (-V) at said second output terminal.

5. An uninterruptible power supply as recited in claim 1, further comprising an output capacitor (C) operatively coupled to said load terminals.

6. An uninterruptible power supply as recited in claim 1, wherein said output voltage is characterized by a quasi-square waveform.

7. An uninterruptible power supply as recited in claim 1, wherein said transistors Q3 and Q4 are alternately driven from said conducting state to said non-conducting state at a frequency of approximately 20 kHz;

wherein said output voltage is characterized by a quasi-square waveform with a frequency of approximately 60 Hz; and

wherein the battery voltage is approximately 12 Volts DC and the quasi-square output voltage varies between +160 Volts and -160 Volts.

8. An uninterruptible power supply (UPS), comprising:

(a) a transformer having a primary winding and a secondary winding;

(b) a low voltage converter (02) comprising a battery providing a DC voltage, a first switching device (Q3), a second switching device (Q4), and first drive means (41,

     42) for driving said switching devices from a conducting state to a non-conducting state and vice versa;

wherein said first switching device is operatively coupled to a first terminal of said primary winding of said transformer, said second switching device is operatively coupled to a second terminal of said primary winding, and said battery is operatively coupled to a third terminal of said primary winding, whereby a first AC voltage differential is generated across the secondary winding of said transformer;

(c) a rectifier, having first and second output terminals (12,

     14), for converting said first AC voltage across the secondary winding to a first high DC voltage (V) at said first output terminal and a second high DC voltage (-V) at said second output terminal;

(d) coupled inductor means (60) comprising a first winding (63) operatively coupled to said battery, a second winding (61) operatively coupled to said first output terminal of said rectifier, and a third winding (62) operatively coupled to said second output terminal of said rectifier, wherein said first, second and third windings are wound around a common core;

(e) a snubber circuit operatively coupled to said second and third inductors; and

(f) a high voltage inverter (01) comprising first and second load terminals adapted to be coupled across a load in an emergency situation;

a third switching device (Q1) and a fourth switching device (Q2), and second drive means (43,

     44) for driving said third and fourth switching devices from conducting to non-conducting states, and vice versa, so as to produce a quasi-square output voltage waveform across said load terminals when a load is coupled thereto, said output voltage being characterized by an amplitude that varies between a positive peak (V) and a negative peak (-V).

9. An uninterruptible power supply as recited in claim 8, wherein said snubber circuit comprises a capacitor (C3) in series with a parallel combination of a resistor (R3) and a diode (D1).

10. An uninterruptible power supply as recited in claim 8, wherein said first drive means alternately drives said first and second switching devices from said conducting state to said non-conducting state at an operating frequency in the range of between 10 times the fundamental frequency to about 100 kHz.

11. An uninterruptible power supply as recited in claim 10, wherein said operating frequency is approximately 20 kHz.

12. An uninterruptible power supply as recited in claim 8, wherein the quasi-square output voltage waveform is characterized by a frequency of approximately 50-60 Hz.

13. An uninterruptible power supply as recited in claim 8, wherein each of said first, second, third and fourth switching devices comprises a transistor.

14. An uninterruptible power supply as recited in claim 8, wherein the battery voltage is approximately 12 Volts DC and the quasi-square output voltage varies between +160 Volts and -160 Volts.

15. An uninterruptible power supply as recited in claim 8, wherein said first drive means alternately drives said first and second switching devices from said conducting state to said non-conducting state at a frequency of approximately 20 kHz;

wherein the quasi-square output voltage waveform is characterized by a frequency of approximately 60 Hz;

wherein each of said first, second, third and fourth switching devices comprises a transistor; and

wherein the battery voltage is approximately 12 Volts DC and the quasi-square output voltage varies between +160 Volts and -160 Volts.

16. An uninterruptible power supply as recited in claim 8, further comprising a diode connected between said first inductor and a positive terminal of said battery.

17. An uninterruptible power supply as recited in claim 8, further comprising a diode coupled in with each of said third and fourth switching devices (Q1, Q2).

18. An uninterruptible power supply as recited in claim 15, wherein said snubber circuit comprises a capacitor (C3) is series with a parallel combination of a resistor (R3) and a diode (D1);

further comprising a diode connected between said first inductor and a positive terminal of said battery; and

further comprising a diode coupled in anti-parallel with each of said third and fourth switching devices (Q1, Q2).

19. An uninterruptible power supply (UPS) for generating an AC voltage across a load, the UPS comprising:

a transformer having a primary winding and a secondary winding;

an inverter circuit, configured to connect to a DC power source, coupled to said primary winding, and operative to couple the DC power source to said primary winding and thereby generate an AC voltage on said secondary winding from the DC power source in a first mode and to decouple the DC power source from said primary winding in a second mode; and

a converter/charger circuit coupled to said secondary winding, configured to connect to an AC power source, said converter/charger circuit including a first inductor coupled to said secondary winding and a second inductor inductively coupled to the first inductor and configured to connect to the DC power source, said converter/charger circuit operative to produce the AC output voltage from the AC voltage generated by said inverter circuit in the first mode, to produce the AC output voltage from the AC power source in a second mode, and to couple said secondary winding to the first inductor in at least one of said first and second modes such that energy is transferred from said secondary winding to the DC power source through the first and second coupled inductors.

20. A UPS according to claim 19, wherein said converter/charger circuit comprises:

a rectifier connected to said secondary winding of said transformer; and

a switching circuit that selectively couples the rectifier to the load through the first inductor.

21. A UPS according to claim 20, wherein said first and second inductors comprise respective ones of a pair of windings inductively coupled through a common core.

22. A UPS according to claim 20:

wherein said first inductor comprises a first winding coupled to said secondary winding of said transformer;

wherein said second inductor comprises a second winding connected in series combination with a diode, said series combination of the diode and said first one of the pair of windings configured to connect across the DC power source; and

wherein said first and second windings are inductively coupled through a common core.

23. A UPS according to claim 20:

wherein said rectifier has a first output terminal and a second output terminal;

wherein said switching circuit has a first input terminal and a second input terminal;

wherein said first inductor comprises;

a first winding coupling said first output terminal of said rectifier to said first input terminal of said switching circuit; and

a second winding coupling said second output terminal of said rectifier to said second input terminal of said switching circuit; and

wherein said second inductor comprises a third winding inductively coupled to said first and second windings and configured to connect to the DC power source.

24. A UPS according to claim 23 wherein said first, second and third windings are inductively coupled through a common core.

25. A UPS according to claim 20, wherein said switching circuit is operative to alternately connect said first and second output terminals of the rectifier to the load in the first mode to generate the AC output voltage.

26. A UPS according to claim 25:

wherein said secondary winding of said transformer has a center terminal configured to connect to a first terminal of the load; and

wherein said switching circuit is operative to alternately connect said first and second output terminals of the rectifier to a second terminal of the load in the first mode to generate the AC output voltage.

27. A power supply according to claim 20, wherein said converter/charger circuit further comprises a transfer switch that connects the AC power source to said secondary winding in the second mode, and wherein said switching circuit is operative to selectively connect said secondary winding to the load in the second mode to transfer energy from the AC power source to the DC power source through the coupled first and second inductors.

28. A UPS according to claim 27:

wherein said secondary winding has a center terminal configured to connect to a first terminal of the load;

wherein said transfer switch connects the first terminal of the load and said center terminal of said secondary winding to the AC power source in the second mode; and

wherein said switching circuit is operative to selectively connect said first and second output terminals of said rectifier to a second terminal of the load in the second mode to transfer energy from the AC power source to the DC power source through the coupled first and second inductors.

29. A UPS according to claim 19, further comprising a battery connected to said inverter circuit.

30. A power supply comprising:

a transformer having a primary winding and a secondary winding configured to connect to a first terminal of a load;

a first inverter circuit, coupled to said primary winding and configured to connect to a battery, that applies a DC voltage generated by the battery to said primary winding in alternating polarity to produce a first AC voltage on said secondary winding;

a rectifier circuit, coupled to said secondary winding, that rectifies the first AC voltage to produce first and second rectified DC voltages at respective first and second output terminals thereof; and

a second inverter circuit, coupled to said rectifier circuit and configured to connect to a second terminal of the load, that alternately couples said first and second output terminals of said rectifier circuit to the second terminal of the load at a first frequency to produce a second AC voltage across the load, wherein said first inverter circuit decouples said primary winding from the DC power source when said second inverter circuit switches connections between the second terminal of the load and said first and second output terminals of said rectifier; and

a charging circuit configured to connect to the battery and operative to provide a charging current thereto.

31. A power supply according to claim 30, wherein said charging circuit is coupled to said secondary winding of said transformer and operative to transfer energy from said secondary winding to said battery.

32. A power supply according to claim 31, wherein said charging circuit is operative to inductively transfer energy to the battery.

33. A power supply according to claim 32 wherein said charging circuit comprises:

a first inductor coupled in series with said rectifier circuit and said second inverter circuit; and

a second inductor inductively coupled with said first inductor and configured to connect to the battery.

34. A power supply according to claim 30:

wherein said primary winding has first and second end terminals and a center terminal, said center terminal of said primary winding configured to connect to a first terminal of the battery; and

wherein said first inverter circuit alternately couples said first and second end terminals of said primary winding to a second terminal of the battery at a second frequency greater than said first frequency.

35. A power supply according to claim 34, wherein said second inverter circuit couples both of said first and second output terminals of said rectifier circuit to the second terminal of the load during when said first inverter decouples both of said first and second end terminals of said primary winding from the battery.

36. A power supply according to claim 35, wherein said second inverter circuit couples both of said first and second output terminals of said rectifier circuit to the second terminal of the load and then decouples one of said first and second output terminals of said rectifier circuit from the second terminal of the load before said first inverter circuit connects one of said first and second end terminals of said primary winding to the second terminal of the battery.

37. A power supply according to claim 34, wherein said second frequency is less than 100 kHz.

38. A power supply according to claim 37, wherein said second AC voltage has a fundamental frequency approximately one-half of said first frequency.

39. A power supply according to claim 38, wherein said fundamental frequency of the second AC voltage is approximately 60 Hz, and wherein said second frequency is in a range from ten times said fundamental frequency to 100 kHz.

40. A power supply according to claim 34, wherein said first inverter circuit comprises:

a first switch operative to couple and decouple the first terminal of the battery and said first end terminal of said primary winding; and

a second switch operative to couple and decouple the first terminal of the battery and said second end terminal of said primary winding.

41. A power supply according to claim 40, wherein said first and second switches comprise respective first and second transistors.

42. A power supply according to claim 34, wherein said second inverter circuit comprises:

a first switch operative to couple and decouple said first output terminal of said rectifier and the second terminal of the load; and

a second switch operative to couple and decouple said second output terminal of said rectifier and the second terminal of the load.

43. A power supply according to claim 42, wherein said first and second switches comprise respective first and second transistors.

44. A power supply according to claim 30, further comprising a switch operative to couple and decouple the center terminal of secondary winding and an AC power source.

45. A power supply according to claim 44, wherein said charging circuit and said second inverter circuit cooperatively transfer energy from the AC power source to the battery when said switch couples the AC power source to the center terminal of the secondary winding.

46. A method of generating an AC voltage across a load from a DC voltage produced by a DC power source, the method comprising the steps of:

applying the DC voltage to first end terminal of a primary winding of a transformer in alternating polarity to generate a first AC voltage on a secondary winding of the transformer, the secondary winding having a center terminal connected to a first terminal of the load;

applying the first AC voltage to a rectifier to produce first and second rectified DC voltages at first and second output terminals of the rectifier;

alternately coupling the first and second output terminals of the rectifier to a second terminal of the load at a first frequency to produce a second AC voltage across the load; and

decoupling said primary winding from the DC power source when switching the second terminal of the load between the first and second output terminals of the rectifier.

47. A method according to claim 46, further comprising the step of concurrently coupling the first and second output terminals of the rectifier to the second terminal of the load when the primary winding is decoupled from the DC power source.

48. A method according to claim 46, further comprising the step of inductively transferring energy generated at the first and second output terminals of the rectifier to the DC power source.