Method and apparatus for providing energy to a lighting system

• US 6,081,104 A
• Filed: 11/20/1998
• Issued: 06/27/2000
• Est. Priority Date: 11/20/1998
• Status: Expired due to Fees

• Current Assignee: Applied Power Corp (Carl-Zeiss-Stiftung)
• Original Assignee: Applied Power Corp (Carl-Zeiss-Stiftung)
• Inventors: Kern, Gregory A.
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/197,276
• Time in Patent Office: 585 Days
• Field of Search: 323/268, 323/271, 323/906, 320/101, 320/141, 320/163, 363/97, 363/142
• US Class Current: 323/268
• CPC Class Codes: H02J 9/065 for lighting purposes
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: Y02B 10/70 Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A system for delivering power to a battery and to a load includes a power source that supplies energy to the battery and the load. The battery can be charged by the power source and used to supply energy or power to the load when the power source is unable to provide sufficient energy and power to the load. The system reduces injection of DC current into the load and, as a result, extends the operation life of the load, particularly if the load is an AC lighting or lamp system. The system operates the load in an optimal manner such that battery storage is maintained at near full charge, yet the lighting load operates for a maximum number of hours per night. The benefit of the system is to prevent early failure of either the lighting load or the battery.

Claims

1. An apparatus for supplying energy to a load comprising:

an energy storage devices source;

an energy storage device coupled to said energy source via a first energy converter;

a second energy converter coupled to said energy storage device;

an energy inverter coupled to said second energy converter and the load;

a sensor capable of sensing discharging of said energy storage device; and

a controller coupled to said first energy converter, said second energy converter, and said energy inverter, and said energy inverter, and further wherein said controller slows or stops operation of said second energy converter when estimated state of charge in said energy storage device drops below a threshold limit, whereby said controller maintains actual state of charge in said energy storage device within a state of charge range.

2. The apparatus of claim 1, wherein said energy storage device includes a battery.

3. The apparatus of claim 1, wherein said energy storage source includes a capacitor.

4. The apparatus of claim 1, wherein said energy source includes a solar cell.

5. The apparatus of claim 1, wherein said energy source includes a photovoltaic device.

6. The apparatus of claim 1, wherein said energy source includes a wind turbine.

7. The apparatus of claim 1, including a voltage sensor coupled to said energy source.

8. The apparatus of claim 7, including a voltage sensor coupled to said second energy converter.

9. The apparatus of claim 1, including a sensor capable of sensing charging of said energy storage device.

10. The apparatus of claim 9, wherein said sensor is a current sensor.

11. The apparatus of claim 10, wherein said current sensor is coupled between said first energy converter and said energy storage device.

12. The apparatus of claim 1, wherein said sensor is a current sensor.

13. The apparatus of claim 12, wherein said current sensor is coupled between said storage device and said second energy converter.

14. The apparatus of claim 1, wherein said controller provides timing signals to said first energy converter, said second energy converter, and said energy inverter.

15. The apparatus of claim 1, wherein said controller is coupled to said first energy converter and said second energy converter via a gate drive circuit.

16. The apparatus of claim 1, wherein said controller is coupled to said energy inverter via a gate drive circuit.

17. The apparatus of claim 1, wherein said first energy converter includes a DC-to-DC converter.

18. The apparatus of claim 17, wherein said DC-to-DC converter is configured as a buck converter.

19. The apparatus of claim 1, wherein said second energy converter includes a DC-to-DC converter.

20. The apparatus of claim 19, wherein said DC-to-DC converter is configured as a boost converter.

21. The apparatus of claim 1, wherein said energy inverter includes a DC-to-AC converter.

22. The apparatus of claim 1, including a DC current blocker coupled between said energy inverter and the load such that DC current is prevented from injection into the load.

23. The apparatus of claim 1, wherein said second energy converter includes a chargeable energy storage source.

24. The apparatus of claim 23, wherein said chargeable energy storage source includes a capacitor.

25. The apparatus of claim 24, wherein said capacitor is sized large enough such that load currents do not cause said capacitor to overcharge.

26. The apparatus of claim 24, wherein said capacitor is sized small enough such that the capacitor will charge and discharge with inductive load currents.

27. The apparatus of claim 24, wherein said capacitor has a value in a range between 0.1 and 47 microfarads inclusively.

28. The apparatus of claim 22, wherein said DC blocker includes a capacitor.

29. The apparatus of claim 1, wherein said energy inverter supplies a non-sinusoidal AC signal to the load.

30. The apparatus of claim 29, wherein said non-sinusoidal AC signal approximates an alternating square wave.

31. The apparatus of claim 1, wherein the load includes a lighting system.

32. The apparatus of claim 31, wherein said lighting system includes a high intensity discharge lamp.

33. The apparatus of claim 1, wherein said controller slows or stops operation of said second energy converter when discharging of said energy storage source exceeds a threshold rate.

34. The apparatus of claim 23, wherein said chargeable energy storage source is coupled to said energy inverter and reduces surge currents through said energy inverter into the load.

35. The apparatus of claim 24, wherein said capacitor is a polyester film type capacitor.

36. A method for delivering energy to a lighting system susceptible to damage when supplied with DC current, said method comprising:

charging a chargeable energy storage source;

boosting a first voltage signal from said chargeable energy storage source to or above a first voltage level, wherein said first voltage signal is a DC voltage signal and said first voltage level is greater than about 120 volts;

converting said first voltage signal to a second voltage signal having a second voltage level, wherein said second voltage level is less than about said first voltage level and wherein said converting includes blocking DC current in said first voltage signal such that said second voltage signal is substantially only an AC voltage signal; and

supplying said second voltage signal to the lighting system.

37. The method of claim 36, wherein said first voltage level is at least 140 volts.

38. The method of claim 36, wherein said second voltage level is approximately 120 volts RMS.

39. The method of claim 36, wherein said lighting system includes a high intensity discharge lamp.

58. The method of claim 36, wherein said AC voltage signal is non-sinusoidal.

40. A method of delivering energy to a chargeable energy source and a load, comprising:

converting energy received from an energy source into energy receivable by the chargeable energy source;

estimating state of charge of the chargeable energy source, wherein said estimating includes measuring charging current into said chargeable energy source, measuring discharging current from said chargeable energy source, and computing state of charge for the chargeable energy source based upon accumulated charging current, accumulated discharging current, and estimated capacity of said chargeable energy source; and

converting energy from the chargeable energy source into energy receivable by the load when said charge level of the chargeable energy source is at or above a threshold charge level;

wherein load operation duration is a function of estimated charge level of said chargeable energy source.

41. The method of claim 40, wherein the chargeable energy source includes a battery.

42. The method of claim 40, wherein the chargeable energy source includes a capacitor.

43. The method of claim 40, wherein the load includes a lighting system.

44. The method of claim 42, wherein said lighting system includes a high intensity discharge lamp.

45. The method of claim 40, wherein said converting of energy from the chargeable energy source into energy receivable by the load includes increasing said energy from the chargeable energy source from a first voltage level to a second voltage level.

46. The method of claim 45, wherein said second voltage level is greater than 120 volts.

47. The method of claim 46, wherein said second voltage level is at least 140 volts.

48. The method of claim 40, wherein said converting of energy from the chargeable energy source into energy receivable by the load includes converting a DC signal into an AC signal.

49. The method of claim 48, wherein said AC signal has a voltage level of approximately 120 volts RMS.

50. The method of claim 48, wherein said AC signal has a frequency of approximately sixty hertz.

51. The method of claim 48, wherein said AC signal is non-sinusoidal.

52. The method of claim 51, wherein said AC signal approximates an alternating square wave.

53. The method of claim 40, including blocking DC current from being injected into the load.

54. The method of claim 40, including reducing surge current from reaching the load.

55. The method of claim 40, wherein said converting of energy from the chargeable energy source into energy receivable by the load includes charging and discharging a capacitor.

56. The method of claim 55, wherein said capacitor is sized large enough such that load currents do not cause said capacitor to overcharge.

57. The method of claim 55, wherein said capacitor is a polyester film type capacitor.

59. The method of claim 40, including adjusting said estimated capacity of said chargeable energy source as a function of temperature.

60. The method of claim 40, including adjusting said estimated capacity of said chargeable energy source when charging voltage reaches a constant voltage regulation setpoint.

61. A method for use in operating a chargeable energy source and providing energy to a load to adaptively maintain a state of charge of said chargeable energy source in a high state of charge range, comprising the steps of:

storing initial settings for control variables in memory of a controller, said control variables including an estimated state of charge of said chargeable energy source, a time interval between adjustments of said control variables, a target time period for operating said load based on said chargeable energy source having a maximum state of charge, and a nominal discharge to charge ratio;

operating said controller during said time interval to compute accumulated charging current available for charging said chargeable energy source and accumulated discharging current being discharged from said chargeable energy source;

using said controller to determine an adjusted state of charge based on said estimated state of charge and a product of said nominal discharge to discharge ratio and said accumulated charging current less said accumulated discharging current; and

determining with said controller a load operating time period based on a product of said adjusted state of charge and said target operating time period.

62. The method of claim 61, wherein said control variables further include an estimated capacity of said chargeable energy source at a predetermined temperature, and further including the step of setting with said controller a capacity of said chargeable energy source based on a measured temperature of said chargeable energy source, wherein said adjusted state of charge is determined based on said temperature-based capacity.

63. The method of claim 61, further including, prior to said determining step, the steps of computing an availability of a charging power source coupled to said chargeable energy source and adjusting said target operating time based on said charging power source availability.

64. The method of claim 61, wherein said time interval is less than about 1 second.

65. The method of claim 61, further including the steps of measuring load operating time with said controller and providing energy from said chargeable energy source to said load while said measured load operation time is less than said determined load operating time.

66. Apparatus for adaptively controlling charging of a chargeable energy source by an energy source and discharging of energy from said chargeable energy source to provide energy to a load, comprising:

a current sensor for sensing charging current flowing to the chargeable energy source from the energy source;

a current sensor for sensing discharging current flowing from the chargeable energy source to the load; and

a programmable controller coupled to said current sensors for receiving signals corresponding to said sensed charging and discharging of the chargeable energy source from said sensors, wherein said programmable controller is programmed to;

compute accumulated charging current and accumulated discharging current from said signals received during a predetermined time interval;

determine an adjusted state of charge based on a preset state of charge and a product of a nominal discharge to charge ratio for the chargeable energy source and said accumulated charging current less said accumulated discharging current;

determine a load operating time period based on a product of said adjusted state of charge and a target time period for operating the load preset based on the chargeable energy source having a maximum state of charge; and

operate the load by discharging current from the chargeable energy source for said load operating time.

67. The apparatus of claim 66, further including a temperature sensor coupled between said controller and the rechargeable energy source for sensing temperature of the rechargeable energy source, and wherein said controller further programmed to determined said adjusted state of charge based on said temperature of said rechargeable energy source sensed by said temperature sensor.