METHODS AND SYSTEMS FOR DIMMABLE FLUORESCENT LIGHTING

• US 20100134023A1
• Filed: 12/01/2008
• Published: 06/03/2010
• Est. Priority Date: 12/01/2008
• Status: Active Grant

• Current Assignee: Robert L. Mills
• Original Assignee: Robert L. Mills
• Inventors: MILLS, Robert L.
• Granted Patent: US 8,138,676 B2
• Time in Patent Office: Days
• US Class Current: 315/174
• CPC Class Codes: H05B 41/3922 and measurement of the incident light

Abstract

A system for operating a fluorescent light is provided. The system comprises: a fluorescent lamp with at least one electrode having at least one corresponding heating filament; a filament signal power supply for providing a filament current signal having a filament current frequency, the filament signal power supply connected to create a filament current through the at least one filament; and a plasma signal power supply for providing a plasma power signal having a plasma power frequency, the plasma signal power supply connected to create a plasma current between the at least one electrode and a gas contained in the fluorescent lamp. The plasma power frequency is greater than the filament current frequency.

Claims

1. A system for operating a fluorescent light, the system comprising:

a fluorescent lamp comprising at least one electrode, the at least one electrode comprising at least one corresponding filament;

a filament signal power supply connected to output a filament signal and to create a corresponding filament current through the at least one filament, the filament current having a filament frequency; and

a plasma signal power supply connected to output a plasma signal and to create a corresponding plasma current flowing between the at least one electrode and a gas contained in the lamp, the plasma current having a plasma frequency;

wherein the plasma frequency is greater than the filament frequency.

2. A system according to claim 1 wherein a ratio of the plasma frequency to the filament frequency is 10:

1 or greater.

3. A system according to claim 1 wherein the plasma frequency is 250 kHz or greater.

4. A system according to claim 1 wherein the plasma signal power supply is configurable to control a power of the plasma current flowing between the at least one electrode and the gas such that the plasma current is confined to a confinement region extending from the at least one electrode, the confinement region having a length less than a length of the lamp.

5. A system according to claim 4 wherein the length of the confinement region is less than 50% of the length of the lamp.

6. A system according to claim 4 wherein the length of the confinement region is less than 25% of the length of the lamp.

7. A system according to claim 4 wherein the plasma signal power supply is configurable to control the power of the plasma current to a first power range, such that for plasma current in the first power range, photons are emitted from a first light-emission region extending from the at least one electrode and having a length less than the length of the lamp and photons are not emitted from a first non-light-emission region at an opposing end of the lamp.

8. A system according to claim 7 wherein the length of the first light-emission region is less than 50% of the length of the lamp.

9. A system according to claim 7 wherein the length of the first light-emission region is less than 25% of the length of the lamp.

10. A system according to claim 7 wherein the plasma signal power supply is configured to control the power of the plasma current in response to a dimming input.

11. A system according to claim 7 wherein the plasma signal power supply is configurable to control the power of the plasma current to a second power range, such that for plasma current in the second power range, photons are emitted from substantially an entire length of the lamp.

12. A system according to claim 11 wherein a ratio of a maximum plasma current power for plasma current in the second power range to a minimum plasma current power for plasma current in the first power range is configurable to be 1000:

1 or more.

13. A system according to claim 1 comprising a filament signal power controller configured to control a power of the filament current and to thereby cause a temperature of the at least one filament to be sufficiently high to cause thermionic emission of electrons therefrom and sufficiently low to substantially avoid evaporation of emission material therefrom.

14. A system according to claim 13 comprising a sensor for sensing a parameter correlated with the temperature of the at least one filament and for providing a filament feedback signal indicative of the sensed parameter to the filament signal power controller, wherein the filament signal power controller is configured to provide a filament current control signal to the filament signal power supply, the filament current control signal based at least in part on the filament feedback signal, and wherein the filament signal power supply is configured to adjust the power of the filament current in response to the filament current control signal.

15. A system according to claim 1 wherein the filament signal power supply is configured to commence outputting the filament signal in response to an ON/OFF signal and wherein the plasma signal power supply is configured to commence outputting the plasma signal after a preheat period Δ

, the preheat period Δ

commencing in response to the ON/OFF signal.

16. A system according to claim 15 wherein upon commencing outputting the plasma signal after the preheat period Δ

, the plasma signal power supply is configured to smoothly ramp up a power of the plasma current from zero to a power level determined by a dimming input.

17. A system according to claim 16 wherein the plasma signal power supply is configured to smoothly ramp up the power of the plasma current from zero to the power level determined by a dimming input in a ramp time of greater than or equal to 0.1 seconds.

18. A system according to claim 15 wherein the filament signal power supply is configured to have a first filament signal which causes a corresponding first filament current during the preheat period Δ

and a second filament signal which causes a corresponding second filament current after the preheat period Δ

, wherein the first filament current is greater than the second filament current.

19. A system according to claim 16 wherein the filament signal power supply is configured to have a first filament signal which causes a corresponding first filament current during the preheat period Δ

and a second filament signal which causes a corresponding second filament current after the preheat period Δ

, wherein the first filament current is greater than the second filament current.

20. A system according to claim 15 wherein the filament signal power supply is configured such that a power of the filament current causes a temperature of the at least one filament to be sufficiently high to cause thermionic emission of electrons therefrom and sufficiently low to substantially avoid evaporation of emission material therefrom.

21. A system according to claim 1 wherein the lamp comprises a pair of electrodes at opposing ends of the lamp and the plasma signal power supply is configurable to control:

a power of a first plasma current flowing between a first electrode and the gas contained in the lamp such that the first plasma current is confined to a first confinement region extending from the first electrode into the gas;

a power of a second plasma current flowing between a second electrode and the gas contained in the lamp such that the second plasma current is confined to a second confinement region extending from the second electrode and into the gas;

wherein lengths of the first and second confinement regions are less than a distance between the first and second electrodes.

22. A system according to claim 21 wherein the lengths of the first and second confinement regions are less than 25% of the distance between the first and second electrodes.

23. A system according to claim 21 wherein the plasma signal power supply is configurable to control the power of the first and second plasma currents to a first power range, such that for first and second plasma currents in the first power range, photons are emitted from a first light-emission region extending from the first electrode toward a center of the lamp and from a second light-emission regions extending from the second electrode toward the center of the lamp, the first and second light-emission regions spaced apart from one another by a central non-light-emission region from which photons are not emitted.

24. A system according to claim 23 wherein a length of the first light-emission region and a length of the second light-emission region are less than 25% of the distance between the first and second electrodes.

25. A system according to claim 23 wherein the plasma signal power supply is configured to control the power of the first and second plasma current in response to a dimming input.

26. A system according to claim 23 wherein the plasma signal power supply is configurable to control the power of the first and second plasma currents to a second power range, such that for first and second plasma currents in the second power range, photons are emitted from substantially the entire distance between the first and second electrodes.

27. A system according to claim 26 wherein a ratio of a maximum power of the first plasma current in the second power range to a minimum power of the first plasma current in the first power range is configurable to be 1000:

1 or more.

28. A method for operating a fluorescent light, the method comprising:

providing a fluorescent lamp comprising at least one electrode, the at least one electrode having a corresponding filament;

generating a filament signal which creates a filament current through the at least one filament, the filament current having a filament frequency;

generating a plasma signal which creates a plasma current flowing between the at least one electrode and a gas contained in the fluorescent lamp, the plasma current having a plasma frequency;

wherein the plasma frequency is greater than the filament frequency.

29. A method according to claim 28 comprising controlling a power of the plasma current at the plasma frequency such that the plasma current flowing between the at least one electrode and the gas is confined to a confinement region extending from the at least one electrode, the confinement region having a length less than a length of the lamp.

30. A method according to claim 29 comprising controlling the power of the plasma current to a first power range, such that for plasma current in the first power range, photons are emitted from a first light-emission region extending from the at least one electrode and having a length less than the length of the lamp and photons are not emitted from a first non-light-emission region at an opposing end of the lamp.

31. A method according to claim 30 comprising controlling the power of the plasma current to a second power range, such that for plasma current in the second power range, photons are emitted from substantially an entire length of the lamp.

32. A method according to claim 28 wherein the lamp comprises a pair of electrodes at opposing ends of the lamp and wherein generating the plasma signal comprises:

controlling a power of a first plasma current flowing between a first electrode and the gas contained in the lamp such that the first plasma current is confined to a first confinement region extending from the first electrode into the gas;

controlling a power of a second plasma current flowing between a second electrode and the gas contained in the lamp such that the second plasma current is confined to a second confinement region extending from the second electrode and into the gas;

wherein lengths of the first and second confinement regions are less than a distance between the first and second electrodes.

33. A method according to claim 32 comprising controlling the power of the first and second plasma currents to a first power range, such that for first and second plasma currents in the first power range, photons are emitted from a first light-emission region extending from the first electrode toward a center of the lamp and from a second light-emission regions extending from the second electrode toward the center of the lamp, the first and second light-emission regions spaced apart from one another by a central non-light-emission region from which photons are not emitted.

34. A method according to claim 33 comprising controlling the power of the first and second plasma currents to a second power range, such that for first and second plasma currents in the second power range, photons are emitted from substantially the entire distance between the first and second electrodes.

35. A system for operating a fluorescent light, the system comprising:

a fluorescent lamp comprising at least one electrode, the at least one electrode comprising at least one corresponding filament;

a filament signal power supply connected to output a filament signal and to create a corresponding filament current through the at least one filament, the filament current having a filament frequency; and

a plasma signal power supply connected to output a plasma signal and to create a corresponding plasma current flowing between the at least one electrode and a gas contained in the lamp, the plasma current having a plasma frequency;

wherein the filament signal power supply is configured to commence outputting the filament signal in response to an ON/OFF signal and wherein the plasma signal power supply is configured to commence outputting the plasma signal after a preheat period Δ

, the preheat period Δ

commencing in response to the ON/OFF signal.

36. A system according to claim 35 wherein upon commencing outputting the plasma signal after the preheat period Δ

, the plasma signal power supply is configured to smoothly ramp up a power of the plasma current from zero to a power level determined by a dimming input.

37. A system according to claim 36 wherein the plasma signal power supply is configured to smoothly ramp up the power of the plasma current from zero to the power level determined by the dimming input in a ramp time of greater than or equal to 0.1 seconds.

38. A system according to claim 36 wherein the filament signal power supply is configured to have a first filament signal which causes a corresponding first filament current during the preheat period Δ

and a second filament signal which causes a corresponding second filament current after the preheat period Δ

, wherein the first filament current is greater than the second filament current.

39. A method for operating a fluorescent light, the method comprising:

providing a fluorescent lamp comprising at least one electrode, the at least one electrode comprising at least one corresponding filament;

generating a filament signal which creates a filament current through the at least one filament, the filament current having a filament frequency;

generating a plasma signal which creates a plasma current flowing between the at least one electrode and a gas contained in the fluorescent lamp, the plasma current having a plasma frequency;

wherein generating the filament signal comprises commencing outputting the filament signal in response to an ON/OFF signal and wherein generating the plasma signal comprises commencing outputting the plasma signal after a preheat period Δ

, the preheat period Δ

commencing in response to the ON/OFF signal.

40. A method according to claim 39 comprising, upon commencing outputting the plasma signal after the preheat period Δ

, smoothly ramping up a power of the plasma current from zero to a power level determined by a dimming input.

41. A method according to claim 40 wherein smoothly ramping up the power of the plasma current from zero to the power level determined by the dimming input comprises smoothly ramping up the power of the plasma current from zero to the power level determined by the dimming input in a ramp time of greater than or equal to 0.1 seconds.

42. A method according to claim 39 comprising providing a filament signal comprising:

a first filament signal which causes a corresponding first filament current during the preheat period Δ and

a second filament signal which causes a corresponding second filament current after the preheat period Δ

, wherein the first filament current is greater than the second filament current.