Controlling method and system for RGB based LED luminary

• US 6,507,159 B2
• Filed: 03/29/2001
• Issued: 01/14/2003
• Est. Priority Date: 03/29/2001
• Status: Expired due to Term

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Muthu, Subramanian
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US09/820,517
• Publication Number:
  US 20020171373A1
• Time in Patent Office: 656 Days
• Field of Search: 315/307, 315/308, 362/184, 362/185, 362/800
• US Class Current: 315/307
• CPC Class Codes: G01J 2001/4252 for testing LED's
• CPC Class Codes: G01J 3/51 using colour filters
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A method and a system for controlling a RBG based LED luminary which tracks the tristimulus values of both feedback and reference whereby the forward currents driving the LED luminary are adjusted in accordance with the errors between the feed tristimulus values and the reference tristimulus values until the errors are zero.

Claims

1. A method of controlling an RGB based LED luminary driven by forward currents to produce a mixed light, said method comprising steps of:

acquiring a difference between feedback tristimulus values representative of said mixed light produced by said LED luminary and reference tristimulus values representative of a desired mixed light; and

in response to said acquiring, adjusting said forward currents to decrease said difference between said feedback tristimulus values and said reference tristimulus values until said difference is zero.

2. The method of claim 1, wherein said step of acquiring is carried out in a controller.

3. The method of claim 2 further comprising a step of generating of said feedback tristimulus values.

4. The method of claim 3 wherein said step of generating of said feedback tristimulus values are carried out by photodiodes mounted within an optical assembly of said RGB based LED luminary.

5. The method of claim 3 further comprising a step of receiving said feedback tristimulus values by said controller.

6. The method of claim 5 wherein said tristimulus values are in a CIE 1931 tristimulus system.

7. The method of claim 6 further comprising, before said step of acquiring said difference between said feedback tristimulus values and said reference tristimulus values, a step of transferring said feedback tristimulus values in a new RGB calorimetric system into those in said CIE 1931 tristimulus system.

8. The method of claim 5 wherein said tristimulus values are in a new RGB colorimetric system.

9. The method of claim 8 further comprising, before said step of acquiring said difference between said feedback tristimulus values and said reference tristimulus values, a step of transferring said reference tristimulus values in a CIE 1931 tristimulus system into those in said new RGB colorimetric system.

10. The method of claim 2 further comprising a step of allowing a user to select said desired light at said controller whereby said controller obtains said reference tristimulus values.

11. The method of claim 10 wherein said reference tristimulus values are in the CIE 1931 tristimulus system.

12. The method of claim 2 wherein said step of adjusting further comprises a step of generating control voltages by said controller in response to said step of acquiring of said difference and applying said control voltages to LED drivers so as to adjust said forward currents.

13. The method of claim 1 wherein said steps of acquiring and adjusting are implemented by analog circuitry.

14. The method of claim 1 wherein said steps of acquiring and adjusting are implemented in digital form.

15. The method of claim 14 wherein said steps of acquiring and adjusting are carried out in predetermined time intervals.

16. The method of claim 15 further comprising a step of setting up a timer for generating said time intervals.

17. The method of claim 16 further comprising a step of selecting said desired light by selecting color temperatures and lumen output pre-stored in a memory.

18. A controlling system for a RGB based LED luminary driven by forward currents to produce a mixed light, comprising:

a feedback unit for generating feedback tristimulus values representative of said mixed light produced by said luminary; and

a controller for acquiring a difference between said feedback tristimulus values and reference tristimulus values representative of a desired mixed light and for adjusting said forward currents in accordance to said difference so as to decrease said difference to zero.

19. The controlling system of claim 18 wherein said feedback unit comprises photodiodes with filters mounted within an optical assembly of said RGB based LED luminary.

20. The controlling system of claim 19 wherein said feedback unit further comprises amplifier and signal conversion circuitry for converting output photocurrents of said photodiode to voltage signals with proper amplifications.

21. The controlling system of claim 20 wherein said feedback unit further comprises means for transferring said feedback tristimulus values in a RGB colorimetric system into those in a CIE 1931 tristimulus system.

22. The controlling system of claim 20 wherein said feedback unit further comprises means for sending said feedback tristimulus values to said controller.

23. The controlling system of claim 18 wherein said controller comprises a user interface for a user to select said desired mixed light.

24. The controlling system of claim 23 wherein said controller further comprises means for acquiring said reference tristimulus values representative to said desired mixed light selected by said user.

25. The controlling system of claim 24 wherein said controller further comprises means for transferring said reference tristimulus values in a CIE 1931 tristimulus system into those in a RGB colorimetric system.

26. The controlling system of claim 18 wherein said controller comprises means for generating a control voltage in accordance to said difference between said feedback and reference tristimulus values and applying said control voltage to LED drivers of said RGB based LED luminary so as to adjust said forward currents.

27. The controlling system of claim 18 wherein said controller comprises means for receiving said feedback stimulus values from said feedback unit.

28. The controlling system of claim 18 wherein said controller works in analog circuitry.

29. The controlling system of claim 18 wherein said controller is implemented in a digital form.

30. The controlling system of claim 29 wherein said controller comprises a memory for pre-storing values of color temperatures and lumens that a user may select to represent said desired mixed light.