Color manager for backlight systems operative at multiple current levels

• US 8,193,737 B2
• Filed: 06/08/2009
• Issued: 06/05/2012
• Est. Priority Date: 06/10/2008
• Status: Expired due to Fees

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corp. - Analog Mixed Signal Group, Ltd. (Microchip Technology Incorporated)
• Inventors: Peker, Arkadiy, Ferentz, Alon, Langer, Tamir
• Primary Examiner(s): Ismail, Shawki S
• Assistant Examiner(s): Tran, Jany
• Application Number:
  US12/480,185
• Publication Number:
  US 20090302781A1
• Time in Patent Office: 1,093 Days
• Field of Search: 315/224, 315/247, 315291-311
• US Class Current: 315/307
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A color manager for use with a luminaire constituted of a plurality of different colored light emitting diode based sub-luminaires arranged to produce a combined light. The color manager is constituted of a sampler arranged to output an electrical representation of the optical output of the luminaire, a converter coupled to the output of said sampler and operatively associated with a current selector arranged to select the driving current level of the luminaire from a plurality of current levels. The converter is arranged to convert said electrical representation to a pre-determined calorimetric system in cooperation with a calibration matrix whose values are selected responsive to the selected driving current level. The color manager further comprises a driver operatively associated with the luminaire, the converter and current selector and arranged to drive the luminaire in accordance with the driving current level as selected by the selector.

Claims

1. A color manager for use with a luminaire constituted of a plurality of different colored light emitting diode based sub-luminaires, the sub-luminaires arranged to produce a combined light, the color manager comprising:

a sampler arranged to output an electrical representation of the optical output of the luminaire;

a converter coupled to the output of said sampler and operatively associated with a current selector, the current selector arranged to select the driving current level of the luminaire from a plurality of selectable current levels, said converter comprising a plurality of calibration matrixes each associated with a particular one of the selectable driving current levels, said converter arranged to select the calibration matrix associated with the selected driving current level and to convert said electrical representation to a pre-determined colorimetric system in cooperation with said selected calibration matrix; and

a driver operatively associated with the luminaire, the converter and the current selector, said driver arranged to drive the luminaire in accordance with the driving current level as selected by the current selector.

2. A color manager according to claim 1, wherein each of said calibration matrixes exhibit values responsive to a temperature indication associated with at least one of the colored light emitting diode based sub-luminaires.

3. A color manager according to claim 1, wherein the electrical representation comprises a plurality of sampled light intensities, each associated with one of three colors.

4. A color manager according to claim 1, wherein said sampler comprises an analog to digital converter and is further arranged to receive an output of an RGB sensor.

5. A color manager according to claim 1, wherein said driver exhibits a pulse width modulation signal exhibiting a period, wherein said sampler comprises one of an integrator and an averager, and wherein said electrical representation is a function of an intensity average over said period.

6. A color manager according to claim 1, further comprising a color feedback unit arranged to control the driver such that the combined light produced by the luminaire is maintained substantially at a pre-determined color point.

7. A color manager according to claim 6, wherein said pre-determined color point is white.

8. A color manager according to claim 6, further comprising a difference unit operatively associated with the color feedback unit and arranged to:

receive externally provided target color values and said converted electrical representation in said pre-determined colorimetric system; and

present the color feedback unit with the corresponding difference between the received externally provided target color values and the converted electrical representation.

9. A color manager according to claim 6, wherein said color feedback unit is arranged to generate a control signal, said driver adjusting a duty cycle of at least one of the colored light emitting diode based sub-luminaires responsive to said generated control signal.

10. A color manager according to claim 9, wherein said driver is associated with a pulse width modulation functionality exhibiting said adjustable duty cycle.

11. A color manager according to claim 1, wherein the current selector is arranged to select the driving current level responsive to an external input.

12. A color manager according to claim 1, wherein the current selector is arranged to select the driving current level responsive to an ambient light sensor.

13. A color manager according to claim 1, wherein the current selector is arranged to select the driving current level responsive to a temperature sensor.

14. A method of backlighting comprising:

driving a luminaire constituted of a plurality of different colored light emitting diode based sub-luminaires at a selected one of a selectable plurality of current levels;

providing a converter comprising a plurality of calibration matrixes, each of the calibration matrixes associated with a particular one of the plurality of current levels;

sampling the optical output of the driven luminaire;

selecting the calibration matrix of the plurality of calibration matrixes associated with said selected current level; and

converting, responsive to said selected calibration matrix, said sampled optical output into a pre-determined colorimetric system.

15. A method according to claim 14, wherein said converting is further responsive to a temperature associated with the driven luminaire.

16. A method according to claim 14, wherein said sampled optical output comprises a plurality of sampled light intensities, each associated with one of three colors.

17. A method according to claim 14, wherein the sub-luminaires each comprise a light emitting diode string.

18. A method according to claim 14, wherein said driving comprises generating a pulse width modulated signal exhibiting a period, said sampling comprises one of averaging and integrating, and wherein said sampled optical output is a function of an intensity average over said period.

19. A method according to claim 14, further comprising controlling said driving such that the combined light produced by the luminaire is maintained substantially at a pre-determined color point.

20. A method according to claim 19, wherein said pre-determined color point is white.

21. A method according to claim 19, further comprising:

receiving externally provided target color values; and

outputting a signal representing a function of the difference between said received externally provided target color values and said converted sampled optical output into a pre-determined colorimetric system,

wherein said controlling is responsive to said outputted signal and wherein said predetermined color point is responsive to said externally provided target color values.

22. A method according to claim 19, wherein said driving comprises generating a pulse width modulated signal exhibiting a duty cycle responsive to said controlling.

23. A method according to claim 14, wherein said one of the plurality of driving current levels is selected responsive to an external input.

24. A method according to claim 14, wherein said one of the plurality of driving current levels is selected responsive to an ambient light sensor.

25. A method according to claim 14, wherein said one of the plurality of driving current levels is selected responsive to a temperature sensor.

26. A color manager for use with a luminaire constituted of a plurality of different colored light emitting diode based sub-luminaires, the sub-luminaires arranged to produce a combined light responsive to a selector, the selector arranged to select a drive current level for the light emitting diodes of the luminaire from a plurality of selectable driving current levels, the color manager comprising:

a sampler arranged to output an electrical representation of the optical output of the luminaire;

a driver arranged to drive the luminaire at the selected one of the plurality of driving current levels; and

a converter comprising a plurality of calibration matrixes, each of said plurality of calibration matrixes associated with a particular one of the plurality of selectable driving current levels, said converter coupled to the output of said sampler, in communication with the selector, arranged to select the calibration matrix associated with the selected driving current level, and arranged to convert said electrical representation to a pre-determined colorimetric system in cooperation with said selected calibration matrix.

27. A color manager according to claim 26, wherein said calibration matrix is further selected responsive to a temperature indication associated with at least one of the sub-luminaires.

28. A backlight system comprising:

a luminaire constituted of a plurality of colored light emitting diodes producing a combined white light;

a sampler arranged to output an electrical representation of the optical output of the colored light emitting diodes;

a driver arranged to drive the colored light emitting diodes at a selectable one of a plurality of driving current levels; and

a color controller, comprising a plurality of calibration matrixes, each of the plurality of calibration matrixes associated with a particular one of the plurality of driving current levels, said color controller coupled to the output of said sampler and arranged to select the calibration matrix associated with the selected one of the plurality of driving current levels, said color controller further arranged to convert said electrical representation to a pre-determined colorimetric system in cooperation with said selected calibration matrix.

29. A backlight system according to claim 28, wherein said calibration matrix is further selected responsive to a temperature indication associated with said luminaire.