Controlling method and system for LED-based backlighting source

• US 7,317,288 B2
• Filed: 09/02/2005
• Issued: 01/08/2008
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Lin, Hsin-Wu, Huang, Jyh-Haur, Liu, Jen-Chi
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US11/219,284
• Publication Number:
  US 20070052375A1
• Time in Patent Office: 858 Days
• Field of Search: 315/291, 315/312, 315/246, 315/307, 315/308, 315/169.3
• US Class Current: 315/291
• 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 2320/064 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 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: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

The present invention uses different frequencies to drive the LED strips in the back-lighting source so that the spatial uniformity of the back-lighting source as well as the color levels in the source can be monitored and adjusted. Each individual strip is assigned to a different frequency. Alternatively, the strips are divided into groups and each group is assigned to a different frequency. A group may comprise two or more strips. Furthermore, some groups may have more strips than the other groups and the number of LEDs in one strip may be different from the number in other strips. The brightness uniformity and the color levels in the back-lighting source are sensed by one or more groups of color sensors in R, G and B. The assignment of driving frequencies can be based on the location of the strips.

Claims

1. A method to improve the brightness uniformity in a light source having a plurality of light-emitters divided into a plurality of emitter groups, each group driven by an electrical current to produce light having a light intensity level, said method comprising the steps of:

embedding frequency information in the electrical currents driving the light-emitters in each emitter group;

sensing the light produced by the emitter groups for providing a signal indicative of the sensed light, the sensed light having the embedded frequency information;

determining from the signal the light intensity level of each emitter group based on the embedded frequency information; and

adjusting the electrical currents driving the emitter groups based on the determined light intensity level.

2. The method of claim 1, wherein each of the emitter groups is disposed in a different location in the light source and the embedded frequency information contains information identifying the locations of the emitter groups so that said adjusting is also based on the locations of the emitter groups.

3. The method of claim 1, wherein at least some of the electrical currents driving the emitter groups are provided in current pulses having a pulse width and said adjusting is carried out by changing the pulse width in the electrical currents.

4. The method of claim 1, wherein the light-emitters comprise light emitters in a plurality of colors and the sensed light comprises a plurality of sensed light color components indicative of colors of the light-emitters, and wherein said adjusting is also based on the colors of the light emitters.

5. The method of claim 1, wherein the electrical currents driving the emitter groups are assigned to a plurality of driving frequencies for providing the embedded frequency information and wherein said determining is based on the driving frequencies carried in the sensed light.

6. The method of claim 5, wherein at least some of the emitter groups are further divided such that each group comprises a plurality of emitter strips such that the currents driving the strips in each group have the same driving frequency.

7. A light source driving apparatus for use in a lighting system comprising a light source having a plurality of light-emitters, the light-emitters divided into a plurality of emitter groups, said driving apparatus comprising:

a driving module having a plurality of drivers for providing electrical currents to the emitter groups to produce light having a light intensity level, each electrical current having a driving frequency; and

a controlling module for determining the light intensity level of the emitter groups based on driving frequency information associated with the light intensity level in order to adjust the electrical currents provided by the drivers based on the determined light intensity level of the emitter groups.

8. The light source driving apparatus of claim 7, further comprising:

a light sensing module disposed in relation to the light source to sense the light produced by the emitter groups for providing a signal indicative of the sensed light, the sensed light containing the driving frequency information.

9. The light source driving apparatus of claim 7, wherein the emitter groups are disposed in different locations in the light source and the driving frequency is associated with a location such that the electrical currents are adjusted also based on the locations of the emitter groups.

10. The light source driving apparatus of claim 7, further comprising

a modulation module operatively connected to the driving module for modulating the electrical currents in the emitter groups into a pulse form having a series of pulses, the pulses having a pulse width, wherein the modulation module is also operatively connected to the controller so as to allow the controller to adjust the electrical currents provided by the driving module by changing the pulse width.

11. The light source driving apparatus of claim 10, wherein the sensed light is in the pulse form indicating of said modulating, said system further comprising:

a demodulation module, operatively connected to the light sensing module, for demodulating the signal prior to said determining.

12. The light source driving apparatus of claim 8, wherein the light-emitters comprise light emitters in a plurality of colors and the light produced by the light-emitter groups contains a plurality of color components, and wherein the light sensing module comprises a plurality of sensing elements for sensing the color components to provide the sensed light.

13. The light source driving apparatus of claim 12, wherein the electrical currents are adjusted based on the colors of the light-emitters.

14. A lighting system comprising:

a light source having a plurality of light-emitters divided into a plurality of emitter groups;

a driving module having a plurality of drivers for providing electrical currents to the emitter groups to produce light having a light intensity level, each electrical current having a driving frequency;

a light sensing module disposed in relation to the light source to sense the light produced by the emitter groups for providing a signal indicative of the sensed light, the sensed light containing information of the driving frequencies; and

a controlling module, responsive to the signal, for determining the light intensity level of the emitter groups based on the driving frequency information so as to adjust the electrical currents provided by the drivers based on the determined light intensity level of the emitter groups.

15. The lighting system of claim 14, wherein the emitter groups are disposed in different locations in the light source and the driving frequency is associated with a location such that the electrical currents are adjusted also based on the locations of the emitter groups.

16. The lighting system of claim 14, further comprising

a modulation module operatively connected to the driving module for modulating the electrical currents in the emitter groups into a pulse form having a series of pulses, the pulses having a pulse width, wherein the modulation module is also operatively connected to the controller so as to allow the controller to adjust the electrical currents provided by the driving module by changing the pulse width.

17. The lighting system of claim 16, wherein the sensed light is in the pulse form indicating of said modulating, said system further comprising:

a demodulation module, operatively connected to the light sensing module, for demodulating the signal prior to said determining.

18. The lighting system of claim 14, wherein the light-emitters comprise light emitters in a plurality of colors and the light produced by the light-emitter groups contains a plurality of color components, and wherein the light sensing module comprises a plurality of sensing elements for sensing the color components to provide the sensed light.

19. The lighting system of claim 18, wherein the electrical currents are adjusted based on the colors of the light-emitters.