Adaptive adjustment of light output of solid state lighting panels

• US 7,926,300 B2
• Filed: 03/06/2006
• Issued: 04/19/2011
• Est. Priority Date: 11/18/2005
• Status: Expired due to Fees

• Current Assignee: Brightplus Ventures LLC (IPValuation Partners, LLC)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Roberts, John K., Vadas, Keith J., You, Chenhua
• Primary Examiner(s): Negron; Ismael
• Application Number:
  US11/368,976
• Publication Number:
  US 20070115662A1
• Time in Patent Office: 1,870 Days
• Field of Search: 362/555, 362/561, 362/227, 362/230, 362/228, 362/276, 362/802, 362/800, 345/82, 345/84, 345/597
• US Class Current: 62/612
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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 2320/0693 Calibration of display systems
• 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: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines

Abstract

A lighting panel system includes a lighting panel including a first string of solid state lighting devices configured to emit light at a first wavelength and a second string of solid state lighting devices configured to emit light at a second wavelength, different from the first wavelength, and a current supply circuit configured to supply a drive current to the first string in response to a control signal. A photosensor is arranged to receive light emitted by the panel, and a control system is configured to sample an output signal of the photosensor and adjust the control signal responsive thereto to thereby adjust an average current supplied to the first string by the current supply circuit. Methods of operating a lighting panel are also provided.

Claims

1. A lighting panel system, comprising:

a lighting panel comprising first and second pulsed LED light sources configured to emit narrow band optical radiation having a first dominant wavelength when energized and third and fourth pulsed LED light sources configured to emit narrow band optical radiation having a second dominant wavelength when energized, the second dominant wavelength being different from the first dominant wavelength;

a photosensor configured to be responsive to the first and second dominant wavelengths and configured to provide substantially independent outputs related to the sensed illumination levels in the first and second dominant wavelengths

first, second, third and fourth current sources configured to supply current to the first, second, third and fourth pulsed LED light sources, respectively, in response to control signals; and

a control system coupled to the lighting panel and to the photosensor and configured to provide a feedback loop from the photosensor to the lighting panel by sampling the photosensor output, and, responsive to the photosensor output samples, providing the control signals to the first and second current sources to adjust an average current supplied to at least the first and second pulsed LED light sources,

wherein the control system is further configured to maintain the first and second pulsed LED light sources at different average current levels from one another and to maintain the third and fourth pulsed LED light sources at different average current levels than one another;

wherein the current sources are configured to provide a first on-state current level to the first and second pulsed LED light sources and to provide a second on-state current level, different from the first on-state current level, to the third and fourth pulsed LED light sources; and

wherein the control system is further configured to maintain a ratio of average current levels between the first and second pulsed LED light sources relatively constant while varying the average current level to the first and second pulsed LED light sources and without appreciably changing the on-state current of the first and second pulsed LED light sources.

2. The lighting panel system of claim 1, wherein the control system is further configured to maintain a ratio of average current levels between the third and fourth pulsed LED light sources relatively constant while varying the average current level to the third and fourth pulsed LED light sources and without appreciably changing the on-state current of the third and fourth pulsed LED light sources.

3. The lighting panel system of claim 1, wherein the control system is configured to alter average current levels of the first and second pulsed LED light sources in order to maintain a white point of the lighting panel.

4. A lighting panel system, comprising:

a lighting panel including at least first and second groups of solid state lighting devices configured to emit light having a first color in response to respective first and second drive currents therethrough and a third group of solid state lighting devices configured to emit light having a second color, different from the first color, in response to a third drive current therethrough;

a current supply circuit configured to supply the respective first, second and third drive currents to the first, second and third groups of solid state lighting devices in response to respective control signals;

a control system configured to generate the respective control signals, wherein the control system is configured to cause the current supply circuit to drive the first and second groups of solid state lighting devices at different average current levels; and

a fourth group of solid state lighting devices configured to emit light having the second color in response to a fourth drive current therethrough, wherein the control system is further configured to cause the current supply circuit to drive the third and fourth groups of solid state lighting devices at different average current levels.

5. The lighting panel system of claim 4, wherein the first and second drive currents comprise pulse width modulated current signals, and wherein the control system is further configured to maintain a ratio of average levels of the first and second drive currents relatively constant while varying the average levels of the first and second drive currents without appreciably changing on-state current levels of current supplied to the first and second groups of solid state lighting devices.

6. The lighting panel system of claim 4, wherein the lighting panel comprises first and second bar assemblies arranged to form a lighting surface, wherein the first and third groups of solid state lighting devices are on the first bar assembly and the second group of solid state lighting devices is on the second bar assembly.

7. The lighting panel system of claim 6, wherein the first bar assembly is free of the second group of solid state lighting devices and the second bar assembly is free of the first and third groups of solid state lighting devices.

8. The lighting panel system of claim 4, wherein the first group of solid state lighting devices occupies a first region of the lighting panel and the second group of solid state lighting devices occupies a second region of the lighting panel that is different from the first region of the lighting panel.

9. The lighting panel system of claim 4, wherein the control system is configured to alter average current levels of the first and second groups of solid state lighting devices in order to maintain a color point of a combined light emitted by the lighting panel.

10. The lighting panel system of claim 4, wherein the control signals comprise pulse width modulation (PWM) signals, and wherein the control system is configured to control the average current levels supplied to the first and second groups by varying duty cycles of the PWM signals.

11. The lighting panel system of claim 4, wherein the first, second and third groups of solid state lighting devices comprise respective first, second and third strings of series connected light emitting diodes.