Illumination Devices and Related Systems and Methods

• US 20150015147A1
• Filed: 06/16/2014
• Published: 01/15/2015
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Ketra, Inc. (Lutron Electronics)
• Inventors: Knapp, David J.
• Granted Patent: US 9,295,112 B2
• Time in Patent Office: Days
• US Class Current: 315/155
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H05B 44/00 Circuit arrangements for operating electroluminescent light sources for operating light emitting diodes H05B45/00
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

Illumination devices and related systems and methods are disclosed that can be used for LCD (Liquid Crystal Display) backlights, LED lamps, or other applications. The illumination devices can include a photo detector, such as a photodiode or an LED or other light detecting device, and one or more LEDs of different colors. A related method can be implemented using these illumination devices to maintain precise color produced by the blended emissions from such LEDs. One application for the illumination devices is backlighting for FSC (Field Sequential Color) LCDs (Liquid Crystal Displays). FSC LCDs temporally mix the colors in an image by sequentially loading the red, green, and blue pixel data of an image in the panel and flashing the different colors of an RGB backlight. Precise and uniform color temperature across such a display can be advantageously maintained by continually monitoring ratios of photodiode currents induced by the different colored LEDs in each illumination device as each color is flashed.

Claims

1. A method for controlling light intensity produced by an emission LED, comprising:

measuring light from the emission LED with a photodetector using a signal induced on the photodetector by the emission LED;

measuring a temperature of the photodetector by forcing different currents through the photodetector and measuring a difference between voltages developed across the photodetector; and

adjusting light produced by the emission LED based on the signal induced on the photodetector by the emission LED and the temperature of the photodetector.

2. The method as recited in claim 1, wherein the photodetector and the emission LED are included in a same package.

3. The method as recited in claim 1, wherein the photodetector comprises a silicon photodiode or an LED.

4. The method as recited in claim 1, wherein the step of measuring a temperature comprises forcing different currents through the photodetector when the LED is not emitting light.

5. The method as recited in claim 1, wherein the different currents forced through the photodetector comprise a first current and a second current, which is ten times greater than the first current.

6. A system for controlling the light intensity produced by an LED, comprising:

an LED configured to produce light;

a photodetector configured to receive light from the LED; and

control circuitry configured to utilize the photodetector to determine a measurement for a signal induced on the photodetector by the light from the LED, to determine a temperature measurement by forcing different currents through the photodetector and measuring a difference between voltages developed across the photodetector, and to adjust the light produced by the LED based on the a signal induced on the photodetector by the light from the LED and the temperature of the photodetector.

7. The system as recited in claim 6, wherein the photodetector and the LED are included in a same package.

8. The system as recited in claim 6, wherein the photodetector comprises a silicon photodiode or an LED.

9. The system as recited in claim 6, wherein the different currents are forced through the photodetector when the LED is not producing light.

10. The system as recited in claim 6, wherein the different currents forced through the photodetector comprise a first current and a second current, which is ten times greater than the first current.

11. A method for controlling light intensity produced by an LED, comprising:

measuring light from an LED with a photodetector using a signal induced on the photodetector by the LED;

measuring a temperature by forcing a single current through two photodetectors having different sizes and measuring a difference between voltages developed across the two photodetectors; and

adjusting light produced by the LED based on the signal induced on the photodetector by the LED and the measured temperature.

12. A system for controlling the light intensity produced by an LED, comprising:

an LED configured to produce light;

a first photodetector configured to receive light from the LED;

a second and third photodetector configured to provide a temperature measurement; and

control circuitry configured to utilize the first photodetector to determine a measurement for a signal induced on the first photodetector by the light from the LED, to determine the temperature measurement using the second and third photodetectors, and to adjust the light produced by the LED based on the signal induced on the first photodetector by the light from the LED and the temperature measurement.

13. The system as recited in claim 12, wherein the first, second third photodetectors comprise silicon photodiodes or LEDs.

14. The system as recited in claim 12, further comprising a pair of current sources, each coupled to a cathode of a different one of the second and third photodetectors for forcing a current through the second and third photodetectors.

15. The system as recited in claim 14, wherein the second and third photodetectors differ in size, and wherein the control circuitry is configured to determine the temperature measurement by determining a voltage difference between anodes of the second and third photo detectors.

16. The system as recited in claim 14, wherein the third photodetector is ten times larger than the second photodetector.