LED BACKLIGHT AND ELECTRONIC CONTROL
Embodiments comprise a backlight device and a method for controlling the chromaticity and/or luminance of the backlight device. More particularly, embodiments relate to a backlight device for a display which utilizes an array of LED pairs to create a desired chromaticity and luminance of light, whereby the chromaticity and luminance can be closely monitored and maintained throughout the life of the display. A pair of LEDs are used in an exemplary embodiment where the pair contains two blue LEDs with the first LED coated in a red phosphor and the second LED coated in a green phosphor.
1 . A backlight device comprising:
a first plurality of LEDs comprising a plurality of LEDs which are coated with phosphor of a first color;
a second plurality of LEDs comprising a plurality of LEDs which are coated with phosphor of a second color;
a first power source operatively connected to said first plurality of LEDs;
a second power source operatively connected to said second plurality of LEDs;
a light-sensing device capable of sensing the chromaticity of the light emitted from said first and second plurality of LEDs, and
a controller operatively connected to said first power source, said second power source, and said light-sensing device such that the controller is capable of controlling the power of each power source based on data which is received from said light-sensing device.
2 . The backlight device from claim 1 wherein:
said first plurality of LEDs comprise blue LEDs which are coated in a green phosphor, and
said second plurality of LEDs comprise blue LEDs which are coated in a red phosphor.
3 . The backlight device from claim 1 wherein:
said first plurality of LEDs comprise blue LEDs which are coated in a green phosphor, and
said second plurality of LEDs comprise blue LEDs which are coated in an orange phosphor.
4 . The backlight device of claim 1 wherein said light-sensing device is a photosensor.
5 . The backlight device of claim 4 wherein said controller comprises a microcontroller.
6 . A liquid crystal display backlight device comprising:
a first blue LED which is coated with a green phosphor;
a second blue LED which is coated with a red phosphor; and
circuitry in electrical communication with the first and second LEDs effective for maintaining a desired chromaticity and luminance by controlling the power sent to the respective LEDs.
7 . The backlight device from claim 6 wherein the light output from the LEDs combines to produce white light.
8 . The backlight device from claim 7 wherein said circuitry includes a photometer.
9 . A method for maintaining the chromaticity of a backlight assembly, said method comprising the steps of:
providing a backlight assembly comprising:
a first plurality of LEDs comprising a plurality of LEDs which are coated with phosphor of a first color;
a second plurality of LEDs comprising a plurality of LEDs which are coated with phosphor of a second color;
a first power source operatively connected to said first plurality of LEDs;
a second power source operatively connected to said second plurality of LEDs;
a light-sensing device capable of sensing the chromaticity of the light emitted from said first and second plurality of LEDs, and
a controller operatively connected to said first power source, said second power source, and said light-sensing device such that the controller is capable of controlling the power of each power source based on data which is received from said light-sensing device;
selecting a desired chromaticity range for the light from the backlight assembly;
applying default power levels to said first and second power sources;
measuring the chromaticity of the light from the backlight assembly; and
comparing the measured chromaticity with the desired chromaticity range and adjusting the power of the first and second power sources if the measured chromaticity is not within the desired range.