Illumination Devices and Related Systems and Methods
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.
1 . A method for driving multi-colored LEDs with a single current source and multiple power supplies, comprising:
providing a plurality of different colored LEDs each having a cathode and an anode, the cathodes of the different colored LEDs being coupled together and to a current source, and the anode of each of the different colored LEDs being coupled to one of a plurality of different power supplies; and
sequencing the plurality of different power supplies such that only one power supply provides power to one of the different colored LEDs at any one time.
2 . The method as recited in claim 1 , wherein the providing step comprises providing at least three different colored LEDs, the different colored LEDs being configured to emit colors including red, green, and blue.
3 . The method as recited in claim 1 , further comprising utilizing the different colored LEDs in a backlight for an LCD display.
4 . The method as recited in claim 3 , further comprising utilizing field sequential color with the LCD display.
5 . A system for driving multi-colored LEDs with a single current source and multiple power supplies, comprising:
a plurality of different colored LEDs, each having a cathode and an anode, the cathodes being coupled together and the anodes not being coupled together;
a current source coupled to the cathodes of the plurality of different colored LEDs;
a plurality of different power supplies, each of the different power supplies being coupled to a different anode for the plurality of colored LED; and
power supply circuitry configured to sequence the plurality of different power supplies such that only one of the plurality of different power supplies is configured to provide power to one of the plurality of different colored LEDs at any one time.
6 . The system as recited in claim 5 , wherein the plurality of different colored LEDs comprise at least three different colored LEDs configured to emit colors including red, green, and blue.
7 . The system as recited in claim 5 , wherein the plurality of different colored LEDs reside in a backlight for an LCD display.
8 . The system as recited in claim 7 , wherein the LCD display is configured to use field sequential color.