Programmable LED driver pad

Details Programmable LED driver pad Programmable LED driver pad

1999-04-30

2001-07-24

JeanPierre, Peguy (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

Digital to analog conversion

C348S703000

Reexamination Certificate

active

06266000

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to drivers for light emitting diodes (LEDs), more particularly to drivers for LEDs of different colors.
2. Art Background
With the advent of red, green, and blue light emitting diodes (LEDs) their use in color displays has increased. Separate red, green, and blue LEDs can be combined to produce many colors and intensities of light, for example white light for backlighting displays. Ideally to obtain color balance and provide brightness control while maintaining that color balance, the individual red, green, and blue devices would have the same characteristics, such as efficiency, light output for a given drive voltage and current, and so on. This is unfortunately not the case. LEDs for the different primary colors have widely differing drive requirements, luminous outputs, and efficiencies. Additionally, process variations result in performance differences among LEDs of the same color. Consequently, means must be provided in the LED driver circuitry to allow these differing characteristics to be matched.
What is needed is an LED driver design for incorporating into an integrated circuit that allows varying LED characteristics to be easily accommodated.
SUMMARY OF THE INVENTION
A light emitting diode (LED) driver pad is disclosed which allows for varying LED characteristics to be accommodated digitally. One embodiment of the pad integrates a multiplying digital to analog converter into the driver. A second embodiment of the pad integrates a multiplying digital to analog converter with settable minimum output current. A third embodiment uses one multiplying digital to analog converter multiplexed to operate a plurality of LEDs.


REFERENCES:
patent: 4183046 (1980-01-01), Dalke et al.
patent: 4464726 (1984-08-01), Chiang
patent: 4631522 (1986-12-01), Cabot
patent: 4779029 (1988-10-01), Henderson et al.
patent: 4920344 (1990-04-01), Henderson et al.
patent: 5479189 (1995-12-01), Chesavage et al.

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