Combined exponential/linear RGB LED I-sink digital-to-analog...

Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix

Reexamination Certificate

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Details

C345S082000, C345S084000, C315S312000, C315S313000, C315S291000, C327S533000, C327S534000, C327S535000, C327S536000

Reexamination Certificate

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07551153

ABSTRACT:
Methods and systems to achieve linear and exponential control over a current to drive color LEDs have been achieved. Current digital-to-analog converters (IDAC) comprising each an exponential current digital-to analog converter and a linear IDAC, being cascaded to each other are used for a linear and an exponential control of a current driving a set of color LEDs, preferably RGB LEDs. The linear part of the IDAC, which is converting the mantissa of a floating-point number is used to control the color composition of the color LEDs. The exponential part of the IDAC, which is converting the exponent of the floating-point number is used to control the brightness of the color LEDs. While fading from one color to a next color a linear color change is required. The exponential part of the IDAC is used to dim the LEDs from bright to dark and vice versa. In order to get the visual perception of a linear dimming an exponential current change is required.

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Co-pending U.S. Appl. No. DS-04-044, Filed Nov. 16, 2004, U.S. Appl. No. 10/990,004, assigned to the same assignee as the present invention, “Floating Point ID AC”.

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