Method and apparatus for independent control of brightness and color balance in display and illumination systems
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United States of America Patent
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Sep 9, 2003
Grant Date -
N/A
app pub date -
Feb 26, 1999
filing date -
Feb 26, 1999
priority date (Note) -
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Abstract
A drive circuit for a time sequential color LED based display device allows the overall brightness of a display device to be adjusted without affecting the color balance. The circuit includes a boost switching converter, which provides constant power to each of a plurality of different colored LEDs associated with a pixel, independent of the forward voltage across each LED. The boost switching converter receives a pulse width modulated drive signal for activating each LED, when enabled, during a frame. The on-time of the drive signal varies during each frame according to which LED is to be activated at a particular point in time, to provide the appropriate power to the LED. The LEDs are enabled sequentially during a frame by separate enable signals. The cathode of each LED is connected to a positive power supply voltage when the LED is enabled.
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