Dimming method and device for fluorescent lamps used for backlighting of liquid crystal screens
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United States of America Patent
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-
Apr 14, 1992
Grant Date -
N/A
app pub date -
Jun 21, 1990
filing date -
Jun 30, 1989
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A dimming device, with a brightness dimming ratio of 1 to 1000, for a fluorescent lamp used for the backlighting of a liquid crystal screen comprises a periodic signal generator for delivering rectangular pulses with an adjustable duty cycle. The pulses are synchronized with the image synchronizing signal of the liquid crystal screen. An alternating voltage generator provides power to the lamp only during the pulses. The decrease in tube efficiency for very short pulses allows the required dimming intensity to be achieved without image flickering.
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