Fluorescent backlight flicker control in an LCD display

Details Fluorescent backlight flicker control in an LCD display Fluorescent backlight flicker control in an LCD display

1989-06-28

1993-02-02

Weldon, Ulysses

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340765, 340814, G09G 336

Patent

active

051841177

ABSTRACT:
A personal portable computer having a fluorescent backlit LCD is provided with circuitry for mitigating noticeable flicker of the backlight. The signal driving the backlight is synchronized with the display refresh signal. More particularly, a horizontal sync signal from an LCD driver is applied to a counter which divides the horizontal sync signal by a predetermined amount. The counter is reset after each frame of the display is written by a vertical sync signal. The output of the counter is applied to a pluse width modulator, such as a monostable multivibrator, which provides a signal to the backlight, synchronized with the display refresh signal. The circuitry also allows for the duty cycle of the backlight signal to be adjusted to control the brightness of the display and consequently the power drain on the battery.

REFERENCES:
patent: 3975661 (1976-08-01), Kanatani et al.
patent: 4669053 (1987-05-01), Krenz
patent: 4769753 (1988-09-01), Knudson et al.
patent: 4958915 (1990-09-01), Okada et al.
patent: 5078476 (1992-01-01), Shin
"Microcomputer Displays, Graphics, and Animation" Bruce A. Artwick, 1985, 1984 pp. 64-65.
"Light, Bright, and White" Rash, Wayne, Jr., Byte Magazine, Dec. 1988, pp. 321-324.

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