Constant brightness liquid crystal display backlight control sys

Details Constant brightness liquid crystal display backlight control sys Constant brightness liquid crystal display backlight control sys

1992-05-26

1993-12-21

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

315158, G01J 132

Patent

active

052723275

ABSTRACT:
A LCD backlight system which regulates the light generated by the lamp by controlling the intensity of the light using a photoresistor cell. The current provided to the lamp is controlled by a pulse width modulation (PWM) signal. The PWM signal responds to brightness adjustments by the user and to a photoresistor exposed to the light from the lamp. An operational amplifier circuit controls the PWM signal so that if the lamp is too bright, the current to the lamp is reduced, and if the lamp is too dim, the current to the lamp is increased. When the lamp brightness reaches the appropriate intensity, the output of the operational amplifier is unchanging, causing the intensity of the lamp to remain stable.

REFERENCES:
patent: 4260882 (1981-04-01), Barnes
patent: 4717863 (1988-01-01), Zeiler
patent: 4959755 (1990-09-01), Hochstein
patent: 5012314 (1991-04-01), Tobita et al.
patent: 5030887 (1991-07-01), Guisinger

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