Circuit for creating a variable LCD contrast voltage under compu

Details Circuit for creating a variable LCD contrast voltage under compu Circuit for creating a variable LCD contrast voltage under compu

1991-10-01

1993-08-03

Weldon, Ulysses

Communications: electrical

Land vehicle alarms or indicators

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

340793, 340813, G09G 336

Patent

active

052333396

ABSTRACT:
A method and circuit for controlling the contrast of a liquid crystal display (LCD). The circuit includes a switching regulator circuit which generates a negative voltage at the output thereof, with the switching regulator circuit having a feedback node therein and also having a voltage regulator with a control input therein. An injected current coupled to the feedback node and the control input to the voltage regulator is used to provide a changed negative voltage at the output of the regulator circuit. Control values stored in the memory of a controller are used to select the injected current. The changed negative voltage at the output of the regulator circuit is used to control the contrast of the LCD.

REFERENCES:
patent: 4390874 (1983-01-01), Woodside et al.
patent: 4727414 (1988-02-01), Ranf et al.
patent: 4848876 (1989-07-01), Yamakawa

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