Circuit for controlling bias voltage used to regulate contrast i

Details Circuit for controlling bias voltage used to regulate contrast i Circuit for controlling bias voltage used to regulate contrast i

1993-09-10

1996-07-09

Weldon, Ulysses

Computer graphics processing and selective visual display system

Display peripheral interface input device

Light pen for fluid matrix display panel

345148, G09G 500

Patent

active

055348890

ABSTRACT:
A liquid crystal display (LCD) panel which has its contrast controlled through the use of a pulse width modulation (PWM) circuit contained in the video controller and a contrast control circuit. In response to a particular video refresh mode, the PWM circuit modulates the pulse width of a signal that is an input to the contrast control circuit. The pulse width is changed by the use of a base contrast register and two offset registers. Depending on the video mode, the base register is used alone or is combined with one of the offset registers to provide a signal to indicate the duty cycle of the signal. The pulse width modulated signal is converted to a DC bias contrast voltage which is provided to the LCD panel.

REFERENCES:
patent: 4642690 (1987-02-01), Hinn
patent: 4649432 (1987-03-01), Watanabe et al.
patent: 4905167 (1990-02-01), Yamaoka et al.
patent: 4926166 (1990-05-01), Fujisawa et al.
patent: 4991023 (1991-02-01), Nicols
patent: 5406308 (1995-04-01), Shiki

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