Controlling the brightness of an FED device using PWM on the row

Details Controlling the brightness of an FED device using PWM on the row Controlling the brightness of an FED device using PWM on the row

1998-09-30

2000-11-14

Shankar, Vijay

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

345 98, 345 76, 345100, 345102, 3151691, G09G 322, G09G 336, G09G 330

Patent

active

061476641

ABSTRACT:
A circuit and method for controlling the brightness of a display screen implemented using a flat panel field emission display (FED) screen. Within the FED screen, a matrix of rows and columns is provided and emitters are situated within each row-column intersection. Rows are activated sequentially and separate gray scale information is presented to the columns. When the proper voltage is applied across the cathode and anode of the emitters, they release electrons toward a phosphor spot, e.g., red, green, blue, causing an illumination point. The present invention includes brightness control circuitry positioned across the row drivers for altering row on-time of the applied voltage to the rows causing a uniform change in brightness cross the FED screen. The applied voltage is pulse width modulated to alter the brightness of the FED screen. Because the relative column voltages remain constant within the present invention, gray scale resolution or the gamma or the white point balance of the screen is not compromised as brightness is altered. Brightness is increased for an increase in the on-time window and decreased for a decrease in the on-time window.

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