Fluorescent backlight flicker control in an LCD display
First Claim
1. A control circuit for driving a backlight for a display which mitigates noticeable flicker from the backlight comprising:
- means for receiving a source of signals representative of horizontal sync signals which drive the display; and
means responsive to said receiving means for providing a backlight control signal of a predetermined frequency synchronized to said horizontal sync signal which includes a counter, wherein said counter divides said horizontal sync signal by a predetermined number.
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Accused Products
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.
44 Citations
20 Claims
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1. A control circuit for driving a backlight for a display which mitigates noticeable flicker from the backlight comprising:
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means for receiving a source of signals representative of horizontal sync signals which drive the display; and means responsive to said receiving means for providing a backlight control signal of a predetermined frequency synchronized to said horizontal sync signal which includes a counter, wherein said counter divides said horizontal sync signal by a predetermined number. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A control circuit for driving a backlight of an LCD display which mitigates noticeable flicker comprising:
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means for receiving a source of signals representative of horizontal sync and vertical sync signals which drive the display; a counter, electrically coupled to said receiving means, which divides the horizontal sync signal by a predetermined number and provides a counter output signal; a pulse width modulator which receives said counter output signal and provides an output signal having a predetermined duty cycle, synchronized to said horizontal sync signals; and driving means responsive to said output signal from said pulse width modulator, which provides a backlight control signal for driving a fluorescent backlight without noticeable flicker, synchronized to said horizontal sync signals. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for controlling the flicker of a backlight for a backlit LCD comprising the steps of:
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(a) providing a source of signals representative of horizontal sync signals used to drive the LCD; (b) generating a signal for driving said backlight from said horizontal sync signals having a predetermined frequency;
said predetermined frequency being generated by dividing the frequency of said horizontal sync signals by a predetermined number. - View Dependent Claims (20)
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Specification