Patent ID: 7667415
Filing Date: 2010-02-23
Classification: G09G,H05B,Y02B,Y10S

Abstract:
1. A backlight control device that controls the luminance of a backlight, comprising: an inverter that drives said backlight in response to a dimming pulse signal for controlling a luminance; a designator that designates the duty ratio of said dimming pulse signal; a pulse generator that generates a first pulse signal having a frequency that is an odd number times a vertical synchronization frequency and being pulse-width modulated on the basis of the duty ratio designated by the designator and a vertical synchronizing signal; a frequency divider that frequency-divides the first pulse signal generated by said pulse generator, to output a second pulse signal having a frequency that is one-half that of said first pulse signal; a first logic element that performs a first logical operation on the first pulse signal generated by said pulse generator and the second pulse signal outputted by said frequency divider; a second logic element that performs a second logical operation on the first pulse signal generated by said pulse generator and the second pulse signal outputted by said frequency divider; and a selector that selects an output signal of said first logic element as a third pulse signal in a case where the duty ratio designated by said designator is not less than a predetermined value, while selecting an output signal of said second logic element as a third pulse signal in a case where the duty ratio designated by said designator is less than said predetermined value, to output a third pulse signal having a frequency that is an (odd number/2) times the vertical synchronization frequency as said dimming pulse signal.