BACKLIGHT CONTROL APPARATUS AND DISPLAY APPARATUS

摘要

A PWM generating circuit is adapted to generate a PWM pulse signal the frequency of which is an odd multiple of the vertical synchronizing frequency. A frequency divider circuit frequency divides the PWM pulse signal generated by the PWM generating circuit. An AND gate provides a logical product related to the PWM pulse signal generated by the PWM generating circuit and to the frequency division pulse signal outputted from the frequency divider circuit. An OR gate provides a logical sum related to the PWM pulse signal generated by the PWM generating circuit and to the frequency division pulse signal outputted from the frequency divider circuit. A selector outputs, as a light modulation pulse signal, the output signal of the OR gate when an established duty ratio is equal to or greater than 50 percents, while it outputs, as a light modulation pulse signal, the output signal of the AND gate when the established duty ratio is smaller than 50 percents. In this way, the frequency of the light modulation pulse signal is 5/2 times the frequency of the vertical synchronizing signal.