| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain an LCD back light driving circuit, by which the brightness of a back light is constant regardless of the fluctuation in the output voltage of a battery, and which consumes less electricity, by controlling the duty of an output pulse based on the output of a voltage monitoring means. SOLUTION: The output of a voltage monitoring means 6 is connected to a pulse width modulation control means (hereinafter called 'PWM control means') 7, while the output of the PWM control means 7 is connected to a back light driving means 8. The battery voltage 100 is inputted in the PWM control means 7 through an operational amplifier. The PWM control means 7 changes the duty in accordance with the fluctuation of the voltage 100. With the duty of the output pulse changed in accordance with the fluctuation of the output voltage of the battery, the brightness of the back light is kept constant regardless of such fluctuation; since the brightness of the back light is adjustable through the control of the duty, reduced power consumption is possible at the time when the back light is unnecessary.</p> |
