| 摘要 |
PROBLEM TO BE SOLVED: To make luminous luminance constant independently of the number of cold cathode discharge tube to be driven. SOLUTION: A shift register 21 outputs a signal selecting a cold cathode discharge tube 10 (10-1 to 10-n) to be driven in parallel to a latch circuit 22 in accordance with inputted display data DATA. A counter 23 inputs display data DATA and counts the number of drive. A PWM circuit 24 outputs a driving control pulse P having a pulse width T in accordance with the number of drive to a base of a transistor TR 1 from the counted result by the counter 23. Thereby, the transistor TR 1 in on-controlled, and the cold cathode discharge tube 10 is driven by a driving pulse Q. Here, as the cold cathode discharge tube 10 is driven by the driving pulse Q of a constant current, independently of the number of drive, luminous luminance is made constant. |
