| 摘要 |
PURPOSE:To realize a simple and low cost circuit for a half-lighting of a cold cathode-ray tube. CONSTITUTION:A transistor Q1 is connected between a drive circuit 2 to light a cold cathode-ray tube 1 and a drive power source. In parallel to the transistor Q1, a Zener diode ZD1 is connected. A transistor Q2 to drive the transistor Q1 is driven directly by a digital signal from a microcomputer 3. When the transistor Q1 is ON, the voltage from the drive power source is all fed to the drive circuit 2, and the cold cathode-ray tube 1 is lighted in a normal condition. When the transistor Q1 is OFF, the voltage fed to the drive circuit 2 is fed by reducing the amount of the Zener voltage owing to the voltage drop by the Zener diode ZD1. As a result, the brightness of the cold cathode-ray tube 1 is reduced as the amount of the voltage reduction, and a half-lighting condition of the cold cathode-ray tube 1 is generated. |
