Automatic luminance regulator

Abstract

Abstract PURPOSE: To vary the luminance of a display tube according to a ambient brightness with a simple construction by applying voltage between the collector and the emitter of a luminance reglating transistor to the base thereof after it is divided with a photo detector and a resistance. CONSTITUTION: Transistors Q 1 and Q 2 for regulating luminance are connected in parallel between a filament F of a fluorescent display tube FL and one end of a smoothing capacitor C 1 of a DC power source obtained by rectifying the commertial power source. A transistor Q 3 switches on by a frequency of the commertial power source at a specified duty cycle to secure the minimum luminance of the fluorescent display tube FL. A voltage obtained dividing the voltage between the collector and the emitter of the transistor Q 1 with a photo detector R 3 and a resistance R 4 is applied to the base of the tansistor to vary the level of energization of the transistor Q 1 whereby the luminance of the fluorescent display tube is automatically changed according to the ambient brightness. COPYRIGHT: (C)1981,JPO&Japio

Inventors

• 👤 Yoshiharu Nagahara

Bibliographic Details