AUTOMATIC BRIGHTNESS ADJUSTING APPARATUS

摘要

PURPOSE: An automatic brightness adjusting apparatus is provided to prevent the brightness of a screen from being dropped when the device is switched into a television mode and the screen from becoming a saturation state when it is switched into a monitor mode. CONSTITUTION: A microcomputer(10) outputs a reference oscillation signal in response to horizontal and vertical synchronous signals from a video card that is included in a computer system. A voltage gain adjusting part(40) adjusts a voltage gain in response to a gain adjust control signal according to mode selection inputted from the microcomputer. A video pre-amplifier(50) amplifies or attenuates R, G and B video signals in response to the voltage gain adjust signal, and output a brightness adjust signal. A video output amplifier(60) amplifies the brightness adjust signal and outputs the amplified brightness adjust signal to a cathode ray tube(70).