| 摘要 |
PURPOSE: An automatic brightness limit circuit compensating a response speed is provided to reduce time delay of a micro controller unit, thereby protecting sight and removing flicker. CONSTITUTION: A flyback transformer(300) reduces a change rate of a high voltage of an anode current applied to a cathode ray tube(700) according to a change in brightness. A micro controller unit(400) receives a values changed according to the change rate of the flyback transformer for controlling the value not to exceed a predetermined value. The micro controller unit outputs a PWM(Pulse Width Modulation) control signal to a video preamplifier IC(200) for controlling the video preamplifier IC to control brightness. A compensating circuit(100) is formed of resistances(R3,R4) connected with smoothing circuits(500,600) of input and output sides of the micro control unit in serial, and a condenser(C3) connected with the smoothing circuits in parallel. The compensating circuit compensate the output value until the micro controller unit outputs the PWM control signal.
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