LUMINANCE ADJUSTING CIRCUIT AND ITS METHOD AND VIDEO MONITOR DEVICE EQUIPPED WITH THE SAME LUMINANCE ADJUSTING CIRCUIT AND SYSTEM EQUIPPED WITH THE SAME VIDEO MONITOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a luminance adjusting circuit capable of shortening a time required for converging a control voltage to a reference value. SOLUTION: A CPU 6a of a luminance control part 6 judges whether or not a control voltage Vin indicating the luminance level of a CRT 3 converted into digital data by an A/D converting part 6b is a reference value, and when it is not the reference value, exponentially increases a luminance adjustment value for adjusting luminance according to the size of a difference between the control voltage Vin and the reference value, and applies the luminance adjustment value through an IC control part 6c to a video processing circuit 2 so that the luminance can be adjusted. This processing is repeated so that the control voltage Vin can be converted to the reference value.