Video input level control circuit in a video appliance

A video input level control circuit in a video display device including a video signal output section for signal-processing an RGB video signal inputted from a computer, the circuit comprising:

• a processing section for detecting whether vertical and horizontal synchronous frequency signals are inputted from the Computer, and generating an input level control signal;
• an on-screen display (OSD) section connected to the processing section and outputting an on-screen display signal;
• a video input level control section connected to the processing section and receiving the input level control signal, the video input level control section generating a contrast control signal according to the input level control signal of the processing section;
• a contrast control section connected to the video input level control section and operable to control a contrast voltage level to adjust brightness of a screen of the video display device according to the contrast control signal outputted from the video input level control section;
• and
• an amplifier connected to the contrast control section and the OSD section and amplifying the RGB video signal inputted from the video signal output section according to an output of the contrast control section;
• wherein the processing section generates the input level control signal through first and second output terminals, and the video input level control section includes first and second transistors respectively connected to the first and second output terminals for outputting logic signals, the collector terminals of the transistors being connected to the contrast control section.