Auto-detection circuit and control method for video signals

A display device capable of auto-detecting video sources comprising:

• a plurality of video signal input terminals for receiving video signals;
• a plurality of auto-detection circuits individually coupled to the plurality of video signal input terminals for detecting the video signals by detecting a synchronization signal of the video signal comprising:
• a reception end for receiving the video signal;
• a synchronization signal detector coupled to the reception end for generating a waveform according to a voltage variation of the video signal, comprising:
• a bipolar transistor comprising a base, a collector, and an emitter coupled to a ground;
• a capacitor coupled between the reception end and the base of the bipolar transistor;
• a first resistor having one end coupled between the capacitor and the base of the bipolar transistor, and another end coupled to a voltage source;
• a second resistor having one end coupled between the capacitor and the base of the bipolar transistor, and another end coupled to the ground;
• and
• a third resistor having one end coupled to the collector of the bipolar transistor, and another end coupled to the voltage source;
• a peak value detector coupled between the collector of the bipolar transistor and the third resistor for determining a peak value of the waveform;
• a peak value detector coupled to the synchronization signal detector for determining a peak value of the waveform;
• a direct current voltage level switch coupled to the peak value detector for switching an output voltage to a first direct current voltage level or a second direct current voltage level;
• and
• an output end coupled to the direct current voltage level switch for outputting the output voltage;
• and
• a video source decision device coupled to the plurality of auto-detection circuits for determining a source of the video signals according to detection results of the plurality of auto-detection circuits.