Patent ID: 8266336

Claim:
A video device, comprising: a signal generating circuit configured for generating video signals; an internal resistor connected to the output port of the signal generating circuit and matching with an external resistor of an external device; a detecting circuit connected to two ends of the internal resistor through two input ports thereof, and configured for detecting voltages of the two ends of the internal resistor and outputting a voltage difference there between; the detecting circuit comprising a first comparator, the positive terminal of the first comparator being connected to a first end of the internal resistor through a first resistor, the negative terminal of the first comparator being connected to a second end of the internal resistor through a second resistor, the positive terminal of the first comparator being grounded through a third resistor, the negative terminal of the first comparator being connected to the output port of the first comparator through a fourth resistor; a controlling circuit connected to the output port of the detecting circuit, and configured for determining whether or not the external device is connected to the video device according to the voltage difference, and outputting a controlling signal to the signal generating circuit; the controlling circuit comprising an N-type triode and a first MOSFET; the output port of the first comparator being connected to the base of the N-type triode through a fifth resistor, the base of the N-type triode being grounded through a first capacitor, the emitter of the N-type triode being grounded, the collector of the N-type triode being connected to a power supply through a sixth resistor and connected to the gate of the first MOSFET, the source of the first MOSFET being grounded, the drain of the first MOSFET being connected to the output port of the controlling circuit; and an auxiliary detecting circuit connected to the output port of the controlling circuit, and configured for generating an auxiliary detecting signal transmitted to the internal resistor.