Circuit capable of automatically identifying touch screen and host machine for all-in-one machine

A circuit capable of automatically identifying a touch screen and a host machine for an all-in-one machine is characterized by comprising a touch screen universal serial bus (USB) interface, an internal host machine USB interface, an external host machine USB interface, a power switching circuit and a signal switching circuit, wherein the power switching circuit comprises two power switching tubes and a switching circuit, the switching circuit comprises an audion Q3, a resistor R8 and a resistor R10, a power supply VBUS3 of the external host machine USB interface is connected with a switching control end of the signal switching circuit through a resistor R3, and signal output of the signal switching circuit is connected with a signal receiving end of the touch screen USB interface. Compared with the prior art, the circuit has the advantages that switching between the internal host machine and the external host machine can be conducted automatically without any mechanical switch.