External power supply identification circuit aiming at large-current touch device and electronic signature screen

The utility model is suitable for the field of electronics and provides an external power supply identification circuit aiming at a large-current touch device and an electronic signature screen. The circuit comprises a USB detection unit, a DC detection unit, an identification control unit and a filtering unit, wherein the USB detection unit is used for generating a USB detection signal when an external USB power supply supplies power; the DC detection unit is used for generating a DC detection signal and DC power supply voltage when an external DC supplies power; the identification control unit is used for outputting the USB power supply voltage only when receiving the USB detection signal, and stopping outputting the USB power supply voltage when receiving the DC detection signal; the filtering unit is used for filtering the USB power supply voltage or the DC power supply voltage. According to the external power supply identification circuit aiming at the large-current touch device, when no external power supply adapter exists, a small-current USB power supply is utilized; when the USB power supply supplies power insufficiently, the external power supply adapter supplies power, and the USB power supply circuit is blocked, so that the current of the power supply adapter is prevented from flowing backwards to a USB bus, and the problem that the USB power supply supplies power insufficiently is solved.