The utility model relates to a take power supply switching circuit of isolation control function, including a switch circuit, a MCU controller, a detection circuitry, still include an on -off control chip and an external power source, the MCU controller connect in detection circuitry reaches between the on -off control chip, and this on -off control chip and this external power source meet, under circuit overload condition, detection circuitry produces the high level and feeds back to the MCU controller, this MCU controller producing signals reaches on -off control chip, this on -off control chip pass through external power source control switch's shutoff, carry out overload protection. The utility model discloses an operating condition that the power supply switching circuit utilized detection circuitry to judge supply circuit when supply circuit transships, adds external power source through the on -off control chip and closes switch circuit, carries out the automatic protection, has guaranteed circuit overload protection's stability and security.