The invention discloses an automatic lock power-off protecting equipment that can be disposed in electronic devices. The electronic device includes a power supplying device and a primary functional circuit, the power supplying device is coupled to the primary functional circuit through an electronic switch, to make the primary functional circuit access the power needed for the operation through the power end of the electronic switch. The automatic lock protecting equipment includes a low-voltage starting cut-off device and a low-voltage reactor, wherein the low-voltage starting cut-off device is coupled to the electronic switch for controlling the conducting or cut-off of the electronic switch, and the low-voltage reactor is coupled to the power supply end and the low-voltage starting cut-off device. When short-circuit occurs on the power supply end, the low-voltage reactor will make the low-voltage starting cut-off device to shut the electronic switch, to cut off the power supply of the primary functional circuit. |