Patent ID: 8254074

Claim:
A power control circuit to disconnect a power supply of an electronic device from an alternating current (AC) power source when the electronic device is turned off, the power control circuit comprising: a switch circuit connected to the AC power source and the power supply of the electronic device; a sampling circuit connected to a line of the AC power source to sample current of the line of the AC power source and output a sampling signal; and a controller connected to the sampling circuit and the switch circuit to determine whether the sampling signal is within a predetermined range, and turn off the switch circuit if the sampling signal is within the predetermined range to disconnect the power supply from the AC power source; wherein if the sampling signal is not within the predetermined range, the controller turns on the switch circuit to connect the power supply of the electronic device to the AC power source, the switch circuit comprises an NPN transistor and a relay, an emitter of the transistor is grounded, a base of the transistor is connected to the controller, a collector of the transistor is connected to the relay, and the relay is connected between the power supply of the electronic device and the AC power source; when the transistor is turned off, the relay and the switch circuit are turned off, and the AC power source is disconnected from the power supply of the electronic device; when the transistor is turned on, the relay and the switch circuit are turned on, and the power supply of the electronic device is connected to the AC power source.