Patent ID: 8520418

Claim:
A power source circuit, comprising: a first input terminal; a second input terminal cooperating with the first input terminal for connecting to an external AC power; a first output terminal; a second output terminal connected to ground; a limiting resistor; a sampling resistor; a rectifier comprising a first node, a second node, a third node, and a fourth node, wherein the first node is connected to the first input terminal through the limiting resistor, the second node is connected to the second input terminal, the third node is connected to the first output terminal, the fourth node is connected to the second output terminal through the sampling resistor; the rectifier is configured to convert the AC current from the external AC power to a DC current and output the DC current from the first output terminal and the second output terminal; a control circuit comprising two sampling input nodes respectively connected the two ends of the sampling resistor and a control output node, wherein the control circuit is configured to output a first control signal via the control output node when the DC current is greater than a predetermined value and output a second control signal via the control output node when the DC current is less than or equal to the predetermined value, wherein the predetermined value is less than a current value of a load connected to the power source circuit and operating normally; and a switch circuit comprising a control input node connected to the control output node and two connection nodes respectively connected to the two ends of the limiting resistor, wherein the switch circuit is configured to short-circuit the two connection nodes when receiving the first control signal and disconnect the two connection nodes when receiving the second control signal.