Abstract: A control circuit for controlling a power supply is revealed. The control circuit is used to generate a switching signal for switching the power supply. The control circuit has a detection terminal for detecting a status of the power supply. A first protection circuit is coupled to the detection terminal and to receive a first detection signal via the detection terminal, and the first protection generates a limit signal in response to the first detection signal, for limiting output of the power supply. A second protection circuit is coupled to the detection terminal and to receive a detection signal via thereto, and the second protection generates a protecting signal, for cutting off the output of the power supply, in response to the first detection signal.