A switching regulator includes a power stage circuit, an auxiliary winding, a start-up switch, and a power switch controller circuit. The power switch controller circuit includes a multifunction pin, a start-up controller circuit, and a feedback compensation circuit. The multifunction pin is coupled to a control terminal of the start-up switch, to deliver different signals with different functions under at least two different modes, respectively. The start-up controller circuit generates a start-up signal in a start-up mode, wherein the start-up signal is delivered to a control terminal of the start-up switch through the multifunction pin. An output terminal of the feedback compensation circuit is coupled to the multifunction pin, to provide a compensation signal at the multifunction pin in an operation mode.