An isolated switching converter has a primary switch and a control circuit. The control circuit has a first sampling circuit, a second sampling circuit, a compensation circuit and a feedback control circuit. The first sampling circuit is coupled to an auxiliary winding of a transformer to receive a voltage on the auxiliary winding and is configured to generate a first feedback signal having an alternating current signal indicative of an output voltage. The second sampling circuit is coupled to the auxiliary winding through a first rectifier and is configured to generate a second feedback signal having a direct current signal indicative of the output voltage. The compensation circuit is configured to generate a compensation signal based on the first feedback signal, the second feedback signal and a reference threshold. The feedback control circuit is configured to generate a primary control signal of the primary switch based on the compensation signal.