Disclosed are a feedback control circuit and a method thereof. The feedback control circuit includes a voltage comparator, a calibration voltage generator and processor. The voltage comparator receives a middle-point voltage and a calibration voltage, compares the middle-point voltage and calibration voltage, and outputs a reference voltage pulse signal. The calibration voltage generator generates the calibration voltage and outputs it to a switch driving circuit and the voltage comparator. The processor compares the pulse widths of the reference voltage pulse signal and a predetermined voltage pulse signal, and accordingly outputs a control signal to the calibration voltage generator to fine tune the calibration voltage. The switch driving circuit outputs a switch driving signal to a switching regulating circuit to adjust the timing when to turn on or off switches in the switching regulating circuit.