A switching converter has four switches and a control circuit. The control circuit provides a first drive signal to control a first switch and a second drive signal to control a second switch based on a first set signal, and provides a third drive signal to control the third switch and a fourth drive signal to control the fourth switch based on a second set signal. When an output voltage is larger than an input voltage, an on-time period of the third switch is adaptively adjusted according to the input voltage, the output voltage and a first parameter. When the output voltage is less than the input voltage, the on-time period of the third switch is adaptively adjusted according to the input voltage, the output voltage and a second parameter.