A control circuit for a switching converter, where: in a first operation state, the control circuit controls a switching period of the switching converter to remain unchanged, controls a turn-on time of a power transistor in the switching converter to be not less than a minimum turn-on time in each switching period, and controls a turn-off time of the power transistor to be not less than a minimum turn-off time; in a second operation state, the control circuit controls the turn-on time of the power transistor to be the minimum turn-on time in each switching period, and adjusts the switching period to further reduce a duty cycle; and in a third operation state, the control circuit controls the turn-off time of the power transistor to be the minimum turn-off time in each switching period, and adjusts the switching period to further increase the duty cycle.