Switching mode power supplies (SMPS) and control methods used thereof are disclosed. An exemplifying SMPS is coupled to control an inductive device. The SMPS comprises a voltage divider and a peak controller. The voltage divider comprises a resistor and a controllable resistor connected in series through a connection node. The resistance of the controllable resistor is variable, controlled by a control signal. The voltage divider generates a limiting signal at the connection node based on a line voltage at a line voltage power node. The peak controller controls a peak current flowing through the inductive device according to the limiting signal.