Provided is regulation of a line current. The regulation of the line current includes comparing a reference voltage with a line sensing voltage to generate a feedback voltage, and controlling a switching operation of a power switch using the feedback voltage. The reference voltage may be a voltage having a constant level, a voltage which varies according to an output current, or a voltage which follows a sine wave to compensate a power factor. Provided is sensing of an output current. The sensing of the output current includes sensing the output current using a feedback voltage corresponding to a voltage between both terminals of an inductor connected to a power switch, a peak of current flowing through the power switch, and a switching cycle of the power switch.