A converter is disclosed for using at least one switch to convert an input signal to a square wave signal, and using the square wave signal to generate an output voltage. The converter converts the square wave signal by a switching operation of a switch and generates the output voltage, and includes a switch controller for controlling the switching operation. The switch controller generates a first signal VCT having a first period that varies according to an output voltage, controls the switching operation of the switch by using the first signal, detects the output voltage, a first current Ids2 flowing through the switch, and a level of the first signal, and controls a burst mode according to the detection results.