The present invention relates to a switch controller and a converter having the same. The converter according to the present invention includes a power transfer device that transmits input power to an output terminal as output power, a power switch connected to a first end of the power transfer device and that controls power transmission of the power transfer device, and a switch controller that controls switching operation of the power switch. The switch controller receives an output voltage detection signal corresponding to an output voltage according to the power transmitted from the power transfer device, generates a duty control signal corresponding to a difference between the output voltage detection signal and a reference signal for controlling the output voltage, and determines turn-on/off of the power switch by using the duty control signal, and a DC gain of a feedback transfer function between the reference signal and the output voltage has a constant value.