The present invention relates to a switch controller and a converter including the same. The switch controller generates an oscillating voltage determining a switching frequency alternately switching a high-side switch and a low-side switch, senses a power source voltage supplied to the switch controller, and maintains the high-side switch and the low-side switch in the turn-off state in a case that the change of the power source voltage is not generated after one of the high-side switch and the low-side switch is turned off according to the oscillating voltage.