According to an embodiment, a direct current to direct current (DC-to-DC) converter includes a power stage, a generating circuit, a voltage dividing circuit, a subtractor and a controller. The power stage converts an input voltage to a first output voltage. The generating circuit generates a reference voltage by selecting one of candidate voltages in accordance with a level of the first output voltage. The voltage dividing circuit divides the first output voltage to obtain a second output voltage. The subtractor calculates a differential voltage between the reference voltage and the second output voltage. The control circuit generates a control signal to control the level of the first output voltage based on the differential voltage.