A direct-current (DC)-DC converter includes a converting circuit including an inductor element. The converting circuit is configured to generate an output voltage from an input voltage based on a switching operation. An inductor current emulator is configured to adjust at least one parameter for changing a current peak value of the inductor element in response to a change in a level of the input voltage and is configured to generate an internal voltage based on the at least one parameter, which is adjusted. The inductor current emulator is configured to generate a control signal for controlling the switching operation such that current of the inductor element has a pattern corresponding to a pattern of the internal voltage.