A direct current-to-direct current (“DC-DC”) converter includes: a first converter which outputs a first power voltage in a normal mode or a power saving mode based on a inductor current generated therein, where the first converter operates in a first driving manner in the normal mode, and operates in a second driving manner in the power saving mode; a second converter which outputs a second power voltage based on a inductor current generated therein, where the second converter operates in a third driving manner in the power saving mode, and a magnitude of the second power voltage in the power saving to mode is different from that in the normal mode; and a mode selector which supplies a mode control signal to the first and second converters, where the first and second converters are driven in the normal mode or the power saving mode based on the mode control signal.