A DC-DC converter comprising: a first converter of a boost type configured to output a first output voltage by adjusting a level of an input voltage according to a first pulse control signal applied to a first switch element; a first light emitter disposed at an output terminal of the first converter; a second converter of a buck type connected to the output terminal of the first converter and configured to output a second output voltage by adjusting a level of the input voltage or the first output voltage according to a second pulse control signal applied to a second switch element; a second light emitter disposed at an output terminal of the second converter; and a controller configured to generate said first and second pulse control signals to be applied to the first and second switch elements according to a driving mode of the first and second light emitters and configured to control a switching operation of the first and second switches according to the generated first and second pulse control signals, characterized in that the first output voltage is greater than the input voltage, and the second output voltage is smaller than the first output voltage and the input voltage, wherein the driving mode comprises: a first driving mode in which both the first and second light emitters are turned on; a second driving mode in which the first light emitter is turned on and the second light emitter is turned off, and a third driving mode in which the first light emitter is turned off and the second light emitter is turned on, wherein the first converter is disposed between a battery part and the first light emitter to boost the applied input voltage according to a switching operation of the first switch element to output the first output voltage, the battery part including a first battery supplying a first input voltage and a second battery supplying a second input voltage smaller than the first input voltage; and wherein the second converter is disposed between an output terminal of the first converter and the second light emitter to output the second output voltage by stepping down the input voltage or the first output voltage output through the first converter according to a switching operation of the second switch element. a first converter of a boost type configured to output a first output voltage by adjusting a level of an input voltage according to a first pulse control signal applied to a first switch element; a first light emitter disposed at an output terminal of the first converter; a second converter of a buck type connected to the output terminal of the first converter and configured to output a second output voltage by adjusting a level of the input voltage or the first output voltage according to a second pulse control signal applied to a second switch element; a second light emitter disposed at an output terminal of the second converter; and a controller configured to generate said first and second pulse control signals to be applied to the first and second switch elements according to a driving mode of the first and second light emitters and configured to control a switching operation of the first and second switches according to the generated first and second pulse control signals, characterized in that the first output voltage is greater than the input voltage, and the second output voltage is smaller than the first output voltage and the input voltage, wherein the driving mode comprises: a first driving mode in which both the first and second light emitters are turned on; a second driving mode in which the first light emitter is turned on and the second light emitter is turned off, and a third driving mode in which the first light emitter is turned off and the second light emitter is turned on, wherein the first converter is disposed between a battery part and the first light emitter to boost the applied input voltage according to a switching operation of the first switch element to output the first output voltage, the battery part including a first battery supplying a first input voltage and a second battery supplying a second input voltage smaller than the first input voltage; and wherein the second converter is disposed between an output terminal of the first converter and the second light emitter to output the second output voltage by stepping down the input voltage or the first output voltage output through the first converter according to a switching operation of the second switch element. a first driving mode in which both the first and second light emitters are turned on; a second driving mode in which the first light emitter is turned on and the second light emitter is turned off, and a third driving mode in which the first light emitter is turned off and the second light emitter is turned on, wherein the first converter is disposed between a battery part and the first light emitter to boost the applied input voltage according to a switching operation of the first switch element to output the first output voltage, the battery part including a first battery supplying a first input voltage and a second battery supplying a second input voltage smaller than the first input voltage; and wherein the second converter is disposed between an output terminal of the first converter and the second light emitter to output the second output voltage by stepping down the input voltage or the first output voltage output through the first converter according to a switching operation of the second switch element.