The present invention can increase the efficiency by controlling the frequency of the ramp signal according to the load size DC-DC converter, and relates to its driving method, and changing the level of the ramp signal in response to the set signal to the second voltage from the first voltage and, in response to a reset signal lamp oscillator for changing the level of the ramp signal to the first voltage from the second voltage; And, a ramp signal control unit that when it exceeds a reset reference voltage level is previously set in the ramp signal from the ramp oscillator and outputting the reset signal on the basis of the size of the load (load) control the frequency of the set signal a characterized in that it comprises.