If the difference betWeen an input voltage and an output voltage becomes smaller, the speed at Which the inductor current changes sloWs doWn. As a result, the time period
required from When the sWitch is turned on till When the reset signal is generated becomes longer. Additionally, the reset signal is generated depending on the second comparing signal that is a signal almost linearly rising With time. Accordingly, if the second comparing signal is set so as to moderately rise With time, the time period from When the sWitch is turned on till When the reset signal is generated becomes longer. If the time period until the reset signal is generated becomes longer as described above, the time ratio in Which the sWitch is held ON increases. If the time ratio of the sWitch increases, a predetermined output voltage can be generated With a loWer input voltage.