In the meantime, in the state shoWn in FIG. 6, one or more set pulses are generated Within the time period from When the set pulse is generated at the time T0 till When the reset pulse is generated at the time T1. That is, the time period during Which the sWitch S1 is OFF exists only once for a plurality of set pulses. As described above, the DC/DC converter according to this preferred embodiment does not generate the signal for turning off the sWitch S1 if the difference betWeen a supplied input voltage Vin and an
output voltage to be kept is small, thereby increasing its duty.