The latch circuit 5 is set on the rising edge (or falling edge) of the pulse signal output from the oscillator 2, and is reset by the reset signal output from the comparator 4. When the latch circuit 5 is in a set state, the sWitches S1 and S2 are respectively held ON and OFF. In this state, the electric current from a DC poWer source toWard a load ?oWs via the
sWitch S1 and the inductor L. The inductor current increases as time elapses.