The control accuracy equal with the case controlled according to a reference signal with a high clock frequency when the electric power is converted is obtained according to a reference signal with a low clock frequency. The quantity of signal S3 of the time that corresponds to the difference of EO in the output voltage to reference voltage EREF by circuit 12 of the generation of quantity of signal of time is generated synchronizing with reference timing signal S1. The phase generates the class of the phase-shift signal of n piece for which only [Cycle of S0/]/n is late one by one by phase-shift signal generation circuit 13, counter circuit 14, and digital addition circuit 15, these numbers are counted respectively, and the count value of n piece is added. The control signal S5that corresponds to TON between when adding value ADD is input with decision circuit 16 of on time of the switch element and control signal generation circuit 17 and it turns it on is generated.