A load driving device has a switch N1, a driver that performs on/off control of the switch in accordance with SWON, a comparator that compares Vdet1 with Vth, and based on a result of the comparison, generates IPEAKDET, an ADC that converts Vdet1 into ADCOUT, a DAC that converts IPEAKSET into Vth, and a logic portion that, upon receiving inputs of IPEAKDET and ADCOUT, outputs SWON and IPEAKSET. The logic portion includes a computation circuit that calculates Y1 by using a computation equation expressed by Y1=AVE×α+&Dgr;×Ton/2 (where Y1: a signal value of IPEAKSET; AVE: an average current set value of an output current; α: an adjustment coefficient for AVE; Ton: an on period; &Dgr;: a change rate of AVCOUT). The computation circuit determines α in accordance with computation mode setting signals ISO and PFC.
