A first to an n-th current sources supply a first to an n-th charging currents, respectively. A sequence control circuit allows an x-th charging current of the first to the n-th charging currents to charge a capacitor for generating an x-th soft-start signal. The variable x is an integer and satisfies an inequality of n.gtoreq.x.gtoreq.1. Before a y-th charging current is allowed to charge the capacitor for generating a y-th soft-start signal, the sequence control circuit stops charging the capacitor by the x-th charging current and discharges the capacitor toward a ground potential. The variable y is an integer different from the variable x and satisfies an inequality of n.gtoreq.y.gtoreq.1.