A current detection circuit generates a pulse signal Sd based on a voltage Vd corresponding to a current I flowing through a solenoid coil, and feeds the pulse signal Sd back to a PWM circuit of a switch controller. The PWM circuit generates a pulse signal Sr having a predetermined duty ratio, based on a comparison between the fed back pulse signal Sd and a voltage value corresponding to a first current value or a second current value, and supplies the pulse signal Sr to a pulse supplying unit. The pulse supplying unit supplies the pulse signal Sr as a first pulse signal S1 and/or a second pulse signal S2 to a gate terminal G of a MOSFET.