To reduce the capacity of a Zener diode by increasing the voltage being applied to an exciting coil and reducing generation of heat from transistors.

An exciting coil L1 and a switching element section 10 are connected in series with a power supply voltage VDD and switching element sections 20, 30 are connected, respectively, in parallel with the exciting coil L1. The switching element section 10 supplies a current I1 from the power supply voltage VDD to the exciting coil L1 when a drive signal S1 is turned on and generates flyback currents I2, I3 from the exciting coil L1 when the drive signal S1 is turned off. The switching element section 20 supplies a flyback current I2 to the exciting coil L1 when a drive signal S2 is turned on and the drive signal S1 is turned off. The switching element section 30 supplies a flyback current I3 to the exciting coil L1 when the drive signal S1, S2 are turned off.