PURPOSE: To reduce power loss by connecting a switching element through a diode in parallel with a winding.

CONSTITUTION: A winding L is connected at one end with a power terminal VCC, and grounded at the other end through a diode D3, the first transistor Q1 and a current detecting resistor RS connected in a Darlington configuration. The second transistor Q1 of Darlington configuration is connected through the first diode D1 in parallel with the winding L, and an energy discharging circuit having the second diode D2 and a Zener diode ZD is connected in parallel. The second transistor Q2 is turned ON during the OFF period of the first transistor Q1, a current based on the storage energy of the winding L continuously flows to perform a smoothing action. Since the first and second transistors are not connected in series with the winding, a current from the power source is not supplied simultaneously to the transistors. Thus, power loss is reduced.