PURPOSE: To reduce the energy consumption of the resistance, etc., of a switching circuit, in which coils are connected in series so that a coil can bias a transistor in the forward direction when a switch is turned off by connecting a Zener diode between the source of the transistor and resistance terminal of the coil.

CONSTITUTION: A transistor 22, diode 5, and switch 4 are connected in series in this order between both power supply terminals of a DC voltage source 1. The cathode of the diode 5 is connected to the gate of the transistor 22 and a DC voltage course 14, resistance 15, and coil 2 are connected between the power supply terminal and gate of the switch 4 so that the coil 3 can be brought on the gate side. In addition, since a Zener diode 25 is connected between the source of the transistor 22 and the terminal of the coil 3 on the resistance 15 side, the energy consumption of the resistance 15, etc., can be reduced and the energy accumulated in the coil 3 can be effectively utilized.