PURPOSE: To improve the durability and to realize a low cost, as well as to make a stabilized power source unnecessary, by providing a first and a second switching means, a diode, an analog-digital converting means, and a microcomputer.
CONSTITUTION: The voltage value of one system of unstabilized power source 1 for solenoid driving is taken in to a microcomputer 6 by sampling by an A/D converter (converting means) 7, and the duty of the PWM is operated and decided to make the voltage applied to a solenoid 2 in a specific constant voltage at every sampling. Then, an FET 3 (the first switching means) is PWM controlled to make in a specific voltage applied to the solenoid 2, when the solenoid 2 is driven, and an FET 4 (the second switching means) is made ON during this operation. By the ON of the FET 4, a circulating current flows to the solenoid 2 through the diode 5 and the FET 4, during the period the FET 3 is OFF in the PWM operation section, and a continuous current flows to the solenoid 2 adding to the driving current during the means 3 is ON, so as to realize a high speed driving stably.
KIMURA SHINSUKE