Patent ID: 7126805

Claim:
A device for driving a solenoid, comprising: a power supply; a switching element connected between said power supply and said solenoid in series therewith; a current circulating diode connected in parallel to a series circuit comprising said solenoid so that the cathode of said current circulating diode is connected between said switching element and said solenoid; a current detecting circuit for detecting an actual current flowing through said solenoid; PID computing means for computing an on-duty value and an off-duty value according to a difference between a target current and said actual current detected by said current detecting circuit, and outputting said on-duty value and said off-duty value; PWM duty driving means for generating a PWM duty signal according to inputting of said on-duty value and supplying said PWM duty signal to said switching element to on/off control said switching element; and a reverse voltage applying means comprising: a second switching element connected between the negative electrode of said power supply and said solenoid in series therewith; a second current circulating diode connected in parallel to a series circuit composed of said switching element and said solenoid so that the cathode of said second current circulating diode is connected between said power supply and said switching element; an absolute value calculating means for calculating the absolute values of said on-duty value and said off-duty value; an inverter for inverting the signs of said on-duty value and said off-duty value; a NAND circuit adapted to input an output from said absolute value calculating means and an output from said inverter; and a driver circuit for on/off controlling said second switching element according to an output from said NAND circuit, wherein said reverse voltage applying means is capable of applying a voltage of said power supply as a reverse voltage to said solenoid according to inputting of said off-duty value when said switching element is off.