Patent ID: 7336470

Claim:
A solenoid drive device comprising: a solenoid ( 30 ) whose one end is connected to a ground; a switching element ( 33 , SW) which is connected between the other end of said solenoid and a power source, and switches on/off a current path between said solenoid and said power source; a regenerative circuit ( 34 , 32 , 61 ) which is connected between the ground and the other end of said solenoid, and flows a current generated by a counterelectromotive force generated at said solenoid when said switching element is switched off; a sample hold circuit ( 35 , 36 , 62 ) which samples and holds a signal representing a level of a current flowing through said regenerative circuit when said switching element is switched off, and outputs the signal as a current detection signal; a control circuit which controls a timing for switching on/off said switching element based on the current detection signal from said sample hold circuit; and a computing circuit ( 38 ) which sets, based on a length of a period during which said switching element is switched on, a timing at which said sample hold circuit should carry out said sampling in a term, occurring immediately after the period, during which said switching element is switched off, wherein said control circuit, each time the current detection signal is supplied from said sample hold circuit, adjusts the length of the period during which said switching element is switched on, such that the current detection signal supplied from said sample hold circuit becomes constant.