SOLENOID DRIVER CONTROL CIRCUIT WITH INITIAL BOOST VOLTAGE

摘要

A solenoid driver control circuit in which solenoid current is sensed comparator means comprising two separate comparators (24, 25) receives the solenoid current sensed signal (45) and maximum and minimum reference threshold levels which determine maximum and minimum current limits (Imax, Imin; Hmax, Hmin) for solenoid current during pull-in excitation and hold excitation. Pull-in time (T1) is defined by a monostable multivibrator (33) reacting to a control pulse (41) to produce a predetermined pull-in time pulse (41) to produce a predetermined pull-in time pulse (43) independent of sensed solenoid current. During pull-in time a boost driver switch (53) applies high boost voltage to a power source terminal (16) which supplies solenoid current, and in response to achieving the maximum pull-in current limit (Imax) lower battery voltage is provided at the power source terminal. If the maximum pull-in current limit does not occur within a predetermined time (tb1) after pull-in initiation, then the lower battery voltage is applied to the power source terminal.