The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 16, 1988
Filed:
Sep. 26, 1986
Adelore F Petrie, Arlington Heights, IL (US);
Thomas F Karlmann, Schaumburg, IL (US);
Steven G Parmelee, Algonquin, IL (US);
Arthur J Edwards, Hoffman Estates, IL (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
An improved dual limit solenoid driver control circuit is disclosed in which solenoid current is sensed and provided as an input to two separate comparators (24, 25). Each comparator receives, during a solenoid pull-in (initial) period (T.sub.1), fixed maximum and minimum reference threshold levels which determine the maximum and minimum current limits (I.sub.max, I.sub.min) for solenoid current during initial pull-in excitation. Subsequently during a hold period T.sub.2 following the pull-in period, each of the comparators receives different maximum and minimum thresholds so as to establish holding solenoid current limits (H.sub.max, H.sub.min). The outputs of the compartors are connected as inputs to a set/reset flip flop (32) whose output controls the operation of a solenoid driver circuit (15). A monostable multivibrator (33) reacts to an initial control pulse (41) to produce a predetermined pull-in time pulse (43) that results in the maximum and minimum pull-in solenoid current limits. The comparator thresholds are provided by a fixed resistor divider circuit (27, 29, 31) which receives a pull-in signal from the monostable multivibrator. The pull-in period (T.sub.1) is independent of the sensed solenoid current, and the switching thresholds are fixed and independent of the magnitude of the solenoid current during the pull-in and hold periods. The above configuration provides improved performance and stability, and is readily implemented with just a few components.