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:
Sep. 14, 1993
Filed:
Oct. 24, 1991
Donald J Ashley, Endicott, NY (US);
Mark K DeMoor, Endicott, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A temperature compensated overcurrent and/or undercurrent detector monitors current through a solenoid or other load and signals when the load current exceeds an upper limit or falls below a lower limit. Such a signal may indicate a failure of another circuit which supplies the load current via a load transistor. This other circuit which supplies the load current is temperature compensated, and likewise the detector is temperature compensated so it can be set to signal an overcurrent or undercurrent condition when the load current varies a small amount from a predetermined range. The load transistor has an on-resistance which passes the load current and varies with temperature. The temperature compensation for the detector is provided in part by two pilot transistors which are integrated with the load transistor such that as the load transistor heats-up due to the load current passing through the on-resistance, the pilot transistors heat-up due to heat conduction from the load transistor. Each pilot transistor also has an on-resistance which varies proportionally or similarly to the on-resistance of the load transistor. A current source is coupled to the on-resistance of each pilot transistor to generate reference voltages above and below the acceptable range of voltages sensed by the sensor representing an acceptable range of load currents.