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:
Dec. 29, 1992
Filed:
Jul. 31, 1990
Ronald W Holling, Lincoln Township, Berrien County, MI (US);
Robert R Williams, Lincoln Township, Berrien County, MI (US);
Bonifacio D Malana, Evansville, IN (US);
Whirlpool Corporation, Benton Harbor, MI (US);
Abstract
A fail-safe control system for operating a power relay to energize an electrical load such as a resistive heating element in a cooking apparatus includes first and second driving transistors connected in series with the control winding of the power relay and a source of power. A logic circuit, such as a microcomputer, produces pulses having specified characteristics at a single output port in order to energize the control winding. A circuit interconnecting the output port of the logic circuit with the driving transistors includes a first branch connected with the first transistor and a second branch connected with the second transistor. The first branch of the circuit includes an operational amplifier connected by a capacitor with the logic circuit output port in a manner that the first branch will drive the first transistor for a sufficiently long period of time initially in order to energize the relay control winding and cause the power relay to pull in. Thereafter, the first branch will only drive the first transistor if presented with pulses of much shorter duration; however, the shorter-duration pulses are capable of holding in the power relay. The second branch includes an operational amplifier connected directly with the logic circuit output port to apply all pulses produced at the output port to the second driving transistor.