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:
Jul. 14, 1987
Filed:
Dec. 09, 1985
Applicant:
Inventor:
John M Leuthen, Claremore, OK (US);
Assignee:
Hughes Tool Company, Houston, TX (US);
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H02H / ;
U.S. Cl.
CPC ...
361 91 ; 361101 ; 363 56 ;
Abstract
A protection circuit for a power transistor cuts off the transistor if an overcurrent condition occurs. The protection circuit includes control transistors that are switched on and off to alternately supply positive voltage to the base of the power transistor to turn it on and negative voltage to turn it off. A control circuit provides signals to the control transistors to turn them on and off. A latch has an input connected across the collector and emitter of the power transistor for monitoring the voltage. If the voltage exceeds a threshold level at the latch, the latch will provide a disabling output to the control circuit to turn off the power transistor.