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:
Nov. 28, 1995
Filed:
Dec. 14, 1993
Minoru Ishikawa, Kawasaki, JP;
Kimitada Ishikawa, Kawasaki, JP;
Fuji Electric Co., Ltd., Kawasaki, JP;
Abstract
A DC electromagnet apparatus that can prevent an excessive making coil current caused by changes in a power supply voltage. The electromagnet has an operation coil, a switching device, and a current detecting resistor connected in series. A one-shot pulse generating circuit produces a one-shot pulse having a pulse width corresponding to the duration of the making coil current flowing through the operation coil to close the electromagnet. A Miller circuit generates, based on the one-shot pulse, a trapezoidal pulse having a predetermined rising rate, a predetermined peak value, and a pulse width substantially equal to that of the one-shot pulse. A comparator produces an ON control signal that controls the switching device in such a manner that the making coil current becomes proportional to the trapezoidal pulse.