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. 26, 2003
Filed:
Sep. 18, 2001
Jiro Abe, Sagamihara, JP;
Yosuke Hamada, Odawara, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A magnetic disk drive uses a back electromotive force sensor that detects the back electromotive force produced in a VCM actuator without being affected by fast changes of current during a high-speed control sampling cycle, and that enables configuration of a fast, high-band speed control system. A back electromotive force sensor for disk drives has a first circuit that detests the coil terminal voltage of a voice coil motor and outputs that value as a band limited signal that is a constant multiple-of that value, a second circuit that detects a drive current in the voice coil motor and outputs a voltage signal proportional to that drive current, and a computation circuit that takes the difference between the output of said first circuit and the output of said second circuit.