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:
Feb. 13, 1990
Filed:
Jun. 16, 1988
Applicant:
Inventors:
Assignee:
Matsushita Electric Industrial Co., Ltd., Kadoma, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H02P / ;
U.S. Cl.
CPC ...
318254 ; 318138 ;
Abstract
A phase difference between a counter-electromotive voltage induced in a driving coil and a voltage which is applied to the driving coil is detected by comparison of a terminal voltage of the driving coil and a reference voltage. A frequency of a voltage-control oscillator which controls switching of the voltage applied to the driving coil is varied by an output signal made by the comparison, and the phase difference is controlled to be reduced to zero.