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. 07, 1993
Filed:
Apr. 17, 1992
Rolf Muller, Schwarzwald, DE;
Papst Licensing GmbH, Spaichingen, DE;
Abstract
A circuit for controlling a d.c. motor (10) is provided with a current-limiting arrangement (27), designed as a time-delay amplifier, responding at a certain current value by interrupting the supply of current to the motor (10), and then after a certain time, determined e.g. by internal timing elements (46, 47, 49, 54), switching the current supply to the motor (10) on again. The switching operations occurring in such a motor, i.e., the pulse-duration/pulse-gap ratio and the pulse repetition frequency, are a function of the back-EMF that is induced in the motor (10) as a result of its rotation. This situation is exploited for the following purpose: to make the threshold value of the current-limiting arrangement high when the pulse-duration/pulse-gap ratio is high, namely e.g. when the application of current to the motor is practically continuous; and, in contrast thereto, to reduce this threshold value to, for example, one half when the pulse-duration/pulse-gap ratio is low, such as is characteristic when the motor is at a standstill and during start-up. In this way the motor, if blocked against rotation, draws power of a value substantially lower than at rated operation and, for this reason, cannot become overheated even if it is blocked against rotation, and during start-up no excessive values of start-up current can develop.