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:
Oct. 26, 1982
Filed:
Jul. 17, 1980
Hitachi, Ltd., Tokyo, JP;
Abstract
There is provided a control circuit for a DC brushless motor suitable for use in acoustic devices or data cassette recorders which comprises a rotor magnet rotating synchronously with the motor rotor, three or more-phase stator windings opposing the rotor magnet and spaced apart therefrom by a slight gap, winding drive circuits for supplying exciting current to the stator windings, and Hall elements for detecting angular positions of the rotor magnet and producing output voltages supplied to the winding drive circuits. The control circuit further comprises a limit voltage setting circuit for setting two limit voltages respectively having upper and lower amplitudes which are symmetrically variable with respect to the central potential of the upper and lower amplitudes, an amplifier circuit associated with each of the Hall elements and amplifying the output voltage from the Hall element with respect to the central potential, and an amplitude limiter circuit limiting upper and lower amplitudes of the amplified output voltage from the amplifier circuit not to exceed the two reference voltages, thereby producing a trapezoidal waveform which in turn is applied to the winding drive circuit.