Electric motor control device

• US 6,922,032 B2
• Filed: 01/27/2004
• Issued: 07/26/2005
• Est. Priority Date: 01/27/2003
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Maeda, Norihiro
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US10/765,302
• Publication Number:
  US 20040183490A1
• Time in Patent Office: 546 Days
• Field of Search: 318360-363, 318370-375, 369/50, 369/53, 360/74.1
• US Class Current: 318/373
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/24 Arrangements for stopping

Abstract

In the driving operation of a sensorless three-phase motor to be used in a rotation at a comparatively low speed (approximately 2000 RPM or less) and to be bipolar driven, the number of rotations and a rotating position are accurately detected from an induced voltage and a reverse rotation brake is applied in an accurate phase, and furthermore, a short brake is applied at a set rotation number signal or less also in braking. Consequently, it is possible to prevent phase switching from being carried out in an erroneous timing and to prevent a rotation in a reverse direction by an inertia.

Claims

1. A control device of an electric motor for driving the electric motor having multi-phase windings in response to output signals having a predetermined phase difference from each other, comprising;

a plurality of comparing means for comparing a terminal potential of each of the multi-phase windings with a middle potential of the multi-phase windings, and driving timing signal generating means for generating a timing signal for outputting each of the output signals based on a result of the comparison carried out by each of the comparing means; and

rotation number detecting means for detecting the number of rotations of the electric motor based on the result of the comparison obtained by the comparing means,

wherein when the rotation of the electric motor is to be stopped, the driving timing signal generating means is controlled to apply a reverse rotation brake until the number of rotations of the electric motor is reduced to be a predetermined number of rotations by the rotation number detecting means, and the driving timing signal generating means is then controlled to apply a short brake until the rotation of the electric motor is stopped.