Technique for controlling current limiter of motor

Details Technique for controlling current limiter of motor Technique for controlling current limiter of motor

1999-08-30

2001-03-27

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Constant motor current, load and/or torque control

C318S434000, C388S903000, C361S031000

Reexamination Certificate

active

06208099

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my application APPARATUS AND METHOD OF CONTROLLING CURRENT LIMITER OF MOTOR filed with the Korean Industrial Property Office on Sep. 12, 1998 and there duly assigned Serial No. 37670/1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor controlling technique, and more particularly, to a technique for controlling a current limiter of a motor for limiting current supplied to the motor by controlling the current limiter according to the rotational speed of the motor so that accurate control of the motor according to the type of execution mode is possible.
2. Description of the Related Art
In general, a motor controlling apparatus uses a current limiter to protect the motor from overcurrent. The current limiter limits current supplied to the motor according to a voltage supplied to a control port. That is, the current limiter cuts off the current supplied to the motor when a voltage under a threshold value is supplied to the control port. When a voltage over the threshold value is supplied, the current limiter increases the current supplied to the motor in proportion to the level of the supplied voltage.
According to conventional technology, since a uniform voltage level is supplied to the control port of the current limiter, the current supplied to the motor is limited to a particular value regardless of the type of execution mode.
In a VCR, a slow playback mode, which is one of a group of special playback modes, is for displaying an image more slowly than a normal playback mode, which is accomplished by periodically repeating a still mode and the normal playback mode. When the slow playback mode is executed by repeating the normal playback mode and the still mode, control of a brake in the motor is needed. Control of the brake is generally performed by supplying a reverse voltage to the motor for a predetermined time to reduce the speed of the motor so that a tape runs for a predetermined time and the motor comes to a stop. In this state, since the motor stops out of a target position according to a load, characteristic picture motion in a screen is not displayed smoothly.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide a technique for controlling a current limiter of a motor by controlling the amount of current which is limited by the current limiter according to the rotational speed of the motor according to a playback mode so that accurate control of the motor is possible.
Accordingly, to achieve the above object, there is provided an apparatus for controlling a current limiter of a motor for protecting the motor by limiting the amount of electric current supplied to the motor and controlling a driving force of the motor, which comprises: a frequency detector for detecting the rotational frequency of the motor; a limiter controller for generating a current limiter control signal corresponding to the rotational frequency detected by the frequency detector; and a current limiter for limiting the amount of current supplied to the motor in accordance with the current limiter control signal.
To achieve another aspect of the object of the present invention, there is provided a method of controlling a current limiter of a motor for protecting the motor by limiting the amount of current supplied to the motor according to a current limiter control signal and controlling the driving force of the motor, which is achieved by (A) setting a duty cycle value D
0
of a pulse width modulation signal which is the current limiter control signal for each mode, (B) determining whether the present execution mode corresponds to a mode for altering a limit amount of current of the current limiter, (C) detecting a rotational frequency f
c
of the motor, and (D) if it is determined in step (B) that the present execution mode is the mode for altering the limit amount of current, altering D
0
set in step (A) according to the value of f
c
.


REFERENCES:
patent: 3935520 (1976-01-01), Johnson, III
patent: 3947738 (1976-03-01), Oliver
patent: 4433370 (1984-02-01), Karadsheh et al.
patent: 4544868 (1985-10-01), Murty
patent: 5303156 (1994-04-01), Matsuoka et al.
patent: 5825597 (1998-10-01), Young

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