Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-11-25
2001-09-25
Hindi, Nabil (Department: 2753)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053370
Reexamination Certificate
active
06295261
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 62798/1997, filed Nov. 25, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk drive, and more particularly, to a method and apparatus for controlling a revolution speed of a spindle motor for driving an optical disk.
2. Description of the Related Art
An optical disk drive rotates an optical disk by using a spindle motor and reads information recorded in the optical disk by detecting a change of a laser beam reflected from the optical disk. The optical disk drive is classified into several types according to functions, and each type of optical disk drive includes a disk loading/unloading mechanism, a spindle motor for rotating the optical disk, an electronic circuit for reproducing information read from the optical disk, and a controller which controls a flow of commands, states of flags, and data communication between the electronic circuit and a host such as a personal computer.
In reading information from the optical disk, the optical disk drive rotates the spindle motor depending on CLV (Constant Linear Velocity) control or CAV (Constant Angular Velocity) control, and reads digital information, in the form of an RF (Radio Frequency) signal, recorded in the optical disk by using an optical pickup.
To control revolution of the spindle motor, the controller detects a present revolution speed (i.e., RPM (Revolutions Per Minute)) of the spindle motor. For example, the drive detects the revolution speed by reproducing synchronous information arranged at regular intervals in the information read from the optical disk. Alternatively, the drive can detect the revolution speed by using a Hall sensor prepared in the spindle motor. When the revolution speed of the spindle motor is over 8× speed (8×216 RPM), it is preferable to detect the revolution speed by using hardware such as the Hall sensor in controlling the revolution speed. The above methods of detecting the revolution speed of the spindle motor ar both well known.
In controlling the revolution speed of the spindle motor by CAV control, the controller provides a spindle motor drive with a PWM (Pulse Width Modulation) signal shown in
FIGS. 1A
to
1
C. The spindle motor driver then drives the spindle motor according to the PWM signal. Subsequently, the controller receives an FG (Frequency Generator) signal (including revolution velocity information) from the spindle motor and controls a pulse width of the PWM signal according to the FG signal. The controller outputs the PWM signal of
FIG. 1A
during a kick interval to kick up the revolution speed of the spindle motor to a target RPM, and outputs the PWM signal of
FIG. 1B
during a brake interval to brake down the spindle motor. Further, when the spindle motor reaches the target RPM, the controller outputs the PWM signal of
FIG. 1C
to maintain the target RPM. It is noted from
FIGS. 1A
to
1
C that the PWM signal has a different pulse width according to operation intervals of the spindle motor.
Conventionally, even when the spindle motor reaches and maintains the target RPM, the controller continues to output the PWM signal of
FIG. 1C
fluctuating between a maximum level and a minimum level at regular intervals, which leads to an increase in the current consumption and instability of a spindle servo. That is, when the PWM signal goes to the minimum level from the maximum level and vice versa, a current is abruptly supplied to the spindle motor through the spindle motor driver, thereby causing an increase in the current consumption. Further, fluctuation of the PWM signal between the maximum level and minimum level brings about an instantaneous change of the revolution speed of the spindle motor, which causes instability of the spindle servo.
Moreover, the great voltage difference between the maximum level and the minimum level may be the cause of heat generation in the controller, and the continuous fluctuation of the PWM signal may overload the controller. Further, since the spindle motor reaches the target RPM depending upon the PWM signals for the kick and brake operations, it takes a relatively long time to reach the target RPM.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of stably maintaining a revolution speed of a spindle motor.
It is another object of the present invention to provide a method of reducing a time required in reaching a desired revolution speed of a spindle motor.
It is still another object of the present invention to provide a method of controlling a revolution speed of a spindle motor with reduced current consumption.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a method of controlling a revolution speed of a spindle motor in an optical disk drive. In the method, target RPMs and actual PWM signal values for maintaining the target RPMs are calculated according to recording linear velocities of an optical disk, and stored in a memory. The spindle motor is controlled by a PWM signal value greater than an actual PWM signal value for maintaining a desired target RPM until an RPM of the spindle motor reaches the target RPM. Further, the spindle motor is controlled by the actual PWM signal value for maintaining the target RPM, when the RPM of the spindle motor reaches the target RPM.
REFERENCES:
patent: 5686807 (1997-11-01), Kusano et al.
patent: 2-164294 (1990-06-01), None
Amsung Electronics Co., Ltd.
Hindi Nabil
Staas & Halsey , LLP
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