Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1983-10-17
1986-09-23
Shoop, Jr., William M.
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
318599, 318318, 318315, H02P 500, H02P 516
Patent
active
046137998
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a motor velocity control circuit rotatably driving a disc at constant linear velocity. This invention improves the method of picking up synchronous signals for driving the disc at constant linear velocity from the same on which are recorded the synchronous signals together with information signals, such as video, sound, etc. and aims at provision of a motor velocity control circuit for rotatably driving the disc including the motor starting period of time by phase-comparing data signal reproduced by the disc, or demodulated clock signal in synchronism with the data signal, and an output of a reference oscillator.
BACKGROUND ART
Recently, a compact disc digital audio system has been developed and in the limelight which records information signals, such as video or sound, in minute hollows (called the pits) on the disc and reads out and reproduces the recorded information by use of the ray, such as the laser ray, the disc being regulated to rotate at constant linear velocity so that the motor for rotatably driving the disc is adapted to be sequentially changeable of the number of rotations per minute following movement of a pickup.
Since the control signal controlling the motor is formed on the basis of data signal recorded on the disc, a method has been proposed which detects the synchronous signal with the longest data signal from the data signals reproduced by the pickup to thereby control the number of rotations of motor so that its time intervals are constant.
The above method includes a method of feeding to an integrated circuit the data signal detected from the disc to thereby detect the peak value by the longest synchronous signal, or that of picking up the longest synchronous signal of data signal by FM-detecting the data signal, the detection of peak value by the integrated circuit and pickup of synchronous signal by FM-detection being impossible during the start of motor, the pickup of data signal itself being almost impossible unless the disc is driven previously at constant linear velocity, thereby requiring another circuit which rotatably drives the motor by some way until it rotates at about the predetermined linear velocity during the starting. Therefore, the problem has been created in that the construction is complicated.
DISCLOSURE OF THE INVENTION
The data signal reproduced by the disc is distributed covering about 400 to 500 kHz around the frequency component of about 430 kHz on the basis of the coding system of compact disc digital audio system. Paying attention to the 430 kHz frequency spectrum, a means is provided which compares the data signal including a large amount of 430 kHz frequency component with the reference signal of reference oscillator, thereby driving and controlling the disc by error voltage of the comparison means at constant linear velocity including the start of motor.
A means to divide the data signal and reference signal is provided so that the dividing ratio of the dividing means changes during the start, the rotation at constant linear velocity and the stop of motor, so that the motor starts quickly, is rotated at constant linear velocity, and is stopped rapidly by the braking action of an electromagnet brake.
Also, at least one of the demodulated clock signal in synchronism with the data signal reproduced from the disc and reference signals of the reference oscillator, is compared by the comparison means through the dividing means, so that the error voltage can drive and control the disc including the starting of motor, and the dividing ratio of the dividing means is changed in the starting, rotation at constant linear velocity and the stop of motor, whereby it is possible to start the motor quickly and stop it rapidly. Paying attention to that when the motor rotates at constant linear velocity, the demodulated signal is multivibrating in the neighborhood of the central frequency of 4.3218 MHz, since the coding system of compact disc digital audio system standardizes that the data signal is of magnitude of 3 to 11
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Ip Shik Luen Paul
Sanyo Electric Co,. Ltd.
Shoop Jr. William M.
Tottori Sanyo Electric Co. Ltd.
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