JPH07262679A - Reproduction velocity controlling device - Google Patents

Abstract

PURPOSE:To prevent a motor from its reversely rotational runaway by sending a signal which controls the rotation of a disk based on a velocity control signal to a microcomputer to detect whether the motor is reversely rotating or not. CONSTITUTION:The motor control voltage generates a control voltage to cause the disk to rotate normally or reversely. A rotation direction signal 24 is sent to a microcomputer 21 in the form of MSB, the highest order bit of a binary numeral, a coded value of the maximum width of pulses used for information on the detection. The microcomputer 21 judges the MSB='0' to find that the motor control voltage which causes the reverse rotation of the disk is generated. Next, when no data are reproduced for a certain period or longer, the microcomputer 21 judges that the disk is reversely rotating. Then the microcomputer 21 sends a control voltage DUTY which forcibly causes the disk to rotate normally to a PWM modulator 22 to control the disk motor drive circuit 23 and to cause the disk 1 to rotate normally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk reproducing apparatus in which a digital signal is recorded at a constant linear velocity, and more particularly to a control apparatus suitable for preventing runaway due to reverse rotation of the disk.

[0002]

2. Description of the Related Art The PCM recording system is characterized in that it is not affected by the distortion of the recording medium and that the sound quality is not deteriorated when used in audio equipment. A compact disc (hereinafter abbreviated as a CD) is a typical PCM-recorded disc-shaped medium. In the CD, the digitally converted signal is further modulated and recorded as a signal train having several different pulse widths.

When recording a digital signal on a disc,
The recording is performed at a constant linear velocity (hereinafter abbreviated as CLV). An example of an apparatus for reproducing such a digital signal is disclosed in Japanese Patent Laid-Open No. 61-126665. When the disc rotation is started or when the pickup position is randomly moved (hereinafter referred to as track jump), the rotation is controlled by CLV. Therefore, the maximum pulse width within a certain sample section is used as a velocity detection signal, Playback speed is controlled. In the above conventional example, the pulse width of the reproduction signal of the disk at the time of start-up and the track jump is a predetermined critical value (upper limit of the maximum pulse width of the reproduction signal)
Is counted, and if the count value is equal to or less than the specified number, it is determined that the data is correctly read. Then, the maximum pulse width equal to or less than the critical value is set as the speed detection signal for each sample section, and the reproduction speed is controlled by the signal. In this way, the normal rotation runaway when a pulse having a large width is generated due to a scratch or the like is prevented.

[0004]

In the conventional method, the speed of the motor is detected from the maximum pulse width of the reproduction signal. Therefore, if the maximum pulse width is longer than 11T (T is a unit clock), it is determined that the disk is rotating slowly, and the direction for rotating the disk faster, that is, the motor speed control by the motor control voltage that rotates the disk forward Is done. On the contrary, if it is shorter than 11T, it is determined that the disk is rotating fast, and the speed of the motor is controlled by the direction of rotating the disk slowly, that is, the motor control voltage for rotating the disk in the reverse direction.

Therefore, the disk is controlled to the CLV rotation speed by the above motor control voltage.

However, if the disc rotates in the opposite direction,
Since the speed control of the motor is performed by the pulse width of the reproduction signal, for example, when the disk reversely rotates at a speed such that the pulse width is shorter than 11T, it is judged by the speed detection that the disk is rotating faster, and the disk is further rotated. Since a motor control voltage for rotating the motor in the reverse direction is generated, a reverse runaway may occur. However, the above-mentioned conventional example does not consider reverse runaway prevention.

[0007]

In order to solve the above-mentioned problems, an apparatus for rotating a disk to reproduce a signal from the disk reproduces a digitally recorded signal and detects a speed from the reproduced signal. A voltage generating means for generating a voltage for driving the disk motor according to the speed detecting means, a switching means for switching the output of the voltage generating means and a fixed voltage, and a disk motor driven by the output of the switching means. Drive means and a reproduction state detecting means for detecting a state where data cannot be reproduced from the reproduction signal, and a judging means for judging reverse rotation by the output of the reproducing state detecting means and the output of the speed detecting means is provided. It is characterized by that.

Further, the output of the reproduction state detecting means outputs a signal indicating a state in which the data cannot be reproduced when the synchronization signal cannot be detected from the reproduction signal by the synchronization signal detecting means.

Further, the output of the reproduction state detecting means outputs a signal indicating a state in which the data cannot be reproduced by the error correcting means when the number of error data in the reproduction signal is larger than a prescribed value.

[0010]

When the discriminating unit discriminates that the disc is rotating in the reverse direction, the discriminating unit switches the switching unit so as to output a fixed voltage (in this case, a voltage for positively rotating the disc). By this switching, a positive rotation control voltage is output to the motor driving means, and the motor driving means forcibly rotates the disk in the forward direction. Therefore, the reverse rotation runaway of the disk can be prevented.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a system for preventing reverse rotation runaway of a motor according to the present invention.

The digital signal recorded on the disk 1 is reproduced by the pickup 3, and the signal is reproduced by the preamplifier 4
Sent to and amplified. Reference numeral 5 is an EFM demodulation circuit, which shapes the EFM signal waveform and performs EFM demodulation. The reproduction data is written from the EFM demodulation circuit 5 to the RAM 7 and sent to the error correction circuit 6 for correction. The correction result of the error correction circuit 6 is sent to the interpolation circuit 8. The interpolation circuit 8 performs interpolation processing such as average value interpolation on the data that cannot be corrected by the correction circuit 6. The output of the interpolation circuit 8 is sent to the DAC 9.

The reproduced data is sent from the EFM demodulation circuit 5 to the sync signal detection circuit 10 to detect the sync signal.
If the sync signal is not detected from the reproduction data, the reproduction state detection signal 20 indicating the state in which the data cannot be reproduced is output.

Reference numeral 11 is an encoding circuit for binary encoding the pulse width of the reproduced signal, and 12 is a maximum pulse width detection circuit for comparing the pulse widths encoded by the encoding circuit 11 and detecting the maximum pulse width. is there. Reference numeral 13 is a speed detection circuit A for detecting the rotation speed of the disk based on the maximum pulse width detected by the maximum pulse width detection circuit 12. Reference numeral 14 is a speed detection circuit B for detecting the rotation speed of the disk from the cycle of the sync signal in the steady state where the sync signal is correctly reproduced. Reference numeral 15 is a switching circuit for switching the outputs of the speed detection circuits A and B at the start-up when the sync signal cannot be correctly reproduced and at the time of a track jump and in a steady state where the sync signal is correctly reproduced. The outputs of the speed detection circuits A and B switched by the switching circuit 15 are sent as the detected speed information 16 through the control voltage switching circuit 17 to the PWM conversion circuit 22 which converts the speed information into the motor control voltage DUTY.
Further, a part of the speed information is sent to the microcomputer 21 as a disc rotation direction signal 24 (hereinafter referred to as a rotation direction signal) indicating the rotation direction of the disc 1. Based on the disc rotation direction signal 24 and the reproduction state detection signal 20 output from the synchronization signal detection circuit 10, the microcomputer 21 determines whether the disc 1 is rotating in the reverse direction. When the microcomputer 21 determines that the disk 1 is rotating in the reverse direction, the microcomputer 21 controls the control voltage switching signal 18 for switching the fixed voltage DUTY by the fixed voltage output circuit 19 and the motor control voltage DUTY by the detected speed information 16. Output to the voltage switching circuit 17. The fixed voltage circuit 19 is a circuit that generates a control voltage DUTY forcibly rotating the disk 1 in the forward direction. The motor control voltage DUTY is sent from the PWM conversion circuit 22 to the disk motor drive circuit 23 by the control voltage switching circuit 17 and converted into the motor control voltage to control the motor.

FIG. 2 shows the maximum pulse width of the disk 1 vs. PWM.
The relationship of DUTY after conversion is shown. Further, the binary numbers shown side by side on the vertical axis in FIG. 2 are an example in which the maximum pulse width of the reproduced signal is encoded into a binary number by the encoding circuit 11 in FIG.
Speed detection is performed based on the coded information of the maximum pulse width. In the speed detection circuit 13 in FIG. 1, the PWM conversion DUTY is determined from the detected rotation speed of the disk 1. As shown in FIG. 3, when the maximum pulse width 11T is used as a reference and the detected maximum pulse width is 12T or more, that is, when the rotation is slow, the PWM conversion DUTY is set to 100% and the disc 1
Generates a motor control voltage that speeds up the rotation of the motor. On the contrary, if it is less than 10T, that is, if the rotation is fast,
WM DUTY is set to 0% to generate a motor control voltage that slows the rotation of the disk 1 (that is, reversely rotates). As a result, the disk 1 can be controlled at the CLV rotation speed.

The motor control voltage causes the disk 1 to rotate forward,
A control voltage for reverse rotation is generated. The MSB of the most significant bit of the value obtained by encoding the maximum pulse width into a binary number as the detected speed information that is the information of the motor control voltage (hereinafter referred to as M
(Abbreviated as SB) is used as the rotation direction signal 24 by the microcomputer 21.
By sending the voltage to the disk motor drive circuit 23, the microcomputer 21 can know to which direction the voltage for rotating the disk 1 is being sent to the disk motor drive circuit 23, and can be used as a material for determining the reverse rotation runaway in the microcomputer 21.

Next, the microcomputer 21 of this disc reproducing apparatus
An example of the processing flow for preventing the reverse rotation of the disk in FIG. 3 will be described with reference to FIG. First, speed detection circuit 1
In 3, the rotation speed information of the disk is represented by a binary number. As shown in FIG. 2, the most significant bit MSB of the binary number generates a motor control voltage of forward rotation when MSB = "1" and reverse rotation when MSB = "0". Therefore, by sending this binary MSB to the microcomputer 21, the microcomputer 2
In 1, it is possible to know what kind of speed information is sent to the PWM conversion circuit 22.

The microcomputer 21 first determines whether MSB = "0". This judgment is made regarding whether or not a motor control voltage for rotating the disk in the reverse direction is generated. Next, when the data cannot be reproduced for a certain time or longer, the microcomputer 21 determines that the disk is rotating in the reverse direction. Here, since the disk 1 is rotating at CLV, the disk 1 is rotating the fastest when the signal on the innermost circumference of the disk is reproduced. For example, if the reverse rotation motor control voltage is applied for the longest time when the rotation is stopped while the data on the innermost circumference is being reproduced, if the reverse rotation motor control voltage is continuously applied for a longer time than this time, the disc May rotate in the opposite direction. Therefore, this time can be used as a criterion for determining whether the reverse rotation is performed.
When the microcomputer 21 determines that the disk 1 is rotating in the reverse direction, the microcomputer 21 sends a control voltage DUTY forcibly rotating in the positive direction to the PWM conversion circuit 22 to control the disk motor drive circuit 23. The disk 1 is rotated normally. Thereby, reverse rotation runaway can be prevented.

FIG. 4 is a block diagram showing another embodiment of the system for preventing the reverse rotation runaway of the motor according to the present invention.
The same numbers as in FIG. 1 indicate the same.

As in the first embodiment, the digital signal recorded on the disc 1 is reproduced by the pickup 3,
The signal is sent to the preamplifier 4 and amplified. 5 is EF
The M demodulation circuit waveform-shapes the EFM signal and performs EFM demodulation. The reproduced data is sent from the EFM demodulation circuit 5 to the sync signal detection circuit 10. Further, the reproduced data from the EFM demodulation circuit 5 is written in the RAM 7 and sent to the error correction circuit 6 to perform error correction. The correction result of the error correction circuit 6 is sent to the interpolation circuit 8. The interpolation circuit 8 performs interpolation such as average value interpolation on the data that cannot be corrected by the correction circuit 6. The output of the interpolation circuit 8 is sent to the DAC 9. Here, in the error correction circuit 6, when the number of correction flags indicating the number of error data in the reproduced data is very large, the upper limit value of the correction flag is actually set, and when the value exceeds that value, , And outputs a reproduction state detection signal 25 indicating that data cannot be reproduced. With this signal, the microcomputer 21 can determine that reverse rotation is performed as in the first embodiment, and can prevent reverse rotation.

[0022]

According to the present invention, the microcomputer detects the reverse rotation of the disk based on the signal for detecting and outputting the state in which the data cannot be reproduced and the signal indicating the rotating direction of the disk from the disk rotation speed detecting section. Therefore, when reverse rotation of the disk occurs, a control voltage for forcibly rotating the disk motor drive by the microcomputer to forward rotation is sent, and it becomes possible to prevent reverse rotation runaway of the disk.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between maximum pulse width and PWM DUTY.

FIG. 3 is a diagram showing a flow of reverse rotation runaway prevention processing for a disk.

FIG. 4 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Disc, 2 ... Motor, 3 ... Pickup, 4 ... Preamplifier, 5 ... EFM demodulation circuit, 6 ... Error correction circuit, 7
... RAM, 8 ... Interpolation circuit, 9 ... DAC, 10 ... Sync signal detection circuit, 11 ... Encoding circuit, 12 ... Maximum pulse width detection circuit, 13 ... Speed detection circuit A, 14 ... Speed detection circuit B,
15 ... Startup / steady state switching circuit, 16 ... Speed information, 17 ... Control voltage switching circuit, 18 ... Control voltage switching signal, 19 ... Fixed voltage circuit, 20 ... Reproduction state signal, 21 ... Microcomputer, 22
… PWM converter circuit, 23… Disk motor drive circuit, 2
4 ... Rotation direction signal, 25 ... Reproduction state signal.

Claims (3)

[Claims] 1. A device for rotatably driving a recording medium on a disk to read a signal from the recording medium, speed detecting means for reproducing a digitally recorded signal and detecting a speed from the reproduced signal,
The voltage generating means for generating a voltage for driving the disk motor according to the speed detected by the speed detecting means, the switching means for switching the output of the voltage generating means and the fixed voltage, and the output of the switching means for the disk Drive means for driving the motor, further reproduction state detection means for detecting a state in which data cannot be reproduced from the reproduction signal, judgment means for judging reverse rotation by the output of the reproduction state detection means, and output of the speed detection means. A playback speed control device characterized by being provided. 2. The reproduction speed control device according to claim 1, wherein the reproduction state detecting means includes a synchronization detecting means, and the data is reproduced when the synchronization signal cannot be detected from the reproduction signal by the synchronization signal detecting means. A reproduction speed control device characterized by outputting a signal indicating a state in which reproduction is impossible. 3. The reproduction speed control device according to claim 1, wherein the reproduction state detecting means includes an error correcting means, and the error correcting processing is performed by the error correcting means.
A reproduction speed control device, which outputs a signal indicating that data cannot be reproduced when the number of error data in the reproduction signal is larger than a prescribed value.