JPS58154382A - Rotating speed controller for recording medium in digital signal reproducer - Google Patents

Abstract

PURPOSE:To eliminate the variation in the rotation of a disc due to lack of bit or displacement of a track by providing a forcibly resetting circuit for specifying the maximum value of the reset period of a lamp wave generator. CONSTITUTION:A reproduction signal from a preamplifier 28 is inputted to a zero cross detector 30, the output of which is inputted to a double edge detector 32. The output of the detector 32 is inputted to a pulse generator 40 and a gate circuit 42 as a forcibly resetting circuit. The lamp wave of a lamp wave generator 34 is controlled by the output of a gate circuit 42, the output of which is applied through a peak hold circuit 36, a differential amplifier 20 and an amplifier 26 to a motor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational speed control device for a recording medium in an apparatus for reproducing a disk-shaped recording medium on which digital signals are recorded concentrically or spirally at a constant linear velocity.

The conventional general configuration of this glaze rotation speed control device is as follows.
Shown in the figure. The disc-shaped recording medium 10 (hereinafter referred to as a disk) has a pit period To and a minimum reversal interval Tm1n.
(Tm1a = 3 T(1) to maximum reversal interval Tma
Digital signals up to x (Tmax = 11 T6) are recorded in a spiral shape at a constant linear velocity.

This disk drive 10 is rotationally driven by a motor 12, and a digital signal recorded thereon is reproduced by a pickup 14. A tacho generator 16 for detecting the rotational speed of the motor 12 is connected to the motor 12, and a voltage corresponding to the rotational speed of the motor 6 is obtained from a low-pass filter 18 that smoothes the output of the tacho generator 16, and the signal is a differential signal. It is applied to one input side of amplifier 20. Further, the pickup 14 is equipped with a position detector 22 for detecting the reproduction position in the radial direction of the disc 10, and the output of this is converted by a position/voltage converter 24 into a voltage corresponding to the reproduction position. That signal is applied to the other input of differential amplifier 20. The deviation signal of the meat input signal output from the differential amplifier 20 is transmitted to the amplifier 2 which drives the motor 2.
6, and the rotational speed of the motor 20 is controlled so that the deviation signal always has a constant value. In other words, the disc 12 is moved at a predetermined speed corresponding to the playback position of the pickup 14.
is rotated so that the reproduction linear velocity of the pickup 14 relative to the disk 12 becomes constant, and the pit period of the reproduced digital signal becomes constant.

However, the conventional rotational speed control device described above has the following problems. First, in order to obtain the desired control accuracy, a highly accurate and highly reliable position detector 22 is required, and it is a national problem to construct this part at a low cost.
Adding a mechanical position detection mechanism to the pickup 14 brings about various restrictions. In principle, disk 10
Although the signal recording linear velocity is constant as described above, in reality, a disc 10 containing fluctuations in recording linear velocity occurs.

In this case, in the above-mentioned conventional apparatus, the fluctuation in the recording linear velocity of the disk 10 directly appears as a 11-period fluctuation in the reproduced signal, and no effect of compensating for the fluctuation in the recording linear velocity can be obtained.

A rotational speed control device shown in FIG. 2 has already been proposed to overcome the drawbacks of the conventional devices described above. The configuration and operation of the device shown in Figure 2 are shown in Figure 3, which shows the signal waveforms of each part.
This will be explained with reference to the figures.

Note that the same reference numerals are given to the same or corresponding parts as in FIG. 1, and the description thereof will be omitted.

In FIG. 2, a digital signal is recorded on the disk 10 under the same conditions as above, and this signal is read by the pickup 14 and amplified by the preamplifier 28, resulting in a waveform as shown in FIG. A reproduced signal A is obtained. This reproduced signal is input to the zero cross detection circuit 30,
The waveform is shaped into a square wave signal B whose polarity is inverted at the zero-cross point of the reproduced signal A. The double edge detection circuit 32 detects a small width when the polarity of the output signal B of the zero cross detection circuit is reversed.
Outputs e-rus signal C. The ramp wave generation circuit 34 is reset by the pulse signal C from the double edge detection circuit 32, and outputs a ramp wave whose voltage increases with time until the next pulse signal 0 is input. The peak hold circuit 36 has a sufficiently large discharge time constant compared to the maximum inversion interval Tmax, and holds and outputs the peak value of the ramp wave output voltage of the ramp wave generating circuit 340.

The output signal E of the peak hold circuit 36 and the reference voltage from the reference voltage source 38 are applied to two input sides of the differential amplifier 20, respectively. A deviation signal of the meat input signal output from the differential amplifier 20 is input to an amplifier 26 that drives the motor 12, and the rotational speed of the motor 12 is controlled so that the deviation signal is always at a constant value.

Here, when the rotational speed of the disk 10 is a regular speed commensurate with the playback position of the pickup 14, the playback signal output from the preamplifier 28 has an inversion interval of Tm1n to Tmax and its polarity as described above. is reversed. At this point in time when the polarity of signal A is reversed, the ramp wave generation circuit 34
is reset, the amplitude of the ramp wave corresponding to the signal with the maximum inversion interval Tmax becomes maximum. Reversal interval Tm
Since the signal whose ax corresponds to Tmax is recorded on the disk 10 at regular intervals, the peak hold circuit 36
As shown in FIG. 3E, the output voltage E of
The peak value of the ramp wave corresponding to a x is maintained approximately.

The reference voltage of the reference voltage source 38 is set so that the deviation signal output from the differential amplifier 20 becomes a predetermined value in this state, and the control circuit is maintained in this state. The motor 120 rotation speed.

In this way, the rotational speed control device shown in FIG. 2 uses the signal reproduced from the disk 10 to generate the rotational speed control signal, so in principle the bit rate is independent of the signal recording linear velocity of one disk 10. A reproduced signal with a constant period can be obtained, and the position detection mechanism of the pickup 14 described above is not required.

However, in the apparatus shown in FIG. 2, the following new interpolation occurs. That is, in the apparatus shown in FIG. 2, it is assumed that a signal of the maximum reversal interval Tmax is recorded on the disk 10 at regular intervals, and the rotation speed of the disk 100 is controlled based on the reproduced signal AK. Therefore, if there is a missing bit on the disk 10 or a track deviation occurs, and the reversal interval of the reproduced signal becomes larger than the maximum reversal interval Tmax, the amplitude of the ramp wave generation circuit 34 increases, and its amplitude increases. As a result, an abnormal voltage is held in the peak hold circuit 36 at the next stage, and this appears as a fluctuation in motor rotations of 20 revolutions.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to eliminate the drawback of the conventional device shown in FIG. An object of the present invention is to provide a rotation speed control device that achieves the following.

″°°4 In order to achieve the above object, the present invention provides a method for resetting the above-mentioned ramp wave generation circuit in the apparatus shown in FIG.
The present invention is characterized in that a forced reset circuit is provided for regulating the maximum value of the N period to the maximum inversion interval Tmax or a value slightly larger than this.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 4 shows the configuration of a rotational speed control device according to an embodiment of the present invention, and FIG. 5 shows its operating waveforms. This device is the device shown in FIG. 2 described above with the addition of a pulse generator 40 and a gate circuit 42 as the above-mentioned 7-way 11-way circuit, and all other parts are the same as the device shown in FIG. 2. They are the same, and redundant explanation of the same parts will be omitted. The pulse generator 40 is a retriggerable monostable multivibrator that is triggered by the output signal C of the double edge detection circuit 32 and outputs a pulse signal F having a width slightly longer than the maximum inversion interval Tmax. The gate circuit 42 is controlled by the output signal F of this pulse generator 40. The double edge detection circuit 32
The output 0 is used as the reset signal G of the ramp wave generation circuit 34.
It is configured to apply as follows. The input/output logic characteristics of the gate circuit 42 are as clear from FIG. Then, the output signal G is fixed at H level.

Therefore, the ramp wave D' generated by the ramp wave generation circuit 34
The maximum amplitude of is 1. This is determined (limited) by the pulse width output from the e-pulse generator 40.

The pulse width of this pulse generator 40 is set to be slightly longer than the maximum inversion interval Tmax, as described above. As a result, even if the inversion interval of the reproduced signal A becomes longer than the maximum inversion interval Tmax due to missing bits or track misalignment on the disk 10, an abnormal voltage is generated in the peak hold circuit 36 at the next stage. The rotational speed of the motor 12 can be kept to a minimum.

FIG. 6 shows the configuration of a rotational speed' control device according to a second embodiment of the present invention. This device is obtained by adding a forced reset circuit consisting of a rectangular wave oscillator 44, an N-ary counter 46, and an OR gate 48 to the device shown in FIG. The rectangular wave oscillator 44 oscillates at a period equal to the pit period T0.

The N-ary counter 46 converts the output signal of the square wave oscillator 44 into N
=Tmax/T6 An output signal is generated every time the nozzles are counted. The output signal of this N-ary counter 46 and the output signal C of the double edge detection circuit 32 are connected through an OR gate,
This signal G is applied as a reset signal G to the ramp wave generation circuit 34, and also serves as a reset signal to the N-ary counter 46. With this configuration, the maximum value of the reset cycle of the ramp wave generation circuit 34 is limited to N x T6=Tmax by the output of the N-ary counter 46. As a result, the same effects as in the embodiment described above are achieved.

As explained in detail above, according to the rotational speed control device according to the invention, the pickup position detection @ mechanism is unnecessary, the desired rotational speed can be controlled based on the reproduction signal, and Even if an abnormality occurs in the reproduced signal due to dropout or track deviation, fluctuations in rotational speed can be kept to a minimum.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional general rotation speed control device, FIG. 2 is a block diagram of another conventional rotation speed control device,
Figure 3 is a waveform diagram of each part of the device shown in Figure 2, Figure 4 is a block diagram of the first embodiment of the present invention, Figure 5 is a waveform diagram of each part of the equipment shown in Figure @4, and Figure 6 is a diagram of the main unit. FIG. 3 is a block diagram of a second practical example of the invention. Identical members in each figure are given the same reference numerals, and 10 is a disk (
recording medium), 12 is a motor, 14 is a pickup, 30
is a zero cross detection circuit (waveform shaping circuit), 32 is a double edge detection circuit, 34 is a ramp wave generation circuit, 36 is a peak hold circuit, 20 is a differential amplifier, 26 is an amplifier, 40
42 is a gate circuit, 44 is a square wave oscillator, 46 is an N-ary counter, and 48 is an OR gate. Agent: Patent attorney Shin Kuzuno - (1 other person) Figure 3, Figure 4, Written amendment to the procedure (Spontaneous) June 7, 1980 To the Commissioner of the Japan Patent Office 1, Indication of the case, Recording medium of patent application No. 57-34966 Rotational speed control device 3, relationship with the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Jinhachibe Katayama 4, Agent Address: 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo, Detailed description of the invention of Specification 1 subject to amendment. More than 1:・400

Claims (3)

[Claims] (1) In a device that reproduces a recording medium in an N-circular or spiral manner at a constant linear velocity, a digital signal with a bit period T from a minimum inversion interval Tm1n to a maximum inversion interval Tmax is reproduced from the recording medium. A waveform shaping circuit that shapes the waveform of a digital signal, a double edge detection circuit that generates a pulse signal when the polarity of the output signal of this waveform shaping circuit changes, and a ramp wave generation circuit that is reset by the output signal of this double edge detection circuit. a forced reset circuit that regulates the maximum value of the reset cycle of the ramp wave generation circuit to the maximum reversal interval Tmax or a value slightly larger than this; and a forced reset circuit that holds the peak value of the ramp wave output from the ramp wave generation circuit. a differential amplifier for determining the deviation between the output voltage of the peak hold circuit and a reference voltage from a base voltage source; and a motor for rotationally driving the recording medium according to the output of the differential amplifier. 1. A rotational speed control device for a recording medium in a digital signal reproducing device, comprising: an amplifier for controlling a rotational speed, and controlling the rotational speed so that the deviation is constant. (2) In the device according to claim (1), the forced reset circuit is triggered by the output of the double edge detection circuit and the maximum inversion interval Tmax is
A triggerable Norms generator that outputs a pulse signal with a slightly longer width and a gate circuit controlled by the output of this pulse generator are provided, and the output of the double edge detection circuit is connected to the output of the double edge detection circuit through this gate circuit. A rotation speed control device for a recording medium in a digital signal reproducing device configured to apply the signal as a reset signal to a ramp wave generation circuit. (3) In the device according to claim (1), the forced reset circuit includes a rectangular wave oscillator that oscillates at a period equal to the bit period T, and is reset by the output of the double edge detection circuit, and the rectangular A counter is provided that outputs one pulse signal every time the output of the wave oscillator is increased ('rmax/T6), and the output of this counter and the output of the double edge detection circuit are OR gated to generate the ramp wave. A rotational speed control device for a recording medium in a digital signal reproducing device configured to be applied as a circuit reset signal.