JPH02287968A - Rotation driving device for optical disk - Google Patents

Abstract

PURPOSE:To contrive a stable rotating speed control by setting the gain by a size of a disk. CONSTITUTION:A size detector 15 leads out an output of a high level and an output of a low level to a line 16, when the diameter of a compact disk 3 is 12cm, and when the diameter is 8cm, respectively. An output of the detector 15 is supplied to a base of a transistor 34 in a driving circuit 14. An emitter is grounded, and a collector is connected to a connecting point 35 of resistance Rf, R1 through a resistance R2. In such a way, by switching the gain in the circuit 14 by the diameter of the disk, a rotating speed of the disk 3 can be controlled stably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary drive device for a disc playback device that plays back a plurality of types of optical discs of different sizes. The present invention relates to an optical disc rotation drive device suitable for use in compact disc playback devices and the like.

In conventional technology, for example, in a compact disc playback device, the gain of a drive system that rotates the disc so that its linear velocity is constant must be changed in accordance with the diameter of the disc. In other words, in the drive system, the voltage applied to the motor that rotationally drives the disk is ■(S), and the motor shaft rotation speed is W(
S), and using the Laplace operator S, it can be expressed as shown in FIG. 2 and the first equation.

However, R: Motor armature DC resistance L: Motor armature inductance,: Motor torque constant,: Motor back electromotive force constant T: Motor generated torque T, : Loss torque D: Viscous friction coefficient of armature shaft I: TFI current Current: Moment of inertia of motor shaft load. Normally, L/R<<1, D''; 0, and the transfer function G (S) is: Dl: outer diameter of the disk DO = inner diameter of the disk Based on this third equation, when the diameter is 12 c rn A comparison of the disc and an 8 cm disc is shown in Table 1 as an example.

It can be expressed as.

The moment of inertia J of the motor shaft load is the sum of the moment of inertia J of the motor armature and the moment of inertia J0 of the disk, and is usually J, (Jo. Therefore, only the moment of inertia Jo of the disk Considering, t is the thickness of the disk, ρ is the mass per unit volume of the disk, and this first
In the table, fc is the linear frequency of the gain curve, which can be expressed as follows, and the values shown in Table 1 are R=20
(Ω), Ky=Kt= 1, 2X 1
This is the value when 0-2(N-m/A>).

Therefore, the theoretical gain curve when G (I=O)=OdB is as shown in FIG. In this third [21, reference numeral 11 is straight i18 cr r
It is a disk Ilj group of n, and the 9 reference mark 12 has a diameter of 12
This is the case for a cm disc. As is clear from Fig. 3, the line frequency of the 8cm disc is 0, 2
(Hz) or higher, the 8cm disc is approximately 14 d
B: High gain.

Further, FIG. 4 shows actual measured values of the open loop characteristics of the drive system shown in FIG. Indicates the thirst characteristics of the crn disk.

If the disk diameters differ in this way, it is necessary to switch the gain. However, in typical prior art, 1
Optimized for 2cm discs.

Problems to be Solved by the Invention In the prior art as described above, as is clear from FIGS. 3 and 4, when playing an 8cm disc,
The gain becomes excessive. Therefore, when such a compact disc playback device is used in a vehicle, so-called hunting occurs when playing an 8 cm disc due to the influence of vehicle body vibration, making control unstable.

Also, when the gain is optimized for an 8cm disk, 1
When playing a 2cm disc, there is insufficient gain and it is not possible to correct rotational irregularities caused by vehicle body vibration.

An object of the present invention is to provide an optical disk rotation drive device that can always obtain optimal gain for disks of different sizes.

Means for Solving the Problems The present invention provides a motor for rotationally driving an optical disk, a size detection/setting means for detecting or setting the size of the disk, a linear velocity of the disk being rotationally driven, and a predetermined setting value. a deviation detecting means for detecting a deviation between the disk size and the size detecting/setting means, and a gain is set small when the disk size is small so that the detected deviation is zero in response to the outputs of the size detecting/setting means and the deviation detecting means. , and a driving means for driving the motor.

Operation The motor that rotationally drives the optical disk is driven by the drive means so that the deviation between the linear velocity of the disk detected by the deviation detection means and a predetermined set value becomes zero. On the other hand, the size of the rotationally driven disk is automatically detected by a size detection/setting means or detected/set based on an input operation by an operator. The driving means responds to the output of the size detection/setting means and sets the gain to a small value when the disk size is small.

Therefore, when a small-diameter disk with a small moment of inertia is being rotationally driven, the gain is set to be small, and thereby it is possible to prevent rotational speed control from becoming unstable due to excessive gain. Furthermore, when a disk with a larger moment of inertia than the small-diameter disk is being rotated, the gain is set to a large value. rotation speed control can be performed.

Embodiment FIG. 1 is a block diagram showing the electrical configuration of a compact disc playback device 1 according to an embodiment of the present invention. A compact disc 3 placed on a turntable 2 is rotationally driven by a spindle motor 4. The information recorded on the compact disc 3 is transferred to the optical pickup 5.
is detected by the waveform shaping circuit 7 via the amplifier circuit 6.
is input. The data signal from the waveform shaping circuit 7 is subjected to signal processing such as error correction by the signal processing circuit 18, and then converted to an analog acoustic signal by the digital/analog conversion circuit 8 and then derived. The acoustic signal from the digital/analog conversion circuit 8 is applied to a speaker 10 via, for example, a power amplification circuit 9, and is converted into sound.

Further, the output from the amplifier circuit 6 is given to the tracking servo circuit 11 and the focus servo circuit 12, and the output from the waveform shaping circuit 7 is given to the rotational speed servo circuit 20. The tracking servo circuit 11 corrects the deviation of the optical pickup 5 in the radial direction of the compact disc 3 based on the output from the amplifier circuit 6, so that the optical pickup 5 accurately traces the track on the compact disc 3. I can do it. Based on the output from the amplifier circuit 6, the focus servo circuit 12
A one-rotation speed servo circuit 20 that adjusts the focus of the objective lens in the optical pickup 5 controls the spindle motor 4 based on the output from the waveform shaping circuit 7 so that the linear velocity of the compact disc 3 is constant.

The rotational speed servo circuit 20 includes a deviation detection circuit 13 and a drive circuit 14. The output from the waveform shaping circuit 7 is given to the phase comparison circuit 21 of the deviation detection circuit 13, and this phase comparison circuit 21 is connected to the voltage controlled oscillation circuit 22.
The phase of the oscillation signal and the output from the waveform shaping circuit 7 are compared, and an output based on the difference is derived to the voltage controlled oscillation circuit 22. ? The 4-voltage controlled oscillation circuit 22 includes a phase comparison circuit 2
Oscillation is performed at a frequency based on the output from the signal processing circuit 18 and the phase comparison circuit 23, thereby creating a reproduced clock signal, which is applied to the phase comparison circuit 21 and to one input of the signal processing circuit 18 and the phase comparison circuit 23. These phase comparator circuit 21 and voltage-controlled m oscillation circuit 22 form a phase-locked loose circuit.

A crystal oscillator 2 is connected to the other input of the phase comparison circuit 23.
4 is input, and the phase comparison circuit 23 outputs an output corresponding to the phase difference between the reproduced clock signal and the reference clock signal to the phase compensation circuit 31 of the drive circuit 14. The reference clock signal from the crystal oscillator 24 is also given to one input of a frequency comparison circuit 25, and the data signal from the waveform shaping circuit 7 is input to the other input of this frequency comparison circuit 25. ing.

The frequency comparison circuit 25 compares the frequencies of the reference clock signal and the data signal, and outputs an output corresponding to the difference to the phase compensation circuit 31.

The phase compensation circuit 31 corrects the phase delay of the error output corresponding to the output from the phase comparison circuit 23 and the frequency comparison circuit 25, and then outputs it to the inverting input terminal of the operational amplifier 32 via the resistor Ri.

The non-inverting input terminal of this operational amplifier 32 is grounded, and its output is input to a power amplification circuit 33 and is negatively fed back via resistors Rf and R1. The output from the power amplifier circuit 33 is given to the spindle motor 4, and the spindle motor 4 is thus rotationally driven.

The spindle motor 4 is, for example, a DC brushless motor.

A size detector 15 is provided in association with the turntable 2, and this size detector 15 detects that the compact disc 3 placed on the turntable 2 has a diameter of 1
When the disc is 2 cm, a high level output is derived to the line 16, and when the disc is 8 cm, a low level output is derived. Note that the setting of the disk size may be automatically performed by the size detector 15 as described above, or may be set by an input operation by the operator.

The output of size detector 15 is applied to the base of transistor 34 in drive circuit 14 . This transistor 34
The emitter of is grounded, and the collector is connected to resistor R2.
It is connected to the connection point 35 between the resistors Rf and R1 via.

Therefore, the gain GV between the input and output signals of the operational amplifier 32 is expressed as follows when the resistance values of the resistors R1, R2, Ri, and Rf are expressed with the same reference symbols, and normally R1<<Rf. Since we set,
When using an 8cm disc, GV1=R1moRf
...(7).

Thus, the compact disc playback device 1 according to the present invention
Now, since the gain in the drive circuit 14 is switched between a 12 cm disc and an 8 cm disc, the optimal gain can always be obtained when controlling the rotational speed of the compact disc 3. Therefore, as mentioned in the prior art section, when playing an 8 cm disc, there is no possibility of excessive gain resulting in unstable control, and when playing a 12 cm disc, vibration resistance due to insufficient gain will not occur. Deterioration can be suppressed.

In this way, with always optimal gain, Compact Disc 3
can be stably rotated.

Effects of the Invention As described above, according to the present invention, when the size of the disk to be rotationally driven is small, the gain is set to a small value. is set small. Therefore, it is possible to prevent rotational speed control from becoming unstable due to excessive gain. Further, when a disk having a larger moment of inertia than the small-diameter disk is rotationally driven, the gain is set to be large.

Therefore, deterioration of seismic characteristics due to insufficient gain can be suppressed. In this way, stable rotational speed control can be performed regardless of the disk size.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of a compact disc playback device 1 according to an embodiment of the present invention, FIG. 2 is a block diagram of a drive system in the compact disc playback device, and FIGS. 3 and 4 are 8 cm It is a graph showing the difference in gain between a disk and a 12 cm disk. DESCRIPTION OF SYMBOLS 1... Compact disc playback device, 3... Compact disc, 4... Spindle motor, 5... Optical pickup, 8... Digital/analog conversion circuit, 11... Tracking servo circuit, 12. ... Focus servo circuit, 13... Deviation detection circuit, 14...
- Drive circuit, 15... Size detector, 18... Signal processing circuit, 20... Rotation speed servo circuit, 32...
Operational amplifier, 34... Transistor agent Patent attorney Number of strokes Keiichi Jun tear number (Hz)

Claims (1)

[Scope of Claims] A motor that rotationally drives an optical disk, a size detection/setting means that detects or sets the size of the disk, and detects a deviation between the linear velocity of the disk being rotationally driven and a predetermined set value. and a deviation detecting means for detecting and driving the motor in response to the outputs of the size detecting/setting means and the deviation detecting means, and setting a small gain when the disk size is small so that the detected deviation becomes zero. What is claimed is: 1. A rotational drive device for an optical disc, comprising: drive means for driving an optical disc.