JPH0536214A - Optical disk device - Google Patents

Abstract

PURPOSE:To make a reproducing speed continuously variable by providing an oscillation rough adjustment circuit for roughly adjusting the oscillation frequency of a VCO so as to make the LPF output of a PLL circuit the center of a VCO control variable range. CONSTITUTION:When a motor circuit 5 for rotating an optical disk is controlled so that the oscillation frequency of a VCO 3 constituting the PLL circuit with a phase comparison recording PD 1 and an PF 2 is synchronized with an oscillation frequency from a basic oscillation circuit VCO 11, a rough adjustment is operated by an oscillation rough adjustment restraint circuit 12 so that the output of the LPF 2 comes within the control changeable range of the VCO 3. Thus, even when the output of the LPF deviates from an average reference voltage, the control oscillation frequency of the VCO 3 is varied and followed stably. Further, an offset may be added to the inputted voltage of the VCO 3 so that the serial component of the outputted voltage of a comparator PD 1 comes within the control variable range of the VCO 3 by the circuit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an optical disk device having a variable reproduction speed.

[0002]

2. Description of the Related Art In an optical disc apparatus, a laser beam is applied to the surface of the optical disc through a pickup, the reflected laser beam is received and converted into an electric signal, and then the EFM.
The signal is obtained, the information recorded on the optical disc surface is reproduced, and the rotation of the optical disc is controlled. In FIG. 5, the EFM signal is compared with the frequency-divided output from the 1/2 frequency divider 4 by the phase detector 1, and the low-pass filter (LPF) 2 extracts the low-frequency component of the phase difference signal to obtain a voltage-controlled oscillator. It is supplied as a control signal for (VCO) 3. The oscillation output from the VCO 3 is frequency-divided by the 1/2 frequency divider 4 and supplied to the phase comparator 1. The EFM signal of f _PD = 4.3218 MHz is also input to the signal processing circuit 8 and the VCO
Based on the clock signal of f _VCO = 8.6436 MHz from 3, the known digital signal processing is performed to obtain a reproduced digital signal. This digital signal is converted into an analog signal in the D / A converter 9 and then output from the speaker 10. The motor circuit 5, based on the oscillation output from the VCO 3 and the output from the signal processing circuit 8,
The motor 7 is driven to rotate. F from the crystal oscillator circuit 6
The oscillation output of _OSC = 16.9344 MHz is supplied to the signal processing circuit 8 and the motor circuit 5.

In the conventional optical disc device (for example, CD) shown in FIG. 5, E obtained from the read RF signal is used.
The FM signal includes a 2.16 MHz clock component, and the PLL circuit including the phase comparator 1, LPF2, VCO3, and 1/2 divider 4 extracts a 4.32 MHz bit clock synchronized with this clock. Be done.
In the phase comparator of the PLL circuit, the phase comparison is performed for each edge of the EFM signal with the bit clock of 4.32 MHz which is the output from the 1/2 frequency divider 4. The average output value from the phase comparator becomes about + V / 2 (V is the power supply voltage of the circuit system), and when the output frequency from the VCO 3 becomes higher, the average value decreases, and conversely increases. The motor circuit 5 internally divides the frequency of the VCO 3 and the frequency of the oscillation circuit 6 and controls the rotation of the motor 7 so that the respective frequencies are synchronized. The signal processing circuit 8 has a built-in RAM,
Demodulated data is stored with a clock (write clock) with the clock from the VCO 3 as a reference, and is read and reproduced with the clock from the oscillator circuit 6.

[0004]

Although the conventional optical disk device is constructed as described above, the reproduction speed cannot be continuously changed, and there is a problem in terms of usability.

Therefore, an object of the present invention is to provide an optical disk device in which the reproduction speed is continuously variable.

[0006]

In order to solve the above-mentioned problems, an optical disk device according to an aspect of the present invention has a phase comparator, a low-pass filter and a voltage controlled oscillator for a clock component obtained from a reproduction signal from the optical disk. In an optical disc device that controls a motor that rotates the optical disc so that the oscillation frequency of the voltage controlled oscillator of the PLL circuit is synchronized with the oscillation frequency from the basic oscillation circuit by the PLL circuit, the output of the low-pass filter is It is configured to include an oscillation coarse adjustment control circuit for adjusting the phase of the oscillation frequency of the voltage controlled oscillator while centering the control variable range of the voltage controlled oscillator. An optical disk device according to another aspect of the present invention synchronizes a clock component obtained from a reproduction signal from an optical disk with a PLL circuit having a phase comparator, a low pass filter and a voltage controlled oscillator, and oscillates the voltage controlled oscillator of the PLL circuit. In an optical disk device that controls a motor that rotates the optical disk so that the frequency is synchronized with the oscillation frequency from the basic oscillation circuit, the DC component of the output voltage of the phase comparator is at the center of the control variable range of the voltage controlled oscillator. Therefore, an oscillation coarse adjustment control circuit for adding an offset to the input voltage of the voltage controlled oscillator is provided.

[0007]

According to the present invention, when controlling the optical disk rotating motor so that the oscillation frequency of the voltage-controlled oscillator that constitutes the PLL circuit together with the phase comparator and the low-pass filter is synchronized with the oscillation frequency from the basic oscillation circuit, the low-pass filter is used. Voltage is controlled so that the oscillation frequency is roughly adjusted while the output of is in the center of the control variable range of the voltage controlled oscillator, or the DC component of the output voltage of the phase comparator is in the center of the control variable range of the voltage controlled oscillator. By providing an oscillation coarse adjustment control circuit that adds an offset to the input voltage of the oscillator, reproduction at a continuous speed is possible.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of an optical disk device according to the present invention. In FIG. 1, the components designated by the same reference numerals as those in FIG. 5 indicate the same components. In this embodiment, the oscillation circuit 6 in FIG. 1 is replaced with a voltage controlled oscillator (VCO) 11 having a variable oscillation frequency, and an oscillation coarse adjustment control circuit 12 for roughly adjusting the oscillation frequency of the VCO 3 is provided. The configuration is different. FIG. 2 shows a specific circuit example of the LPF 2, VCO 3 and oscillation coarse adjustment control circuit 12 in FIG. Since the output from the phase comparator (PD) 1 is a 3-state output, the center voltage is set to + V / 2 by the resistors R1 and R2, and the output of the loop filter 21 of the LPF 2 is the operational amplifier 22. Is amplified by. Here, if R3 and R4 are set to substantially equal values, the output of the operational amplifier 22 is output with an average reference voltage of about 0V. Therefore, as the playback speed of the optical disk changes, the operational amplifier 2
When the output voltage of 2 changes and deviates greatly from the average reference voltage, the VCO 3 of the PLL circuit cannot follow and becomes unstable. In order to solve this problem, in this embodiment, the output of the LPF 2 is the average reference voltage (0 in this example).
Even if it deviates from V), the central oscillation frequency of the VCO 3 is changed so that the average reference voltage is controlled around 0V. The VCO 3 of this example has a varicap V for fine adjustment.
C1 and a varicap VC2 for coarse adjustment are provided. In this circuit, the bias system for the varicap VC2 is omitted for simplicity of explanation.

An equivalent circuit of the VCO 3 shown in FIG. 2 is shown in FIG. The AC equivalent circuit is shown in (B). R is a resistor for performing DC feedback so that the DC operating voltage has the maximum amplitude centered on the power supply voltage. The varicap VC1 is used as a fine adjustment capacitor, and the varicap VC2 is used as a coarse adjustment capacitor. The capacitor C4 is for cutting direct current. The oscillation frequency is the combined capacitance C of the coil L and the capacitor.
Depending on _TOTAL , f _VCO = 1 / 2π√ (L ・ C _TOTAL ) [HZ]. Where C _TOTAL is C _TOTAL = 1 / ((1 / VC2) +1 / ((1 / C1 + 1 / VC1 + 1 / C2) + C3))
[F].

FIG. 4 shows another circuit example of the oscillation circuit section of the embodiment shown in FIG. This embodiment is suitable when the VCO is capable of oscillation over a relatively wide range. This circuit is effective when the change width of the VCO input voltage is wide and the output from the LPF 2 cannot be synchronized in a wide range. In this example, the offset voltage is added to the input voltage of the VCO so that the average reference voltage from the phase comparator (PD) 1 does not change significantly, and the oscillation frequency of the VCO becomes the center of the oscillation frequency to be controlled. To For that purpose, an oscillation coarse adjustment control circuit 12 is provided, the output from the phase comparator 1 is converted into an average DC voltage by the LPF 2, this voltage is amplified, compared with a reference voltage (corresponding to the same voltage as the average reference voltage), and compared. The output is obtained as a DC voltage by the LPF2.
The control is performed by adding the DC voltage thus obtained to the input voltage of VCO3. In the above embodiment, the operational amplifier and the adder of the loop filter are constructed by one. Of course, the addition with the input voltage may be performed on the input side of the LPF 2 or the input side of the VCO 3.

According to the present invention, as described above, the master clock for signal processing can be made variable by the VCO, and the synchronization range of the EFM-PLL can be expanded. Therefore, the playback speed of the optical disk can be continuously controlled by changing the oscillation frequency of the VCO back and forth,
Barrier Pulvic playback is also possible. Further, since the VCO is divided into fine adjustment and coarse adjustment, and the control in the loop is mainly performed by the fine adjustment varicap, the loop gain can be set to a constant value in an optimum state, and the coarse adjustment is performed only in the low range in the loop. Since it is controlled by the adjusting varicap, the PLL loop is stable, and a wide range of synchronization is possible.

[0012]

As described above, according to the optical disk device of the present invention, not only the reproducing speed can be continuously varied, but also stable and wide range synchronization can be realized.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of an optical disk device according to the present invention.

FIG. 2 is a partial concrete circuit diagram in the embodiment of FIG.

FIG. 3 is a circuit diagram of a main part of the circuit shown in FIG.

FIG. 4 is a circuit diagram of another main part of the circuit shown in FIG.

FIG. 5 is a configuration block diagram of a conventional optical disc device.

[Explanation of symbols]

1 Phase Comparator (PD) 2 Low Pass Filter (LPF) 3, 11 Voltage Controlled Oscillator (VCO) 4 1/2 Divider 5 Motor Circuit 6 Oscillation Circuit 7 Motor 8 Signal Processing Circuit 9 D / A
Converter 10 Speaker 12 Oscillation rough adjustment control circuit

Claims (2)

[Claims] 1. A clock component obtained from a reproduction signal from an optical disk is synchronized by a PLL circuit having a phase comparator, a low-pass filter and a voltage controlled oscillator, and the oscillation frequency of the voltage controlled oscillator of the PLL circuit is a basic oscillation circuit. In an optical disc device for controlling a motor for rotating the optical disc so as to be synchronized with the oscillation frequency of the voltage controlled oscillator, the oscillation frequency of the voltage controlled oscillator is controlled so that the output of the low pass filter is at the center of the control variable range of the voltage controlled oscillator. An optical disk device comprising an oscillation coarse adjustment control circuit for coarsely adjusting the optical disc. 2. A clock component obtained from a reproduced signal from an optical disk is synchronized by a PLL circuit having a phase comparator, a low pass filter and a voltage controlled oscillator, and the oscillation frequency of the voltage controlled oscillator of the PLL circuit is a basic oscillation circuit. In an optical disk device for controlling a motor for rotating the optical disk in synchronism with the oscillation frequency from the above, the voltage control is performed so that the DC component of the output voltage of the phase comparator is at the center of the control variable range of the voltage controlled oscillator. An optical disk device comprising an oscillation coarse adjustment control circuit for adding an offset to an input voltage of an oscillator.