JPH0469084A - Spindle servo device - Google Patents

Abstract

PURPOSE:To regulate relative gain of both a speed servo system and a phase servo system by selectively connecting a capacitive impedance element in response to the operation mode of each servo system to the output line of a PWM circuit of a motor driver. CONSTITUTION:When only a speed servo system is operated, a transistor Q is turned OFF, and a capacitor C is not connected to the output line of a PWM circuit 11. When a phase servo system is operated in addition to the speed servo system, the transistor Q is turned ON, the capacitor C is connected to the output line of the PWM circuit. Thus, when the phase servo system is operated, a voltage is provided even in a high impedance zone by the connection of the capacitor C. Accordingly, the gain of the phase servo system can be apparently raised. Since the gain can be freely set by the capacity of the capacitor C to be connected, an optimum gain can be set.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a spindle servo device for an information recording disk playing device.

Background Art A performance device for information recording disks (hereinafter simply referred to as disks), such as digital audio disks and video disks called CDs (compact disks), is equipped with a device that moves an information reading spot of a pickup relative to the disk in the circumferential direction. A spindle servo device to control the speed is essential.

This spindle servo device has a speed servo system that drives and controls the spindle motor based on the speed difference between the detected rotational speed of the disc and a reference rotational speed during startup, and a speed servo system that controls the drive of the spindle motor based on the speed difference between the detected rotational speed of the disc and the reference rotational speed. It has a phase servo system that drives and controls the spindle motor based on the servo system, and is configured to automatically switch between the two servo systems depending on whether a reproduction synchronization signal is detected.

Incidentally, in recent years, with the digitalization of servo circuits, the use of ICs and common use of circuits is progressing.

When using an IC-based servo circuit, it is common practice to add external elements such as resistors and capacitors to absorb variations in the circuit system and adjust the gain of each servo system. However, when considering the case where an IC-based servo circuit is shared by both the speed servo system and the phase servo system, it is difficult to adjust the relative gains of both servo systems. In other words, if you use one servo system as a reference and adjust the gain using external elements,
Due to this adjustment, the gain of the other servo system will also be adjusted in the same way.

Summary of the Invention [Object of the Invention] Therefore, the present invention provides a spindle servo device that enables relative gain adjustment of both the speed servo system and the phase servo system even when the servo circuits are shared. The purpose is to provide.

[Structure of the Invention] A spindle servo device according to the present invention includes a motor for rotationally driving a disk, a speed difference detection means for detecting a speed difference between a detected rotational speed of the disk and a reference speed, and a reference signal for a reproduction synchronization signal from the disk. and a PWM circuit that generates a pulse signal with a pulse width according to the speed difference or the speed difference and the phase difference and uses it as a drive signal for the motor. The configuration includes a capacitive impedance element and a connection control means for selectively connecting the capacitive impedance element to the output line of the PWNi circuit.

[Operation of the Invention] In the spindle servo device according to the present invention, a capacitive impedance element is selectively connected to the output line of a PWM circuit, which is a motor drive circuit, depending on the operation mode of each servo system.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an example of the configuration of, for example, a CD player equipped with a spindle servo device according to the present invention. In the figure, a disk 1 is rotationally driven by a spindle motor 2, and the recorded information is transferred to an optical pickup 3.
read by. The output signal of pickup 3 is E
F M (Eight to Fourteen Mo
This read EFM signal is a RF amplifier 4, and is then supplied to an EFM demodulation circuit 6 via a frame synchronization detection circuit 5, and is also supplied to a clock extraction PLL circuit 7. Clock extraction PLL circuit 7
In this case, a bit-synchronized clock is generated by phase-locking to the clock included in the read EFM signal. E
The demodulated output of the FM demodulation circuit 6 is subjected to error correction by an error correction circuit 8, and then converted to an analog signal by a D/A converter 9 and output as a reproduced audio signal.

Next, a spindle servo device according to the present invention will be explained.

The speed servo system is for controlling the rotation of the spindle motor 2 to a range that allows the frame synchronization detection circuit 5 to reproduce the frame synchronization signal from the read EFM signal. In this speed servo system, the speed difference detection circuit 1o is configured to detect the speed difference between the detected rotational speed of the disk 1 and the reference speed using the characteristics of the CD format signal. That is, in the CD format signal, the unit channel bit length is T (T = 1/4.3218
MJ (z>, data group consists of 3T to LIT, 5
One frame is made up of 88T. For example, if we focus on IIT, which is the maximum reversal interval,
The interval should be the same no matter where on the disk 1 it is located. Therefore, the speed difference detection circuit 10 generates an f/V conversion signal corresponding to a detection signal obtained by comparing a period n times the maximum inversion interval (for example, n-2) with a reference period, By comparing this signal with a reference value, a speed difference signal of the detected rotational speed of the disk 1 with respect to the reference speed is obtained (for example, JP-A-59-7
(See Publication No. 1164). This speed difference signal is the switch SW
The signal is supplied to the PWM circuit 11 via I.

On the other hand, in the phase servo system, the reference clock oscillator 1
A phase difference detection circuit 13 is provided to detect the phase difference between the frame synchronization signal from the frame synchronization detection circuit 5 and the crystal-accurate reference clock output from the crystal precision reference clock outputted from the PWM circuit 11 through the switch SW2. supplied to The supply of the speed difference signal and the phase difference signal to the PWM circuit 11, that is, switching control of the switches SWI and SW2 is performed by the sabot controller 14.

The servo controller 14 is constituted by a microcomputer, and under the control of the processor, the spindle motor 2 is accelerated when the system is started up, and when it reaches a predetermined rotational speed, it is maintained at a constant speed, and then a focus servo loop (not shown) is started. and a tracking servo loop (not shown). After the tracking servo loop is closed, first, a control signal S1 for turning on (opening) the switch SWI is output. Thereby, the PWM circuit 11 controls the rotation of the spindle motor 2 to the extent that the frame synchronization signal can be reproduced using a pulse signal having a pulse width corresponding to the speed difference signal obtained by the speed difference detection circuit 10. When a frame synchronization signal is detected in the frame synchronization detection circuit 5, the servo controller 14 outputs a control signal S2 to turn on (open) the switch SW2 in response to this frame synchronization signal.

As a result, the PWM circuit 11 detects the relative movement speed of the information reading spot of the pickup 3 in the circumferential direction with respect to the disk 1 using a pulse signal having a pulse width corresponding to the phase difference signal obtained by the phase difference detection circuit 13 in addition to the speed difference signal. The rotation of the spindle motor 2 is controlled so that the speed is constant linear velocity (CLV).

One end of a capacitor C, for example, as a capacitive impedance element is connected to the output line of the PWM circuit 11, and the other end of the capacitor C is connected to the collector of a transistor Q whose emitter is grounded. transistor Q
The output of the AND gate 15 is applied to the base of the . A
The ND gate 15 uses two people to control the control signals Sl and S2 output from the servo controller 14. That is,
When only the speed servo system is acting, the transistor Q is in an off state and the capacitor C is not connected to the output line of the PWM circuit 11, but when the phase servo system is acting in addition to the speed servo system, , the transistor Q is turned on, and the capacitor C is connected to the output line of the PWM circuit 11. As a result, when the phase servo system is operating, there is a voltage even in the high impedance section as shown in Figure 2 due to the connection of capacitor C, so it is possible to increase the gain of the phase servo system, although it appears to be higher. It will be possible.

Further, since the gain can be freely set depending on the capacitance of the connected capacitor C, it is possible to set the optimum gain.

In the above embodiment, the case where the gain of the phase servo system was adjusted by connecting the capacitor C was explained, but as shown in FIG.
When only the speed servo system is operating, by connecting the capacitor C, the speed servo system can be It is also possible to configure it so that the gain of .

As described in detail, in the spindle servo device according to the present invention, capacitive impedance elements are selectively connected to the output line of the PWM circuit, which is a motor drive circuit, according to the operation mode of each servo system. With this configuration, even if the servo circuit is shared by the speed servo system and the phase servo system, relative gain adjustment of both servo systems is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of, for example, a CD player equipped with a spindle servo device according to the present invention, and FIG.
The figure is a waveform diagram of an output pulse of a PWM circuit showing how the waveform changes depending on the connection of a capacitor, and FIG. 3 is a block diagram showing only the main part of another embodiment of the present invention. Explanation of symbols of main parts 2... Spindle motor 3... Optical pickup 5... Frame synchronization detection circuit 6... EFM demodulation circuit 7... ...Clock extraction PLL circuit 10...
・Speed difference detection circuit 11...PWM circuit 13・
...Phase difference detection circuit 14 ... Servo controller applicant Pioneer Corporation

Claims (2)

[Claims] (1) A motor for rotationally driving an information recording disk, a speed difference detection means for detecting a speed difference between the detected rotational speed of the information recording disk and a reference speed, and a position of a reproduction synchronization signal from the information recording disk with respect to the reference signal. A spindle servo device comprising: a phase difference detection means for detecting a phase difference; and a PWM circuit that generates a pulse signal having a pulse width according to the speed difference or the speed difference and the phase difference and uses it as a drive signal for the motor. A spindle servo device comprising: a capacitive impedance element; and connection control means for selectively connecting the capacitive impedance element to an output line of the PWM circuit. (2) The spindle servo device according to claim 1, wherein the connection control means controls the connection of the capacitive impedance element upon detection of the reproduction synchronization signal.