JPS621175A - Servo-circuit - Google Patents

Abstract

PURPOSE:To reduce the heating of a pickup and to improve the control capacity by detecting the relative mechanical vibration of the pickup to a recording medium and making the gain of a servo-loop high when a level is high and making the gain of the servo-loop low when the level is low, in accordance with the level of its detected mechanical vibration. CONSTITUTION:A vibration detecting circuit 22 is a circuit for outputting a control signal TG for switching the gain to a gain switching circuit 20, detects the level of a relative mechanical vibration between a disk and a pickup from the magnitude of a tracking error signal, sets the gain switching circuit 20 to a high level when its vibration level is higher than a prescribed threshold level, and sets said circuit to a low level when said level is lower than the threshold value. In this way, when the vibration level is high, the good controllability is obtained by a high servo-capacity and when the vibration level is low, the power consumption decreases, the heating of a tracking actuator 18 is reduced, the life of a laser oscillator is extended, and the burden of a power source circuit is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a focus system for controlling the relative position between a recording medium and a pickup in an information recording/reproducing device such as a compact disc player, a video disc player, or a tape recorder. For servo circuits such as servos and tracking servos, power consumption is reduced without reducing servo performance by changing the gain of the servo loop in response to disturbances such as external vibrations, disk eccentricity, and warping. .

(Prior art) For example, in a car-mounted compact disc player,
In order to satisfy the vibration resistance performance, it is required to float the mechanism unit from the vibration source and improve the servo ability to read signals from the disk. In order to improve servo performance, it is necessary to considerably increase the servo gain of the focus actuator and tracking actuator of the pickup within a range that ensures stability.

However, when the servo gain is increased, the current flowing through the actuator increases, and the pickup generates considerable heat, which changes the optical output of the laser oscillator inside the pickup, affecting the servo gain characteristics, and even causing the laser This will shorten the life of the oscillator.

Also, if the current flowing is large, the load on the power supply circuit will also be large. Power increases.

Such inconveniences apply not only to compact discs but also to other information recording and reproducing apparatuses that control the position of a pickup with respect to a recording medium, such as a tape recorder, using a servo loop.

(Problems to be Solved by the Invention) The present invention aims to solve the problems in the conventional technology and provide a servo circuit that reduces 8!1 power consumption without reducing servo performance. It is something to do.

[Means for solving problems]

This invention detects the relative mechanical vibration of the pickup with respect to the recording medium (due to external imaging, disk eccentricity, warping, etc.), and determines whether the level is high or low depending on the level of the detected mechanical vibration. When the level is low, the gain of the servo loop is set high, and when the level is low, the gain of the servo loop is set low.

[Operation] According to the solving means of the present invention, the gain is increased when the vibration level is large, so that high servo performance can be obtained. Also, since the gain is lowered when the vibration level is low, power consumption can be reduced, and in this case,
Since the vibration level is low, there is no problem in control even if the gain is lowered.

〔Example〕

An embodiment of the invention is not shown in FIG. In this example,
A case is shown in which mechanical vibration is detected using tracking error detection signal 0 and the gain of the tracking servo loop is changed depending on the level of the detected mechanical vibration.

In FIG. 1, a PIN diode 10 is built into the pickup device and outputs a signal (tracking error detection signal) corresponding to a tracking error. This tracking error detection signal corresponds to relative mechanical vibration of the pickup with respect to the disk. The output of the PIN diode 10 is supplied to a tracking actuator 18 via a preamplifier 12, a phase compensation amplifier 14, a gain switching circuit 20, and a dry-up 16 to correct tracking errors.

The gain switching circuit 20 is composed of resistors R1 and R2 and a transistor Q1, and when the transistor Q1 is off, the servo gain becomes a high gain, and when the transistor Q1 is on, the voltage is divided by the resistors R1 and R2 and becomes a low gain.

The imaging detection circuit 22 is a circuit that outputs a control signal TG for gain switching to the gain switching circuit 20, and detects the level of relative mechanical vibration between the disk and the pickup from the magnitude of the tracking error signal. However, if the vibration level is higher than a predetermined threshold, the gain switching signal TO=
'O' is output to set the gain switching circuit 20 at a high level, and if it is low, a gain switching signal TG="1" is output and the gain switching circuit 22 is set at a low level.

Therefore, when the vibration level is high, good controllability is achieved by high servo capability, and when the swing J level is low, power consumption is reduced and the tracking actuator 1
8, the life of the laser generator is shortened, and the load on the power supply circuit is also reduced.

High gain interrupt signal TR input to vibration detection circuit 22
GL performs a track jump for searching when selecting a song or when the servo is completely off, but after this, the loop gain is forcibly switched to high gain.

[Example of configuration of vibration detection circuit 22] An example of the configuration of the vibration detection circuit 22 shown in FIG. 1 is shown in FIG.

In FIG. 2, the tracking error detection signal TE is
It is input to the weighting circuit 30.

The weighting circuit 30 is a filter circuit that passes only frequency bands such as external vibrations and disc eccentricity applied to the set body of an in-vehicle compact disc player, etc.
It limits the band so that it does not work on other frequency components.

The bias circuit 32 has threshold values V on the + side and - side of gain switching.
+, V- output. Setting these thresholds V+ and V- is important, and in terms of vibration resistance, it is necessary to always obtain performance equivalent to that at high gain.
If it is small, there will be too many high gain modes, and the intended purpose cannot be achieved. After all, the threshold values V+ and V- can satisfy the vibration resistance performance. Try to make the range as large as possible.

Further, the values of the thresholds V+ and V- are determined by taking into account the gain value in the low gain mode. In other words, if the low gain value is low, only small vibrations can be tracked, so the threshold value V+,
It is necessary to reduce V-, but if the low gain value is high, it can follow slightly larger vibrations, so the threshold value V+
, V- can be made a little higher.

The comparators 34 and 36 have the same value V+ set by the bias circuit 32 as the tracking error detection signal TE output from the weighting circuit 30.

■Compare each with -. Peak hold circuit 38.4
0 is the time until the movement of the tracking actuator 18 (Fig. 1) is controlled by the servo voltage and converged when the comparators 34 and 36 detect that the tracking error detection signal TE exceeds the threshold V+, V-. In time, the outputs of the comparators 34 and 36 are held for a certain period of time, and the high gain state is maintained during that time.

The outputs of the peak hold circuits 38 and 40 are sent to the adder circuit 42.
The logical sum is taken at , and input to the high gain interrupt circuit 46 via the inverter 44 .

The high gain interrupt circuit 46 performs a track jump for searching during normal song selection or when the servo is completely disconnected due to excessive external vibration, but after that, the high gain interrupt signal TRGL forces the high gain This is to switch to .

The output signal of the high gain interrupt circuit 46 is transmitted to the inverter 48.
The drive circuit 50 is driven via the drive circuit 50.
The output signal TG turns on and off the transistor Q1 of the gain switching circuit 20 shown in FIG. 1 to switch the servo loop gain.

The operation of the circuit of FIG. 2 is shown in FIG. In Figure 3 ■
~■ are signal waveform diagrams of the respective parts shown as ■~■ in FIG.

Tracking error detection signal TE is sent to bias setting circuit 3
2, the output of the comparators 34 and 36 is 1", the output of the drive circuit 50 is "1", and the gain switching circuit 20 (first
Transistor Q1 in the figure is turned on and the tracking servo loop is switched to low gain.

Tracking error detection signal TES threshold V+ or V-
If it is larger than that, the output of the corresponding side of the cossiparators 34° and 36 becomes “0′°, and this is held for a certain period of time by the peak hold circuit 38 or 40, during which time the output of the drive circuit 50 becomes “0” and the gain is switched. circuit 20
transistor Q1 is turned off and the tracking servo loop is switched to high gain.

[Specific example of the circuit shown in Figure 2] A specific example of the vibration detection circuit 22 shown in FIG. 2 is shown in FIG.

In FIG. 4, the weighting circuit 30 includes a resistor R3,
Configure a filter circuit with R4 and capacitors C3 and C4,
Only the frequency bands of external vibrations, disk eccentricity, warping, etc. are allowed to pass.

The bias circuit 32 includes resistors R5 and R6 and a variable resistor V R
, 1 to set the threshold values V+ and V-.

The peak hold circuit 38 is composed of a resistor R7 and a capacitor C7, and when the + side of the tracking error detection signal TE exceeds the threshold ■+ and the output of the comparator 34 becomes "0", the capacitor C7 is discharged, and then the capacitor C7 is Charge with a time constant of Therefore, the peak hold circuit 38
, the + side of the tracking error detection signal TE is the threshold value V+
When the value exceeds 0°, outputs “0°°” for a certain period of time.

The peak hold circuit 40 is similarly configured.

The adder circuit 42 is constituted by a NAND circuit, and outputs "1" when the tracking error signal TE exceeds the threshold value (+) or V- and the output of the peak hold circuit 38 or 40 becomes 110 It.

The output of the adder circuit 42 is input to the inverting drive circuit 50 via an inverter 44, a high gain interrupt circuit 46, and an inverter 48, each of which is formed of a NAND circuit.

The drive circuit 50 connects the output of the inverter 48 to a resistor R9.
It is input to transistor Q2 via.

The emitter of the transistor Q2 is grounded, and the collector is connected to the base of the transistor Q3 via a resistor R10. The emitter of the transistor Q3 is connected to the power supply voltage Vcc, and the resistor R11 is connected between the base and the emitter.
A control signal TG is taken out from the collector.

Therefore, when the tracking error signal TE does not exceed the threshold value ■+ or V-, the drive circuit 50G,
tTG=+Vcc (= "1"), the transistor Q1 of the gain switching circuit 20 in FIG. 1 is turned on, and the tracking servo loop gain becomes low gain.

Also, if the tracking error signal TE is the threshold ■+ or ■
-, the drive circuit 50 TE≠+Vcc (=
"O"), and the transistor Q of the gain switching circuit 20
1 is turned off and the tracking servo loop gain becomes high gain.

Furthermore, when the high gain interrupt signal -rRGL (="0") is input, the output of the high gain interrupt circuit 46 is forced to 1.
and the tracking servo loop gain becomes high gain.

[Example of change]

In the embodiment described above, mechanical vibrations were detected using a tracking error detection signal, but a signal such as a focus error detection signal may also be used.

Furthermore, not only the tracking servo loop but also other servo loops such as the focus servo loop can be controlled simultaneously.

Further, the present invention can be applied not only to compact disc players and video disc players but also to all servo loops that cause a pickup to follow a recording medium such as a tape recorder.

〔Effect of the invention〕

As explained above, according to the present invention, the servo loop gain is changed depending on the magnitude of mechanical vibration, so that the following effects can be obtained.

■ During normal times with little vibration, the servo loop gain is lowered, reducing power consumption. Therefore, the heat generated by the pickup is reduced, the life of the laser oscillator built in the pickup is extended, and heat dissipation from the drive IC becomes easier. Further, the power supply circuit can be downsized. Furthermore, when the pickup temperature increases, the servo loop gain tends to decrease and the dust resistance characteristics tend to deteriorate, but this invention does not have such a risk because it generates little heat.

■ A sharpener with large vibrations increases the loop gain, so
Improves control ability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the vibration detection circuit 22 shown in FIG. 1. FIG. 3 is an operational waveform diagram of FIG. 2. FIG. 4 is a specific example of the circuit shown in FIG. 2. 20... Gain switching circuit, 22... Vibration detection circuit. (TRGL-□σ) Figure 3 Figure I

Claims (1)

[Claims] Means for detecting relative mechanical vibration of a pickup with respect to a recording medium; when the level of the detected mechanical vibration is high, the gain of a positioning servo loop of the pickup is increased; 1. A servo circuit comprising gain changing means for lowering the gain of a positioning servo loop.