JPS628338A - Tracking servo circuit - Google Patents

Abstract

PURPOSE:To cope titled circuit with also a spring support type actuator by providing a high frequency equalizer circuit and a low frequency equalizer circuit and applying drive control to the actuator based on an overlapped output of each output. CONSTITUTION:A tracking error signal via a pre-stage part of the high frequency equalizer circuit 2 is fed to the low frequency equalizer circuit 3. The tracking error signal subject to low frequency correction by the low frequency equalizer circuit 3 is fed to a post-stage of the high frequency equalizer circuit 2 and overlapped on the tracking error signal subject to high frequency correction. The tracking error signal outputted from the high frequency equalizer circuit 2 is fed to a drive circuit 4, from which a drive signal for the tracking actuator 5 is obtained. The tracking actuator 5 is the spring support actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking servo circuit in a disc player.

There are generally two types of pickup actuators used in disc players that play discs such as digital audio discs (so-called compact discs): spring-supported type and active type.

In this spring-supported actuator, if there is an eccentricity in the disk, only that eccentric valve is constantly biased, and based on the biased position, the spot light is emitted in the direction and amount of deviation according to the polarity and signal level of the tracking error signal. An action is taken to bias the

On the other hand, in the tracking servo, in order to reliably pull in the tracking servo when the servo shifts from the oven state to the closed state, conventionally, an analog switch is inserted in series in the signal line of the servo circuit, and the tracking servo system In the unstable region, that is, in the region where the servo works in the direction of increasing the relative speed between the track and the spot light, the analog switch is in the open state ().
, the analog switch is closed only in a stable region where the servo system operates in a direction in which the relative speed decreases. In other words, by closing the analog switch, a half-wave waveform is generated on the signal line, and this half-waveform signal is applied to the actuator as a braking force, thereby increasing the relative speed at which the spot light crosses the recording track. This makes it possible to reliably pull in the tracking servo.

In this way, conventional tracking servo circuits are configured to generate half-wave waveforms using analog switches that open/close signal lines. This has the disadvantage that it is difficult to integrate it into an IC compared to using a switch that grounds the line. However, if a switch of the type that simply grounds the signal line is used, in the case of the spring-supported actuator mentioned above, the bias voltage that should be applied to the actuator depending on the amount of eccentricity will be zero when the signal line is grounded by the switch. Therefore, the servo operation based on the bias position corresponding to the amount of eccentricity will not be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a tracking servo circuit that can be applied to a spring-supported actuator and that can be easily integrated into an IC.

A tracking servo circuit according to the present invention includes a first equalizer circuit that has a switch means for selectively grounding a signal line and that corrects the frequency characteristics of high-frequency components of a tracking error signal; A control means for controlling the switching means to turn on, and a second equalizer circuit for correcting the frequency characteristics of the low frequency component of the tracking error signal, and superimposing each output of the first and second equalizer circuits. The configuration is such that the spring-supported actuator is driven and controlled based on the output.

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

In FIG. 1, a tracking error generation circuit 1 performs tracking of the polarity and signal level according to the direction and amount of deviation of the relative position of the spot light (recorded information detection point) and the recording track of the disk in the disk radial direction. An error signal is generated. Methods for generating this tracking error signal include three-beam method, push-pull method,
There are methods such as heterodyne method. The tracking error signal is supplied to the high frequency equalizer circuit 2 via the resistor R1. This high frequency equalizer circuit 2 includes operational amplifiers OP+, OR
3. Comprised of capacitors C+ and C2 and resistors R2 to R8, and corrects the frequency characteristics of the high frequency components of the tracking error signal. This high frequency equalizer circuit 2 is provided with a switch SW 1 for selectively grounding the signal line.

The tracking error signal that has passed through the front stage of the high-frequency equalizer circuit 2 is supplied to the low-frequency equalizer circuit 3. The low frequency equalizer circuit 3 includes operational amplifiers OP3 and OR3, capacitors C3 and C4, and resistors R9 to Rn, and corrects the frequency characteristics of the low frequency components of the tracking error signal. The tracking error signal subjected to low frequency correction by the low frequency equalizer circuit 3 is supplied to a subsequent stage of the high frequency equalizer circuit 2, and is superimposed on the tracking error signal subjected to high frequency correction. The tracking error signal output from the high frequency equalizer circuit 2 is supplied to the drive circuit 4 and becomes a drive signal for the tracking actuator 5. The tracking actuator 5 is a spring supported actuator.

A switch SW 2 for controlling opening and closing of the servo loop is connected between the input line of the high frequency equalizer circuit 2 and the ground.

The tracking error signal output from the tracking error generation circuit 1 is also supplied to the zero cross detection circuit 6. The zero-crossing detection circuit 6 generates an output when the tracking error signal crosses the zero level, and supplies the output to the opening/closing control circuit 7 at the next stage. The opening/closing control circuit 7 also receives as input a high-level on-track signal indicating that the spot light is on the recording track, and controls the opening/closing of the switch SW1 connected to the high frequency equalizer circuit 2 based on these two inputs. .

FIG. 2 shows the waveforms of each part of FIG. 1 during a track jump, and (a) to (e) show the signals of each part of FIG.
The waveforms a) to (e) are shown correspondingly.

To explain the circuit operation of FIG. 1 with reference to the waveform diagram of FIG.
b) generates a high-level pulse (C) with a small pulse width when the on-track signal (a) crosses the zero level, and the opening/closing control circuit 7 generates a zero-crossing detection output (C ) is generated until the on-track signal (a) is not input and the zero-cross detection output (C) is generated. When the output (d) of the opening/closing control circuit 7 is at a high level, the switch S W + is turned off (opened), and when it is at a low level, it is turned on (closed). By opening and closing the swing S W +, a half wave waveform as shown in FIG.

As a result, when searching for a target track, for example, the tracking servo can be reliably pulled in just as the tracking servo shifts from the oven state to the closed state. In addition, a half-wave waveform is generated by the switch SW + that grounds the signal line, but the low-frequency components of the tracking error signal caused by disk eccentricity, etc. are passed through the low-frequency equalizer circuit 3 provided as a separate circuit. Since it is superimposed on the output of the rear high frequency equalizer circuit 2, even if the high frequency side signal line is grounded, the eccentric component is always supplied to the actuator 5, and the actuator 5 is of the spring supported type. There is no problem even if it is an actuator.

1 shell omz As explained above, according to the tracking servo circuit according to the present invention, a high-frequency equalizer circuit and a low-frequency equalizer circuit are provided, and the half-wave waveform for applying braking force to the actuator is applied to the high-frequency equalizer. It is generated by a type of switch that grounds the signal line in the circuit, and the eccentric component is configured so that it passes through a low-frequency equalizer circuit and is superimposed on the output of the high-frequency equalizer circuit, making it compatible with spring-supported actuators. This means that it can be easily integrated into an IC.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a waveform diagram of signals of various parts in the figure. Explanation of symbols of main parts 1... Tracking error generation circuit 2...
・・High frequency equalizer circuit 3 ・・・Low frequency equalizer circuit 5 ・・・Actuator tool l Concave tail 2 (Fig. Ce)

Claims (1)

[Claims] A tracking servo circuit for driving and controlling a spring-supported tracking actuator for biasing a recording information detection point in the disk radial direction in accordance with a tracking error signal, the circuit having a switch means for selectively grounding a signal line, and having a switch means for selectively grounding a signal line; a first equalizer circuit that corrects a frequency characteristic of a high frequency component of the tracking error signal; a control means that controls the switch means to turn on at a zero-crossing timing of the tracking error signal;
a second equalizer circuit that corrects a frequency characteristic of a low frequency component of the tracking error signal, and drive control of the actuator based on a superimposed output of each output of the first and second equalizer circuits. Features a tracking servo circuit.