JPH0536611U - Optical disk player tracking servo circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the convergence of tracking servo immediately after a track jump in pause, still, manual search, multi-speed, etc. [Structure] A jump signal is input to a monostable multivibrator 5. The tracking error signal input side of the resistor R1 is connected to the ground by the series circuit of the resistor R8 and the digital transistor Q1, and the constant current input side of the resistor R5 is connected to the ground by the series circuit of the resistor R9 and the digital transistor Q2. The output terminals of the monostable multivibrator 5 are digital transistors Q1 and Q2.
Is connected to the base circuit of. The monostable multivibrator 5 has the digital transistor Q1 for a period longer than the period of the tracking coil pulse current at the time of the tracking jump and the period when the analog switch S1 is closed.
And make Q2 conductive.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tracking servo circuit of an optical disk player, and more particularly to a tracking servo circuit that makes good settling immediately after a track jump in pose, still, manual search, multi-speed, etc.

[0002]

[Prior Art]

 In operations such as pause, still, manual search, and multi-speed operations in an optical disk player that reproduces a laser disk, track jumps that jump the laser spot to adjacent tracks are continuously performed.

An example of such a conventional tracking servo circuit is shown in FIG. As shown in the figure, the tracking error signal obtained from the optical pickup is input to the inverting input terminal of the operational amplifier 1 via the resistor R1 and also to the tracking logic circuit 4. The non-inverting input terminal of the operational amplifier 1 is connected to the ground, and the output terminal is connected to the inverting input terminal via the impedance Z2.

The output terminal of the operational amplifier 1 is also connected to the inverting input terminal of the operational amplifier 2 via the series circuit of the resistors R3 and R4. Further, the connection point of the resistors R3 and R4 is connected to the ground by the series circuit of the capacitor C1 and the analog switch S1. The constant current sources I1 and I2 are connected to one end of a resistor R5 via analog switches S2 and S3, respectively, and the other end of the resistor R5 is connected to an inverting input terminal of the operational amplifier 2.

The non-inverting input terminal of the operational amplifier 2 is connected to the ground, and the output terminal of the operational amplifier 2 is connected to the ground via the series circuit of the tracking coil 3 and the resistor R6. The connection point B between the tracking coil 3 and the resistor R6 is connected to the inverting input terminal of the operational amplifier 2 via the parallel circuit of the resistor R7 and the capacitor C2.

The tracking logic circuit 4 receives a jump signal in addition to the tracking error signal and turns on / off the analog switches S2 and S3.

In the above configuration, in the reproducing state of the laser disk, the tracking logic circuit 4 opens the analog switches S2 and S3, and the analog switch S1 is also opened, so that the tracking servo is on.

The tracking error signal is inversely amplified by the impedance ratio of the resistor R1 and the impedance Z2, and further inverted and amplified by the resistance ratio of the resistor R3 and the resistor R4 in the series circuit, and appears at the connection point B. An electric current is supplied to the tracking coil 3. The capacitor C2 is provided for phase compensation. The tracking coil 3 is arranged in the magnetic field, and the objective lens integrated with it is moved so that the laser spot follows the signal pit train.

A slider servo circuit (not shown) drives the slider motor so that the DC component of the voltage at the connection point B, which is proportional to the tracking coil current, decreases, and the slider motor causes the laser spot of the optical pickup to output a signal. The slider on which the optical pickup is mounted is sent toward the outer circumference of the disk so that it can follow the pit train.

In a mode in which track jumps such as pause and still are repeated, the analog servo switch S1 is closed during the jump period to reduce the tracking servo gain, and as shown in FIG. Is output. When a jump signal is input, the tracking logic circuit 4 closes the analog switches S2 and S3 before and after, and supplies a reverse current to the tracking coil 3 before and after. As for the voltage at the point B proportional to the tracking coil current shown in FIG. 3B, a forward / reverse voltage pulse appears during the period T.

With such a pulse-shaped tracking coil current, the tracking servo with a reduced gain causes the laser spot to jump to an adjacent track. After the jump is completed, the analog switch S1 is opened, the tracking servo is applied, and the signal is reproduced. FIG. 3C shows that the tracking error signal at the point C fluctuates greatly during the jump period.

[0012]

[Problems to be solved by the device]

 The conventional tracking servo circuit described above has a problem in that the analog switch S1 is opened after the jump is completed and the tracking servo is rapidly returned to the original high gain, so that the convergence is not smoothly performed and the settling time becomes long.

The constant current sources I1 and I2 are also used as a brake current source at the time of track search. During track search, the tracking servo is repeatedly turned on and off while the optical pickup is being sent at a predetermined speed by the slider motor.

In the tracking-off period, the objective lens oscillates in a sine wave centered on the neutral position of elastic support, and the brake current having the constant current source I1 or I2 as a signal source converges the oscillation of the objective lens. It is passed through the tracking coil 3. The end of the tracking servo off period is detected due to the decrease in the frequency of the tracking error signal, and the tracking servo is turned on.

As described above, since the constant current sources I1 and I2 are used as the brake current sources at the time of track search, the constant current sources I1 and I2 of the constant current sources I1 and I2 are set to have the optimum tracking coil current during the jump. The strength could not be set, and the laser spot could not be smoothly jumped to the adjacent track.

The present invention has been made in view of the above points, and the purpose thereof is to achieve smooth convergence by appropriately changing the tracking servo gain after the end of the jump. It is to provide a tracking servo circuit for an optical disc player.

Another object of the present invention is to provide a tracking servo circuit of an optical disk player capable of setting the tracking coil current at the time of jump to an optimum value independently of the brake current at the time of track search. Is.

[0018]

[Means for Solving the Problems]

 The tracking servo circuit of the optical disk player of the present invention is an optical disk that causes pulse currents in opposite directions to flow back and forth to the tracking coil each time a jump signal is received at the time of a track jump and lowers the servo gain during the period of the pulse current. In the tracking servo circuit of the player, a monostable multivibrator that outputs a pulse output for a certain period after receiving a pulse-shaped jump signal is provided, and a semiconductor switch that attenuates the tracking error signal by the pulse output and the tracking coil are sent. The semiconductor switch is configured to conduct with a semiconductor switch that divides the input current serving as a signal source of the pulse current.

[0019]

[Action]

 According to the tracking servo circuit of the present invention, pulse currents in opposite directions are sent back and forth to the tracking coil at the time of track jump, and the servo gain is lowered during that time so that the laser spot jumps to the adjacent track. Although the servo gain increases after the pulse current is stopped, the tracking error signal input to the tracking servo circuit is attenuated by the semiconductor switch that is made conductive by the pulse output of the monostable multivibrator, and the entire servo The gain is kept lower than when the normal tracking servo is on.

After the lapse of a predetermined period after the pulse current of the tracking coil is stopped, the pulse output of the monostable multivibrator is stopped and the semiconductor switch for attenuating the tracking error signal is opened, and the servo gain of the entire tracking servo circuit is normally set. The tracking servo is turned back on. In this way, after the track jump, the gain of the tracking servo is increased in two steps, so that the laser spot smoothly converges on the signal pit train.

Further, since the pulse output of the monostable multivibrator causes the semiconductor switch for shunting the input current, which is the signal source of the pulse current to be passed through the tracking coil, to be conductive, by appropriately setting the resistance value of the shunt circuit, The tracking coil current during a track jump can be set independently of the brake current during a track search, and can be set to the optimum value for jumping to an adjacent track. In this way, the laser spot can be smoothly jumped to the adjacent track.

[0022]

【Example】

 A tracking servo circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment, and parts having the same functions as those shown in the conventional example are designated by the same reference numerals.

In the circuit of the embodiment, the jump signal is input to the monostable multivibrator 5 in addition to the tracking logic circuit 4. The input side of the tracking error signal of the resistor R1 is connected to the ground by the series circuit of the resistor R8 and the digital transistor Q1, and the constant current input side of the resistor R5 is connected to the ground by the series circuit of the resistor R9 and the digital transistor Q2.

The output terminal of the monostable multivibrator 5 is connected to the base circuits of the digital transistors Q 1 and Q 2. The structure and operation of the other parts are similar to those of the conventional circuit shown in FIG.

In the above configuration, in a mode in which track jumps such as pause and still are repeated, a jump signal is output from a microcomputer (not shown) as shown in FIG. 3A. When the jump signal is input, the tracking logic circuit 4 closes the analog switches S2 and S3 back and forth during the period T shown in FIG. 3 (b), and supplies the tracking coil 3 with a backward current before and after. Meanwhile, the analog switch S1 is closed and the tracking servo gain is lowered, and the laser spot jumps to the adjacent track.

When the jump signal is input, the monostable multivibrator 5 outputs a high level for a predetermined period longer than the 2T period shown in FIG. 3B to make the digital transistors Q1 and Q2 conductive. Immediately after the pulse current of the tracking coil stops, the analog switch S1 is opened and the servo gain increases, but since the digital transistor Q1 is conducting, the tracking error signal is attenuated and the tracking servo to the target track is lightly applied. .

Further, after a certain period of time, the digital transistor Q1 is cut off, the tracking servo gain is returned to the normal high state, and the target track is surely tracked.

Further, the currents of the constant current sources I1 and I2 which are the pulse current sources of the tracking coil are shunted by the resistor R9 and the digital transistor Q2. During the track search, the digital transistor Q2 is in the cutoff state, and the brake current is set to the optimum value by setting the resistance values of the resistors R5 and R7. By setting the resistance value of the resistor R9, the tracking coil pulse current at the time of the track jump is set to the optimum value.

[0029]

[Effect of the device]

 According to the tracking servo circuit of the present invention, the tracking coil pulse current at the time of track jump is set to the optimum value independently of the brake current at the time of track search. Further, after the jump is completed, the gain of the tracking servo is gradually increased to improve the convergence of the servo, and the settling time is shortened.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a tracking servo circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a conventional tracking servo circuit.

FIG. 3 is a waveform chart of a signal showing an operation of the tracking servo circuit.

[Explanation of symbols]

 1 Operational Amplifier 2 Operational Amplifier 3 Tracking Coil 4 Tracking Logic Circuit 5 Monostable Multivibrator Q1 Digital Transistor Q2 Digital Transistor

Claims (1)

[Scope of utility model registration request] 1. A tracking servo circuit of an optical disk player, wherein pulse currents in opposite directions are sent back and forth to a tracking coil each time a jump signal is received during a track jump, and a servo gain of the pulse current is reduced in a tracking servo circuit. A monostable multivibrator that outputs a pulse output for a certain period after receiving the jump signal of, a semiconductor switch that attenuates a tracking error signal by the pulse output, and an input current that becomes a signal source of the pulse current that flows in a tracking coil A tracking servo circuit of an optical disk player configured to be electrically connected to a semiconductor switch that divides the current.