JPH0752563B2 - Offset correction circuit for feed devices such as signal conversion heads - Google Patents

Description

The present invention relates to an offset correction circuit of a feeding device such as a signal conversion optical head of a CD player.

[Prior Art] In a CD (Compact Disc) player, a DC voltage corresponding to a tracking error is picked up by a pickup amplifier motor (linear motor) via a differential amplifier (drive amplifier).
It is known that a differential amplifier feeds the feed motor speed detection signal negatively to the differential amplifier to feed the pickup at a constant speed.

[Problems to be Solved by the Invention] By the way, since the gain of the drive amplifier is generally large, the offset voltage also has a considerably large value, and even if the voltage based on the tracking error is zero, the motor drive voltage is generated and the pickup is In some cases, it may start moving or move easily, which makes accurate servo difficult.

Further, when the CD player is tilted and tilts (mechanical offset) in the pickup feed direction, the load of the drive amplifier increases to correct this, which adversely affects the servo. Further, if the inclination is large, the pickup may start moving in a stopped state.

Therefore, a first object is to provide an offset correction circuit that can correct a mechanical offset. A second object is to provide an offset correction circuit that can easily correct electrical and mechanical offsets.

[Means for Solving the Problem] The offset correction circuit of the invention for achieving the above-mentioned first object will be described with reference to the reference numerals of FIGS. 1 and 4 showing an embodiment. A motor 4 for giving a feed to the motor 4, a speed detection means for obtaining a speed detection voltage corresponding to the speed of the motor 4, and a negative feedback control of the speed of the motor 4 by the speed detection voltage. A circuit for correcting an offset in a feeding device, which comprises a differential amplifier 10 for obtaining an output corresponding to a difference between a drive input voltage of the motor 4 and the speed detection signal, the differential amplifier 10 comprising: A forward feed reference drive voltage input terminal B for applying a forward feed reference drive input voltage Vr to the differential amplifier 10 and the forward feed reference drive input voltage Vr to the differential amplifier 10 have substantially the same absolute value and polarity. Is the opposite A backward feed reference drive voltage input terminal C for giving a backward feed reference drive input voltage −Vr, a feed control signal input terminal D for giving a feed control signal to the differential amplifier 10, and each of the input terminals. A first switch SW1 for selectively connecting B, C, and D to the differential amplifier 10, and a positive drive voltage memory M2.
The reverse drive voltage memory M3 and the data corresponding to the output voltage of the differential amplifier 10 obtained when the differential amplifier 10 is connected to the forward feed reference drive voltage input terminal B. It corresponds to the output voltage of the differential amplifier 10 which is obtained when the positive drive voltage memory M2 is written as the drive voltage Va and the differential amplifier 10 is connected to the reverse feed reference drive voltage input terminal C. A memory input circuit for writing data to the reverse drive voltage memory M3 as a reverse drive voltage −Vb, and Va based on outputs Va−Vb read from the forward and reverse drive voltage memories M2 and M3. An operation circuit 13 for performing an operation of −Vb / 2 and a means for correcting the drive voltage of the motor 4 based on the output of the operation circuit 13 when the differential amplifier 10 is connected to the feed control input terminal D. Be equipped The one in which the features.

Further, the offset correction circuit of the invention for achieving the second object is provided with a motor 4 for feeding the object to be fed.
A speed detection means for obtaining a speed detection voltage corresponding to the feed speed of the motor 4, and a drive input voltage of the motor and the speed so as to negatively control the feed speed of the motor by the speed detection voltage. A circuit for correcting an offset in a feeding device including a differential amplifier 10 for obtaining an output corresponding to a difference with a detection means,
A first terminal A connected to ground and the differential amplifier
A second terminal B for applying a forward feed reference drive input voltage Vr to 10 and a reverse feed whose absolute value is substantially equal to the forward feed reference drive input voltage Vr to the differential amplifier 10. Third terminal C for providing reference drive input voltage -Vr
A fourth terminal D for applying a feed control signal to the differential amplifier 10 and the first, second, third and fourth terminals A, B, C, D to the differential amplifier 10. The first switch SW1 selectively connected to the first, second and third memories M
The data corresponding to the output voltage of 1, 2, and M3 and the differential amplifier 10 obtained when the differential amplifier 10 is connected to the first terminal A is set as an offset voltage ± V0, and the first memory is set. Write to M1, the differential amplifier 10 is the second
Differential amplifier obtained when connected to terminal B of
The output of the differential amplifier 10 obtained when the data corresponding to the output voltage of 10 is written in the second memory M2 as the forward drive voltage Va and the differential amplifier 10 is connected to the third terminal C. A memory input circuit for writing data corresponding to the voltage to the third memory M3 as a reverse drive voltage −Vb, and the first, second and third memories M1, M2,
Based on the output ± V0, Va, −Vb read from M3,
(Va−Vb / 2) ± V0 arithmetic circuit 13, and when the differential amplifier 10 is connected to the fourth terminal D, the drive voltage of the motor 4 is calculated based on the output of the arithmetic circuit 13. It is characterized by comprising a means for correcting.

[Operation] In the invention of claim 1, the forward drive voltage memory M2
And the data including the information of the inclination of the feeding device is written in the reverse driving voltage memory M3. Arithmetic circuit 13 is memory M2, M3
A signal for correcting the inclination (mechanical offset) is formed based on the output of

Data corresponding to the offset (electrical offset) of the differential amplifier 10 (including the drive amplifier) is written in the first memory M1 of the invention of claim 2. Second and third memories
Data including mechanical offset information is written in M2 and M3. By performing a predetermined calculation in the arithmetic circuit 13, a correction signal for correcting both the electrical offset and the mechanical offset can be obtained. The correction signal is applied to the differential amplifier 10 or an independent correction drive circuit connected to the motor.

[First Embodiment] Next, a CD player and its offset correction circuit according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the CD player is a recording medium disc 1
This rotation motor 2, an optical head or pickup 3, a feed motor 4 including a linear motor (linear actuator), a reproducing circuit 5, and a tracking control circuit 6
And a feed control circuit 7.

The pickup 3 is configured to project a light beam 8 on the disk 1 and read a signal by the reflected beam 9. Further, the objective lens (not shown) facing the disk 1 is horizontally moved to perform tracking control. The tracking control can also be performed by rotating a mirror arranged in the beam path or moving a laser light source.

The feed motor 4 is a linear motor (linear actuator) having the same principle as a voice coil composed of a permanent magnet and a movable coil arranged in this magnetic field, and is applied to the pickup 3 with substantially no holding torque. Are combined.
A pickup is connected to the movable coil, and a differential amplifier 10 is connected to the drive coil.

FIG. 1 shows the feed motor control circuit 7 including an offset correction circuit in detail. The first terminal A selected by the first switch SW1 is connected to the ground. Second terminal (forward feed reference drive voltage input terminal) B
Is a voltage required to obtain a forward feed at a predetermined speed by the feed motor 4 (hereinafter referred to as a forward feed reference drive input voltage Vr
Called). A third terminal (reverse feed reference drive voltage input terminal) C supplies a voltage (hereinafter, referred to as reverse feed reference drive input voltage -Vr) necessary for obtaining a feed at a predetermined speed by the feed motor 4. It is the terminal to do. The fourth terminal D is a feed control signal input terminal for applying a DC voltage corresponding to the tracking error during the reproducing operation.

The output of the switch SW1 is connected to the non-inverting input terminal of the differential amplifier 10 as a drive circuit via the resistor R1. The output terminal of the differential amplifier 10 incorporating the drive amplifier is connected to the feed motor 4.

In order to perform negative feedback control of the feed motor 4, a speed detection coil 11 for detecting the feed speed of the feed motor 4 is provided, and this is connected to the inverting input terminal of the differential amplifier 10. The speed detection coil 11 as speed detection means generates a speed detection voltage by interlinking with the magnetic flux of the feed motor 4.

An analog-digital (A / D) converter 12 is connected to the output terminal of the differential amplifier 10 in order to obtain electrical offset information and mechanical offset information. First switch S
3 obtained by inserting W1 into terminals A, B and C
The second switch SW2 is A to sort the data of the type
It is connected to the / D converter 12. The contacts a, b, and c of the second switch SW2 have first, second, and third memories, respectively.
M1, M2, M3 are connected. Therefore, the A / D converter 12 and the second switch SW2 can be called a memory input circuit.

The arithmetic circuit 13 connected to the first, second and third memories M1, M2, M3 includes a polarity inverting circuit 14, a first adding circuit 15,
It is composed of a 1/2 division circuit 16 and a second addition circuit 17, and obtains electrical and mechanical offset correction data.

The second adder circuit 17 is connected to the non-inverting input terminal of the differential amplifier 10 via a digital / analog (D / A) converter 18, a variable resistor R2, and a third switch SW3.

In this CD player, an offset correction operation is performed when the power is turned on or immediately before playing. That is, first, the first switch SW1 is connected to the first terminal A, and the second switch S1 is connected.
W2 is applied to the contact a, and the third switch SW3 is turned off. As a result, the non-inverting input terminal of the differential amplifier 10 becomes the ground level, and an electrical offset voltage V0 is obtained at the output of the differential amplifier 10, which is converted into a digital signal by the A / D converter 12 and then converted into a first digital signal. Is written in the memory M1.

Next, the first switch SW1 is connected to the second terminal B, the second switch SW2 is turned on at the contact b, and the third switch SW3
Turn off. The forward feed reference drive input voltage Vr is applied to the second terminal B, and if the electrical offset and the mechanical offset are zero, the forward reference drive voltage Vd is applied to the output terminal of the differential amplifier 10. Is given. However, if the offset voltage of the differential amplifier 10 is + V0 and the voltage corresponding to the fact that the pickup 3 is easily moved in the positive direction based on the inclination of the CD player is + Vc, the forward feed reference drive is performed. The input voltage Vr has an unnecessarily large value, and the feed motor 4 is in a feed state at a predetermined speed or higher. The speed detection coil 11 detects this state and negatively feeds back to the differential amplifier 10. As a result, the differential amplifier
10 generates an output voltage (forward drive voltage) Va obtained by subtracting the mechanical offset voltage Vc. The relationship between the forward drive voltage Va, the forward drive voltage Vd, and the mechanical offset voltage Vc is as shown in FIG. 3, and can be represented by Va = Vd−Vc.

The data of the positive drive voltage Va is written in the second memory M2.

Next, the first switch SW1 is connected to the third terminal C to input the negative direction feed reference drive input voltage -Vr, the second switch SW2 is turned on to the contact c, and the third switch SW3 is connected. Keep off. In the case of reverse feed, the mechanical offset voltage becomes negative with respect to reverse feed. Therefore, only the output corresponding to the reverse feed reference drive input voltage −Vr is used to feed motor 4.
The feed rate cannot be set to the predetermined rate, and the feed rate decreases. When the feed speed decreases, the speed detection coil
The voltage of 11 also decreases, the negative feedback value decreases, and as a result, the absolute value of the output voltage (reverse driving voltage) -Vb of the differential amplifier 10 increases, and the feeding state at the predetermined speed is stabilized. Therefore,
A voltage −Vb = − (Vd + Vc) having an absolute value higher by the mechanical offset voltage Vc than the absolute value of the reverse feed reference drive voltage −Vd in the absence of the mechanical offset voltage Vc is obtained from the differential amplifier 10. This is written in the third memory M3.

When the writing of the data to the first to third memories M1 to M3 is completed, the voltages Va and −Vb including the mechanical offset voltages Vc in the forward and reverse directions from the second and third memories M2 and M3, respectively.
Are read out and added by the first addition circuit 15. Voltage
Va is Vd−Vc and voltage −Vb is − (Vd + Vc). Therefore, when Va + (− Vb) is calculated, Va + (− Vb) = Vd−Vc−Vd−Vc = −2Vc. In the dividing circuit 16 which is 1/2 the output stage of the first adding circuit 15, -2Vc is divided by 2 to obtain -Vc, which is input to the second adding circuit 17. On the other hand, the electrical offset voltage V0 obtained from the first memory M1 is converted into a value −V0 whose polarity is inverted by the polarity inversion circuit 14 in the next stage and input to the second addition circuit 17. In the second adder circuit 17, the electrical offset voltage −V0 and the mechanical offset voltage −Vc are added, and an output of −Vc−V0 is obtained. -Vc-V0 is converted into an analog correction signal by the D / A converter 18.

During normal play, the first switch SW1 is connected to the terminal D, the second switch SW2 is turned on at the contact d, and the third switch SW2 is turned on.
The switch SW3 of is controlled to be turned on. As a result, the correction voltage −Vc−V0 is added to the DC voltage corresponding to the tracking error TE.
Are added and become the input of the differential amplifier 10.

In the description with reference to FIG. 3, since the electrical offset voltage V0 is the positive electrode and the mechanical offset voltage Vc is also the positive electrode,
The value obtained by subtracting V0 and Vc from the tracking error DC voltage is the drive input. For example, if it is assumed that the DC voltage corresponding to the tracking error is Vd in the square feed, this will not be the output of the differential amplifier 10 as it is, and the value obtained by subtracting Vc and V0 from this (Vd−Vc−V0 = V1) is the difference. The output of the dynamic amplifier 10 is controlled. On the other hand, in the case of reverse feed, assuming that the DC voltage corresponding to the tracking error is −Vd, the voltage having the absolute value of | −Vd | + | V0 | + | Vc | = | V2 | Control so that the output becomes. In FIG. 3, the mechanical offset voltage Vc is positive, but when it is negative, the outputs of the first adder circuit 15 and the 1/2 divider circuit 16 are positive. When the electrical offset voltage V0 is negative,
The input of the polarity inverting circuit 14 becomes negative and the output becomes positive.

As described above, according to this embodiment, it is possible to easily correct the electrical offset and the mechanical offset (inclination) and perform the feed control.

Second Embodiment Next, an offset correction circuit according to the second embodiment of FIG. 4 will be described. However, in FIG. 4, parts that are substantially the same as those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted. In this embodiment, the output of the D / A converter 18 is the differential amplifier 10
It is not input to the drive amplifier 19, but is input to the drive amplifier 19 provided separately. The drive amplifier 19 is connected to the lower end of the feed motor 4 by the contact b of the third switch SW3. The contact a of the third switch SW3 is turned on during the period in which the offset voltages V0 and Vc are detected. Differential amplifier during normal feed control
A composite value of the output voltage of 10 and the output voltage of the drive amplifier 19 is applied to the feed motor 4.

With this configuration, the dynamic range of the differential amplifier 10 does not deteriorate due to the correction. Since the gain of the drive amplifier 19 can be set to 1 or very small, this offset voltage can be ignored.

[Modifications] The present invention is not limited to the above-described embodiments, but can be modified. For example, it is also applicable to a case where the pickup is attached to a rotating arm and the arm is rotated by a voice coil motor or the like. The drive amplifier may not be built in the differential amplifier 10, but the drive amplifier may be provided independently.
Further, an adder for adding the DC voltage corresponding to the tracking error and the offset correction voltage may be added. Further, instead of providing the memories M1, M2, and M3 independently, a specific address of the common memory may be used as a write area for VO, Va, and Vb. Further, the present invention can be applied to a case where a constant voltage is supplied as the drive voltage instead of supplying the DC voltage corresponding to the tracking error. Also, the electrical offset voltage
When V0 correction is unnecessary, the part related to this may be omitted. The switches SW1 to SW3 may be electronic switches.

[Effects of the Invention] As is apparent from the above, according to the invention of claim 1, (Va-Vb) / 2 can be easily obtained as a signal indicating the correction amount of the inclination (mechanical offset) of the fed device. Therefore, the mechanical offset can be easily corrected.

According to the invention of claim 2, both the mechanical offset correction and the differential amplifier offset (electrical offset) correction can be easily performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an offset correction circuit according to a first embodiment of the present invention, FIG. 2 is a block diagram showing the principle of a CD player, FIG. 3 is a diagram showing a voltage relation of each part, FIG. FIG. 6 is a block diagram showing an offset correction circuit of a second embodiment. 10 ... Differential amplifier, 11 ... Speed detection coil, 13 ... Arithmetic circuit, SW1, SW2, SW3 ... Switch, A ... First terminal,
B: second terminal, C: third terminal, D: fourth terminal, M1, M2, M3 ... memory.

Claims (2)

[Claims] 1. A motor (4) for giving a feed to an object to be fed, speed detection means for obtaining a speed detection voltage corresponding to a feed speed by the motor (4), and the motor by the speed detection voltage. A feed provided with a differential amplifier (10) for obtaining an output corresponding to a difference between the drive input voltage of the motor (4) and the speed detection voltage so as to perform negative feedback control of the feed speed of (4). A circuit for correcting an offset in a device, comprising: a forward feed reference drive voltage input terminal (B) for applying a forward feed reference drive input voltage (Vr) to the differential amplifier (10), Reverse feed for applying to the differential amplifier (10) a reference feed input voltage (-Vr) of reverse feed whose absolute value is substantially equal to the reference feed input voltage (Vr) of forward feed and whose polarity is opposite. Reference drive voltage input terminal (C), The differential amplifier control signals Ri feed control signal input terminal for applying (10) and (D), the respective input terminals (B, C, D) of the differential amplifier (10)
A first switch (SW1) selectively connected to the memory, a forward drive voltage memory (M2), a reverse drive voltage memory (M3), and the differential amplifier (10) for the forward drive reference. Data corresponding to the output voltage of the differential amplifier (10) obtained when connected to the drive voltage input terminal (B) is stored in the memory (M2) for the positive drive voltage as the positive drive voltage (Va). The data corresponding to the output voltage of the differential amplifier (10) obtained when the differential amplifier (10) is connected to the reverse feed reference drive voltage input terminal (C) is written. A memory input circuit for writing to the reverse drive voltage memory (M3) as (-Vb), the forward drive voltage (Va) and the forward drive voltage (Va) and the forward drive voltage memory (M2, M3). Reverse drive voltage (-
Vb) is read out, and the differential amplifier (10) is connected to the operation circuit (13) for calculating (Va-Vb) / 2 as a signal indicating the correction amount of the control error due to the inclination of the fed object, and the feed control input terminal (Va-V) obtained from the arithmetic circuit (13) when connected to (D)
b) / 2, and means for correcting the drive voltage of the motor (4) based on (2) / 2. 2. A motor (4) for feeding an object to be fed, speed detection means for obtaining a speed detection voltage corresponding to a feed speed by the motor (4), and the motor by the speed detection voltage. To correct the offset in a feeding device provided with a differential amplifier (10) for obtaining an output corresponding to a difference between the drive input voltage of the motor and the speed detection voltage so as to perform negative feedback control of the feeding speed of And a second terminal (B) for applying a forward drive reference drive input voltage (Vr) to the differential amplifier (10), the first terminal (A) being connected to the ground. ) And a reverse feed reference drive input voltage (-Vr) whose absolute value is substantially equal to and opposite in polarity to the forward feed reference drive input voltage (Vr), to the differential amplifier (10). 3rd terminal (C), and feed control signal A fourth terminal (D) for supplying the differential amplifier (10) to the differential amplifier (10), and the first, second, third and fourth terminals (A, B, C,
A first switch (SW1) for selectively connecting D) to the differential amplifier (10), first, second and third memories (M1, M2, M3), and the differential amplifier (10 ) Is connected to the first terminal (A), the data corresponding to the output voltage of the differential amplifier (10) obtained as the offset voltage (± V0) is stored in the first memory (M1). Write, the differential amplifier (10)
Data corresponding to the output voltage of the differential amplifier (10) obtained when is connected to the second terminal (B) is stored in the second memory (M2) as a forward drive voltage (Va). Writing, the differential amplifier (10) is connected to the third terminal (C).
A memory input circuit for writing data corresponding to the output voltage of the differential amplifier (10) obtained when connected to the third memory (M3) as a reverse driving voltage (-Vb), From the first, second, and third memories (M1, M2, M3) to the offset voltage (± V0), the forward drive voltage (Va),
The reverse drive voltage (-Vb) is read out, and a signal indicating the correction amount of the offset voltage of the differential amplifier (10) and the correction amount of the control error due to the inclination of the fed object is given as [±
(Va−Vb) / 2] ± V0 obtained from the arithmetic circuit (13) when the differential amplifier (10) is connected to the fourth terminal (D), and the arithmetic circuit (13) is obtained. ± (Va-Vb)
/ 2] ± V0, and means for correcting the drive voltage of the motor (4), and an offset correction circuit for the feeding device.