JP2708652B2 - Square wave forming circuit and seek control device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

(Contents) Industrial application field Conventional technology (FIGS. 13 to 16) Problems to be solved by the invention (FIG. 17) Means for solving the problems (FIG. 1) Action Embodiment (a) Rectangular Description of the first embodiment of the wave forming circuit (FIGS. 2 to 4) (b) Description of the first embodiment of the optical disk device (FIGS. 5 and 6) (c) Second embodiment of the rectangular wave forming circuit Description of Examples (FIGS. 7 to 11) (d) Description of Second Embodiment of Optical Disc Apparatus (FIG. 12) (e) Description of Another Embodiment Effect of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular wave forming circuit using a variable feedback amount hysteresis comparator and a seek control device using the same.

An optical disk device (including a magneto-optical disk device) has an advantage that its storage capacity is larger than a magnetic disk device, and has attracted attention as an external storage device.
In such an optical disk device or the like, a track error signal is obtained from the reflected light from the optical disk, and the track error signal is sliced by a comparator to generate a track crossing signal, thereby detecting a track position and a speed. , Seek control.

For this reason, there is a demand for a technique capable of accurately generating a track-crossing signal even when a noise and an offset are added to the track error signal.

[0005]

2. Description of the Related Art FIG.
4 is an explanatory diagram of a track zero cross signal, and FIG. 15 is an explanatory diagram of a track crossing operation.

As shown in FIG. 13, an optical head 3 for irradiating an optical disk 2 with a light beam to an optical disk (magneto-optical disk) 2 rotated by a spindle motor (not shown), and the optical head 3 in the radial direction of the optical disk 2 (Voice coil motor) 1 to be driven.

On the other hand, as shown in FIG.
Has tracks arranged between the guide grooves, and reflects light reflected from the optical disk 2 by irradiation of the optical head 3 with the light beam.
2 split photodetector 3 via objective lens 31 of optical head 3
0, the light receiving outputs A and B of the two-segment photodetector 30
Is obtained by a TES (track error) signal creation circuit 10 to create a track error signal TES.

The track error signal TES is offset-compensated by an offset compensating circuit 11, the phase of a high frequency component is advanced by a phase advance circuit 12, and input to a power amplifier 16 via a track servo switch 13 and an adder 14.
A track actuator coil (not shown) that drives the objective lens 31 in the track direction is driven to control the light beam to follow the track.

On the other hand, the track error signal TES of the phase advance circuit 12 forms a sine wave of a cycle every track traverse, and this track error signal TES is input to the high-speed comparator 15 and, as shown in FIG. Then, a track zero-cross signal TZC is generated, and the track zero-cross signal TZC is counted by the track counter 17, whereby the control unit (MPU) 4 determines the position of the optical head 3,
The speed is obtained, and seek control of the voice coil motor 1 is performed via the digital / analog converter 22 and the power amplifier 24.

Further, a lens position signal LPOS indicating the position of the objective lens 31 of the optical head 3 is generated by a lens position creation circuit 18, and a high frequency component is advanced by a phase advance circuit 19, and the control unit 4 switches the switch 21 during a seek operation. Is turned on, and the lens position signal LPOS is
To lock the objective lens 31.

The digital-to-analog converter 20
Is provided for inputting a track actuator control signal to the adder 14 at the end of a seek, driving a track actuator coil, and performing a lens seek by the objective lens 31 to obtain a stable seek positioning. .

In such an optical disk device, the comparator 15 slices the track error signal TES at a constant slice level (analog center voltage Vref) as shown in FIGS. The signal TZC was generated.

By the way, as shown in FIG. 15, the track of the optical disc 2 has an ID portion (pre-pit portion).
In the ID section, since the guide groove is interrupted, noise on the spike is added to the track error signal TES as shown in the figure.

For this reason, from the ID part to the rear part of the ID,
The track error signal TES is broken, an extra pulse is generated in the track zero cross signal TZC obtained by slicing the track error signal TES to a zero level, and accurate track crossing cannot be reproduced, resulting in a track position error and a speed error.

FIG. 16 is an explanatory diagram of the prior art. As disclosed in Japanese Patent Application Laid-Open No. 3-36813, for example, a rectangular wave forming circuit capable of removing noise on an input signal has a hysteresis circuit in which an output is positively fed back to an input side to have a hysteresis characteristic. Comparators are known.

The hysteresis comparator 15 corresponds to FIG.
As shown in FIG. 6A, the input signal (track error signal) TES is supplied to the negative side of the comparator 150 and the analog reference voltage (DC offset voltage) Vr is supplied to the positive side.
ef is input via a resistor R3, the output side is connected at + Vcc via a resistor R1, the output voltage is DC-coupled by a resistor R2, and positively fed back to the positive input side.

In such a rectangular wave forming circuit, hysteresis corresponding to the output can be given to the slice level, which is effective for noise removal. This hysteresis width is
The feedback amount can be changed by making the feedback amount variable. For example, in Japanese Patent Application Laid-Open No. 3-36813, a resistor R4 and a switch SW are provided in parallel with the feedback resistor R2, and when the control unit 4 turns off the switch SW, the hysteresis width is reduced. Becomes large, and when the switch SW is turned on, the hysteresis width becomes small.

In the prior art, as shown in FIG. 16B, when there is a large amount of high-frequency noise waiting for reception, the switch SW is turned on, the hysteresis width is increased as Wa, and noise is cut off. At the time of low frequency in a normal reception state, the switch SW is turned off, and the hysteresis width is controlled to be small like Wb to form a rectangular wave.

[0019]

FIG. 17 is a diagram for explaining a problem of the prior art. By the way, the track error signal TE
Since S is a sine wave having a frequency corresponding to the moving speed of the optical head 3, during the low-speed seek, the frequency of the track error signal TES is low and the high-speed seek is performed as shown in FIG. 17B, the frequency of the track error signal TES is high as shown in FIG.

As described above, the track error signal TES is
The frequency varies depending on the seek speed, and the higher the seek speed, the higher the frequency becomes, which is about 500 kHz, and as shown in FIG. 17B, due to the band characteristics and filter characteristics of the amplifier such as the track error signal generation circuit 10, etc. There is a phenomenon that the amplitude of the high-frequency signal decreases.

For this reason, if the hysteresis width is increased in the high frequency range and the hysteresis width is reduced in the low frequency range in order to remove the high frequency noise of the prior art, the following problem occurs.

Since the hysteresis width is small for the track error signal TES at the time of low-speed seek which is not limited by the amplitude, the noise on the track error signal TES is weak and the noise removal margin is small.

As shown in FIG. 17B, with respect to the reduced amplitude of the track error signal TES during the high-speed seek, the hysteresis width becomes excessively large, and in particular, the margin for the offset of the track error signal TES decreases.

Accordingly, it is an object of the present invention to provide a rectangular wave forming circuit capable of forming a rectangular wave with an appropriate hysteresis for an input signal whose amplitude changes according to the frequency.

Another object of the present invention is to provide a seek control device which can convert a position signal whose frequency and amplitude change according to the speed into a rectangular wave with an appropriate hysteresis and perform seek control.

[0026]

FIG. 1 is a diagram illustrating the principle of the present invention. A first aspect of the present invention is a hysteresis comparator 15 which slices an input signal by a predetermined voltage and feeds back an output of a comparator 150 that outputs a rectangular wave to an input side, and a feedback of the hysteresis comparator 15. A control unit 4 for controlling the amount according to the frequency of the input signal, and a feedback circuit of the hysteresis comparator 15.
Between the differentiating circuits R2 and C1 and the differentiating circuits R2 and C1.
A series circuit of a resistor R4 and a switch SW is provided in parallel with the resistor R2.
The control unit 4 controls the switch SW),
When the input signal has a low frequency, the hysteresis width is increased,
When the input signal has a high frequency, the hysteresis width is controlled to be small.

According to the second aspect of the present invention, the moving parts 1 and 3
A position signal of a frequency corresponding to the moving speed is
Output of the comparator 150 that outputs a square wave
Hysteresis comparator 1 which feeds back to the input side
5 and the position and velocity of the moving parts 1 and 3 from the rectangular wave output.
And a control unit 4 for driving and controlling the moving units 1 and 3
The control unit 4 determines a distance to which the moving units 1 and 3 should move.
, The feedback of the hysteresis comparator 15
By controlling the amountAt low speed seeks where the distance to move is short
Has a large hysteresis width,Long distance to move high
During fast seekIs characterized by controlling the hysteresis width to a small value.
Sign.

[0028] Claim 3 of the present invention is based on claim 2,
The moving parts 1 and 3 are moved by light from the optical disc 2.
An optical head 3 for outputting a read error signal;
And a drive unit 1 for driving the track 3.
Input to the hysteresis comparator 15
And obtaining a track crossing signal .

[0029]

[0030]

[0031]

[0032]

[0033]

According to the first aspect of the present invention, the feedback circuit is a differential circuit.
R2, C1 in parallel with the resistor R2 of the differentiating circuit R2, C1
Is provided with a series circuit of a resistor R4 and a switch SW.
Since the feedback circuit is connected by AC connection and returns,
The amount becomes the output change, and the hysteresis width is set to the reference voltage.
On the other hand, it can be symmetrical, and the input signal noise and offset
Can be made larger .

According to a second aspect of the present invention, a seek control device is provided.
First, the positions and speeds of the moving units 1 and 3 are obtained from the rectangular wave output.
The control unit 4 that drives and controls the moving units 1 and 3 includes a moving unit.
According to the moving distances of the first and third, that is, the moving speed,
To control the amount of feedback of the
And the position signal during a low-speed seek with a short moving distance
At the wave number, the hysteresis width is large, and the moving distance is long.
When the position signal in fast seek is high frequency,
The cis width can be controlled to be small, and the speed of the moving parts 1 and 3 can be controlled.
Hysteresis for position signal of frequency and amplitude according to
It can be converted to a rectangular wave by width, and the position and speed can be detected accurately.
And stable seek control becomes possible .

According to a third aspect of the present invention, the moving units 1 and 3
Output track error signal by light from optical disk 2
Optical head 3 for driving, and drive unit 1 for driving optical head 3
And the track error signal to the hysteresis comparator.
Input to the radiator 15 to obtain the track crossing signal.
Noise caused by the ID portion of the optical disc 2 and the adjustment of the optical head 3
Misalignment, temperature fluctuation, offset due to optical disc tilt
However, the amplitude of the track error signal TES changes.
Can form a cross-track signal with the largest margin width,
The seek operation becomes stable .

[0036]

[0037]

[0038]

[0039]

[0040]

【Example】

(a) Description of the first embodiment of the rectangular wave forming circuit FIG. 2 is an explanatory diagram of the first embodiment of the present invention, and FIGS. 3 and 4 are explanatory diagrams of the operation of the first embodiment of the present invention (parts 1 and 2). Part 2).

In FIG. 2A, the configuration of the hysteresis comparator 15 is the same as that of FIG. 16. When the input signal TES is at a high frequency, the control unit 4 turns off the switch SW and outputs the input signal TES. When the TES has a low frequency, the switch SW is turned on.

This operation will be described with reference to FIGS. 2B and 2C. Assuming that the feedback resistance of the circuit of FIG. 2A is only R2, the equivalent circuit is as shown in FIG. 2B. The low / high of the square wave output is represented by a switch.

At this time, assuming that the resistance R1 is sufficiently smaller than the resistances R2 and R3, an equivalent circuit shown in FIG. 2C is obtained. When the output is high, the potential Vh at the point a is expressed by the following equation (1). )
It is shown by the formula.

[0044]

(Equation 1)

On the other hand, the potential Vl at point a when the output is low
Is represented by the following equation (2).

[0046]

(Equation 2)

Therefore, the hysteresis width W is Vh-Vl
Therefore, R3 · Vcc / (R2 + R3) is obtained. Here, when the switch SW is turned off, the hysteresis width W2 is R3 · Vcc / (R2 + R3), but when the switch SW is turned on, the hysteresis width W1 is:
R3 · Vcc / (R ′ + R3), where R ′ is R2 · Rcc
R4 / (R2 + R4).

Since R2> R ', W2 <W1. Therefore, as shown in FIG.
For the ES, the switch SW is turned on and the hysteresis width is set to a large W1, and for the high frequency input signal TES, the switch SW is turned off and the hysteresis width is set to a small W2. A rectangular wave can be formed with an appropriate hysteresis according to each amplitude, and a sufficient margin for noise and offset can be obtained.

Incidentally, since the feedback circuit of this embodiment is constituted by DC coupling, as shown in FIG.
The width Vh 'of the potential at the point a when the output is high with respect to the reference voltage Vref is expressed by the following equation (3).

[0050]

(Equation 3)

The potential width Vl 'at the point a when the output is low with respect to the center Vref is expressed by the following equation (4).

[0052]

(Equation 4)

From the equations (3) and (4), when a single power supply is used, the potential width V when Vcc = 2 · Vref is obtained.
h ′ and Vl ′ become equal, and the hysteresis is the center Vr
It is symmetric with respect to ef.

Alternatively, if both positive and negative power supplies are used, the hysteresis becomes positive and negative symmetric, and the margin can be maximized. (b) Description of First Embodiment of Optical Disc Device FIG. 5 is a configuration diagram of an optical disc device according to a first embodiment of the present invention.
FIG. 6 is a diagram for explaining the operation of the optical disk apparatus according to the second embodiment of the present invention.

In FIG. 5, the same components as those shown in FIG. 13 are indicated by the same symbols, and the difference from FIG. 13 is that the track traversing signal generation circuit 15 uses the hysteresis comparator 15 in FIG. It is a point that is configured.

The operation will be described with reference to FIG. 6. Prior to seeking, the control unit (MPU) 4 controls the track counter 17
The number of seek tracks is set, the switch SW of the hysteresis comparator 15 is turned off, the hysteresis width is set to a small W2, the acceleration voltage value is output to the digital / analog converter 22, and the voice is output via the power amplifier 24. The coil motor 1 is driven to accelerate.

At this time, the switch 21 is turned on, the lens position signal LPOS is input to the power amplifier 16, and the track actuator coil is servo-controlled to prevent the track actuator from running out of control. The track actuator is fixed to the neutral point by LPOS.

As a result, the optical head 3 moves, a track error signal TES having a sine wave shape is generated from the track error signal generation circuit 10, and the track crossing signal generation circuit 1 is generated.
5, the track zero cross signal TZ with the hysteresis width W2
Converted to C.

The track counter 17 counts down at the rise of the track zero cross signal TZC and indicates the number of remaining tracks. The control unit 4 reads the contents of the track counter 17 at regular intervals by the built-in timer TM.
The number of remaining tracks is obtained, and the actual speed is calculated from the difference from the previous number of remaining tracks to be read.

When the actual speed reaches a predetermined set speed, the control unit 4 terminates the acceleration, and thereafter outputs a drive voltage value corresponding to the difference between the set speed and the actual speed to the digital / analog converter 22, and the power amplifier 24 The speed of the voice coil motor 1 is controlled via the.

When the number of remaining tracks of the track counter 17 reaches a predetermined deceleration start point, a drive voltage value corresponding to the difference between the commanded speed and the actual speed according to the predetermined deceleration curve is output to the digital / analog converter 22. The deceleration control of the voice coil motor 1 is performed via the power amplifier 24.

Further, at the end of the deceleration, the number of remaining tracks of the track counter 17 is read, the track interval is measured with time, the actual speed is calculated, and the digital / analog converter of the drive voltage value of the difference between the command speed and the actual speed is used. 22, the switch 21 is turned off, the track servo control by the lens position signal LPOS is inhibited, the deceleration voltage value at the actual speed is output to the digital / analog converter 20, and the track is output via the power amplifier 16. Drive control (lens seek) of the actuator.

At this time, since the frequency of the track error signal TES decreases and the amplitude is not limited, the switch SW is turned on and the hysteresis width is set to a large value W1.
In this case, since the positioning is performed not only by the deceleration control of the voice coil motor 1 but also by the control of the track actuator, the track positioning of the light beam is stabilized, and the quick positioning becomes possible.

When reaching the target track, the output to the digital / analog converter 20 is stopped, the switch 13 is turned on, the track servo control of the track actuator is performed by the track error signal TES, and the objective lens is controlled by the track actuator. 31
A double servo for controlling the voice coil motor 1 via the power amplifier 24 is executed by a lens position signal LPOS corresponding to the movement amount of.

The objective lens 3 is controlled by the double servo.
The optical head 3 is moved by the voice coil motor 1 while the track following control is performed by the movement of 1 to hold the objective lens 31 at the center point.

As described above, the control unit 4 determines the track position,
A track crossing signal TZC for obtaining an actual speed is converted to a track crossing signal generation circuit 15 having a hysteresis width corresponding to the amplitude.
Therefore, even if there is a change in the amplitude of the track error signal TES, the track crossing signal TZC that accurately reflects the track crossing without overdetection due to the noise of the ID section or the like, the offset of the track error signal TES, and undetection. As a result, a track count error and a speed detection error can be prevented, and an accurate and stable seek operation can be performed.

Further, even in a seek at a long distance, as shown in FIG.
Since the frequency of the track error signal TES suddenly increases from the start of the seek, the hysteresis width is set to a small value W2 from the start of the seek, and the hysteresis width is increased when the frequency of the track error signal TES at the end of the seek decreases. , An optimum hysteresis width according to the amplitude of the track error signal TES is set, the margin is maximized irrespective of the amplitude, and the track count error,
Accurate and stable seek operation is possible by preventing speed detection errors.

Further, in the case of a short-distance seek of less than 100 tracks, the lens seek is performed by a track actuator, and the speed does not reach the maximum speed. Therefore, the control unit 4 determines whether the seek is a short-distance seek or a long-distance seek. Then, if it is a short-distance seek, the seek is started with the switch SW kept off.

(C) Description of the Second Embodiment of the Rectangular Wave Forming Circuit FIG. 7 is a block diagram of a second embodiment of the present invention, FIG. 8 is an explanatory diagram of the second embodiment of the present invention, and FIGS. FIG. 11 is a diagram (parts 1 to 3) illustrating the operation of the second embodiment of the present invention.

Before describing this embodiment, the problems of the first embodiment shown in FIG. 2 will be described.
As shown in FIG. 2, the servo zero point of the track error signal TES is biased to Vref, and the hysteresis in FIG. 2 decreases to Vl when the track error signal TES becomes higher than the hysteresis as shown in FIG. When TES falls below hysteresis, Vh
And the noise on the track error signal TES can be prevented from being detected.

However, when using a single power supply, FIG.
As shown in (B), in order to operate the analog circuit in a positive or negative manner, the analog reference (D
(C offset) voltage Vref is provided on the plus side, and is used as an analog zero voltage so that it can operate positively and negatively.

The analog reference voltage Vref is extremely stable and is suitable as a reference voltage for slices. However, since it is about 1.8 volts and + Vcc is about 5 volts, it satisfies the above-mentioned symmetric condition. Figure 4
As shown in (A), the hysteresis becomes positive / negative asymmetric with respect to the analog reference voltage Vref, and the following problem occurs.

As shown in FIG. 4A, the hysteresis width on the high side is small and the track error signal TES on the negative side is small.
Erroneous detection is likely to occur due to the detection of noise on the image.

If there is an offset in the track error signal TES itself (for example, if there is an offset on the upper side in FIG. 4), over-detection and erroneous detection of the track zero cross signal TZC occur, and the margin for the offset decreases.

In order to make the hysteresis symmetrical between positive and negative, the use of both positive and negative power supplies complicates the power supply circuit, necessitates an analog circuit that operates on the positive and negative power supplies, and increases the circuit scale.

Next, a second embodiment will be described. In FIG. 7, the same components as those shown in FIG. 16 are indicated by the same symbols, and the hysteresis comparator is connected to the minus side of the comparator 150. , An input signal (track error signal) TES to the plus side, an analog reference voltage (DC offset voltage) Vref via a resistor R3, the output side via + Rcc via a resistor R1, and the output voltage via a resistor R2 and a capacitor. The differential circuit of C1 performs negative feedback on the positive input side, and a series circuit of a resistor R4 and a switch SW is provided in parallel with the resistor R2.

This operation will be described with reference to FIG. 8. If the feedback resistor in FIG. 7 is considered to be only R2, the circuit shown in FIG. 8A is obtained, and its equivalent circuit is as shown in FIG.
A low / high square wave output is represented by a switch.

At this time, assuming that the resistance R1 is sufficiently smaller than the resistances R2 and R3, an equivalent circuit shown in FIG. 8C is obtained. The operation of this equivalent circuit when the output changes from low to high will be described with reference to FIG.

When the output changes from low to high, the voltage Vcc is connected to the resistor R2, and the resistance R
2. To the voltage Vref via the capacitor C1 and the resistor R3,
The current i flows.

Here, assuming that the charge stored in the capacitor C1 is q, the current i is dq / dt [A], the terminal voltage Vc of the capacitor C1 is q / C1, and the voltage drop Vr of the resistors R2 and R3 is (R2 + R3 ) · I.

Therefore, the difference between the voltage Vref and the voltage Vcc is expressed by the following equation (5).

[0082]

(Equation 5)

When the equation (5) is rearranged, the following equation (6) is obtained.

[0084]

(Equation 6)

By integrating both sides of the equation (6), the following equation (7) is obtained.
It becomes an expression.

[0086]

(Equation 7)

In the equation (7), K is an integration constant,
When this is set to -1nQk and the equation (7) is modified,
Equation (8) is obtained.

[0088]

(Equation 8)

From equation (8), equation (9) is obtained.

[0090]

(Equation 9)

Here, as an initial condition, q0 = −Cl ·
Since Vref and t = 0, substituting this into equation (9) gives -Cl.Vref = Cl (Vcc-Vref) -Qk. From the above equation, the integration constant Qk becomes Qk = Cl.Vcc. .

By substituting this into the equation (9), the charge quantity q is obtained as the following equation (10).

[0093]

(Equation 10)

Therefore, the voltage Vc between the terminals of the capacitor C1 is obtained.
(= Q / C1) is represented by the following equation (11).

[0095]

[Equation 11]

The current i is obtained by differentiating equation (10) and
2)

[0097]

(Equation 12)

Thus, the potential Va at the point a is represented by the following equation (13).

[0099]

(Equation 13)

That is, as shown in FIG. 9B, when the output changes from low to high, the potential Va at point a becomes Vcc · R
3 / (R2 + R3) rises, attenuates as shown in the figure, and finally converges to Vref.

Next, the operation when the output changes from high to low in the equivalent circuit of FIG. 8C will be described with reference to FIG. The change of the output from high to low means that the resistor R2 is grounded by the switch SW, and the voltage Vref is grounded via the resistor R3, the capacitor C1, and the resistor R2.
The current i flows.

Here, assuming that the charge stored in the capacitor C1 is q, the current i is dq / dt [A], the voltage Vc between the terminals of the capacitor C1 is q / C1, and the drop voltage Vr of the resistors R2 and R3 is (R2 + R3 ) · I.

Therefore, the voltage Vref is expressed by the following equation (14).

[0104]

[Equation 14]

By rearranging this equation (14) and integrating both sides,
The following equation (15) is obtained.

[0106]

(Equation 15)

In equation (15), K is an integration constant, which is set to -1nQk, and equation (16) is obtained by modifying equation (15).

[0108]

(Equation 16)

From equation (16), equation (17) is obtained.

[0110]

[Equation 17]

Here, as an initial condition, q0 = −C1
Since (Vcc-Vref) and t = 0, this is represented by (17)
When substituted into the equation, −C1 (Vcc−Vref) = C1 · Vref−Qk, and from the above equation, the integration constant Qk becomes Qk = C1 · Vcc.

By substituting this into the equation (17) to obtain the electric charge q, the following equation (18) is obtained.

[0113]

(Equation 18)

Accordingly, the terminal voltage Vc of the capacitor C1 is obtained.
(= Q / C1) is given by the following equation (19).

[0115]

[Equation 19]

The current i is obtained by differentiating equation (18) and
0)

[0117]

(Equation 20)

Thus, the potential Va at the point a is expressed by the following equation (21).

[0119]

(Equation 21)

That is, as shown in FIG. 10B, when the output changes from high to low, the potential Va at point a becomes Vcc ·
R3 / (R2 + R3) falls, attenuates as shown in the figure, and finally converges to Vref.

The time constant 1 / C1 (R2 + R
If 3) is made small and the decay time is made long, the expected shortest period of the track error signal TES is as shown in FIG.
(B), the position indicated by the dotted line in FIG.
A feedback amount of cc · R3 / (R2 + R3) is obtained.

As a result, as shown in FIG.
In the initial state, the hysteresis is not positive / negative symmetric, but the hysteresis immediately becomes positive / negative symmetric about the analog reference voltage Vref according to the result of comparison with the input signal TES, and the width is Vcc · R3 / (R2 + R3), and the track error It is necessary to set smaller than the minimum amplitude of the signal TES.

For this reason, as shown in FIG. 11B, the noise margin on the track error signal TES increases, and the margin for the offset of the track error signal TES also increases. The signal TZC is obtained.

Here, when the switch SW is off, the hysteresis width is Vcc · R3 / (R2 + R3), but when the switch SW is turned on, the resistance value R ′ of the differentiating circuit is obtained.
Is R2 · R4 / (R2 + R4), the hysteresis width is Vcc · R3 / (R ′ + R3), and the hysteresis width can be made variable.

Here, the control unit 4 determines that the track error signal TES has a low frequency because the lens seek by the track actuator is performed during the short-distance seek of less than 100 tracks and the speed is reduced before the speed reaches the maximum speed. Since the amplitude is not limited by the amplifier, the control unit 4
Turns on the switch SW, increases the hysteresis width, and in a long-distance seek, the speed reaches the maximum speed, the track error signal TES becomes a high frequency, and the amplitude is limited by the amplifier. Is turned off, the hysteresis width is reduced, and a hysteresis width corresponding to the amplitude of the track error signal TES is obtained.

As a result, the input signal can be sliced with a hysteresis width according to the amplitude of the input signal.
A sufficient margin for the offset can be obtained.

(D) Description of Second Embodiment of Optical Disc Apparatus FIG. 12 is a block diagram of an optical disc apparatus according to a second embodiment of the present invention. 12, the same components as those shown in FIG. 13 are denoted by the same symbols, and the differences from FIG.
The point is that the track crossing signal generation circuit 15 is configured by the hysteresis comparator of FIG.

This operation is the same as that of FIG. 6, and prior to seeking, the control unit (MPU) 4
The number of seek tracks is set, the switch SW of the hysteresis comparator 15 is turned off, the hysteresis width is set to a small W2, the acceleration voltage value is output to the digital / analog converter 22, and the voice is output via the power amplifier 24. The coil motor 1 is driven to accelerate.

At this time, the switch 21 is turned on, the lens position signal LPOS is input to the power amplifier 16, and the track actuator coil is servo-controlled to prevent the track actuator from running out of control. The track actuator is fixed to the neutral point by LPOS.

As a result, the optical head 3 moves, and the track error signal generating circuit 10 generates a sinusoidal track error signal TES.
5, the track zero cross signal TZ with the hysteresis width W2
Converted to C.

The track counter 17 counts down at the rise of the track zero cross signal TZC and indicates the number of remaining tracks. The control unit 4 reads the contents of the track counter 17 at regular intervals by the built-in timer TM.
The number of remaining tracks is obtained, and the actual speed is calculated from the difference from the previous number of remaining tracks to be read.

When the actual speed reaches a predetermined set speed, the control unit 4 terminates the acceleration, and thereafter outputs a drive voltage value corresponding to the difference between the set speed and the actual speed to the digital / analog converter 22, and the power amplifier 24 The speed of the voice coil motor 1 is controlled via the.

When the remaining number of tracks of the track counter 17 reaches the scheduled deceleration start point, a drive voltage value of the difference between the command speed and the actual speed according to the scheduled deceleration curve is output to the digital / analog converter 22. The deceleration control of the voice coil motor 1 is performed via the power amplifier 24.

Further, at the end of the deceleration, the number of remaining tracks of the track counter 17 is read, the track interval is measured in time, the actual speed is calculated, and the digital / analog converter of the drive voltage value of the difference between the command speed and the actual speed is used. 22, the switch 21 is turned off, the track servo control by the lens position signal LPOS is inhibited, the deceleration voltage value at the actual speed is output to the digital / analog converter 20, and the track is output via the power amplifier 16. Drive control (lens seek) of the actuator.

At this time, since the frequency of the track error signal TES decreases and the amplitude is not limited, the switch SW is turned on and the hysteresis width is set to a large value W1.
In this case, since the positioning is performed not only by the deceleration control of the voice coil motor 1 but also by the control of the track actuator, the track positioning of the light beam is stabilized, and the quick positioning becomes possible.

When reaching the target track, the output to the digital / analog converter 20 is stopped, the switch 13 is turned on, the track servo control of the track actuator is performed by the track error signal TES, and the objective lens is controlled by the track actuator. 31
A double servo for controlling the voice coil motor 1 via the power amplifier 24 is executed by a lens position signal LPOS corresponding to the movement amount of.

The objective lens 3 is controlled by the double servo.
The optical head 3 is moved by the voice coil motor 1 while the track following control is performed by the movement of 1 to hold the objective lens 31 at the center point.

As described above, the control unit 4 determines the track position,
Since the track crossing signal TZC for obtaining the actual speed is generated from the track crossing signal generation circuit 15 having a hysteresis of positive / negative symmetry, accurate detection without overdetection due to noise of the ID section or the like and offset of the track error signal TES without undetection. A track crossing signal TZC reflecting the track crossing is obtained, and a track count error and a speed detection error are prevented, and an accurate and stable seek operation can be performed.

Even in a long-distance seek, as shown in FIG. 12, since the frequency of the track error signal TES rapidly increases from the start of the seek, the hysteresis width is set to a small W2 from the start of the seek. When the frequency of the track error signal TES becomes low, the hysteresis width is set to a large value W1 to set an optimum hysteresis width according to the amplitude of the track error signal TES. Prevents counting mistakes and speed detection mistakes, and enables accurate and stable seek operations.

Further, in the case of a short distance seek of less than 100 tracks, a lens seek by a track actuator is performed, and the speed is reduced before the speed reaches the maximum speed.
The control unit 4 determines whether it is a short-distance seek or a long-distance seek, and if it is a short-distance seek, starts the seek while keeping the switch SW on.

(E) Description of Other Embodiments In addition to the above-described embodiments, the present invention can be modified as follows. Although the optical disk device has been described as an example, the present invention can also be applied to a magneto-optical disk device.
It can be applied to other AC signals.

Although the signal is fed back to the positive side of the hysteresis comparator, it can be realized by feeding back to the negative side. In the feedback circuit, a plurality of series circuits of a switch and a resistor may be provided in parallel with the resistor of the feedback circuit, and the hysteresis width may be varied in a plurality of stages.

As described above, the present invention has been described with reference to the embodiments.
Various modifications are possible within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0144]

As described above, according to the present invention,
The following effects are obtained. The amount of feedback of the hysteresis comparator of the square wave forming circuit is changed according to the frequency of the input signal.The hysteresis width is large at low frequencies, and the hysteresis width is small at high frequencies. Even if the amplitude of the input signal decreases, a rectangular wave that accurately reflects the input signal can be output.

At low frequencies, the hysteresis width is large.
When the frequency is high, the hysteresis width is small, so that even if the amplitude of the high frequency input signal decreases, the maximum margin can be obtained for the amplitude of the input signal. The feedback circuit is composed of differentiating circuits R2 and C1 and the differentiating circuit R
2, the resistor R4 and the switch SW are connected in parallel with the resistor R2 of C1.
Since a series circuit is provided, the feedback circuit
Since the feedback continues, the amount of feedback becomes the output change and
The steric width can be symmetric with respect to the reference voltage,
Greater margin for signal noise and offset
Can be done. The control unit 4 that drives and controls the moving units 1 and 3 includes:
3 according to the moving distance of 3, that is, the moving speed.
Since the feedback amount of the comparator 15 is controlled, the moving distance is
When the position signal at short low speed seek is low frequency,
For high speed seeks with a large steresis width and long travel distance
When the position signal is high frequency, the hysteresis width is
Frequency corresponding to the speed of the moving parts 1 and 3.
Number and amplitude position signals into square waves with appropriate hysteresis width
Conversion, accurate position and speed detection, stable
Can be controlled.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an explanatory diagram of a first embodiment of a rectangular wave forming circuit of the present invention.

FIG. 3 is an operation explanatory view (part 1) of the first embodiment of the present invention;

FIG. 4 is a diagram (part 2) for explaining the operation of the first embodiment of the present invention;

FIG. 5 is a configuration diagram of a first embodiment of the optical disk device of the present invention.

FIG. 6 is an operation explanatory diagram of the first embodiment of the optical disk device of the present invention.

FIG. 7 is a configuration diagram of a second embodiment of the rectangular wave forming circuit of the present invention.

FIG. 8 is an explanatory view of a second embodiment of the present invention.

FIG. 9 is a diagram (part 1) for explaining the operation of the second embodiment of the present invention;

FIG. 10 is a view for explaining the operation of the second embodiment of the present invention (part 2);
It is.

FIG. 11 is an operation explanatory view of the second embodiment of the present invention (part 3).
It is.

FIG. 12 is a block diagram of a second embodiment of the optical disk device of the present invention.

FIG. 13 is an explanatory diagram of an optical disk device.

FIG. 14 is an explanatory diagram of a track zero cross signal.

FIG. 15 is an explanatory diagram of a track crossing operation.

FIG. 16 is an explanatory diagram of a conventional technique.

FIG. 17 is an explanatory diagram of a problem in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voice coil motor (drive part) 2 Optical disk 3 Optical head 4 Control part (MPU) 10 Track error signal creation circuit 15 Rectangular wave formation circuit (Track crossing signal creation circuit) 17 Track counter

Claims (3)

(57) [Claims] 1. A hysteresis comparator (1) obtained by slicing an input signal at a predetermined voltage and feeding back an output of a comparator (150) for outputting a rectangular wave to an input side.
5) and a control unit (4) for controlling the amount of feedback of the hysteresis comparator (15) according to the frequency of the input signal.
And a feedback circuit of the hysteresis comparator (15) includes a differentiating circuit (R2, C1) and a differentiating circuit (R2, C1).
1) A series circuit of a resistor (R4) and a switch (SW) is provided in parallel with the resistor (R2) of (1), the control unit (4) controls the switch (SW), and the input signal has a low frequency. Wherein the hysteresis width is controlled to be large when the input signal has a high frequency, and the hysteresis width is controlled to be small when the input signal has a high frequency. 2. A method of slicing a position signal of a frequency corresponding to a moving speed from a moving unit (1 and 3) by a predetermined voltage and feeding back an output of a comparator (150) for outputting a rectangular wave to an input side. A hysteresis comparator (15)
A control unit (4) for obtaining the position and speed of the moving unit (1, 3) from the rectangular wave output and controlling the driving of the moving unit (1, 3); The hysteresis comparator (1) corresponds to a distance to be moved by the moving section (1, 3).
5) The amount of movement is controlled so that the distance to be moved is short and low speed
When seeking , increase the hysteresis width and the distance to move.
A seek control device characterized in that the hysteresis width is controlled to be small during a high-speed seek with a long distance. 3. An optical head (3) for outputting a track error signal by light from an optical disk (2), and a driving unit (1) for driving the optical head (3). The seek control device according to claim 2, wherein the track error signal is input to the hysteresis comparator (15) to obtain a track crossing signal.