JP2013182652A - Digital circuit and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-power and stable control circuit in a digital circuit or optical disk device by reducing gains for noises in a control loop and control signals in a high-frequency band that do not need tracking, without generating a phase delay and phase lead.SOLUTION: In the present invention, frequency identification means and gain change means that changes a gain on the basis of the output of the frequency identification means are provided. The frequency identification means includes delay memory means and absolute value calculation means.

Description

  The present invention relates to a digital circuit and an optical disc apparatus, and more particularly to a digital circuit and an optical disc apparatus that reduce power consumption.

  In Patent Document 1, “a primary low-pass filter 4 acting on the analog signal S5 output from the DA converter 5 and a stabilization compensation means for compensating for a phase delay caused by the primary low-pass filter 4 are provided. The output signal of the low-pass filter 4 is input as a current command signal S4 to the current control circuit 3. The primary low-pass filter 4 is a low-pass filter having a corner frequency lower than the sampling frequency determined by the reciprocal of the sampling period. Instead of the filter 4, it can be a notch filter having a cutoff frequency equal to the sampling frequency determined by the reciprocal of the sampling period or a cutoff frequency equal to an integral multiple of the Nyquist frequency determined by ½ of the reciprocal of the sampling period. Is described.

  Patent Document 2 discloses that “a position sensor that detects the position of a servo actuator that moves a drive mechanism, a position controller 2, a speed controller 3, and a position control loop that feeds back and compensates for the position sensor signal. In a servo control device in which a machine driven by a servo actuator has a plurality of machine resonance frequencies, a notch filter having a center frequency adjusted to one of the machine resonance frequencies in the high frequency region, and a cut-off frequency at the center of the notch filter There is a description that “the torque command input stage includes a low-pass filter set between 1 and 2 times the frequency”.

JP 2006-340446 A JP 2005-63362 A

For example, in the actuator control of the optical disc apparatus, an automatic control loop is formed that feeds back a tracking error in order to follow a predetermined recording / reproducing surface or track. Since the actuator can be modeled by a spring, a mass, and a damper and becomes a secondary system, it is necessary to secure a phase margin using a phase compensator. On the other hand, in actuator control, it is required to reduce power consumption. In this case, it is conceivable to reduce the gain over the control band by using a combination of LPF and notch filter. There arises a problem that the phase margin is reduced. Conversely, if the LPF pole is shifted to the high frequency side in order to reduce the influence on the phase margin, the power reduction effect is reduced. Even if there is a signal that does not need to be tracked in the error signal due to scratches or fingerprints on the disk, and the frequency of the signal is in the vicinity of the control band, the response performance of the control system is reduced using an LPF or notch filter However, if the phase margin decreases, the response performance may be deteriorated. Furthermore, if there is resonance in the controlled object or the control loop, it is conceivable to suppress oscillation using a notch filter. However, if the control system band is close to the resonance frequency, the phase margin of the control loop is not small. affect.

  The present invention reduces the gain beyond the control band without reducing the phase margin of the control system, thereby reducing unnecessary power consumption and response to high frequency components that do not need to be tracked included in the error signal. An object of the present invention is to provide a digital circuit and an optical disc apparatus that have high power consumption and low power consumption.

  In order to improve the above problems, the present invention uses, for example, the configuration described in the claims as an example.

  According to the present invention, in a digital circuit, a gain is reduced with respect to noise in a control loop and a control signal that does not require tracking in a high frequency region without causing phase delay or phase advance, and low power and stable digital. A circuit and an optical disk device can be provided.

Explanatory drawing which shows the component of the present Example 1. Explanatory drawing which shows the component of the frequency identification means of this Example 1, and a gain change means. Explanatory drawing of the output level of the frequency identification means of the first embodiment Explanatory drawing which shows the frequency characteristic of the present Example 1. Explanatory drawing which shows the alternative of the frequency identification means of the present Example 1. Explanatory drawing which shows the alternative of the structure of the present Example 1. Component explanatory diagram of the second embodiment Explanatory drawing which shows the component of the frequency identification means of this Example 2, and a gain change means. Explanatory drawing of the output level of the frequency identification means of the second embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 and FIG. 2 are block diagrams showing configurations of an optical disc apparatus and a digital circuit in the first embodiment. In FIG. 1, 1 is a disk, 2 is an optical pickup unit, 3 is a laser diode, 4 is an objective lens, 5 is a focus actuator, 6 is a tracking actuator, 7 is a pickup feed motor, 8 is a detector, and 10 is a focus error signal generation. Means 11, focus control signal generating means 12 focus actuator driving means 20 tracking error signal generating means 21 tracking control signal generating means 22 tracking actuator driving means 23 feed motor control means 24 feed motor Drive means, 30 is a spindle motor for rotating the disk, 31 is a frequency generating means for generating a signal corresponding to the rotation speed of the spindle motor, 32 is a motor control means for controlling the spindle motor to rotate at a predetermined speed, and 40 is F Frequency identification means carcass error signal, 50 is a focus gain changing means, 60 is a frequency identification means of the tracking error signal, 70 is a tracking gain changing means. In FIG. 2, 41 is a delay memory means, 42 is a subtracting means, 43 is an absolute value calculating means, 51 is a gain coefficient a, 52 is a gain coefficient b, and 53 is a switching means.

  Next, an outline of the operation of each block and the relationship between the blocks will be described. In FIG. 1, a laser diode 3 outputs a laser beam, and the output laser beam is condensed on a recording / reproducing layer of a disk 1 via an objective lens 4. Reflected light from the recording / reproducing layer is received by the detector 8 through the objective lens 4. The focus actuator 5 moves the objective lens 4 in the disc rotation axis direction, and the tracking actuator 6 moves the objective lens 4 in the disc radial direction. The feed motor 7 moves the optical pickup unit 2 in the disk radial direction. The detector 8 converts the reflected light into an electrical signal, and sends the converted signal to the focus error signal generation means 10 and the tracking error signal detection means 20. The focus error signal generation unit 10 generates a focus error signal based on the transmitted signal, and sends the generated signal to the frequency identification unit 40 and the gain change unit 50. The frequency identification unit 40 generates a frequency identification signal based on the signal sent from the focus error signal generation unit 10 and the output of the gain change unit 50, and sends the generated signal to the gain change unit 50. The gain changing means 50 selects a gain coefficient based on the signal sent from the frequency identifying means 40, adds the selected coefficient to the signal sent from the focus error signal generating means 10, and generates the focus control signal. Send to means 11. The focus control signal generating unit 11 generates a focus control signal based on the signal sent from the gain changing unit 50 and sends the generated signal to the focus actuator driving unit 15. The focus actuator driving means 15 drives the focus actuator 5 based on the transmitted signal.

  The tracking error signal generation unit 20 generates a tracking error signal based on the transmitted signal, and sends the generated signal to the frequency identification unit 60 and the gain change unit 70. The frequency identification unit 60 generates a frequency identification signal based on the signal sent from the tracking error signal generation unit 20 and the output of the gain change unit 70, and sends the generated signal to the gain change unit 70. The gain changing means 70 selects a gain coefficient based on the signal sent from the frequency identifying means 60, adds the selected coefficient to the signal sent from the tracking error signal generating means 20, and generates the tracking control signal. Send to means 21. The tracking control signal generation unit 21 generates a tracking control signal based on the signal sent from the gain changing unit 70 and sends the generated signal to the tracking actuator driving unit 22 and the feed motor control unit 23. The tracking actuator driving means 22 drives the tracking actuator 6 based on the sent signal. The feed motor control means 23 generates an optical pickup feed signal based on the signal sent from the tracking control signal generation means 21, and sends the generated signal to the feed motor drive means 24. The feed motor driving means 24 drives the feed motor 7 based on the sent signal.

  The spindle motor 30 drives the disk 1. The frequency generation means 31 converts the rotational speed information of the spindle motor 30 into an electrical signal and sends the converted signal to the motor control means 32. The motor control means 32 controls the spindle motor 30 so that the disk 1 rotates at a predetermined rotational speed based on the sent signal.

  Next, the detailed operation of the main block will be described with reference to FIG. The frequency discriminating unit 40 calculates the absolute value of the difference between the signal Sig_a sent from the focus error signal generating unit 10 and the output Sig_c one sample before the gain changing unit 50 by the delay memory unit 41. In other words, the frequency identification means 40 calculates the amount of change in the difference between Sig_a and Sig_c. By calculating in this way, the level of the absolute value becomes a signal indicating the amplitude and frequency of the differential signal. FIG. 3 shows the level when the horizontal axis represents the frequency of the absolute value signal and the vertical axis represents the amplitude. The absolute value signal increases as the frequency of the difference between Sig_a and Sig_c increases and the amplitude level increases.

  The gain changing unit 50 switches the switching unit 53 based on the signal sent from the frequency identifying unit 40 and selects a coefficient to be integrated into Sig_a. In this embodiment, the level of the absolute value sent from the frequency identification means 40 is compared with the threshold value 1, and when it is smaller than the threshold value 1, it is switched to the coefficient 51 side, and when larger than the threshold value 1, it is switched to the coefficient 52 side. Here, the coefficient 51 is a value designed to optimize the frequency characteristic of the focus control system, and the coefficient 52 is set to a value smaller than the coefficient 51. By setting the coefficients in this way, it is possible to remove high-frequency and large-amplitude components from the focus system control signal, and it is possible to reduce current unnecessary for driving the focus actuator. Further, it is possible to reduce the response of the error signal generated when the light spot passes through a scratch or dust on the disk to the sudden high frequency signal, and to realize stable control.

  FIG. 4 shows a transfer function from Sig_a to Sig_c when a signal having a constant amplitude is input to Sig_a. In this case, the phase hardly changes and the gain is reduced by 6 dB at 10 kHz. When the input amplitude is increased, the frequency at which the gain decreases is shifted to the low frequency side, and when the input amplitude is decreased, the frequency at which the gain decreases is shifted to the high frequency side. Therefore, the threshold value 1 needs to be set in consideration of the signal amplitude of the signal component that should not be removed within the control band. As an example of a method for determining the threshold value 1, the signal level of Sig_a is measured for a predetermined period using a low-pass filter having a control band as a cutoff frequency with the control loop closed and coefficient 1 selected. Is a signal amplitude of a signal component that cannot be removed within the control band. In the present embodiment, the gain changing means 50 causes the signal level relative to the frequency to discontinuously decrease in a high frequency region in at least one of the focus error signal, the tracking error signal, the focus drive signal, and the tracking drive signal. The gain of the control loop is changed depending on the frequency of the signal level. In the present embodiment, the gain changing means 50 adds the Sin wave signal having a predetermined amplitude to at least one of the focus error signal, the tracking error signal, the focus drive signal, and the tracking drive signal. The gain of the control loop is changed according to the frequency, and the gain of the control loop is changed according to the amplitude of the Sin wave signal when the Sin wave signal of a predetermined frequency is added.

  As shown in FIG. 5, the input of the delay memory may be Sig_a, but when the change amount of Sig_a changes from the threshold value to the threshold value, the Sig_c change amount may become larger than the expected value, and the expected effect is reduced. To do.

  Further, the gain changing means 50 may perform an operation of selecting the coefficient 1 before the focus control feedback loop is closed and changing the coefficient after the feedback loop is closed. Alternatively, the coefficient may be changed after the feedback loop is closed and the output of the error signal generation means 10 falls within a predetermined range.

  In the focus control feedback loop of the present embodiment, the gain changing means 50 is arranged to be a component of the feedback loop, and the frequency identifying means 40 is arranged not to be a component of the feedback loop. The gain changing means 50 changes the gain based on the output of the frequency identifying means 40, thereby changing the gain of the control loop for the signal in the feedback loop depending on the magnitude and frequency of the signal level. This can be similarly applied to a feedback loop for tracking control. As a result, it is possible to reduce the power of the control system and realize a stable control response.

  In this embodiment, the gain changing means 50 has two coefficients, but the same effect can be obtained by using three or more coefficients. When there are n coefficients, coefficient 51> coefficient 52> ...> coefficient n, threshold 1 <threshold 2 <... <threshold (n-1), and the value of frequency identification means 60 is smaller than threshold 1 Selects coefficient 1, selects coefficient 2 if greater than threshold 1 and less than threshold 2, and selects coefficient n if greater than threshold n.

  Further, a signal obtained by normalizing the output of the focus error signal generation means with the total amount of light obtained from the detector 8 may be used as the input of the frequency identification means 40.

  Further, the frequency identifying means 40 and the gain changing means 50 may be arranged after the focus control signal generating means 11.

  FIG. 6 is a diagram showing an alternative of the optical disk apparatus in the present embodiment. The operations of the frequency identifying means 60 and the gain changing means 70 are basically the same as the operations of the frequency identifying means 40 and the gain changing means 50, and are therefore omitted. However, the threshold value of the gain changing means 70 corresponding to the threshold value 1 may be set independently of the threshold value 1 or may be set to the same value. The coefficients in the gain changing means 70 (not shown) corresponding to the coefficients 51 and 52 may be set independently of the coefficients 51 and 52, or the same values may be set.

  Further, when the focus control signal generating means 11 includes a position complementing means 110, a low frequency compensating means 111, and an adding means 112, which are arranged in parallel, the frequency identifying means 40 and The gain changing means 50 may be arranged in series with the phase compensation means 110 and in parallel with the low frequency compensation means 112. The same applies to the case where the position complementary means 210, the low frequency compensation means 211, and the addition means 212 are included in the components of the tracking control signal generation means 21.

  Finally, the effect of the present embodiment will be described. According to the conventional method, a low-pass filter is inserted into the control system or a control signal is generated as a method for reducing unnecessary current to be controlled and reducing the response of the error signal to the sudden high frequency signal. The filter characteristic in the means is changed to lower the high frequency gain. However, in general, when a gain in a specific frequency range is reduced using a filter, a phase delay occurs, so that the phase margin is lowered. According to the present embodiment, noise signals in a high frequency range can be reduced without substantially causing a phase delay, so that it is possible to reduce the power consumption of the control system and realize a stable control response.

  In the above embodiment, the gain changing unit 50 operates so as to switch the gain coefficient based on the output level of the frequency identifying unit 40, but even if the gain coefficient is calculated based on the output level of the frequency identifying unit 40. Similar effects can be obtained.

Next, the configuration of the optical disk device and the digital circuit in the second embodiment will be described with reference to FIGS.
7 and 8, blocks 1 to 8, 10 to 12, 20 to 24, 30 to 32, and 40 to 43 and 60 are omitted because they are the same as those in the first embodiment. 7, 80 and 90 are gain changing means, and in FIG. 8, 81 is a variable coefficient means.

  Next, operations of the gain changing unit 80 and the variable coefficient unit 81, which are features of the present embodiment, will be described. The gain changing unit 80 calculates the gain coefficient of the variable coefficient unit 81 based on the signal level sent from the frequency identifying unit 40. Specifically, when the output of the frequency identification means 40 is Va, the calculation coefficient is K, and the threshold is Vth, K / Vth is a gain coefficient when Va <Vth, and K / Va is a gain coefficient when Va ≧ Vth. And An example of the above calculation is shown in FIG. FIG. 9 shows gain coefficients calculated when Sig_a has a constant amplitude level and the frequency changes from 10 kHz to 100 kHz.

  By calculating the gain coefficient 81 based on the output level of the frequency discriminating means 40 by these methods, it is possible to effectively reduce the noise signal in the high frequency range, thereby reducing the power consumption of the control system and stabilizing the control response. Can be realized.

  In the first and second embodiments, the high frequency noise is reduced by using the gain changing means and the frequency identifying means for the actuator control of the optical disc apparatus, but the effect of the present invention is not limited to this. In other words, it is a feedback control system such as hard disk drive tracking control, especially when it is necessary to secure a phase margin to realize the stability of the control system, high frequency noise is almost eliminated without reducing the phase margin. It is possible to reduce.

DESCRIPTION OF SYMBOLS 1 ... Disk, 2 ... Optical pick-up unit, 3 ... Laser diode, 4 ... Objective lens, 5 ... Focus actuator, 6 ... Tracking actuator, 7 ... Pick-up feed motor , 8 ... Detector, 10 ... Focus error signal generating means, 11 ... Focus control signal generating means, 12 ... Focus actuator driving means, 20 ... Tracking error conversion means, 21 ... Tracking Control signal generating means, 22 ... tracking actuator driving means, 23 ... feed motor control means, 24 ... feed motor driving means, 30 ... spindle motor, 31 ... frequency generating means, 32 is a motor Control means,
40: Focus error signal frequency identifying means, 50: Focus gain changing means, 60: Tracking error signal frequency identifying means, 70: Tracking gain changing means, 41: Delay memory means, 42 ... subtracting means, 43 ... absolute value calculating means, 51 ... gain coefficient a, 52 ... gain coefficient b, 53 ... switching means,
80... Focus gain changing means 81... Variable coefficient means 110... Focus phase compensation means 111... Focus low frequency compensation means 112. Compensation means 211... Tracking low frequency compensation means 212.

Claims (11)

An optical disk device using an optical pickup,
An objective lens for focusing the light spot on the optical disc;
A focus actuator for driving the objective lens in the direction of the optical disk rotation axis;
A tracking actuator for driving the objective lens in the radial direction of the optical disc;
A detector for converting the reflected light from the optical disc of the light spot into an electrical signal;
A focus error signal generating means for generating a focus error signal based on an output from the detector;
Tracking error signal generating means for generating a tracking error signal based on an output from the detector;
A focus control unit that generates a control signal for positioning the light spot on a predetermined recording / reproducing surface based on the output of the focus error signal generation unit, and a predetermined track based on the output of the tracking error signal generation unit Tracking control means for generating a control signal for positioning to the focus actuator driving means for driving the focus actuator based on the output of the focus control means;
Tracking actuator driving means for driving the tracking actuator based on the output of the tracking control means;
At least one frequency identifying means for identifying a frequency of the focus error signal or a second frequency identifying means for identifying the frequency of the tracking error signal;
At least one gain changing means of a first gain changing means for changing a gain of a control loop for focus control for controlling the optical pickup or a second gain changing means for changing a gain of a control loop for tracking control, Have
In the control loop of at least one of the feedback control circuit for the focus control and the feedback control circuit for the tracking control, the gain changing means is arranged to be a component of the control loop, and the frequency identifying means is the control loop Placed so as not to be a component of the loop,
The gain changing means changes the gain based on the output of the frequency identification means, thereby changing the gain of the control loop for the signal in the control loop depending on the magnitude and frequency of the signal level. An optical disc apparatus characterized by the above. A digital circuit,
Frequency identification means;
Gain changing means,
In the control loop of the feedback control circuit using the digital circuit, the gain changing means is arranged to be a component of the control loop, and the frequency identification means is arranged not to be a component of the control loop,
The gain changing means changes the gain based on the output of the frequency identifying means, thereby changing the gain of the control loop with respect to the signal in the control loop based on the magnitude and frequency of the signal level. A featured digital circuit. A digital circuit according to claim 2, comprising:
2. The digital circuit according to claim 1, wherein the frequency discriminating unit calculates an output signal based on a signal b preceding the input of the gain changing unit and a signal c subsequent to the output of the gain changing unit. A digital circuit according to claim 2, comprising:
The frequency identification means has a delay memory;
The frequency discriminating unit calculates an output signal based on an absolute value of a difference between a signal b before the input of the gain changing unit and a value one sample before the signal c after the output of the gain changing unit. A digital circuit characterized by A digital circuit according to claim 2, comprising:
The gain changing means includes
Having at least two or more gain means (gain means 1, gain means 2,..., Gain means n) and switching means,
A digital circuit that selects gain means to be integrated with an input signal a of the gain changing means based on an output of the frequency identifying means. A digital circuit according to claim 2, comprising:
The gain changing means includes
If the output of the frequency identification means is less than a predetermined value, set a predetermined gain value,
When the output of the frequency identification means is greater than or equal to a predetermined value, a smaller gain value is calculated based on the output of the frequency identification means, the smaller the gain value being less than the predetermined gain value and the higher the output value level of the frequency identification means. A digital circuit characterized by: A digital circuit according to claim 2, comprising:
In the feedback control circuit using the digital circuit,
Switching means for forming a feedback loop;
Error signal convergence detection means for detecting that the controlled object has stably converged within a predetermined control target range;
The gain changing means includes
Based on the output of the convergence detection means, before the control error converges stably within a predetermined control target range, a predetermined gain value is set regardless of the output of the frequency identification means, and the control target is predetermined. A digital circuit characterized in that the gain is changed based on the output of the frequency discriminating means after having converged stably within the control target range. A digital circuit according to claim 2, comprising:
In the feedback control circuit using the digital circuit,
When the feedback circuit has a phase compensator, the gain changing means is installed between a control output and the phase compensator. A digital circuit according to claim 2, comprising:
In the feedback control circuit using the digital circuit,
When the feedback circuit includes a phase compensator and a low frequency compensator, and the phase compensator and the low frequency compensator are arranged in parallel,
The digital circuit, wherein the gain changing means is arranged in series with the phase compensator and arranged in parallel with the low frequency compensator. An optical disk device using an optical pickup,
An objective lens for focusing the light spot on the optical disc;
A focus actuator for driving the objective lens in the direction of the optical disk rotation axis;
A tracking actuator for driving the objective lens in the radial direction of the optical disc;
A detector for converting the reflected light from the optical disc of the light spot into an electrical signal;
A focus error signal generating means for generating a focus error signal based on an output from the detector;
Tracking error signal generating means for generating a tracking error signal based on an output from the detector;
A focus control unit that generates a control signal for positioning the light spot on a predetermined recording / reproducing surface based on the output of the focus error signal generation unit, and a predetermined track based on the output of the tracking error signal generation unit Tracking control means for generating a control signal for positioning to the focus control means, focus actuator driving means for generating a focus drive signal based on the output of the focus control means, and driving the focus actuator;
Tracking actuator driving means for generating a tracking drive signal based on the output of the tracking control means and driving the tracking actuator;
At least one gain changing means of a first gain changing means for changing a gain of a control loop for focus control for controlling the optical pickup or a second gain changing means for changing a gain of a control loop for tracking control, Have
The gain changing means adds a sine wave signal having a predetermined amplitude to at least one of a focus error signal, a tracking error signal, a focus drive signal, and a tracking drive signal according to the frequency of the sine wave signal. An optical disc apparatus characterized by changing the gain of the control loop and changing the gain of the control loop according to the amplitude of the Sin wave signal when a Sin wave signal of a predetermined frequency is added. A digital circuit,
Frequency identification means;
Gain changing means,
In the control loop of the feedback control circuit using the digital circuit, the gain changing means is arranged to be a component of the control loop, and the frequency identification means is arranged not to be a component of the control loop,
The gain changing means changes the gain of the control loop according to the frequency of the sine wave signal when the sine wave signal having a predetermined amplitude is added to the control loop, and adds the sine wave signal of a predetermined frequency. And a gain of the control loop is changed according to the amplitude of the Sin wave signal.

Images