JPS62149043A - Tracking controller - Google Patents

Abstract

PURPOSE:To attain high-efficiency drive of a tracking actuator part by switching and changing a tracking drive voltage in response to the result of external vibration detection. CONSTITUTION:A tracking error signal by an optical pickup 13 and a tracking error signal generating circuit 14 or the like is converted into a pulse width modulation signal via a phase compensation circuit 15 and a PWM conversion circuit 16. The peak level of the pulse width modulation signal is controlled by a 13TL drive circuit 18 amplifying a large voltage V2 in place of a voltage V1 when the vibration is large by using a changeover switch 22 switched depending on the detection result by an external vibration detection circuit 23 and the result is fed to an actuator driving a pickup 13. Thus, the tracking actuator is driven with high efficiency independently of the large/small external vibration and the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a disc playback device such as a compact disc player, and in particular to tracking control that switches the tracking servo gain for a pickup element in response to external vibrations. Concerning improvements to equipment.

[Technical Prelude to the Invention] As is well known, in the field of audio equipment, in order to achieve high-density and high-fidelity recording and reproduction, information signals are converted into digitized data, such as discs. Digital recording and reproducing systems that record on a recording medium such as a magnetic tape or the like and reproduce the recorded information are becoming widespread. Of these, compact discs, which use discs as recording media, are currently the mainstream, in which a bit string corresponding to digitized data is formed on a disc with a diameter of +2 cm, and this is read optically. .

On the other hand, the Compact Disc Player V, which plays compact discs as described above, moves an optical pickup containing a semiconductor laser, a photoelectric conversion element, etc. from the inner circumference of the disc toward the outer circumference in a linear tracking manner. 5, the compact disc is moved at a constant linear velocity ((
', LV) method, the data recorded on the compact disc can be read line by line by rotating the disc.

Here, the optical pickup reads data recorded on the disk by focusing a laser beam emitted from the semiconductor laser onto a bit string of the disk using an objective lens serving as a pickup element. There is. Therefore, in order to prevent the objective lens from shifting from the bit string in the radial direction of the disk, that is, to prevent tracking deviation from occurring, the objective lens is subjected to tracking revolving.

This tracking + tobo generates a tracking error signal corresponding to the tracking deviation of the objective lens based on the data read by the optical double knob, and generates a voltage signal based on this tracking error signal. This is done by supplying the objective lens to a tracking actuator section for moving it in the tracking direction.

By the way, recently [Yo, Compact Disc Play 1]
7 is also becoming smaller and lighter, and it is being promoted to introduce it as a portable device for so-called outdoor use. In such a case, a battery will of course be used as a power source, so designing a compact disc player 87 that consumes less power M and can operate at low voltage will be a major challenge in the future.

Therefore, PWM (Pulse Width Modulation) is currently used because it has a high conversion efficiency from electrical energy to kinetic energy.
Techniques have been used to generate a voltage signal to be applied to the tracking actuator section.

FIG. 4 shows a conventional compact disc player using such PWMi technology.

That is, 11 in the figure is a disk, and the disk motor 12
It is designed to be rotationally driven by.

An optical pickup 13 is installed at the bottom of the disk 11 in the figure so as to be movable in the radial direction of the disk 11. And this optical pickup 13
is moved in the radial direction of the disk 11 by the rotational force of a pickup feed motor (not shown).

Here, when the disc 11 is being played back, a signal obtained from the optical pickup 13 is supplied to the tracking error signal generation circuit 14, so that tracking deviation of an objective lens (not shown) occurring in the optical pickup 13 can be dealt with. A tracking error signal TF is generated.

This tracking signal TE is then supplied to a PWM conversion circuit 16 via a phase compensation circuit 15. The PWM modulation circuit 16 generates a pulse width modulation signal by comparing the levels of the signal output from the phase compensation circuit 15 and the reference triangular wave signal output from the triangular wave generation circuit 17.

Upon completion, the pulse width modulated signal is transmitted to the BTL driving circuit 18.
is supplied to This BTL drive circuit 18 has a power supply terminal 1
The peak level of the pulse width modulation signal is amplified up to the power supply voltage applied to the target optical pickup 13, and the objective lens provided in the optical pickup 13 is moved in the tracking direction.
This is supplied to a tracking 7 processor section (not shown) for stirring, and a tracking nervore is applied here so that the objective lens accurately traces the bit string of the disk 11.

By the way, the above-mentioned dragging (compact disc player 1 equipped with 1-bo means) 1. :J) Then,
For example, if external vibrations are large and tracking errors are likely to occur, it becomes necessary to increase the tracking servo gain in order to keep the objective lens focused on the target bit string. In other words, the tracking servo gain is switched between the normal playback state of the disc 11 and the state where the external force is large.

[Problems with the paradoxical technology] However, in the conventional compact disc player using the PV/M technology as described above, the efficiency when driving the load (tracking actuator part) with the pulse width modulation signal, that is, the efficiency from the electric energy. The following problems arise in terms of conversion efficiency into kinetic energy.

First, the power W when driving a "C load" with a pulse width modulation signal is expressed as W-E2/R, where R is the load resistance and E is the effective voltage of the pulse width modulation signal.

Here, as shown in FIG. 5, if one period of the pulse width modulation signal is T and the instantaneous voltage is e, then the effective voltage E is Wave (harmonic) component en (n=1.2,3
．． ...), and if the maximum voltage of the sine wave component en is E maxn en =Emaxn-5in (nωt+θn), then the effective voltage E is (however, Eo is a direct current (DC) component). Become.

Here, when the pulse width modulation signal shown in FIG. 5 is transformed into a Fourier series, with its peak value as V and its on time as τ, the following is obtained. Then, by substituting ω=2π/T and changing the fortune, we get the following. From this, the effective voltage E can be found as follows.

By the way, the pulse width modulation signal has its DC component E[l
Only (-τv,,'T) is the effective voltage that is substantially converted into kinetic energy), and the others become harmonic components and become hornless, so the direct current component Ea included in the effective ? If we calculate 1 (EO/'E), the conversion efficiency will be calculated by 4C. Also, as is clear from the above equation, the effective degree pressure E is τ/T, that is, the ratio of the on time τ of the pulse width modulation signal to the period T (hereinafter f niter r
It can be seen that the conversion efficiency depends on the duty ratio.

And Figure 6 shows the wave height! Carrier frequency 4 at 111V
A 4.1kHz pulse width modulation signal is supplied to a pure resistor R,
FIG. 3 is a characteristic diagram showing changes in conversion efficiency when the duty ratio is changed. In this case, the period T of the pulse width variable "A" signal is kept constant, and the duty ratio is varied by varying the on time τ.

The characteristic shown by the solid line in the figure is the actually measured DC component level E! ] is divided by the effective voltage E obtained by the actual 1]111. ,Also,
The characteristic shown at the middle point fI'U in the figure is the effective voltage E obtained by calculating the voltage up to the 100th harmonic using the above formula for the actually measured i DC component slope EO, which is 11. It shows the change in theoretical conversion efficiency.

Therefore, as can be seen from FIG. 6, it has become clear experimentally and experimentally that as the duty ratio becomes smaller, that is, as the on-time τ becomes shorter, the conversion efficiency becomes significantly lower.

This means that when trying to obtain the same effective voltage Va from two types of pulse width modulation No. 78 with different peak values as shown in FIGS. 7 and 8, FIG. It is shown that the pulse width modulation signal shown in FIG. 7 has higher conversion efficiency than that shown in FIG.

For this reason, when the disc 11 is being played back without external vibration, the pulse width modulation signal supplied to the tracking actuator section has a long on time and a low peak value.
However, it is necessary to obtain an effective voltage that can be used as a tracking 1 novo gain.

This is advantageous in terms of efficiency.

However, as mentioned above, the pulse width modulation signal supplied to the tracking actuator is high enough to increase the tracking servo gain by changing its duty ratio when external vibrations are large. It is also required that an effective voltage can be obtained.For this purpose, the peak value of the pulse width modulation signal must be set high.

Here, the peak value of the pulse width modulation signal supplied to the tracking actuator section is determined by the power supply voltage applied to the BTL drive circuit 18. Therefore, if the power supply voltage is set high in consideration of when the external vibration becomes large, the ON time of the pulse width modulation signal will be shortened, that is, the duty ratio will be reduced during playback of the disk 17 without external vibration. It must be made small to obtain an effective voltage that can be used with a low tracking servo gain, and as mentioned above, the conversion efficiency becomes extremely poor, resulting in the problem of increased power consumption.

[Purpose of the Invention] This invention was made in consideration of the above circumstances, and is an extremely effective method that can drive the tracking actuator section with high efficiency in both large and small external vibration states, and achieves low power consumption. Good drugging system 1st floor
The purpose of the present invention is to provide an Il device.

[Summary of the invention 1 That is, the tracking according to this invention (1O
The R position includes a tracking error signal generation means for generating a tracking 1 signal corresponding to the tracking deviation of the cough pickup by filling data read from the disk via the pickup, and a tracking error signal generation means for generating a tracking error signal corresponding to the tracking deviation of the cough pickup. : Pulse width modulation means for converting the tracking error signal outputted from the No. 3 generation means into a pulse width modulation signal, and the 11 value level of the pulse width image adjustment signal outputted from the buffless width modulation system. In a disc playback device, the disc playback device is equipped with a drive means that determines the power supply supplied from the outside according to the power supply and constantly supplies it to a tracking actuator that moves the pickup element in the tracking direction. External vibration detection means that detects that the external S value given to 5 has become larger than a predetermined value and generates a detection signal 8, and a power supply voltage that is supplied to the drive means,
Is it set to the first voltage level when no detection signal is generated from the external vibration detector IQ, and when a detection signal is generated from the external vibration detection means? ! By providing a power supply switching means for switching to a second voltage level higher than the voltage level of 41, the trass: It is designed to be able to be driven by electricity, thereby reducing electricity costs.

[Embodiment of the Invention] Below, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, the same parts as in FIG. 4 are indicated by the same symbols, and only the different parts will be explained here. In addition, 20 and 21 in FIG. 1 are power supply terminals 1, respectively. Among these, a low level power supply voltage ■1 is applied to the power supply terminal 20, and to the power supply terminal 2,
A high level power supply voltage v2 higher than the power supply voltage v1
is applied. And these power terminals 20.21
are the first and second fixed contacts 22a of the changeover switch 22
, 22b, respectively.

Here, the changeover switch 22 has a common contact 22c.
is connected to the power input terminal of the [3TL drive circuit 18]. In the changeover switch 22, the movable contact piece 22d, which is always in contact with the common contact 22c, is connected to the first
Switching is performed by selectively connecting to the second fixed contacts 22a and 22b. In this case, the changeover switch 22 selects the movable contact piece 22 (173<first and second fixed contacts 22a) depending on whether the output signal from the external vibration detection circuit 23 is I-level or H level.
, 22b are selectively connected &c.

Here, the external vibration detection circuit 23 determines whether the external S motion given to the compact disc player i is within a predetermined value (within or more than a predetermined range) based on the tracking 1 signal TE. A detection signal of L level is generated when the height is higher than a predetermined value, and a detection signal of H level is generated when the voltage is higher than a predetermined value.

Therefore, in a state where external vibration is small, the power supply voltage v1 is applied to the BTL drive circuit 18, and the peak value of the pulse width modulation signal supplied to the tracking actuator section is kept low, and the duty ratio is increased. Accordingly, the tracking actuator section can be driven in an efficient manner. In addition, in a state where external vibration is large, the power supply V2 is applied to the BTL drive circuit 18, and the tracking actuator)
The pulse width 92 supplied to the oscillator can increase the peak value of the tuning bow, and the tracking servo gain can be increased.

Therefore, according to the configuration of the above embodiment, depending on whether the external vibration is large or small, -C1BTL driving circuit 18 is marked 1]0! By switching the power supply voltage T, the pulse height IMj of the pulse decay modulation signal supplied to the tracking actuator 81 is changed! As a result, tracking servo can be performed efficiently in both large and small external vibration states, and the electric power 'a
It is possible to reduce costs.

Here, FIG. 2 shows the configuration of the BTL drive circuit 18. That is, this is a pair of inputs 9;
The pulse width modulation signal outputted from the PWM conversion circuit 16 is supplied to the switches 24 and 25 in reverse phase, and the switch 21
3.27 and switch 28.29 are turned on and off in an inverse relationship to each other, a mark is placed on the load resistance R (tracking actuator section in this case) and on the power input terminal 30;
''n and tζζ power supply voltage, - is supplied at a duty ratio corresponding to the pulse width modulation signal.

For example, if the power supply voltage V1 is applied to the power supply input terminal 30, the load resistor R is supplied with a pulse width modulated signal having a peak value v1 as shown by the solid line in FIG. In addition, the above '' is connected to the electric J,'2 input terminal 30.
Assuming that a city power source II V 2 is applied, the load resistance R has a wave height of 111 V as shown by the dots in Figure 3.
Two pulse width modulated signals will be supplied.

In this case, as clearly shown in FIG. 3, even if the peak value of the pulse width modulated signal changes, the duty ratio does not change, so 7! ! When the voltage is switched to V2, the dynamic range of the BTL drive circuit 18 can be expanded and the gain can be increased, which is more effective in increasing the tracking servo gain.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications within the scope of the invention.

[Effects of the Invention] Therefore, as detailed above, according to the present invention, the tracking actuator section can be driven with high efficiency in both large and small external vibration states, and extremely low power consumption can be achieved. A good tracking 7-11 Shu device can be provided.

[Brief explanation of drawings]

Fig. 1 is a block configuration diagram showing an example of the drag control device according to the present invention, Fig. 2 is a circuit groove diagram showing the configuration of the BTL driving circuit of the I'i11 embodiment, and Fig. 3 FIG. 4 is a waveform diagram for explaining the operation of the same embodiment; FIG. 4 is a block configuration diagram showing conventional tracking 1!1■ means; FIG.
The figure is a waveform diagram for explaining the pulse width modulation signal, Figure 6 is a characteristic curve diagram showing the relationship between the T-neity ratio and efficiency of the pulse width modulation signal, and Figures 7 and 8 are the problems of the conventional method. FIG. 2 is a waveform diagram for explaining. 11... Disc, 12... Disc motor, 13
. . . Optical pickup, 14. [・Ragging error signal hormonal circuit, 15. . . Phase compensation circuit, 16.
... PWM conversion circuit, 17 ... Triangular wave generation circuit, 18
...BJLI! 1186 circuit, 19...power terminal,
20.21...power terminal, 22...changeover switch,
23...External vibration detection circuit, 24.25...Input terminal, 26-29...Switch, 30...Power input terminal. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 7 Figure 8

Claims (1)

[Claims] tracking error signal generation means for generating a tracking error signal corresponding to the tracking deviation of the pickup element based on data read from the disk via the pickup element; and a tracking error signal outputted from the tracking error signal generation means for pulsing. A pulse width modulation means for converting into a width modulation signal, and a peak level of the pulse width modulation signal outputted from the pulse width modulation means is determined according to an externally supplied power supply voltage, and the pickup element is moved in a tracking direction. and a drive means for supplying a tracking actuator to a tracking actuator section, the external vibration detection means detecting that external vibration applied to the disk reproduction apparatus becomes larger than a predetermined value and generates a detection signal. , the power supply voltage supplied to the drive means is set to the first voltage level in a state where no detection signal is generated from the external vibration detection means, and the power supply voltage supplied to the drive means is set to the first voltage level in a state where a detection signal is generated from the external vibration detection means. A tracking control device comprising: power supply switching means for switching to set a second voltage level higher than the first voltage level.