JPS63178782A - Phase servo-apparatus - Google Patents

Abstract

PURPOSE:To simplify the composition of a circuit, by using arbitrary sampling frequency, and by setting arbitrary frequency characteristic and gain. CONSTITUTION:By the rotating speed of a motor 2 rotating a CD4 with a phase servo-apparatus, beam detecting signal Li obtained by a pickup 6 with laser beams is applied to a synchronizing signal detecting circuit 8, and is detected as synchronous signal Sr. Besides, reference synchronizing signal S0 is obtained from an oscillator 12 via a frequency divider 14. both the signals Sr, S0 are applied to a phase difference counter 24, and the phase difference of both the signals is detected. The input of the data Dp of the phase difference to a PWM circuit 28 via a filter 26 is provided, and pulse-width-modulated output is obtained on a time base, as pulse to compensate for the phase difference. Then, the output is applied to the motor 2 via driver 30, and is controlled so that the rotating linear velocity of the motor 2 may be set to be constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase servo device suitable for controlling the rotation of a motor of an optical disc playback device or the like.

[Conventional technology]

Conventionally, in an optical disc playback device that plays back music information recorded on a compact disc (CD) or the like, as shown in FIG. A phase servo device is used for this purpose.

The rotational linear velocity of the CD 4 is determined by applying a photodetection signal detected through a pickup 6 using laser light as a detection medium to a synchronization signal detection circuit 8, and then generating a synchronization signal Sr shown in F in FIG.
Detected as . The period of the synchronization signal S1 is obtained by detecting the maximum focus 11T recorded on the CD4. On the other hand, a highly accurate oscillator 12 using a crystal oscillator 10
By oscillating a reference signal at , and dividing the frequency of the oscillation signal by a frequency divider 14, a reference synchronization signal S shown in G in FIG. 5 is generated. get. This reference synchronization signal S. and the synchronizing signal Sr reproduced from the CD 4 are applied to the phase comparator 16, and the phase comparator 16 generates a phase difference signal Ph representing the phase difference ΔT between the two, as shown at H in FIG. After setting a necessary servo gain in the gain setting circuit 18 to the phase difference signal Ph generated by the phase comparator 16, necessary frequency components are extracted in addition to the carrier filter 20 and applied to the driver 22. The driver 22 generates a drive output in the direction of decreasing the phase difference ΔT in accordance with the phase difference signal Ph, and feeds it back to the motor 2, so that the rotational linear speed of the motor 2 is controlled to be constant.

[Problem that the invention seeks to solve]

By the way, in this phase servo device, the carrier frequency is as low as 7.35kHz, so the carrier filter 2
0 becomes a large-scale circuit with capacitors and resistors added,
Moreover, it has drawbacks such as the difficulty of setting the gain and filter coefficients.

Therefore, the present invention aims to simplify a large-scale filter and the like, simplify the circuit configuration, and simplify the setting of gains and filter coefficients.

[Means for solving problems]

The phase servo device of the present invention uses a phase difference detection means (phase difference counter 24 ) and phase difference detection means (
a digital filter 26 for obtaining phase difference data of an arbitrary frequency component and an arbitrary gain from the phase difference data detected by the phase difference counter 24);
It is equipped with a signal conversion means (pulse width modulation circuit 28) that converts the phase difference data extracted in the above into a rotational drive signal for the motor 2.

[For production]

With this configuration, the synchronization signal Sr reproduced from the disc (CD4.) and the reference synchronization signal S.

The phase difference ΔT with the phase difference detection means (phase difference counter 24
) is detected as digital value phase difference data, so this phase difference data is applied to the digital filter 26 to obtain phase difference data of necessary frequency components and gains from the phase difference data.

This phase difference data is converted into signal converting means (pulse width modulation circuit 2).
In addition to step 8), by converting the signal into a rotational drive signal for the motor 2 and applying it to the motor 2, the rotational linear velocity of the motor 2 can be controlled to be constant.

〔Example〕

FIG. 1 shows an embodiment of the phase servo device of the present invention.

The rotational speed of the motor 2 that rotates the CD 4 is determined by adding a photodetection signal L1 obtained by a pickup 6 using laser light as a detection medium to a synchronization signal detection circuit 8, and generating a synchronization signal Sr as shown in F in FIG. Detected. Further, a reference signal obtained by an oscillator 12 using a crystal oscillator 10 is frequency-divided by a frequency divider 14 to obtain a reference synchronization signal S shown in G in FIG. get.

Reference synchronization signal S. and the synchronization signal S played from CD4.
, , is added to the phase difference counter 24 as a phase difference detection means that detects the phase difference T between the two as a digital value, and detects the phase difference ΔT between the two as digital data that is a count value of the clock pulse CLK. . The phase difference data D generated by the phase difference counter 24 is applied to a digital filter 26 to extract and output necessary frequency components and gains using a sampling frequency N-fs that is N times the carrier frequency fs. Then, the phase difference data D0 outputted by the digital filter 26 is converted into a drive control signal for the motor 2 by a digital pulse width modulation circuit (PWM circuit) 2 installed as a signal conversion means.
8, the signal is output as a pulse width modulated output (PWM output) VP by comparison with reference data such as reference triangular wave data or sawtooth wave data. This pulse width modulated output VP is obtained as a continuous pulse with a time width that compensates for the phase difference on the time axis.

This pulse width modulation output (2) is applied to the driver 30, and the drive output generated by the driver 30 based on the pulse width modulation output (V) is applied to the motor 2, so that the rotational linear speed of the motor 2 is controlled to be constant.

Next, FIG. 2 shows the digital filter 2 shown in FIG.
6. A specific configuration example of the PWM circuit 28 and driver 30 is shown.

The digital filter 26 includes a data conversion section 32 at its input section, and in this data conversion section 32, the phase difference data D added from the phase difference counter 24,
Sampling frequency N-f that is N times the carrier frequency fs
Zero data D2 is added by s. For example, if the phase difference data Dp from the phase difference counter 24 is taken as A in FIG. 3, and zero data D2 is added to this phase difference data DP with the sampling frequency N-fs=2fs, the data is shown in B in FIG. Converted data D, 2 is obtained.

Further, the filter circuit 34 of the digital filter 26 is
For example, F I R (Finite impulse
It consists of a Re5ponse (finite length impulse response) circuit. In the filter circuit 34, 36
．． 38.40.42.44 is a delay device composed of, for example, a 10-bit memory element, 46.48.50.52.5
4.56 represents a coefficient multiplier that multiplies the coefficients ao and alsaz"', and 58 represents an adder.

Each coefficient ao, al % a2 . . . is set by a control means such as a microcomputer (not shown) together with the sampling frequency N-fs. Therefore, the filter circuit 34 sets the necessary frequency characteristics and gain for the converted data DP2, so that, for example, as shown in C in FIG.
The zero data D2 in Z is converted into an approximate data value between the original data values, and is output as phase difference data Do having a sampling frequency N-fs and a necessary frequency component and gain.

And this phase difference data D. is added to the digital comparator 60 of the PWM circuit 28, and the storage element (RO
M) 62 is compared with reference data DE such as triangular wave data, and pulse width modulation is performed between the digital data. Triangular wave data and sawtooth wave data are previously recorded in the ROM 62 as reference data DE from the control means, and are read out by the read signal R. For example, as shown in D in FIG. 3, the phase difference data D0 is compared with the triangular wave data that is the reference data D, and based on the magnitude relationship between the two, the digital comparator 60 outputs the data as shown in E in FIG. , reference data D, exceeds the phase difference data D0 at H (high) level, and other times at L (
A PWM output V having a low) level is generated as a servo control output.

This PWM output Vp is applied to the base of the switching transistor 64 that constitutes the driver 30, so the transistor 64 outputs the PWM output V.

The motor 2 is electrically conductive during the H period, and the drive current Ir intermittently flows through the motor 2 during the electrically conductive period. That is, if the rotational linear speed of the motor 2 decreases, the conduction period of the transistor 64 increases, and if the rotational linear speed of the motor 2 increases, the conduction period of the transistor 64 decreases, so that the rotational linear speed of the motor 2 increases. It will be controlled at a constant level. Note that the diode 66 is for absorbing back electromotive force of the motor 2.

In this way, by using the PWM output (2) as a rotation drive signal for the motor 2, the transistor 64 can be directly switched, and the driver 30 can be simplified.

In addition, in the embodiment, the phase difference data D of the digital filter 26. The PWM circuit 28 is used as a signal conversion means for obtaining a rotational drive signal for the motor 2 from the digital filter 26, but the PWM circuit 28 is a digital-to-analog converter that converts the phase difference data D0 generated by the digital filter 26 into an analog value that is a rotational drive signal for the motor 2. A similar servo operation can be obtained even if configured.

〔Effect of the invention〕

According to this invention, it is possible to set any frequency characteristic and gain using any sampling frequency, so optimization of servo operation can be realized, and large-scale This eliminates the need for a filter, and the circuit configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the phase servo device of the present invention, FIG. 2 is a block diagram showing the specific configuration of the main parts of the phase servo device shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing a conventional phase servo device, and FIG. 5 is a diagram showing the operation of the phase servo device shown in FIGS. 1 and 4. 2...Motor 4...CD (disc) 24...Phase difference counter (phase difference detection means) 26...
・Digital filter

Claims (1)

[Claims] Phase difference detection means for comparing a synchronization signal reproduced from a disc with a reference synchronization signal and detecting a phase difference between the two as a digital value; and phase difference data detected by the phase difference detection means. A phase servo device comprising: a digital filter for obtaining phase difference data of an arbitrary frequency component and an arbitrary gain; and signal conversion means for converting the phase difference data obtained by the digital filter into a rotational drive signal for a motor.