JPS5857609A - Digital audio disk player - Google Patents

Abstract

PURPOSE:To avoid a mistake of demodulation when the synchronizing signal is dropped out by performing the demodulation by means of a subsynchronizing signal and at the same time to avoid the rotational disturbance of a motor when the synchronizing signal is dropped out by controlling the motor rotation in response to the output of comparison. CONSTITUTION:A synchronizing signal detecting circuit 1 produces a synchronizing signal (a) of a frequency f1 with every detection of a synchronizing part. A differentiating circuit 2 produces fine differential pulses with the signal (a). At the same time, an oscillating circuit 3 generates an oscillating output (d) of a frequency f2 which is N times as high as the signal (a) and supplies it to the 1st frequency dividing circuit 4. Thus the circuit 4 divides the output (d) and transmits a subsynchronizing signal (e). The circuit 2 performs the matching of timing by resetting the circuit 4 with the timing of the synchronizing signal (b). As a result, the stable signal (e) is produced from the circuit 4 with the interpolation of the dropped-out synchronizing signal althrough the signal (b) has a dropout as long as the phase is once matched.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital audio disc player, and particularly to a digital audio disc player that can perform reliable demodulation and rotation control even when a synchronization signal included in a playback signal is lost in detection. This invention relates to a disc player.

A digital audio disc player digitizes audio signals, synchronization signals, etc. and optically records them at high density on the surface of a disc at a constant linear velocity.The signal format recorded on the disc is, for example, as shown in Figure 1. It is determined as shown below. That is, in this method, one frame is made up of a fixed number of bits (for example, 588 bits), and these frames are consecutively recorded on the same disk at a constant linear velocity. The signal format of each frame is the synchronization part A.
and an information section B, and the synchronization section A is located at the beginning of each frame. As shown in Fig. 1, the synchronization section A consists of 22 pits, and when the first 11 bits are continuous and part of the bits, the following 11 bits are continuous @1'', and the first 11 bits are continuous. When the value is '1', the following 11 bits are continuously '0'.
In this case, the first 11 bits are set to be the opposite of the last bit of the previous frame, and in this way the predetermined unit bit ( 1 bit) is “0” or ’
The 7-o-mat consisting of a series of "l" characters is limited to only this synchronization part A in one frame.

That is, the information section B is configured so that a format in which 11 bits of @0'' or ``1'' are consecutive does not occur under any circumstances.

In addition, the information section B always transmits the 61# signal or the
Since the # signal is a continuous signal, the information part B is represented as a continuous signal only over the range of 2<B<t1 bit.

A digital audio disc player configured in this manner can easily obtain a high-fidelity audio signal by optically reading and demodulating the digital information on the disc at a constant linear velocity. It is.

In this case, the most important thing for high-fidelity playback is to extract the synchronization signal necessary for demodulation as a continuous signal without any dropout, and to increase the speed of the disk rotation so that the linear velocity is always constant. It is to perform accurate rotation control.

However, in digital audio disc players, the synchronization signal included in the playback signal is set to a specific pit length and playback is required under conditions of constant linear velocity. Signal detection becomes extremely difficult, and for some reason the detected synchronization signal may be missing. In this case, if a dropout occurs in the synchronization signal, the demodulation section performs the demodulation operation based on this synchronization signal, and therefore demodulation becomes impossible in the missing portion of the synchronization signal. Further, the phase of the synchronization signal is compared with a reference signal, and the rotation of the disk rotation motor is controlled using a signal corresponding to this phase difference, thereby controlling the linear velocity and muddying. In this case, if a synchronization signal is missing, the phase comparison output for the missing synchronization signal will fluctuate greatly, and as a result, the rotation of the disk rotation motor controlled by the phase comparison output will vary greatly. It has the problem of changing.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a Digimol Audio Nice Player that can reliably perform demodulation even when a portion of the detected synchronization signal is missing.

Another object of the present invention is to provide a digital audio disc that can reliably and stably control the rotation of the disc to a predetermined linear velocity even when a part of the detected synchronization signal is missing. The goal is to provide a player. A digital audio disc player according to the present invention will be explained in detail below using one drawing.

FIG. 2 is a circuit diagram of a main part showing an example of a digital audio disc player according to the present invention. In the figure, 1 is a synchronous signal detection circuit that receives a reproduced signal a supplied from a pickup (not shown) as an input, detects the above-mentioned synchronous part A, and generates a synchronous signal, and 2 differentiates the synchronous signal A. 3 is an oscillation circuit that generates a thin differential pulse C synchronized with the rising edge of the differential pulse C, and 3 is an oscillation circuit that outputs an oscillation signal d whose frequency is N times higher than that of the regular synchronization signal outputted from the synchronization signal detection circuit 1. occurs. 4 is a first frequency dividing circuit that divides the oscillation output d supplied from the oscillation circuit 4 by N,
Each time the differential pulse C is supplied from the differentiating circuit 2, it is reset and supplies the sub-synchronizing signal e to a demodulating circuit (not shown).

Reference numeral 5 denotes a second frequency dividing circuit, which outputs a divided output g obtained by frequency-dividing the oscillation output d output from the oscillation circuit 3 by N. 6 is a phase difference detection circuit which inputs the sub synchronization signal e and the branch output g and sends out a phase difference signal at a level corresponding to the phase difference between the two; 7 is a circuit which detects only the low frequency components contained in the phase comparison signal; The rotation control signal 1 is supplied to a motor control circuit (not shown).

In the circuit configured in this manner, the synchronization signal detection circuit 1 generates a synchronization signal a with a frequency f every time it detects the synchronization part A described in FIG. Occur.

The rising portion of this synchronizing signal a is differentiated in a differentiating circuit 2 to generate a thin differential pulse A.

On the other hand, the oscillation circuit 3 has N
An oscillation output d having twice the frequency f is generated and supplied to the first frequency dividing circuit 4. Therefore, the first frequency dividing circuit 4 divides the frequency of the oscillation output d and sends out the sub-synchronization signal e. In this case, the frequency f! of the fourth period signal of the first frequency dividing circuit is f! The frequency f2 of the sash synchronization signal e becomes fl=f. And in this case,
Since the first frequency dividing circuit 4 uses as a reset input the differential output C obtained by differentiating the rising part of the synchronization signal S generated from the differentiating circuit 2, the sub synchronization signal e is generated at the next period of the synchronization signal S which is reset. synchronization is achieved and the phase becomes b =
= e. Therefore, the differentiating circuit 2 adjusts the timing by resetting the first frequency dividing circuit 4 at the timing of the synchronizing signal. For this,
- If phase adjustment is performed, even if the synchronization signal output from the synchronization signal detection circuit 1 is missing, the first frequency divider circuit 4 will generate a stable sub-synchronization signal that has interpolated the missing synchronization signal. A demodulation circuit (not shown) performs a reliable demodulation operation using this sub-synchronization signal e.

On the other hand, the oscillation output d of the oscillation circuit 3 is frequency-divided by N in the second frequency dividing circuit 5, and the frequency-divided output is outputted as g. The frequency f4 of the frequency-divided output g is the same as the frequency f of the synchronizing signal S, but the phases of the two do not always match because the timing is not aligned.

The frequency-divided output g generated in this manner is compared with the sub-synchronization signal e in the phase comparison circuit 6, and a phase difference signal having a level corresponding to the phase difference is output. This phase difference signal is supplied to a motor control circuit (not shown) as a rotation control signal 1 after a high frequency component is removed in a rotor filter. Therefore, the disk rotation motor (not shown) is controlled by a phase-locked loop (PLL) K, and when the phase of the synchronizing signal matches the divided output g of the second frequency divider 50, the readout part of the disc is controlled. It becomes stable at the point when the linear velocity applied reaches a predetermined constant value.

In this case, even if the synchronization signal output from the synchronization signal detection circuit 1 is missing for some reason, the sub synchronization signal e is stably output by interpolating this missing portion. Therefore, this sub-synchronization signal e and the reference signal are frequency-divided and the frequency divided by nine is output g.
The rotation control system, which detects the phase difference between the This will prevent the motor from rotating erratically.

As explained above, the digital audio disc player according to the present invention sends out a sub-sync signal that synchronizes with the detected synchronization signal and interpolates the part when the synchronization signal is missing. By demodulating using the synchronization signal, demodulation errors can be prevented when the synchronization signal is missing. In addition, by comparing the phase of the above sub-signal and the reference signal and controlling the rotation of the motor in accordance with this comparison output, disturbances in the rotation of the motor when the synchronization signal is missing are prevented and stable rotation is maintained. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a signal format of a digital audio disc, and FIG. 2 is a circuit diagram showing an embodiment of a digital audio disc player according to the present invention. 1... Synchronous signal detection circuit, 2... Differential circuit, 3...
- Oscillation circuit, 4... first differentiating circuit, 5... second differentiating circuit, 6... phase comparison circuit, 7... low pass filter.

Claims (2)

[Claims] (1) In a digital audio disc player that detects a synchronization signal included in a playback signal at regular intervals and demodulates the information signal included in the playback signal based on the synchronization signal, the synchronization signal an oscillation circuit that generates an oscillation output having a frequency N times higher than that of the oscillation circuit; A digital audio disc player comprising: a first frequency dividing circuit for generating a sub-synchronizing signal; and demodulating the information signal based on the sub-synchronizing signal. (2) By detecting the synchronization signal included at regular intervals in the reproduced signal, extracting the phase difference signal between the synchronization signal and the reference signal, and supplying it to the motor control circuit, rotation control is performed with a constant linear velocity. In a digital audio disc player, N
an oscillation circuit that generates an oscillation output having twice the frequency; and a sub-synchronization signal that is reset by the rise of the synchronization signal and whose timing is aligned with the synchronization signal by dividing the oscillation output of the oscillation circuit by N. A first frequency dividing circuit, a second frequency dividing circuit that divides the oscillation output of the oscillation circuit by N, and detecting a phase difference between the sub synchronization signal and the output of the second frequency dividing circuit to generate a phase comparison signal. A digital audio disc player comprising: a phase ratio soft circuit that generates a phase ratio, and supplies the phase comparison signal to the motor control circuit as the phase difference signal.