JPS5856259A - Digital audio disk player - Google Patents

Abstract

PURPOSE:To interpolate the speed control with use of the output of a time constant circuit when a synchronizing signal drops out, by providing an analog switch and a time constant circuit at the output side of a phase comparator of a PLL. CONSTITUTION:When a linear speed gets out of the prescribed value, a part of the synchronizing signal drops out of a synchronizing signal detecting circuit 7 and is delivered. As a result, the phase difference signal Q has the big fluctuation. Then an analog switch 9 is opened to stop the signal Q. Thus no signal Q is supplied to a time constant circuit 10 while the signal Q is stopped. The break period of the signal Q is interpolated to avoid a sudden change of the output owing to a large time constant. The output of the circuit 10 which received a signal interpolation is fed to a driving circuit 12 to prevent a sudden change of control for a motor 1. When the synchronizing signal S is detected again, the switch 9 closes again to form a PLL. Then the revolution is continued with a constant linear speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a layer, and in particular to an improvement of a Momesar-2 circuit.

The Digital Society audio disc player digitizes audio signals and synchronization signals and records them optically at high density on the surface of the disc at a linear velocity, and the signal format recorded on the disc is, for example, as shown in Figure 1. It is determined as shown below. In other words, in this method, one frame consists of a certain number of bits (for example, 5
88 bits), and these frames are consecutively recorded on the same disk at a constant linear velocity.

The signal formant of each frame is synchronized@
h and an information section B, and the synchronization section A is positioned at the beginning of each frame. Synchronization part A
consists of 22 bits as shown in Figure 1, and when the first 11 bits are 0'' consecutively, the following 1
If 1 pit becomes ``1'' consecutively, and the first 11 bits are 1n consecutively, the following 11 bits become 0 consecutively.
”. 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 first 11 bits are set to be the opposite of the last bit of the previous frame. For formats in which bits) are 0" or 1#, this synchronization H is used in one frame.
Currently specified only for ISA. In other words, information part B is 0# or 1# in 11-bit units in any case.
It is configured so that a format with a series of . In addition, in order to completely prevent direct current conversion when there is no signal, the information part B is always a continuous signal of "1# signal or 0" over 3 or more focus points, so that the information part B is 2 < B < It will be represented as a continuous signal only over a range of 11 bits.

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

In this case, the most important thing for high-fidelity reproduction is to control the rotation of the disk with high precision so that the linear velocity is constant during reading. For this reason, in a digital audio disc player, the synchronization part A included in the playback signal is detected and used as a synchronization signal, and this synchronization signal is, for example, 7.35KHz.
A phase-locked loop (P
LL) is configured to perform constant linear velocity control.

However, in digital audio disc players, linear velocity fluctuations occur because the reading head moves during, for example, fast forwarding. As mentioned above, the synchronization signal is subject to special conditioning, so it cannot be detected unless the linear velocity matches the normal value, and the synchronization signal is detected when the linear velocity deviates from the normal value. There is a problem that phase lock control cannot be performed due to the small number of disc rotation motors, and as a result, the rotation of the disc rotation motor suddenly changes in an unintended direction.

Therefore, an object of the present invention is to provide a digital audio disc player in which the phase-locked loop operates and the speed of the disc rotation motor can be controlled even when the number of detected synchronization signals decreases to a certain extent. be.

In order to achieve such an object, the present invention provides an analog switch and a time constant circuit on the output side of the phase comparator in the phase lock loop provided in the speed control system of the disk rotating motor, and An eliphase lock loop is constructed by closing the analog switch, and when the synchronization signal is lost, the speed F control is interpolated using the output of the time constant circuit. below,
A digital audio disc player according to the present invention will be explained in detail using the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the digital audio disc player according to the present invention, and particularly shows a speed control system for the disc rotating motor. In the figure, reference numeral 1 denotes a disk that is rotated at high speed by a motor 2, and on the bottom side of this disk 1 there is a sensor that detects the reflected light of the light beam 3 that moves in the radial direction of the disk 1 and irradiates the disk surface. Reading head 4 converting into electrical signals
is provided. Reference numeral 5 denotes an amplifier for amplifying the reproduced signal outputted from the takeover head 4 to a value suitable for signal processing in the subsequent circuit; 6, the amplifier 5 shapes the reproduced signal sound supplied from the amplifier 5 into a pulse waveform; This is a waveform shaping circuit that maintains the synchronization signal detection circuit 7. Then, the synchronization signal detection circuit 7 detects the synchronization section A described in FIG. 1 included in the reproduced signal and outputs a synchronization signal. In other words, since the synchronization section A is constituted by a series of 11 bits 11111 or "0" as described above, the synchronization signal A is generated every time a reproduced signal matching this condition is detected. A phase comparison circuit 8 compares the phases of the synchronization signal supplied from the synchronization signal detection circuit 7 and the reference signal fr, and generates an output corresponding to the phase difference.

Reference numeral 9 denotes an analog switch, which is closed only when a synchronizing signal is supplied from the synchronizing signal detection circuit 7 (only when the synchronizing signal is supplied at a predetermined period) and is supplied from the phase comparator 8. Pass the phase difference signal. ]0 is a time constant circuit provided at the output fllll+ of the analog switch 9, and 11 is a low-pass filter, which has a time constant of 18 times.
Only the low frequency signal is extracted from the output of 10 and output. Reference numeral 12 denotes a motor drive circuit that controls the rotation of the motor 2 in accordance with the signal level supplied from the low-pass filter 1.

In the digital audio disc player configured as described above, when the play mode is set, the motor 2 rotates and the disc 1 is rotated at high speed. On the other hand, the reading head 4 irradiates the lower surface of the disk 1 with a light beam 3 and reads the reflected light, thereby reproducing and outputting digital information on the disk. This reproduced signal is amplified in an amplifier 5, further shaped into a pulse waveform in a waveform shaping circuit 6, and then supplied to a synchronizing signal detection circuit 7. In this case, if the linear velocity of the disc 1 in the irradiated part of the light beam emitted from the reading head 4 is close to a predetermined velocity, the synchronization part λ included in the reproduction signal, that is, 10 Every time a continuous portion of "or '1" is detected, the synchronization signal detection circuit 7 outputs a synchronization signal S.
is generated. This synchronization signal S is phase-compared with a reference signal of, for example, 7.35 KHz, which is the period of the synchronization signal at a predetermined linear velocity, in the phase comparator circuit 8, and a phase difference corresponding to the phase difference between the two is determined. A signal Q is generated and supplied to analog switch 9. The analog switch 9 receives the synchronization signal S generated from the synchronization signal detection circuit 8 as a control signal, and closes to output the phase difference signal Q only when the synchronization signal S is supplied at a predetermined cycle, for example.

8- Phase difference signal Q taken out via analog switch 9
is supplied to the low-noise filter 11 via the time constant circuit 10, whereby its high frequency 'ME is removed and only the low frequency component is output as a rotation control signal. Therefore,
The motor drive circuit 12 controls the linear velocity to a predetermined constant value by controlling the rotation of the motor 2 in response to the rotation control signal output from the rotor filter 11. Therefore, these circuits constitute a phase-locked loop and are controlled so that the linear velocity is always constant.

Next, if the linear velocity deviates from the predetermined value by a relatively large amount due to the fast-forwarding mode of reading spatula 4 or some other cause, the 11-bit portion of the same period is lengthened or reduced to 12-bit. Alternatively, since it is detected as 10 bits, the synchronizing signal detection circuit 7 outputs the synchronizing signal A with part of it missing. As a result, in the part where the synchronization signal S is missing,
Since the compared input to the phase comparator circuit 8 is disconnected, the output phase difference signal Q will fluctuate greatly. However, since the analog switch 9 uses the synchronization signal S output from the synchronization signal detection circuit 7 as a control input, it becomes open in the part where the synchronization signal S is missing, and the phase difference signal Q fluctuates greatly. Prevent sending. As a result, the phase difference signal Q is not supplied to the second time constant circuit 10 during the non-detection period of the synchronization signal S, but since it has a relatively large time constant, the phase difference signal Q is Interpolate to prevent sudden changes in output. In this way, the signal-interpolated output of the time constant circuit 10 is supplied to the motor drive circuit 12 via the low-noise filter 11, whereby rotation control is performed and sudden change control of the motor l is prevented. .

Then, when the synchronization signal S is detected again, the analog switch 9 closes again to form a phase-locked loop, so that the rotation control operation is performed and the rotation continues at a constant linear velocity.

In the above embodiment, a case was explained in which a time constant circuit was provided on the output side of the analog switch 9, but this may be used if the low pass filter 11 has a sufficient time constant. .

As explained above, the digital audio disc player according to the present invention has a control system that compares the phase of the synchronization signal included in the reproduced signal with a reference signal and controls the rotation of the motor in accordance with the phase difference signal. If the synchronization signal cannot be detected, the phase difference signal is cut off to prevent the transmission of the suddenly changing phase signal, and in the new period of the phase difference signal, the time constant circuit interpolates the phase difference signal. It is something to do. Therefore, even if a part of the detected synchronization signal is dropped due to some reason, sudden change control of the motor can be prevented and stable rotation control can be achieved, which is an excellent effect.

[Brief explanation of drawings]

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. DESCRIPTION OF SYMBOLS 1...Disk, 2...Motor, 3...Original beam, 4...Reading head, 5...Amplifier, 6...
Waveform shaping circuit, 7... Synchronous signal detection circuit, 8... Phase comparison circuit, 9... Analog switch, 10... Time constant circuit, 11... Low pass filter, 12... Motor drive circuit .

Claims (1)

[Claims] (1) By detecting the synchronization signal included at regular intervals in the reproduced signal, extracting the phase difference signal between this synchronization signal and the reference signal, and continuously supplying it to the motor control circuit, rotation at a constant linear velocity is achieved. In a digital audio disc player equipped with a rotation control system for controlling. an analog switch that is closed only during a predetermined detection period of the synchronization signal and allows the phase difference signal to pass; and the phase difference signal is supplied through the analog switch;
a circuit that retains all of the phase difference signals supplied immediately before the open state and supplies the same to the motor control circuit when the synchronization signal deviates from a predetermined detection period and the analog switch enters the open state. A digital audio disc player characterized by: