JPS6342344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a squelch device, and more particularly, the present invention relates to a squelch device, and more specifically, a squelch device that detects a time-base error having a value corresponding to a frequency difference and a phase difference between a time-base signal detected from a video disk and a predetermined reference signal. The present invention relates to a squelch device that controls a time axis signal using a voltage and suppresses a control operation at a desired time.

On a video disc, a time axis signal is recorded in a spiral along with a video signal, an audio signal, etc. In order to reproduce these recorded signals, a video disc player is equipped with a spindle motor that rotates the video disc, a recorded signal detection means that detects the recorded signals, and the like. Additionally, a time axis correction control mechanism is used to accurately reproduce these recorded signals. Even if there is eccentricity of the video disk, center deviation of the disk mounting part of the turntable, or jitter of the recording signal itself, it is possible to change the recording signal detection means in the tangential direction of the recording signal recorded spirally, or to change the direction of the spindle motor. A control operation such as changing the rotation period is performed, and the time axis signal is corrected to match a predetermined constant reference signal. On the other hand, when there is no need to perform a control operation, for example, when there is no recording signal detection means on the video disk, or during the time from the start of play until the video disk rotates at a constant speed, the control operation is suppressed, that is, a squelch operation is performed. , and a squelch device is required.

In the prior art, as shown in FIG. 1, when the microcomputer 1 determines that a control operation is to be performed to make the time axis signal coincide with the reference signal, the microcomputer 1 supplies a high level signal to the terminal 2. Therefore, transistor 3 becomes conductive, and operational amplifier 4 operates as an active filter with a gain of 30-100. The time axis error voltage corresponding to the time axis error charged in the capacitor 5 is transmitted to the recording signal detection means 9 via the operational amplifier 6, the phase correction circuit 7, the operational amplifier 4 and the voltage controlled oscillation circuit 8.
It is applied to the coil 10 provided at , and performs a control operation. When the microcomputer 1 determines that the squelch operation is to be performed, the microcomputer 1 applies a low level signal to the terminal 2. Therefore, transistor 3 is cut off, and operational amplifier 4 operates as a voltage follower with a gain of 1. Therefore, since a sufficient gain cannot be obtained in the operational amplifier 4, the control operation does not work sufficiently, that is, a squelch operation occurs. However, for example, the time axis error is large during the time from the start of play until the video disc rotates at a constant speed, and therefore the time axis error voltage charged in the capacitor 5 is high, so the squelch operation does not work sufficiently. The signal is applied to the voltage controlled oscillation circuit 8 via the operational amplifier 4 operating as a voltage follower, and performs a control operation. As a result, the recording signal detection means is moved abnormally, and other control mechanisms such as the control mechanism for changing the recording signal detection means 9 in the radial direction of the video disk are affected.

In the prior art of FIG. 1, the time base error voltage shown in FIG. 3 is derived from the phase comparator 12 on line 14. A reference signal is applied from the microcomputer 1 to the terminal 11 via a line 31, and a time axis signal detected from the video disk is applied to the line 26. line 3
As shown in FIG. 3, a signal that becomes low level is applied to terminal 2 from terminal 2 after the turntable on which the video disc is mounted reaches a constant rotation speed. The signal shown in FIG. 3 is applied from the microcomputer 1 to the line 33, and when this line 33 becomes high level, the transistor 1
5 remains conductive, and a squelch operation is performed. FIG. 3 shows the output waveform of the video terminal.

In such prior art, transistor 15 remains continuously conductive and the squelch operation continues. Therefore, if the time axis error is large during the period from when the turntable starts rotating until it starts rotating at a constant speed, the charging voltage of the capacitor 5 will leak, resulting in incomplete squelch operation. .

An object of the present invention is to provide a squelch device that can perform a complete squelch operation.

The present invention detects a frequency difference and a phase difference between a time axis signal detected from a video disc and a predetermined reference signal using a phase comparator 12, and detects a time axis corresponding to the frequency difference and phase difference. In a squelch device that derives an error voltage to a signal line 14, performs time axis correction using the time axis error voltage from this line 14, and suppresses this time axis correction operation, a connection between the line 14 and the ground is provided. A capacitor 5 is connected, and a switching element 15 is also connected between the line 14 and ground, and the squelch operation signal is derived from the means 1 for deriving a squelch operation signal indicating that a squelch operation is to be performed. means 17 for keeping the switching element conductive when the squelch operation signal is on, and for making and cutting off the switching element based on the reference signal when the squelch operation signal is not derived;
A squelch device is characterized by comprising:

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a simplified block circuit diagram of one embodiment of the present invention, in which parts corresponding to the prior art shown in FIG. 1 are given the same reference numerals. When the microcomputer 1 determines to perform a control operation, it outputs a high-level signal to the terminal 2.
When it is determined to suppress the control operation, that is, to perform a squelch operation, a low level signal is outputted to the terminal 2 as a squelch signal. The microcomputer 1 also outputs a pulse with a predetermined constant frequency to the terminal 11 as a reference signal. Recorded signal detection means 9 detects video signals, audio signals, time axis signals, etc. recorded on the video disc. This recording signal detection means 9 has a coil 10. By energizing this coil 10, the recording signal detecting means 9 is changed in the recording signal tangential direction. Recording signal detection means 9 derives a time-domain signal of the detected recording signal to one input of phase comparator 12 via line 26 . The other input of the phase comparator 12 is connected via a line 27 to the terminal 11 and is therefore provided with a reference signal. Phase comparator 12 derives error voltages on lines 13 and 14 in response to the frequency and phase differences between the time-domain signal applied to one input and the reference signal applied to the other input. Line 13 is connected to the inverting input of operational amplifier 6 and to the output of operational amplifier 6. Therefore, the operational amplifier 6 operates as a voltage follower with a gain of 1. Line 14 is connected to the non-inverting input of operational amplifier 6. Between line 14 and ground,
Capacitor 5 is connected. This capacitor 5 includes a transistor 15 as a switching element.
are connected in parallel.

The base of the transistor 15 is connected to the output of the NAND gate 17 via a resistor 16 and grounded via a pull-down resistor 18.
Terminal 2 is connected to one input of NAND gate 17, and terminal 11 is connected to the other input of NAND gate 17.

The output of operational amplifier 6 is applied via line 28 to the input of phase compensation circuit 7. The phase compensation circuit 7 outputs a compensation voltage to lines 19 and 20 as a voltage corresponding to the time axis error voltage in a direction that reduces the input voltage in accordance with the input voltage applied to the input. Line 19 is connected to the inverting input of operational amplifier 4 and grounded. Line 20 is connected to the non-inverting input of operational amplifier 4. A series circuit consisting of resistors 21 and 22 is connected between the output of operational amplifier 4 and the inverting input of operational amplifier 4. A capacitor 23 is connected in parallel to this resistor 21 . Therefore, the operational amplifier 4 always operates as an active filter with a gain of 30 to 100.
The output of this operational amplifier 4 is connected via line 29 to the input of a voltage controlled oscillator 8. The voltage controlled oscillator 8 changes its oscillation frequency in response to the voltage applied to its input, and supplies the oscillation signal to a coil 10 provided in the recording signal detection means 9. Also,
An oscillation signal may be applied to control a spindle motor (not shown).

When the microcomputer 1 determines to perform a control operation, a high level signal is applied to the terminal 2. A reference signal is applied to the terminal 11, and therefore an inverted reference signal is derived from the output of the NAND gate 17. Therefore, transistor 15 is conductive during the high level period of the inverted reference signal and is cut off during the low level period of the inverted reference signal. That is, sampling is performed. When a frequency difference and a phase difference exist between the reference signal and the time-domain signal detected by the recording signal detection means 9, the transistor 15
During the period when the capacitor 5 is cut off, the time axis error voltage is charged in the capacitor 5. This time axis error voltage passes through the operational amplifier 6, the phase correction circuit 7, the operational amplifier 4, the voltage controlled oscillation circuit 8, and the coil 10 of the recording signal detection means 9, so the time axis control mechanism works and the time axis error voltage is A control operation is performed so that it becomes zero. Therefore, the time domain signal corresponds to the reference signal.

When the microcomputer 1 determines to perform a squelch operation, a low level signal is applied to the terminal 2. Therefore, the output of the NAND gate 17 becomes high level regardless of the reference signal applied to the terminal 11. In response, transistor 15 becomes conductive. Therefore, the time axis error voltage is discharged through the transistor 15 and always becomes zero. Accordingly, the output of the operational amplifier 6, the output of the phase correction circuit 7, the output of the operational amplifier 4, and the output of the voltage controlled oscillation circuit 8 are all zero, and the coil 10 provided in the recording signal detection means 9 is energized. Never. In the prior art shown in Figure 1, even when performing a squelch operation, the coil 1
Although the coil 10 is energized, in the present invention, when performing a squelch operation, the coil 10 is energized.
is de-energized, which can save energy. Furthermore, when the squelch operation is performed, the recorded signal detection means 9 is not driven in the tangential direction of the recorded signal recorded in a spiral manner, which affects the control mechanism (not shown) in the radial direction of the recorded signal. Never.

The embodiment shown in FIG. 2 above will be further explained with reference to FIG. 4. The time axis error voltage shown in FIG. 4 is derived from the line 14. A reference signal shown in FIG. 4 is applied from the microcomputer 1 to the terminal 11 via the line 31. A signal is applied from the line 34 to the terminal 2, which becomes high level after the turntable on which the video disk is mounted reaches a constant rotation speed, as shown in FIG. 4. Therefore
A pulse as shown in FIG. 4 is given from the NAND gate 17. This pulse has a waveform that is an inversion of the reference signal after the turntable rotates at a constant speed. FIG. 4 shows the output waveform of the video terminal.

Therefore, the transistor 15 is conductive except in the burst signal section where the time axis error appears. In this way, the transistor repeatedly turns on and off in synchronization with the reference signal, thereby constantly discharging the voltage charged in the capacitor. In the present invention, the capacitor 5
By constantly discharging the charged charge of
It is important to be able to complete the squelch operation.

As described above, according to the present invention, the signal representing the time axis error voltage is grounded and always kept at zero during squelch, so that the squelch operation can be performed reliably. In particular, in the present invention, since the charge in the capacitor is constantly discharged by a switching element such as the transistor 15, it is possible to complete the squelch operation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the prior art, FIG. 2 is a simplified block diagram of an embodiment of the present invention, and FIG.
1 is a waveform diagram for explaining the operation of the prior art shown in FIG. 1, and FIG. 4 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 2. 1... Microcomputer, 4, 6... Operational amplifier, 5, 23... Capacitor, 7... Phase correction circuit,
8... Voltage controlled oscillation circuit, 9... Recording signal detection means,
10... Coil, 12... Phase comparator, 13, 14,
19, 20, 26-29... line, 16, 18,
21, 22...Resistance.

Claims (1)

[Claims] 1. A time-domain signal detected from a video desk;
The phase comparator 12 detects the frequency difference and phase difference with a predetermined reference signal, and derives the time axis error voltage corresponding to the frequency difference and phase difference to the signal line 14. In a squelch device that performs time axis correction using a time axis error voltage and suppresses this time axis correction operation, a capacitor 5 is connected between the line 14 and the ground, and a capacitor 5 is connected between the line 14 and the ground. Further, when the switching element 15 is connected and the squelch operation signal is derived from the means 1 for deriving the squelch operation signal indicating that the squelch operation is to be performed, the switching element is kept conductive and the squelch operation is performed. means 17 for conducting and cutting off the switching element based on said reference signal when no signal is derived;
A squelch device comprising: