JPH0649013Y2 - Synchronous coupling device - Google Patents

Description

The present invention relates to a synchronous coupling device, and more particularly to a synchronous coupling device with improved performance.

(Prior Art) FIG. 2 is a block diagram showing an example of a conventional synchronous coupling device.

In the figure, reference numeral 1 is an input terminal to which an external synchronizing signal is input. From this input terminal 1, a video signal received by a television receiver, a reproduced video signal reproduced from a video tape recorder (VTR), a video disc or the like. Is supplied as an external synchronization signal. This external synchronization signal is input to one of the phase comparators 2 and also to the signal detection circuit 3.

The output of the phase comparator 2 is the input terminal a of the switch circuit SWB.
And the oscillator 5, and the output of the switch circuit SWB is supplied to the oscillator 4. The input terminal b of the switch circuit SWB is grounded.

The signal detection circuit 3 detects the presence or absence of an external synchronization signal input from the input terminal 1 and supplies the detection output to the control circuit 6.

Reference numeral 9 is an input terminal to which a color burst signal is input, and from this input terminal 9 is included in a color video signal received by a television receiver and a playback video signal played back from a video tape recorder (VTR) or a video disc. A color burst signal is provided. This color burst signal is input to one of the phase comparators 10 and also to the signal detection circuit 11.

The output of the phase comparator 10 is the input terminal c of the switch circuit SWB.
Is supplied to.

The signal detection circuit 11 detects the presence / absence of a color burst signal input from the input terminal 9 and outputs the detection output thereof to the control circuit 6
Supply to.

The oscillator 4 is a stable 4f _SC (f _sc is the color subcarrier frequency)
Is a crystal oscillator (VXO) that outputs a clock signal (hereinafter, may be referred to as a clock), and the oscillator 5 is a voltage-controlled oscillator (VCO) that outputs a clock of 4f _{sc with} a wide fluctuation range.

The control circuit 6 outputs a control signal according to the detection output supplied from the signal detection circuits 3 and 11 and the mode selection signal input from the input terminal 7, and supplies this control signal to the switch circuits SWB and SWA, respectively. Switch circuit SWB
And control SWA switching.

The oscillator 4 fixedly oscillates a clock of 4f _sc (f _sc is a color subcarrier frequency) because the oscillation control signal is fixed to a certain value when the switch circuit SWB is switched to the input terminal b side. To do.

The output of the oscillator 4 is supplied to the input terminal a and the 1/4 frequency divider 12 of the switch circuit SWA, and the output of the oscillator 5 is supplied to the other input terminal b of the switch circuit SWA.

Output switched by switch circuit SWA (output of oscillator)
Is input to the 1/910 frequency divider 8 where it is divided into a frequency division ratio of 1/910 to be a horizontal cycle pulse (horizontal synchronizing pulse) and input to the other side of the phase comparator 2. .

The phase difference voltage (oscillation control signal) between the two is the switch circuit SW
While controlling the oscillator 4 via B, the oscillator 5 controls the oscillator 5, and the oscillation frequencies of the oscillator 4 and the oscillator 5 move so that the phase difference becomes zero, and the outputs of the oscillator 4 and the oscillator 5 pass through the switch circuit SWA. It is output as a clock.

As described above, in the loop of the phase comparator 2 → oscillator 4 or oscillator 5 → 1/910 frequency divider 8, the oscillator 4 or the oscillator 5 is cycled in the horizontal cycle of the external synchronization signal from the input terminal 1.

The output of the oscillator 4 is input to the 1/4 frequency divider 12,
Here, the frequency is divided into a 1/4 frequency division ratio, which is converted into a pulse of the color subcarrier frequency (f _sc ) and input to the other side of the phase comparator 10.

The phase difference voltage (oscillation control signal) between the two is the switch circuit SW
The oscillator 4 is controlled via B, the oscillation frequency of the oscillator 4 moves so that the phase difference becomes zero, and the output of the oscillator 4 is output as a subcarrier.

As described above, the phase comparator 10 → oscillator 4 → 1/4 frequency divider 1
In the loop of 2, the oscillator 4 is synchronized with the cycle of the color burst signal from the input terminal 9.

(Problems to be solved by the invention) However, the conventional synchronous coupling device described above is
Since the oscillator 5 has two oscillators that output the same frequency clock, (1) there are two oscillators with the same frequency.
Mutual interference occurs between two oscillators (beat is generated),
As a result, the function of synchronous coupling is deteriorated.

(2) It is difficult to lock the color burst signal to determine the horizontal phase of the horizontal sync pulse (horizontal sync pulse), and as a result, a jitter component remains in the horizontal phase, and the function of synchronous coupling appears to be apparent. , Worse.

Due to the above two problems, the performance could not be sufficiently exerted in fulfilling the function of the synchronous coupling.

Therefore, the present invention solves the above-mentioned problems of the conventional technology,
An object of the present invention is to provide a synchronous coupling device with improved performance.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention outputs a stable clock signal, and a first oscillator whose oscillation operation / non-operation is controlled, and a clock with a wide variation range. Outputs a signal and oscillates
A second oscillator whose non-operation is controlled, a third oscillator which outputs a stable clock signal having a frequency different from the clock signals output from the first and second oscillators, and an output of the first oscillator And a second switching circuit for switching and outputting the output of the second oscillator, a second switching circuit for switching and outputting the output of the first oscillator and the output of the third oscillator, and A first detection circuit for detecting the presence or absence of an external sync signal, a second detection circuit for detecting the presence or absence of an input color burst signal, a detection output of the first detection circuit, and the first and second switching circuits In accordance with a mode selection signal instructing the switching of the above, only one of the first oscillator and the second oscillator is controlled to oscillate, and the output is switched to the output of the oscillating oscillator. To turn off the first switching circuit. A first control circuit for controlling switching, a detection output of the first detection circuit, a detection output of the second detection circuit, and a mode selection signal for instructing switching of the first and second switching circuits. A second control circuit for controlling switching of the second switching circuit, a first phase comparator for phase comparison between the output of the first switching circuit and the input external synchronization signal, and the third A second phase comparator for phase comparing an oscillation output of an oscillator and the input color burst signal, and a detection output of the first detection circuit are supplied, and when the input external synchronization signal is present, the first phase comparator is provided. A first oscillation frequency of the first oscillator is controlled according to the output of the comparator, and the oscillation frequency of the first oscillator is fixed to a first predetermined value when the input external synchronization signal is not present. Oscillation control means and the second detection circuit Path detection output is supplied and the input color burst signal is present, the oscillation frequency of the third oscillator is controlled according to the output of the second phase comparator, and when the input color burst signal is absent, Second oscillation control means for controlling the oscillation frequency of the third oscillator to be fixed to a second predetermined value, and the oscillation frequency of the second oscillator is always the output of the first phase comparator. The present invention provides a synchronous coupling device characterized by being controlled according to the above.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a synchronous coupling device according to the present invention.

In the figure, 21 is an input terminal to which an external synchronizing signal is input. From this input terminal 21, a video signal received by a television receiver, a reproduced video signal reproduced from a video tape recorder (VTR), a video disc or the like. Is supplied as an external synchronization signal. This external synchronization signal is input to one of the phase comparators 22 and also to the signal detection circuit 23.

The output of the phase comparator 22 is supplied to one input terminal a of the switch circuit SW2 (first oscillation control means) and the oscillator 25, and the output of the switch circuit SW2 is supplied to the oscillator 24. Then, the other input terminal b of the switch circuit SW2 is grounded.

The signal detection circuit 23 detects the presence or absence of the external synchronization signal input from the input terminal 21, and outputs the detection output to the control circuit 26 and
While being supplied to 30 respectively, this detection output is supplied to the switch circuit SW2 as a switching control signal.

The switch circuit SW2 (first oscillation control means) is switched to the input terminal a side when an external synchronizing signal is input, and switched to the input terminal b side when there is no input. When the oscillator 24 is switched to the input terminal b side, the oscillation control signal is fixed to a certain constant value, so that the clock of 4f _sc (f _sc is a color subcarrier frequency) is fixedly oscillated.

Reference numeral 31 is an input terminal to which a color burst signal is input, and from this input terminal 31, it is included in a color video signal received by a television receiver and a playback video signal played back from a video tape recorder (VTR) or a video disc. A color burst signal is provided. This color burst signal is input to one of the phase comparators 32, while the signal detection circuit 33
Entered in.

The output of the phase comparator 32 is supplied to one input terminal a of the switch circuit SW4 (second oscillation control means), and the output of the switch circuit SW4 is supplied to the oscillator 34. The input terminal b below the switch circuit SW4 is grounded.

The signal detection circuit 33 detects the presence or absence of a color burst signal input from the input terminal 31 and outputs the detection output to the control circuit.
While being supplied to 30, the detection output is supplied to the switch circuit SW4 as a switching control signal.

The switch circuit SW4 (second oscillation control means) is switched to the input terminal a side when the color burst signal is input, and switched to the input terminal b side when there is no input. When the oscillator 34 is switched to the input terminal b side, the oscillation control signal is fixed to a certain constant value, so that the clock of 2f _sc (f _sc is a color subcarrier frequency) is oscillated fixedly.

Oscillator 24 is a stable 4f _sc (f _sc is the color subcarrier frequency)
It is a crystal oscillator (VXO) that outputs the clock of
Reference _numeral 5 is a voltage controlled oscillator (VCO) that outputs a 4f _sc clock with a wide variation range, and oscillator 34 is a crystal oscillator (VXO) that outputs a stable 2f _sc clock.

The control circuit 26 outputs a control signal according to the detection output supplied from the signal detection circuit 23 and the mode selection signal input from the input terminal 27, and outputs this control signal to the oscillator 24 and the oscillator.
25 and switch circuit SW1 respectively, and oscillator 2
4, Oscillation operation / non-operation of oscillator 25 and switch circuit SW
Controls the switching of 1.

However, an inverter 28 is connected between the control circuit 26 and the oscillator 25, and when one of the oscillator 24 and the oscillator 25 is controlled to operate, the other is controlled to be non-operational. The oscillator is set to non-operation, and only one of the oscillators is controlled to operate at all times.

The control circuit 30 outputs a control signal in accordance with the detection output supplied from the signal detection circuits 23 and 33 and the mode selection signal input from the input terminal 27, and supplies this control signal to the switch circuit SW3. Controls SW3 switching.

The output of the oscillator 24 is supplied to one input terminal a of the switch circuit SW1 while being input to the 1/4 frequency divider 36,
Here, the frequency is divided into 1/4, and the pulse of the color subcarrier frequency (f _sc ) is supplied to the other input terminal b of the switch circuit SW3.

The output of the oscillator 25 is supplied to the other input terminal b of the switch circuit SW1.

The switch circuit SW1 is switched to the input terminal a side when the oscillator 24 is operating, and switched to the input terminal b side when the oscillator 25 is operating.

Here, the mode selection signals (“L” and “H”) input from the input terminal 27, the presence / absence of detection of the external synchronization signal by the signal detection circuit 23, and the presence / absence of detection of the color burst signal by the signal detection circuit 33. And switch circuits SW1, SW2, SW3, SW
4 and switching circuit SW1 output A (oscillator 24,
The following table 1 summarizes the correspondence relationship between the operation / non-operation of 25) and the output B of the switch circuit SW3.

The output A (output of the oscillator) switched by the switch circuit SW1 is input to the 1/910 frequency divider 29, where it is divided into a division ratio of 1/910 and a pulse of a horizontal cycle (horizontal synchronization pulse). Is input to the other side of the phase comparator 22.

The phase difference voltage (oscillation control signal) between the two is the switch circuit SW
The oscillator 24 and the oscillator 24 are controlled so that the phase difference is zero while controlling the oscillator 24 via
The oscillation frequency of 25 moves, and the outputs of the oscillator 24 and the oscillator 25 are output as a clock via the switch circuit SW1.

As described above, the phase comparator 22 → oscillator 24 or oscillator
25 → 1/910 Divider 29 loop with oscillator 24 or oscillator
The output of 25 is synchronized with the horizontal cycle of the external synchronizing signal from the input terminal 21.

Further, the output of the oscillator 34 is input to the 1/2 frequency divider 35, where it is divided by a frequency division ratio of 1/2, and the color subcarrier frequency (f _sc )
Pulse of the switch circuit SW3 and one input terminal a
And the other of the phase comparators 32.

The phase difference voltage (oscillation control signal) between the two is the switch circuit SW
The oscillator 34 is controlled via 4 and the oscillation frequency of the oscillator 34 moves so that the phase difference becomes zero, and the output of the oscillator 34 is colored via the 1/2 divider 35, the switch circuit SW3 and the process circuit 37. It is output as a subcarrier.

As described above, the phase comparator 32 → oscillator 34 → 1/2 divider 3
The loop of 5 synchronizes the output of the 1/2 frequency divider 35 with the color burst signal from the input terminal 31.

This operation is performed by the APC (Aut
The same function as the omatic phase control circuit.

Then, in the synchronous coupling device having the above-described configuration, the mode selection signal is switched according to the signal to be handled, and the oscillator is switched depending on the presence or absence of the external synchronization signal and the color burst signal, for example, the color burst signal like the RGB camera signal. When handling a signal that does not have the above, it is the case of "III" in Table 1 above, and similarly when handling a color video signal received by a television receiver, it is the case of "IV" in Table 1 above. Also, in the case of handling a reproduced video signal reproduced from a VTR or the like which does not have a color burst signal, it is the case of "VII" in Table 1 above, and similarly when handling a reproduced video signal of a normal VTR, This is the case for “VIII” in Table 1.

(Effect of the Invention) As described above, according to the synchronous coupling device of the present invention, by providing two kinds of oscillators that output clocks of different frequencies, clocks of the same frequency do not oscillate simultaneously. It is possible to prevent the occurrence of beats due to mutual interference between two oscillators that output a clock of the same frequency, and determine the horizontal phase of the horizontal period pulse (horizontal synchronization pulse) independently of the color burst signal. As a result, stable output can be obtained without leaving a jitter component in the horizontal phase, the performance of synchronous coupling can be improved, and an oscillator that outputs a stable clock and a clock with a wide fluctuation range can be output. It is equipped with an oscillator to switch between these oscillators according to the signals to be handled. It has the feature that it can have

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a synchronous coupling device according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional synchronous coupling device. 21 …… External sync signal input terminal, 22,32 …… Phase comparator, 23,33 …… Signal detection circuit, 24 …… Oscillator, 25 …… Oscillator, 26,30 …… Control circuit, 27 …… Mode selection Signal input terminal, 28 …… Inverter, 29 …… 1/910 frequency divider, 31 …… Color burst signal input terminal, 34 …… Oscillator, 35 …… 1/2 divider, 36 …… 1/4 minute Frequency, 37 …… Process circuit, SW1, SW2, SW3, SW4 …… Switch circuit.

Claims (1)

[Scope of utility model registration request] 1. A first oscillator which outputs a stable clock signal and whose oscillation operation / non-operation is controlled, and a clock signal which has a wide fluctuation range and which is operated / oscillated.
A second oscillator whose non-operation is controlled, a third oscillator which outputs a stable clock signal having a frequency different from the clock signals output from the first and second oscillators, and an output of the first oscillator And a second switching circuit for switching and outputting the output of the second oscillator, a second switching circuit for switching and outputting the output of the first oscillator and the output of the third oscillator, and A first detection circuit for detecting the presence or absence of an external sync signal, a second detection circuit for detecting the presence or absence of an input color burst signal, a detection output of the first detection circuit, and the first and second switching circuits In accordance with a mode selection signal instructing the switching of the above, only one of the first oscillator and the second oscillator is controlled to oscillate, and the output is switched to the output of the oscillating oscillator. To turn off the first switching circuit. A first control circuit for controlling switching, a detection output of the first detection circuit, a detection output of the second detection circuit, and a mode selection signal for instructing switching of the first and second switching circuits. A second control circuit for controlling switching of the second switching circuit, a first phase comparator for phase comparison between the output of the first switching circuit and the input external synchronization signal, and the third control circuit. A second phase comparator for phase comparing an oscillation output of an oscillator and the input color burst signal, and a detection output of the first detection circuit are supplied, and when the input external synchronization signal is present, the first phase comparator is provided. A first oscillation frequency of the first oscillator is controlled according to the output of the comparator, and the oscillation frequency of the first oscillator is fixed to a first predetermined value when the input external synchronization signal is not present. Oscillation control means and the second detection circuit Path detection output is supplied and the input color burst signal is present, the oscillation frequency of the third oscillator is controlled according to the output of the second phase comparator, and when the input color burst signal is absent, Second oscillation control means for controlling the oscillation frequency of the third oscillator to be fixed to a second predetermined value, and the oscillation frequency of the second oscillator is always the output of the first phase comparator. A synchronous coupling device characterized in that it is controlled according to.