JPH05137023A - Horizontal synchronizing signal separator circuit - Google Patents

Abstract

PURPOSE:To always separate and output 8 horizontal synchronizing signal by providing a monostable multivibrator, an OFF, and an OR circuit and transmitting the equivalent pulses near the equivalent pulse existing at 8 position where this pulse is taken out as a horizontal synchronizing signal. CONSTITUTION:When an equivalent pulse of an input composite synchronizing signal (a) is omitted, the negative polarity pulse output (e) of a monostable multivibrator 3 that should be originally available is not availeble. In this case, the output (h) of a monostable multivibrator a is set at an H level at only a point near the equivalent pulse existing at a position where the pulse is taken out as a horizontal synchronizing signal through a 100p consisting of the monostable multivibrators 7 and a, an OFF 5 and an OR circuit 6. Then en AND circuit 9 secures an AND between the output (h) end the positive polarity output (b) of the multivibretor 3. Thus e normal horizontal synchronizing signal is obtained. In other words, the equivalent pulse part existing at the middle of the equivalent pulse of the position where the pulse is taken out as a horizontal synchronizing signal is not instructed not to answer despite the omission of the equivalent pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal synchronizing signal separation circuit for separating a horizontal synchronizing signal from a composite synchronizing signal and outputting the same in a television receiver or the like, and more particularly to a technique for eliminating the influence of missing equivalent pulses. Regarding

[0002]

2. Description of the Related Art A composite synchronizing signal, which is transmitted by combining a horizontal synchronizing signal and a vertical synchronizing signal in a television receiver or the like, has a vertical synchronizing signal period and three horizontal scanning periods before and after the period (hereinafter, referred to as a horizontal scanning period). In the period (denoted as T _H ), as is well known, the horizontal synchronizing signal is not the normal period T _H but an equivalent pulse of T _H / 2 period, and the pulse width is narrow. Therefore, it is necessary to separate and output the horizontal synchronizing signals having the same pulse duration as the period T _H of the equivalent pulse and the same pulse width.

Conventionally, a generally used horizontal synchronizing signal separation circuit is a circuit in which a non-triggerable monostable multivibrator and an ordinary monostable multivibrator are connected in series. In this circuit, the period of the equivalent pulse as described above has the same period T _H as the normal period, and the horizontal synchronizing signal having the same pulse width can be separated and output. However, in the circuit described above, if the equivalent pulse is lost for some reason, a normal horizontal synchronizing signal cannot be output, which causes a problem that the horizontal synchronizing is disturbed. In order to solve the above-mentioned problem, as a horizontal sync signal separation circuit capable of outputting a normal horizontal sync signal even if the equivalent pulse is missing, a circuit described in Japanese Patent Laid-Open No. 2-55474 and There is a circuit shown in FIG.

FIG. 3 is a block diagram of the horizontal synchronizing signal separation circuit, and FIGS. 4 and 5 are timing charts of the signal waveforms in FIG. The circuit of FIG. 3 separates and outputs the horizontal synchronizing signal of the regular horizontal scanning period T _H even if the equivalent pulse of the input composite synchronizing signal is lost due to a transmission failure or the like. Operation in this case Will be explained.
In FIG. 3, the composite synchronization signal a having the waveform shown in FIG. 4A is input from the input terminal 1 and supplied to the non-retriggerable monostable multivibrator 11. However, it is assumed that the input composite synchronizing signal a lacks the equivalent pulse indicated by the broken line at time t ₄ . At time t ₁ , the non-retriggerable monostable multivibrator 11 is triggered by the leading edge of the composite synchronizing signal a to be at the H level, and is re-activated until the end of the pulse width T ₁₁ as shown in FIG. 4B. A non-retriggerable operation is performed in which the trigger is not accepted and the L level is reached when the period of the pulse width T ₁₁ has passed. Then, at time t ₂ , the output v that is triggered again and becomes H level
Is taken out and supplied to the retriggerable monostable multivibrator 12 and the monostable multivibrator 14. In this case, the pulse width T _11, since (T _H / 2) <is set to be in the relation of T ₁₁ <T _H, Nonritorigaburu monostable multivibrator 11 is not retriggered at time t ₃ , Its output v becomes the L level after continuing the H level for the pulse width T ₁₁ from the time t ₂ . The retriggerable monostable multivibrator 12 is triggered by the rising edge of the input signal v, and normally outputs a pulse that goes to the L level after continuing the H level for the pulse width T ₁₂ . However, the pulse width T ₁₂ at this time is set so that T _H <T ₁₂ <(3T _H / 2) is satisfied, and the retriggerable monostable multivibrator 12 has an output even during the H level period. Times t ₁ and t ₂ to accept retrigger
Is continuously retriggered and the H level period of the output is extended.

However, at time t ₄ , FIG.
Since the equivalent pulse of the input composite synchronizing signal a is missing as indicated by the broken line in FIG. 5, the non-retriggerable monostable multivibrator 11 is not triggered and the output signal v holds the L level. Therefore, as shown in FIG. 4C, the retriggerable monostable multivibrator 12 outputs an output x that becomes L level after T ₁₂ hours from time t ₂ and is supplied to the monostable multivibrator 13. Monostable multivibrator 13, between time t ₄ ~t _5, as shown in FIG. 4 (D), the triggered at the falling edge of the input signal x, the L level after continuing H level only pulse width T ₁₃ Output a pulse signal y. The signal y is
The signal is supplied to the clear terminal CL of the non-retriggerable monostable multivibrator 11, and the output of the non-triggerable monostable multivibrator 11 is cleared while the signal y is at the H level. Since the pulse width T ₁₃ at this time is set to satisfy the relationship of (3T _H / 2) <(T ₁₂ + T ₁₃ ) <2T _H , the non-retriggerable monostable multivibrator 11 operates at time t ₅ At time t ₆ , the output signal v is not triggered because of the clearing operation but is triggered again, and the output signal v becomes H level. Also,
The monostable multivibrator 14 is triggered by the rising edge of the output signal v of the non-retriggerable monostable multivibrator 11, and has a pulse width T as shown in FIG.
_The pulse signal z having ₁₄ (where 0 <T ₁₄ < _TH ) is output. This pulse signal z is output from the output terminal 2 as a horizontal synchronizing signal. The output signal v shown in FIG.
The period is 2T _H becomes part by lack of equalizing pulse at time t _4, but the horizontal sync signal so that the missing one, in the television receiver or the like, as is well known,
Has no effect on synchronization.

[0006]

However, in the circuit shown in FIG. 3, when there are a plurality of missing equivalent pulses,
Depending on the position where the equivalent pulse is missing, there is a problem in that the horizontal synchronizing signal to be output is phase-shifted by the T _H / 2 period and the horizontal synchronizing of the television receiver or the like is disturbed. The above problem will be described below with reference to FIG. Figure 5
The input composite synchronizing signal a is shown in (A). However, it is assumed that the input composite synchronizing signal a lacks the equivalent pulse indicated by the broken line at the times t ₄ and t ₆ . The operation before time t ₆ is the same as that in FIG. At time t ₆ , FIG.
Since the equivalent pulse of the input composite synchronizing signal a is missing as shown by the broken line in (A), the non-retriggerable monostable multivibrator 11 is not triggered and the output signal v holds the L level and the retriggerable single The output of the stable multivibrator 12 and the output of the monostable multivibrator 13 also remain at L level. The output signal y of the monostable multivibrator 13 is supplied to the clear terminal CL of the non-retriggerable monostable multivibrator 11, but the output signal v of the non-retriggerable monostable multivibrator 11 has nothing during the L level period. It has no effect.
Therefore, the non-retriggerable monostable multivibrator 11 is retriggered at time t ₇ , becomes H level as shown in FIG. 5B, does not accept retrigger until the end of the pulse width T ₁₁ , and the pulse is not received. When the period of width T ₁₁ has passed, a non-retriggerable operation is performed in which the L level is reached. Then, the monostable multivibrator 14 is triggered by the rising edge of the output signal v of the non-retriggerable monostable multivibrator 11, and an output signal z having a pulse width T ₁₄ as shown in FIG. 5E is obtained, That is output terminal 2
Is output as a horizontal synchronizing signal. The output signal z shown in FIG. 5 (E), the period in part, by the lack of an equivalent pulse at time t _4, t ₆ is 5T _H / 2, and the horizontal synchronizing signal phase-shifted by T _H / 2. Therefore, a malfunction occurs, and stable synchronization cannot be maintained in the television receiver or the like.

The present invention has been made to solve the above problems, and even if the equivalent pulse of the input composite synchronizing signal is lost, no malfunction occurs regardless of the position of the loss of the equivalent pulse. It is an object of the present invention to provide a horizontal sync signal separation circuit that can always separate and output a normal horizontal sync signal.

[0008]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, according to the present invention, the first monostable multivibrator (for example, 3 in FIG. 1 to be described later) is triggered by the leading edge of the input composite sync signal and outputs each pulse of positive polarity and negative polarity of the pulse width T _HD . And the data input is fixed to the H level, the data input is latched at the rising edge of the negative pulse output of the first monostable multivibrator to output the positive pulse, and the clear terminal input is at the L level. The first D flip-flop that clears the output during the period (for example, corresponds to 4 in FIG. 1 described later)
And a _second pulse that is triggered by the rising edge of the input pulse and outputs positive and negative pulses having a pulse width T 2
Of the monostable multivibrator (e.g., corresponding to 8 in FIG. 1 described later) and the data input are fixed at the H level, and the data input is latched at the rising edge of the negative pulse output of the second monostable multivibrator to positively A second D flip-flop that outputs a sex pulse and clears the output while the clear terminal input is at L level (for example, 5 in FIG. 1 described later).
And an OR circuit for outputting the OR of each pulse of the first and second D flip-flops (see, for example, FIG.
6), and triggered by the rising edge of the output pulse of the OR circuit, and outputs a negative pulse having a pulse width T ₁ .
A third monostable multivibrator that applies this negative pulse output to the input of the second monostable multivibrator and the clear terminals of the first and second D flip-flops (e.g., corresponding to 7 in FIG. 1 below). And the first and second
AND circuit for outputting AND of each positive pulse output of the monostable multivibrator (for example, corresponding to 9 in FIG. 1 described later), and each of the pulse widths T _HD , T ₁ ,
T ₂ and horizontal scanning period T _H is _{T HD <(T H / 2} ) T HD <T 2 (T H / 2) <T 1 <(T H -T HD) T H <(T 1 + T 2) < It is configured to have a (3T _H / 2) relationship.

[0009]

The first monostable multivibrator is triggered at the leading edge of the input composite sync signal and has a positive polarity with a pulse width T _HD ,
Each pulse of negative polarity is output. This negative polarity pulse output is given as a clock pulse to the first D flip-flop whose data input is fixed to the H level, and the first D flip-flop latches the data input at the rising edge of this clock pulse, Output the pulse that becomes level. This output, after passing through the OR circuit, is given to the third monostable multivibrator, and the third monostable multivibrator is triggered by the rising edge of the signal and outputs a negative polarity pulse having a pulse width T ₁ . The negative pulse output is applied to the clear terminals of the first and second D flip-flops, and the output of the first and second D flip-flops is set to the L level at the moment when the L level is reached, and the clear operation is performed. .. That is, the first D flip-flop becomes L level by the operation of the third monostable multivibrator at the next moment when the output becomes H level,
After that, it operates so as not to respond to the output pulse of the first monostable multivibrator input during the period of the pulse width T ₁ . Further, the negative pulse output of the third monostable multivibrator is given to the second monostable multivibrator, and the second monostable multivibrator is triggered by the rising edge of the input pulse and has a positive pulse width T ₂ . sex,
Each pulse of negative polarity is output. This negative polarity pulse output is given as a clock pulse to the second D flip-flop whose data input is fixed at the H level, and the second D flip-flop latches the data input at the rising edge of the clock pulse, Output the pulse that becomes level. In the second D flip-flop, normally, at the rising of the negative pulse output of the second monostable multivibrator, the clear operation is performed by the negative pulse output of the third monostable multivibrator. Remains at the L level. But the second
In the case where the negative pulse output of the monostable multivibrator of (1) is in the L level period, the equivalent pulse of the input composite synchronizing signal is missing, and the negative pulse output of the first monostable multivibrator which should be supposed is not present. Causes the second D flip-flop to output a pulse which becomes H level due to the rising of the negative polarity pulse output of the second monostable multivibrator. This output goes through the OR circuit and then goes to the third
, And the third monostable multivibrator is triggered by the rising edge of the signal and outputs a negative pulse having a pulse width T ₁ . This negative polarity pulse output is applied to the clear terminals of the first and second D flip-flops, and at the moment when it goes to the L level, a clear operation is performed to bring the outputs of the first and second D flip-flops to the L level. .. That is, the second D flip-flop becomes L level by the operation of the third monostable multivibrator at the next moment when the output becomes H level, and thereafter does not accept the clock during the period of T ₁ , and First D
The flip-flop also operates so as not to respond to the output pulse of the first monostable multivibrator input during the period T ₁ . Due to the loop of the second and third monostable multivibrators, the second D flip-flop, and the OR circuit, the equivalent pulse of the input composite synchronizing signal is lost, and the first monostable multivibrator which should be supposed to be Even if there is no negative pulse output, it is possible to not respond to the equivalent pulse portion in the middle of the equivalent pulse at the position taken out as the horizontal synchronizing signal. Therefore,
The positive pulse output of the second monostable multivibrator is at the H level only near the equivalent pulse at the position taken out as the horizontal synchronizing signal, and the first pulse in the AND circuit is used.
By taking the AND between the positive output of the monostable multivibrator and the horizontal sync signal, only the horizontal synchronizing signal can be output. That is, regardless of the position where the equivalent pulse of the input composite synchronizing signal is missing, the horizontal synchronizing signal is T _H / 2.
It is possible to always separate and output a normal horizontal synchronizing signal without causing a malfunction of phase shifting for a period.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific contents of the horizontal synchronizing signal separation circuit of the present invention will be described below with reference to the accompanying drawings. 1 is a block diagram of an embodiment of a horizontal synchronizing signal separation circuit of the present invention, FIG.
2 is a timing chart showing the signal waveform of FIG. In FIG. 1, the composite synchronizing signal a having the waveform shown in FIG. 2A is input from the input terminal 1 and supplied to the monostable multivibrator 3. However, the input composite synchronizing signal a is at time t ₄
It is assumed that the equivalent pulse indicated by the broken line at t ₆ and t ₆ is missing. First, at time t ₁ , the negative pulse output g of the monostable multivibrator 7, which is an input to the clear terminals CL of the D flip-flops 4 and 5, is at the H level, the output d of the D flip-flop 4 and the D flip-flop 5 are at the same time.
The output e of is at the L level. At this time, the monostable multivibrator 3 is triggered at the leading edge of the input composite synchronizing signal a at time t _{1 and} has a positive pulse b with a pulse width T _HD as shown in FIGS. 2B and 2C. And the negative pulse c. The pulse width T at this time
_HD is set to T _HD <(T _H / 2). The D flip-flop 4 latches the data input fixed to the H level at the rising edge of the negative pulse output c of the monostable multivibrator 3. Therefore, the output d becomes H level as shown in FIG. This output d passes through the OR circuit 6 and is then applied to the monostable multivibrator 7 as an OR circuit output signal f. The monostable multivibrator 7 is triggered by the rising edge of the output signal f of the OR circuit 6 and outputs a negative polarity pulse g having a pulse width T ₁ as shown in FIG. Since the negative pulse g of the monostable multivibrator 7 is applied to the clear terminal CL of the D flip-flop 4, D
The flip-flop 4 is cleared as shown in FIG.
The output changes to the L level, as shown in, and the latch by the clock is prohibited during the T ₁ period. Pulse width T ₁ of the at this _{time, (T H / 2) <} T 1 <(T H -T HD) because they are set as the intermediate, such as at time t ₃ in the composite synchronizing signal a pulse Pulse, that is, the equivalent pulse existing in the middle of the equivalent pulse at the position to be taken out as the horizontal synchronizing signal is not responded. Next, the monostable multivibrator 8 is triggered by the rising edge of the output signal g of the monostable multivibrator 7, and as shown in FIG.
A positive pulse h having a pulse width T ₂ as shown in (I),
Each pulse i of negative polarity is output. At this time, the negative polarity pulse i is applied to the clock terminal of the D flip-flop 5, but within the H level period of the negative polarity pulse i, the negative polarity pulse of the monostable multivibrator 3 is generated in the D flip-flop 4. When the output c is input, the negative pulse g of the monostable multivibrator 7 is applied to the clear terminal CL of the D flip-flop 5, so that the D flip-flop 5 is latched by the clock during the period T _1. Since a clearing operation for prohibiting is carried out, the output e remains at the L level as shown in FIG.
Further, the pulse width T ₂ at this time is set to T _HD <T _{2 TH} <(T ₁ + T ₂ ) <(3T _H / 2).

Next, consider a case where at time t ₄ , the equivalent pulse shown by the broken line is missing, and there is no output of the negative pulse c of the monostable multivibrator 3 which is supposed to be. At this time, as shown in FIG. 2 (E), the D flip-flop 5 latches the data input fixed to the H level at the rising edge of the negative pulse i of the monostable multivibrator 8 and becomes the H level pulse. Output e. The output e of the D flip-flop 5 passes through the OR circuit 6,
Monostable multivibrator 7 as the OR circuit output signal f
Applied to. The monostable multivibrator 7 is triggered by the rising edge of the output signal f of the OR circuit 6,
A negative polarity pulse g having a pulse width T ₁ as shown in (G) is output. At the next moment, the negative polarity pulse g of the monostable multivibrator 7 is applied to the clear terminal CL of the D flip-flop 5, so that the D flip-flop 5 outputs the clear operation as shown in FIG. Changes to the L level, and the latch by the clock is prohibited during the T ₁ period. Also in the D flip-flop 4, since the negative pulse g of the monostable multivibrator 7 is applied to the clear terminal CL of the D flip-flop 4, the clear operation for prohibiting the latch by the clock during the T ₁ period is performed. The output remains at the L level as shown in 2 (D). Therefore, the monostable multivibrator 7, 8,
Due to the loop of the D flip-flop 5 and the OR circuit 6, even when the equivalent pulse of the input composite synchronizing signal is missing and the negative pulse output of the monostable multivibrator 3 which should be supposed to be is not present, the pulse at time t ₅ It is possible to make no response to any intermediate pulse, that is, an equivalent pulse existing in the middle of the equivalent pulses at the position taken out as the horizontal synchronizing signal. As described above, the positive pulse output h of the monostable multivibrator 8 becomes H level only near the equivalent pulse at the position taken out as the horizontal synchronizing signal. A normal horizontal synchronizing signal can be obtained by calculating the AND of the output h and the positive output b of the monostable multivibrator 3 by the AND circuit 9. That is, FIG.
As shown in (J), when the equalizing pulse of a composite sync signal is missing at time t ₄ and t _6, the horizontal synchronizing signal extracted by _{t 1, t 2, t 8} , the time t ₄ and t ₆ periodic part by lack of equivalent pulses horizontal synchronizing signal is output as a 3T _H in. In the above example, two horizontal synchronizing signals are lost due to the loss of the equivalent pulse, but as is well known in television receivers and the like, it does not affect the synchronization at all. As described above, even when the equivalent pulse of the input composite synchronizing signal is lost at the times t ₄ and t ₆ and the negative pulse output of the monostable multivibrator 3 which should be originally present is not present, the monostable multivibrator 7, 8, the D flip-flop 5 and the OR circuit 6 loop to generate a time t ₅ or t _7.
It is possible not to respond to the equivalent pulse portion existing in the middle of the equivalent pulse at the position taken out as the horizontal synchronizing signal. Therefore, the horizontal sync signal is T _H /
A malfunction such as shifting for two periods does not occur, and stable synchronization is maintained in a television receiver or the like. Even if any equivalent pulse other than the times t ₄ and t ₆ is missing, the normal operation is performed in the same manner as above.

[0012]

As described above, according to the present invention, the present invention is configured as described in the claims, and the equivalent pulse is passed only in the vicinity of the equivalent pulse at the position taken out as the horizontal synchronizing signal. Therefore, there is no influence of the equivalent pulse existing in the middle of the equivalent pulse at the position taken out as the horizontal synchronizing signal. Therefore, even if the equivalent pulse of the input composite sync signal is lost due to a transmission failure, etc., regardless of the position of the drop of the equivalent pulse, a normal horizontal sync signal with no malfunction can always be separated and output. It is possible to obtain a practically excellent effect that it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a horizontal sync signal separation circuit of the present invention.

FIG. 2 is a timing chart showing the signal waveform of FIG.

FIG. 3 is a block diagram of a prior art horizontal sync signal separation circuit.

FIG. 4 is a timing chart showing the signal waveforms of FIG.

5 is a timing chart showing the signal waveform of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Input terminal 2 ... Output terminal 3 ... Monostable multivibrator 4, 5 ... D flip-flop 6 ... OR circuit 7, 8 ... Monostable multivibrator 9 ... AND circuit 10 ... Output terminal 11 ... Non-triggerable monostable multivibrator 12, 14 ... Monostable multivibrator 13 ... Retriggerable monostable multivibrator

Claims (1)

[Claims] 1. A first monostable multivibrator, which is triggered at the leading edge of an input composite sync signal, outputs positive and negative pulses having a pulse width T _HD , and a data input fixed at an H level. A first D that latches the data input at the rising edge of the negative polarity pulse output of the first monostable multivibrator to output a positive polarity pulse and clears the output while the clear terminal input is at L level Triggered by flip-flop and rising edge of input pulse, pulse width T
_{The second} monostable multivibrator which outputs each pulse of ₂ positive polarity and the negative polarity, and the data input is fixed to the H level, and the data is output at the rising edge of the negative pulse output of the second monostable multivibrator. A second D flip-flop that latches the input, outputs a positive polarity pulse, and clears the output while the clear terminal input is at the L level, and the OR of each pulse of the first and second D flip-flops. And a negative pulse having a pulse width T ₁ that is triggered by the rising edge of the output pulse of the OR circuit, and outputs the negative pulse output to the input of the second monostable multivibrator and the first pulse. A third monostable multivibrator applied to the clear terminal of the second D flip-flop, and each of the first and second monostable multivibrators. AND circuit for outputting AND of the positive polarity pulse output of the above, and each of the pulse widths T _HD , T ₁ , T ₂ and the horizontal scanning period T _H is T _HD <(T _H / 2) T _{HD <T 2 (T H / 2} ) <T 1 <(T H -T HD) T H <(T 1 + T 2) <(3T H / 2) a horizontal synchronizing signal separation circuit, characterized in that it has a relationship ..