JPH0832835A - Synchronization separator - Google Patents

Abstract

PURPOSE:To provide an output of a signal obtained by separating a synchronizing signal from a composite signal by interrupting a signal output separated from the video signal when only the video signal is inputted. CONSTITUTION:This separator consists of a synchronization separator means, a 1st pulse generating means 3, a 2nd pulse generating means 4, and a logic arithmetic means 5 generating a signal depending on the input of a video signal only or the input of a composite signal, and a switching means 6 controlling the output signal of the synchronization separator means by an output of the means 5. Since a signal separating the synchronizing signal is outputted only when the input signal is a composite signal, the separation of the video signal when the video signal is inputted is prevented. Thus, the control of the power supply circuit of the image display device or limit of power are made stable with high accuracy depending on the presence of the synchronizing signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention outputs a signal separated from the sync signal when a composite signal is input as an input signal and does not output when only a video signal is input. The present invention relates to a sync separation device optimal for controlling a power supply circuit of a display device or limiting a power supply power.

[0002]

2. Description of the Related Art A conventional sync separation circuit is disclosed in Japanese Patent Laid-Open No. 56-8.
Since the base of the transistor is fixedly biased by a bias circuit composed of a voltage divider circuit as in Japanese Patent No. 0966, if the potential of the emitter of the transistor is lower than the potential of the base potential of the transistor minus the base-emitter voltage of the transistor. , The transistor is ON
State. Since the composite signal is input from the emitter side, by setting the period during which the potential of the emitter drops as the part of the synchronization signal, a signal in which the part of the synchronization signal is separated is output to the collector of the transistor. However, when only the video signal is input as the input signal, a period in which the potential of the emitter drops in the video signal portion occurs, and a signal in which the video signal portion is separated is output from the collector side.

[0003]

In the above prior art, when a composite signal is input as an input signal, the sync separation circuit operates normally and outputs a signal in which the sync signal part is separated, but only the video signal is output. Even when input, the sync separation circuit operates and outputs a signal obtained by separating the video signal portion. Therefore, when a composite signal is input, it is necessary to output a signal in which the sync signal portion is separated, and not to output a separated signal when only a video signal is input.

[0004]

In order to solve the above-mentioned problems, a circuit for determining whether an input signal is a composite signal or only a video signal is provided, and when the composite signal is input, the sync signal portion is separated. A circuit is provided for outputting a signal and not outputting a separated signal when only a video signal is input.

[0005]

With the newly provided circuit, it is determined whether the input signal is the composite signal or only the video signal, and when the composite signal is input, the signal separated from the sync signal is output.
When only the video signal is input, the separated signal can be prevented from being output. Therefore, the control of the power supply circuit or the limitation of the power supply power can be stabilized accurately with the presence or absence of the synchronization signal.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

When a composite signal is input to the input terminal 1, a signal obtained by separating the sync signal portion is output from the sync separating means 2 and is input to the switching means 6 and the first pulse generating means 3.

The first pulse generating means 3 is set to a time constant wider than the vertical synchronizing period and narrower than the vertical blanking period, and the time constant is determined from the rising or falling changing point of the signal separating the sync signal portion. A pulse that is in a High state is generated for the time. But,
The cycle of the signal obtained by separating the sync signal part is narrower than the vertical sync period (including the horizontal sync signal) and narrower than the set time constant period, so that the output is always re-triggered to the high state. The output is input to the second pulse generating means 4 and the logical operation means 5.

The second pulse generating means 4 is triggered by the changing point of the rising or falling of the output of the first pulse generating means 3, and has a time constant L wider than the vertical period, L.
It is set to generate a pulse in the ow state. At this time, the output of the first pulse generating means 3 is always in the High state and there is no change in rising or falling, so the second pulse generating means 4 does not operate,
The output is always in the High state and is input to the logical operation means 5.

The logic operation means 5 receives the high state of the output of the first pulse generating means 3 and the high state of the output of the second pulse generating means 4, so that the output is high.
The state becomes the h state and is input to the switching means 6.

The signal separated by the sync separation means 2 is added to the switching means 6, and when the signal output from the logical operation means 5 is in the high state, the signal output from the sync separation means 2 is output as it is.

When only the video signal is input to the input terminal 1, when the video content is a signal other than a black pattern, for example, a white pattern, a signal obtained by separating the video signal portion is output from the sync separating means 2, and the switching means 6 is provided. Is input to the first pulse generating means 3.

Since the period of the signal obtained by separating the video signal portion is wider than the vertical blanking period, the first pulse generating means 3
Then, a pulse that is wider than the period of the set time constant and is momentarily in the Low state in the vertical cycle is output. The output is input to the second pulse generating means 4 and the logical operation means 5.

The second pulse generating means 4 is set to a time constant wider than the vertical period, and the first pulse generating means 3
Since it is wider than the cycle of the pulse output in step 3, the output is always re-triggered to be in the low state and input to the logical operation means 5.

The logical operation means 5 outputs the pulse output from the first pulse generation means 3 and the output from the second pulse generation means 4.
Since the Low state is input, the output becomes the Low state and is input to the switching means 6.

Similarly, in the black pattern, since the separated signal is not output from the sync separation means 2, there is no rise or fall change. Therefore, since the first pulse generating means 3 is not triggered, the output of the first pulse generating means 3 is always in the Low state, and the second pulse generating means 4
Is input to

Since the output of the first pulse generating means 3 is in the low state and there is no change in rising or falling, the output of the second pulse generating means 4 is always in the high state and is input to the logical operation means 5.

The logical operation means 5 has a low state of the output of the first pulse generating means 3 and Hi of the second pulse generating means 4.
Since the gh state is input, the output becomes the Low state and is input to the switching means 6.

The switching means 6 does not output the signal separated by the sync separation means 2 when the signal output from the logical operation means 5 is in the low state. Therefore, when a composite signal is input to the output terminal 7, a signal obtained by separating the sync signal portion can be output, and when only a video signal is input, the separation signal can not be output.

Next, the waveforms shown in FIGS. 2, 3 and 4 will be described.

FIG. 2 shows a waveform operation when a composite signal is input as the input signal A.

When the input signal A is input to the input terminal 1, the output of the sync separation means 2 becomes the waveform of the signal B obtained by separating the sync signal portion of the input signal A, and the first pulse generation means 3
Is input to

Since the first pulse generating means 3 is set to generate a pulse having a time constant wider than the vertical synchronizing period and narrower than the vertical blanking period, the signal B obtained by separating the synchronizing signal portion is input. In this case, the falling edge of the pulse changes at intervals shorter than the time constant set by the first pulse generating means 3, so that the retrigger is repeated. Therefore, the output signal C of the first pulse generating means 3 is always High.
The state becomes the h state, and it is input to the logical operation means 5 and the second pulse generation means 4.

The second pulse generating means 4 operates so as to generate a time constant pulse wider than the vertical period by using the falling change point of the output signal C of the first pulse generating means 3 as a trigger. However, since the output signal C of the first pulse generating means 3 at this time has no change in the falling edge, the output signal D of the second pulse generating means 4 is always in the High state and is input to the logical operation means 5. .

The logical operation means 5 has an output signal C from the first pulse generating means 3 and an output signal D from the second pulse generating means 4.
Since both are always in the high state, the output signal E of the logical operation means 5 is always in the high state and input to the switching means 6.

Since the switching means 6 is turned on only when the output signal E from the logical operation means 5 is in the high state, the switching means 6 outputs the signal B obtained by separating the sync signal portion as it is.

FIG. 3 shows a waveform operation when a white pattern of only a video signal is input as the input signal A.

When a white pattern of only the video signal of the input signal A is input to the input terminal 1, the sync separating means 2 becomes a signal B which is a separated video signal portion and is input to the first pulse generating means 3.

Since the first pulse generating means 3 is set so as to generate a pulse having a time constant wider than the vertical synchronizing period and narrower than the vertical blanking period as described above, the portion of the video signal is separated. When the output signal B is input,
When the trailing edge of the pulse changes at an interval longer than the time constant set by the first pulse generating means 3, that is, when it is wider than the vertical blanking period, the pulse is generated in the vertical cycle because it is not retriggered. It is input to the second pulse generating means 4.

Since the second pulse generating means 4 is set longer than the vertical period and is retriggered at the changing point of the falling edge of the pulse of the output signal C of the first pulse generating means 3, the second pulse generating means 4 is generated. The output signal D of the means 4 is in the low state and is input to the logical operation means 5.

The input of the logical operation means 5 is the pulse of the output signal C of the first pulse generating means 3 and the second pulse generating means 4
The output signal D of the logical operation means 5 is output because the output of the second pulse generation means 4 is in the low state.
Becomes a low state and is input to the switching means 6.

Since the switching means 6 is in the OFF state when it is in the low state, the sync separating means 2 does not output the signal B obtained by separating the video signal portion.

FIG. 4 shows a waveform operation when a black pattern is input as the input signal A with only a video signal.

When the black pattern of only the video signal of the input signal A is input to the input terminal 1, the sync separation means 2 does not output. Therefore, since the first pulse generating means 3 does not trigger, the output signal C of the first pulse generating means 3 is always Lo.
It becomes the w state, and the logical operation means 5 and the second pulse generation means 4
Is input to Since the output signal C of the first pulse generating means 3 has no change in the falling edge, the second pulse generating means 4
The output signal D of is always in the high state and the logical operation means 5
Is input to

Since the output signal C of the first pulse generating means 3 input to the logical operation means 5 is always in the low state and the output signal D of the second pulse generating means 4 is always in the high state, the logical operation is performed. The output signal E of the means 5 is always Low
It becomes a state.

The switching means 6 does not output the separated signal B because it is turned off when the output signal E from the logical operation means 5 is in the low state.

Therefore, in the case of a composite signal, the signal obtained by separating the part of the sync signal output from the sync separating means 2 is output as it is, so that the output signal F can be output to the output terminal 7 and the video signal. In the case of only input, the output of the sync separation means 2 is not output to the output terminal 7.

[0038]

According to the present invention, it is possible to prevent a signal separated from a video signal portion that occurs when only a video signal is input from being output to the output terminal 7. Therefore, the power supply circuit of the image display device is controlled by the separated signal. Alternatively, it is possible to accurately and stably limit the power supply power.

[Brief description of drawings]

FIG. 1 is a diagram showing a sync separation means according to an embodiment of the present invention.

FIG. 2 is a waveform diagram in each part of FIG. 1 when a composite signal is input.

FIG. 3 is a waveform diagram in each part of FIG. 1 when a white pattern is input only with a video signal.

FIG. 4 is a waveform diagram in each part of FIG. 1 when a black pattern is input only with a video signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2 ... Sync separation means, 3 ... First pulse generation means, 4 ... Second pulse generation means, 5 ... Logical operation means, 6 ... Switching means, 7 ... Output terminal, A ... Input signal, B ... the signal separated by the sync separating means, C ... the output signal of the first pulse generating means 3, D ... the second pulse generating means 4
Output signal of E, an output signal of the logical operation means 5, F ... an output signal.

Claims (3)

[Claims] 1. An apparatus for separating / extracting a sync signal component from an input signal, wherein a pulse is output according to the output of the sync separation means and the sync separation means, and the output pulse width is wider than the vertical sync period and vertical. First pulse generating means set to be narrower than the blanking period and second pulse generating means to output a pulse according to the output of the first pulse generating means, the output pulse width of which is set wider than the vertical synchronizing period. A logic circuit that receives the outputs of the first pulse generating means and the second pulse generating means to perform a logical operation; and an output signal of the synchronization separating means, and the output signal of the logic circuit is used as a control signal. When the input signal is a composite signal including at least a video signal component and a sync signal component (hereinafter, referred to as a composite signal), the switching means used is used. Outputs a signal, or when the input signal is a signal which does not include a synchronizing signal component, synchronous separation device characterized in that it does not output a signal. 2. The synchronization separation device according to claim 1, wherein the device is a multi-scan image display device. 3. The sync separation device according to claim 1, which is a television receiver.