JPS5850670Y2 - Reproduction horizontal synchronization signal generator - Google Patents

Description

[Detailed description of the invention] A composite synchronizing signal (
A so-called composite synchronization signal), a horizontal synchronization signal, a vertical synchronization signal, etc. are used, for example, as a reference signal for synchronization in a closed-circuit TV system, or as a reference signal for achieving various other purposes. This has been widely known for a long time.

However, the composite video signal obtained within the TV receiver has
Noise generated within the transmission system may be mixed in, and in such cases, noise may also be mixed in the composite synchronization signal separated from the composite video signal, or the horizontal synchronization signal and vertical synchronization signal. Therefore, the composite synchronization signal, horizontal synchronization signal, vertical synchronization signal, etc. separated from the composite video signal in the TV receiver can be used directly as a reference signal for synchronization or as a reference signal for achieving various purposes. Did you use it?
The presence of noise mixed in with this will hinder the achievement of the intended purpose.

For this reason, for example, in a TV receiver that employs a horizontal synchronization automatic frequency (phase) control circuit (hereinafter referred to as a horizontal synchronization AFC circuit) as a horizontal synchronization circuit, the horizontal circuit To solve the above noise problem by using a pulse generated during a horizontal retrace period (hereinafter referred to as a horizontal retrace pulse) as a horizontal synchronization signal used as a reference for achieving various purposes. is being carried out.

However, the timing of the generation of the horizontal blanking pulse generated in the horizontal circuit of a TV receiver is often slightly shifted forward or backward on the time axis, and the horizontal synchronization adjustment mechanism of the TV receiver is If the horizontal retrace pulse is adjusted, the phase difference with the horizontal synchronizing signal will be quite large.Furthermore, since the horizontal retrace pulse has a wider pulse width than the horizontal synchronizing signal, The horizontal retrace pulse generated by the horizontal retrace pulse can be used as a time reference instead of the horizontal synchronization signal to insert digital or analog signals (e.g., video signals) during specific horizontal scan periods into a composite video signal. Alternatively, when extracting multiplexed signals inserted during a specific horizontal scanning period in a composite video signal, there is a problem in that it is difficult to perform accurate signal insertion and extraction operations.

The present invention is applicable to TV receivers in which a horizontal synchronization AFC circuit is adopted as a horizontal synchronization circuit, and the composite synchronization signal is separated from a composite video signal having a horizontal synchronization signal of pulse τ1 via a synchronization separation circuit. In addition to the first pulse generating circuit, the first pulse generating circuit has a leading edge that substantially coincides with the leading edges of the individual pulses that make up the composite synchronizing signal from the first pulse generating circuit, and has a pulse width that is smaller than the above-mentioned pulse width τ1. Also narrow pulse width τ
2, and also generates a front edge detection pulse Pa having a horizontal synchronization AFC in the TV receiver and
The horizontal retrace pulse Sf of the pulse τ3 generated in the horizontal circuit consisting of the circuit, the horizontal oscillation circuit, and the horizontal output circuit is gated through the gate circuit to generate a pulse with a width τ4 approximately equal to the pulse width τ2. A reproduction horizontal synchronization signal is generated and given as a trigger signal to a second pulse generation circuit, so that a reproduction horizontal synchronization signal having a pulse width τ5 approximately equal to the pulse width τ1 is obtained by the second pulse generation circuit. The present invention provides a signal generating device that solves the above-mentioned conventional problems, and the specific contents thereof will be explained below with reference to the attached drawings.

FIG. 1 is a block diagram of one embodiment of the reproduction synchronization signal generator of the present invention, in which 1 is an input terminal for a composite video signal obtained within a TV receiver, and 2 is a reproduction horizontal synchronization signal input terminal. The composite video signal (FIG. 3a) supplied to the input terminal 1, which is a signal output terminal, is synchronously separated in the synchronous separation circuit SEP.

The composite synchronization signal Sc (Fig. 3) output from the synchronization separation circuit SEP described above is applied to the first pulse generation circuit PG1, and the horizontal synchronization signal sh is applied to the horizontal circuit H, which further provides vertical synchronization. The signal Sv is applied to the vertical circuit (2).

In the illustrated example, the horizontal circuit H is composed of a horizontal AFC circuit 3, a horizontal oscillation circuit 4, and a horizontal output circuit 5. A control signal is generated so that the frequency and phase of the oscillation wave of the horizontal oscillation circuit 4 correspond correctly to the repetition frequency and phase of the horizontal synchronization signal sh by the horizontal retrace pulse Sf generated in the horizontal retrace pulse Sf. and feed it to the horizontal oscillation circuit 4.

Further, the horizontal oscillation circuit 4 drives the horizontal output circuit 5 with an oscillation wave from the horizontal oscillation circuit 4.

The horizontal blanking pulse Sf generated in the horizontal circuit H is supplied to the horizontal AFC circuit 3 as a comparison wave as described above, and is also supplied to the gate circuit G as described later. The horizontal retrace pulse Sf given is:
It goes without saying that each circuit has a required peak value required for circuit operation.

The synthesized synchronization signal Sc shown in FIG. 3 obtained from the synchronization separation circuit SEP described above is given to the first pulse generation circuit PCI, and from this first pulse generation circuit PCI, the synthesized synchronization signal Sc shown in FIG. Then, a leading edge detection pulse Pa having a leading edge that substantially coincides with the leading edges of the individual pulses constituting the composite synchronizing signal Sc and having a narrow pulse width τ2 is sent out.

FIG. 2 is a block circuit diagram of the above-mentioned first pulse generating circuit PG1 having the structure shown in FIG. It is the output terminal of
In order to make the correspondence between the diagram and Figure 2 clear,
The code of the output terminal 1yO is written.

In Fig. 2, INV is an inverter, AND is an AND circuit, and ■ is an integration circuit, and the composite synchronization signal Sc supplied to the input terminal i has its polarity inverted by the inverter INV and is then sent to the AND circuit AND. One is added as an input, and the other input, given a necessary time delay by the integrating circuit, is applied to the AND circuit AND.

As a result, the AND circuit AND outputs a bi-level output pulse only during the period when both inputs are at the bi-level. This results in a pulse Pa.

It goes without saying that the pulse width τ2 of the leading edge detection pulse Pa generated by the first pulse generation circuit PCI shown in the second diagram can be arbitrarily set by changing the integration time constant in the integration circuit (2). In order to output leading edge detection pulses corresponding to individual pulses from the first pulse generation circuit PCI even in the insertion period of the equalization pulse during the vertical blanking period in the composite synchronization signal,
Integrating circuit I must choose its integration time constant to a suitable value.

Incidentally, since the integrating circuit I is provided to give a required time delay to the composite synchronizing signal Sc, other suitable delay circuits may be used in place of this integrating circuit I.

The above-mentioned first pulse generation circuit PG1, for example, differentiates the input synthetic synchronization signal, extracts a differential pulse that protrudes in the negative direction from the differential waveform with an appropriate level detection circuit, and then inverts its polarity through an inverter. There are many other possible configurations, including one in which the

Now, the leading edge detection pulse Pa shown in FIG.
Since the horizontal retrace pulse Sf shown in FIG. Sf and leading edge detection pulse P
Output pulse Pb corresponding to the logical product with a (Fig. 3 e)
is sent to the second pulse generation circuit PG2.

The output pulse pb from the gate circuit G has a repetition period corresponding to the horizontal scanning period, and has a leading edge at approximately the same time position as the leading edge of the horizontal synchronizing signal in the composite synchronizing signal. It also has a pulse width τ4 that is approximately equal to the pulse width τ2 of the leading edge detection pulse Pa shown in FIG. 3C described above.

The second pulse generation circuit PG2 is the gate circuit G described above.
By applying the output pulse pb from 1 as a trigger pulse, a reproduced horizontal synchronizing signal shα as shown in FIG. 3f having the same pulse width as the horizontal synchronizing signal sh is sent to the output terminal 2.

This second pulse generating circuit PG2 may be configured by a monostable multibiflator.

The pulse width τ1 of the horizontal synchronization signal sh, the pulse width τ2 of the leading edge detection pulse Pa, the pulse width τ3 of the horizontal retrace pulse Sf, the pulse width τ4 of the output pulse pb of the gate circuit G, and the reproduced horizontal synchronization signal The mutual relationship between each pulse width, such as the pulse width τ5 of shα, is τ3〉τ〉τ29, τ2÷τ4, τ1 cow τ5, as described above.

As is clear from the above explanation, in the reproduced horizontal synchronization signal generator of the present invention, the synthesized synchronization signal S obtained within the TV receiver is
c through a first pulse generation circuit to create a narrow pulse train Pa having a leading edge approximately equal to the leading edge of the individual pulses of this composite synchronizing signal, and to generate a narrow pulse train Pa having a leading edge approximately equal to the leading edge of the individual pulses of this composite synchronizing signal. The noise-free horizontal retrace pulse Sf generated by the horizontal circuit consisting of the horizontal circuit and the horizontal output circuit is extracted as a gate pulse, and the required pulse width is obtained by each pulse in the Sayama pulse train having the extracted horizontal scanning period. Since the second pulse generation circuit that can generate a pulse with the desired pulse width is used to obtain a reproduced horizontal synchronizing signal with the required pulse width, even if noise is mixed in the synthesized synchronizing signal, the reproduced horizontal No noise appears in the synchronization signal, and in the reproduction horizontal synchronization signal generator of the present invention, the phase of the reproduction horizontal synchronization signal does not change even if horizontal synchronization adjustment is performed. The signal generator effectively utilizes the characteristics of the horizontal synchronization AFC circuit originally installed in TV receivers to obtain a stable reproduced horizontal synchronization signal, so it requires less special circuitry and is simple to use. It has various advantages such as being able to provide a device at low cost with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the reproduction horizontal synchronization signal generator of the present invention, FIG. 2 is a block diagram of an example of the first pulse generation circuit, and FIGS. 3 a to 3 are for explanation. FIG. Lx...input terminal, 2to...output terminal, 3...
Horizontal synchronous AFC circuit, 4...Horizontal oscillation circuit, 5...
Horizontal output circuit, SEP...Synchronization separation circuit, H...Horizontal circuit, ■...Vertical circuit, PGl...First pulse generation circuit, G...Gate circuit, PG2...Second Pulse generation circuit, INV...inverter, AND...
AND circuit, I...integrator circuit.

Claims (1)

[Scope of utility model registration request] In a TV receiver that employs a horizontal synchronization AFC circuit as a horizontal synchronization circuit, a composite synchronization signal separated from a composite video signal having a horizontal synchronization signal with a pulse width τ1 via a synchronization separation circuit is sent to a first pulse generation circuit. and a pulse width τ2 having a leading edge substantially coinciding with the leading edge of the individual pulses constituting the composite synchronization signal from the first pulse generating circuit, and having a pulse width τ2 narrower than the pulse width τ1.
means for generating a leading edge detection pulse Pa having a horizontal synchronization AFC in the TV receiver with the leading edge detection pulse Pa;
A horizontal retrace pulse Sf with a pulse width τ3 generated in a horizontal circuit consisting of a horizontal oscillator circuit, a horizontal oscillation circuit, and a horizontal output circuit is passed through a gate circuit to generate a pulse with a pulse width τ4 approximately equal to the pulse width τ2. means for generating a pulse having a pulse width τ4 as a trigger signal to a second pulse generating circuit; and reproducing horizontal synchronization with a pulse width τ5 approximately equal to the pulse width τ1 by the second pulse generating circuit. A reproducing horizontal synchronizing signal generator comprising means adapted to obtain a signal.