JPS62164379A - Signal generator circuit for blanking - Google Patents

Abstract

PURPOSE:To reduce the number of circuit elements by using a pulse generator consisting of an analog circuit triggered by a synchronizing signal separated from a luminance signal, and a counter counting reference signals. CONSTITUTION:The pulse generator 11 forms a horizontal synchronizing signal HD from the synchronizing signal SS separated from the luminance signal by a synchronous separator circuit 10, while the pulse generator 12 outputs a burst flag pulse FB, and integrates the synchronizing signal inputted to a low-pass filter 13. When an available vertical synchronizing signal VD resets the counter 17 counting the horizontal synchronizing signal HD, a vertical blanking signal V.BLK can be outputted. The vertical blanking signal V.BLK is obtained by counting a chrominance subcarrier fSC outputted from the counter 16 by the 1st counter 14 and forming a pulse waveform. The chrominance subcarrier frequency fSC is set by a reference signal oscillator 15.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a blanking signal generation circuit useful when, for example, converting a baseband color difference signal to form a composite video signal or the like. be.

[Summary of the invention]

The blanking signal generation circuit of the present invention uses the synchronization signal when forming a horizontal blanking signal, a vertical blanking signal, and a burst flag signal indicating a color burst period from a synchronization signal separated from a luminance signal. It uses a pulse generator consisting of an analog circuit that is triggered and a counter that counts the reference signal.

Therefore, the number of circuit elements can be significantly reduced compared to conventional blanking signal generation circuits.

[Conventional technology]

In some color displays of personal computers, television games, electronic cameras, etc., the luminance signal and color signal forming the image signal are processed in a state where they are separated in the baseband band.

In such an image signal, color information is, for example, a baseband color difference signal (RY) and (B
-Y) will be recorded and reproduced.

Therefore, when forming an NTSC composite video signal from such a signal, six color difference signals (R-Y) are used.
, and (B - y) by the color subcarrier frequency orthogonal 2
Signal processing is performed in which the signal is phase modulated, converted into a carrier color signal, and superimposed on the luminance signal.

In this case, if the reproduced color difference signal is converted to a carrier color signal and superimposed on the luminance signal, the carrier color signal modulated by noise will be superimposed during the blanking period of the image signal, and the S /N ratio deteriorates.

Therefore, conventionally, blanking signal generation circuits corresponding to the horizontal blanking period, vertical blanking period, and color burst period are used so that the carrier color signal and color burst signal are superimposed only on predetermined portions of the luminance signal. Signal processing was carried out.

FIG. 4 shows a conventional example of such a blanking signal generation circuit, where l is j! 2 is a vertical sync extraction circuit that forms a vertical sync signal from the sync signal; 3 is a voltage controlled oscillator (V
A phase comparator for controlling the oscillation frequency of CO)4,
The phase comparison between the signal indicating one horizontal period obtained from the counter logic circuit 5 and the separated horizontal synchronization signal is performed.

6 is a reference signal oscillator for forming a color subcarrier fsc, and the output (14, 32 MHz) of this reference signal oscillator 6 is divided by a counter 7, for example, into two color subcarriers with a phase difference of 900. f SC (3,58MHz
) is output.

As described above, the conventional blanking synchronization signal generation circuit first sets the phase comparator 3 so that the oscillation frequency fO of the voltage variable oscillator 4 is an integral multiple of the horizontal oscillation frequency (IH), for example, 260 times. , and counter logic circuit 5
The signal pulses for blanking are counted by controlling the count output of the counter logic circuit by a PLL circuit consisting of a PLL circuit and signal processing the count output of the counter logic circuit by the logic circuit.

That is, as shown in the standard video signal waveform diagram of FIG. 5, a 0.075H horizontal synchronizing signal is output from the HD terminal, and a burst flag signal indicating a 0.119H color burst signal period is output from the BF terminal. A signal indicating a horizontal blanking period of 0.18H is sent from the H-BLK terminal to V
A signal indicating the vertical blanking period is output from the -BLK terminal.

When the color difference signal is modulated by the color carrier signal output from the counter 7 to form a carrier color signal and then superimposed on the luminance signal, the signal indicating the horizontal blanking period and the signal indicating the vertical blanking period are used. The color carrier signal is suppressed.

Further, a composite video signal is formed by superimposing a color subcarrier on a luminance signal only during five signal periods using a burst flag.

[Problem that the invention seeks to solve]

However, in the conventional blanking signal generation circuit, the oscillation frequency of the voltage variable oscillator 4 is determined by the counter logic circuit 5.
For example, since various synchronization signals are output at predetermined points in the video signal period while counting by 0.
In order to output the synchronization signal in a timely manner with an accuracy of about 0.008H, it is necessary to increase the oscillation frequency fo of the voltage variable oscillator, which increases the number of counting stages of the counter 9 and the chic circuit 5 and the number of logic elements. The problem was that I needed something.

Also, in order to make a stable PLL circuit, the circuit becomes complicated,
There is a problem in that it increases costs.

The present invention has been made to alleviate such problems, and provides a blanking signal generation circuit that uses an analog synchronization signal generation circuit to reduce the number of circuit elements.

[Means for solving problems]

The blanking signal generation circuit of the present invention uses a pulse generator using a time constant for the color burst flag signal (BF) and the horizontal synchronization signal (HD), and a pulse generator using a low-pass filter for the vertical synchronization signal. A signal indicating the horizontal blanking period that requires high accuracy (H-B LK
) is generated by applying a reset using a horizontal synchronization signal to a counter that divides the signal from the reference oscillator.

[Effect]

The horizontal synchronization signal, which is close to the falling point of the synchronization signal separated from the luminance signal, and the burst flag signal, which indicates the color burst signal period, are generated by a pulse generator having an appropriate time constant, such as a monostable multi-octablator, etc. formed using. In addition, high accuracy is required for the signal indicating the water mob blanking period, which is relatively far away from the falling point of the synchronization signal, and only this signal requires a reference signal such as a crystal oscillator to be used in the counter that is reset by the horizontal synchronization signal. Let it feed and form.

Therefore, the number of circuit elements in the blanking signal generation circuit can be reduced compared to the conventional one.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 10 is a sync signal separation circuit that separates a sync signal from a luminance signal Y, and 11 is a horizontal sync signal at a predetermined interval every IH (1 water period). A first pulse generator for outputting pulses (HD), for example, a one-shot multi triggered at the falling point from the synchronization signal separation circuit 11, and a reference voltage source;
It is made up of comparators, etc.

12 is a second pulse generator which is similarly triggered by a signal from the synchronization signal separation circuit lo, and this second pulse generator 12 forms a signal corresponding to the color burst period, that is, a burst flag signal BF. It is.

Reference numeral 13 denotes a low-pass filter 5 that integrates the separated synchronization signal, and detects a vertical synchronization signal portion with a wide pulse width, which is often found in a circuit that forms a vertical synchronization signal of a television, for example.

14 indicates a first counter that counts color subcarriers in this embodiment, and is configured to be reset every IH, and as will be described later, output pulses between count values N1 and N2, that is, It generates a horizontal blanking signal H-BLK. Reference numerals 15 and 16 indicate a reference oscillator and a counter for generating a color subcarrier as in the conventional example described above, and output a color subcarrier frequency fs+H with a 90° phase difference.

A second counter 17 counts horizontal synchronizing signals and forms a vertical blanking signal for each horizontal synchronizing signal for one field, for example.

The operation of the blanking synchronization signal of the present invention will be explained below based on the waveform diagram of FIG.

The synchronization signal SS separated from the luminance signal by the synchronization separation circuit IO is transmitted to the first . It is input to a second pulse generator 11, 12 and a low pass filter 13.

The first pulse generator 11 operates at the falling point t of the synchronization signal SS.
1 generates a ramp wave as shown in Ml. and.

The horizontal synchronization signal HD is generated by detecting when this ramp wave Ml reaches the reference voltage El.

Further, the second pulse generator 12 is also triggered at the falling point of the synchronization signal SS and generates the ramp signal M? occurs.

This ramp wave M2 is the reference voltage E2, and E3.
When the signal reaches the maximum value, a burst flag pulse (BF) is output.

In this case, for example, a monostable multibar r-break is used to output the ramp signal, and the period T of the output pulse width is set to be longer than the y2H period and shorter than the H period. Then, it will no longer respond to the synchronization signal of the station H period as shown by the dotted line Z inserted in the vertical blanking period, and if the reference voltages E, E2, and E3 are set to predetermined values, 1 horizontal synchronization signal HD
Then, a burst flag signal BF for color burst blanking can be obtained.

By integrating the synchronization signal input to the low-pass filter 13, a well-known vertical synchronization signal VD is obtained.

When the second counter 17 that counts the horizontal synchronization signal HD is reset using this vertical synchronization signal VD, the second counter 17 outputs a vertical blanking signal V-BLK for setting the vertical blanking period. can do.

The horizontal blanking synchronization signal H@BLK is the counter 16
While counting the color subcarrier fSC output from the first counter 14, a predetermined count value 1, for example, Nl
In this case, the counting start point can be controlled by resetting the first counter 14 using the horizontal synchronizing signal HD.

Since the color subcarrier frequency fsC is set to 3.58 MHz with high precision by the reference signal oscillator 15, the phase error of the horizontal blanking signal H-BLK does not exceed 0.28.5. The conditions of the error range (1 to 1.5.5) specified by the NTSC television system can be fully satisfied.

Note that the first circuit is formed of an analog circuit. Since the horizontal synchronization signal HD and burst flag signal BF output from the pulse generator of gg2 are output close to the falling point of the synchronization signal SS, they can be output with fairly high accuracy even with the time constant circuit. , it is easy to satisfy the error range conditions regulated by the NTSC television waveform.

Figure 3 shows the 1. and a specific circuit example of the second pulse generators 11 and 12.

21 is a monostable multivibrator that is triggered at the falling point of the synchronization signal, 22 is a ramp signal generator that generates a ramp voltage by the output pulse of the monostable multipipe rake, 23 and 24 are level comparators, and 25 is an ex-O
This is an R circuit.

The output pulse width of the monostable multivibrator is set between stations H-H, and the ramp signal generator 22 generates a ramp signal that rises during this pulse width. Since different reference voltages El and E2 are input to the level comparator, when these reference voltages E+ and E2 are set to predetermined values, the burst flag signal corresponding to the above-mentioned horizontal synchronization signal HD and color tost signal period is The rising and falling points can be set.

Then, the ex-OR circuit 25 outputs a pulse signal corresponding to the time difference between the rising points.

This first. The second embodiment of the pulse generator forms a blanking signal using a time constant for forming a ramp signal and a reference voltage value.
Since it is close to the falling point of the signal and the BF multiplied signal synchronization signal, the rising error is extremely small, and an analog circuit can provide sufficient accuracy.

In addition, 1. It goes without saying that other types of analog pulse generators, such as blanking oscillator circuits, may be used as the second pulse generator.

The blanking signal generating circuit of the present invention is a color difference signal (R-
Baseband color signals R, G in addition to Y), , (B-Y)
, B, etc., of course.

〔Effect of the invention〕

As explained above, the blanking signal generation circuit of the present invention can drastically reduce the number of circuit elements compared to the conventional blanking signal generation circuit, and can reduce the cost of the circuit. k) It is possible to output a blanking synchronization signal with sufficient precision.

[Brief explanation of drawings]

Fig. 1 is a blow diagram of the blanking signal generation circuit of the present invention, Fig. 2 is an operation waveform diagram of Fig. 1, Fig. 3 is a circuit diagram showing an example of a pulse generator, and Fig. 4 is a conventional one. A block diagram of a blanking signal generating circuit is shown in FIG. 5, and a waveform diagram of a television signal is shown in FIG. In the figure, 10 is a synchronizing signal separation circuit, 11.12 is a first . A second pulse generator, 13 is a low-pass filter serving as an integrating circuit, 14.17 is il, and a second counter. Figure 1 1-IH-- rlip, + Shusei Saimon Figure 2/\5resΔε壬-Ij]Sketσ1 Figure 3 Figure 4

Claims (1)

[Claims] A first and second pulse generator to which a separated synchronizing signal is input, a low-pass filter, a first counter that is reset by the horizontal synchronizing signal and counting the reference frequency, and an output of the low-pass filter. a second counter being reset and counting the horizontal synchronization signal, forming the horizontal synchronization signal and a burst flag signal from the first and second pulse generators;
A blanking signal generation circuit, characterized in that horizontal and vertical blanking synchronization signals are generated by the outputs of the first counter and the second counter.