JPH06253168A - Horizontal blanking signal generating circuit - Google Patents

Abstract

PURPOSE:To display left and right longitudinal lines in an apparent video image area in a straightforward way by varying the width of a horizontal blanking signal so as to correct fluctuation of a raster width caused by high voltage fluctuation. CONSTITUTION:The circuit is provided with a high voltage fluctuation quantity detection means 13 being a means detecting fluctuation quantity of a high voltage applied to a cathode ray tube(CRT) 8, a means varying the width of a generated horizontal blanking signal and a horizontal blanking signal generating circuit 14 being a means adjusting the width of the horizontal blanking signal generated to make left and right longitudinal lines of a raster displayed on a CRT 8 to be a straight line. Then the left and right longitudinal lines of a raster displayed on the CRT 8 are made to be straight lines by adjusting the width of the horizontal blanking signal generated in response to the fluctuation quantity of a high voltage applied to the CRT 8. Thus, an apparent shape of the video image area is unchanged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal blanking signal generating circuit for a television receiver.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a blanking generation circuit of a conventional television receiver. In the figure, as shown in FIG. 8A, the horizontal blanking signal is generated by electrostatically dividing the horizontal collector pulse with the capacitors 1 and 2 and then shaping the pulse into a required level pulse with the Zener diode 3. Generating a horizontal blanking signal. As shown in FIG. 8B, the vertical blanking signal is generated by removing only the pumping pulse portion of the vertical deflection output signal with the Zener diode 4. After that, the vertical and horizontal blanking signals are combined through the diodes 5 and 6 and supplied to the video circuit section via the buffer circuit constituted by the transistor 7 to blank the video signal. The width of the blanking signal generated in this way and the positions of its start point and end point do not fluctuate even if there is a high voltage fluctuation, and are substantially constant.

[0003]

Since the conventional blanking signal generating circuit is constructed as described above, the blanking width is fixed even if the raster width changes due to high voltage fluctuation. As shown in FIG. 9, when the image content in which the bright and dark portions are largely separated and the high-voltage fluctuation is likely to occur is underscanned horizontally on the display of the cathode ray tube (hereinafter, referred to as “CRT”), the fluctuation of the raster width is caused. ,
Immediately, the start and end positions of the video area appear as fluctuations, and the vertical lines on the left and right of the screen are curved, resulting in a problem in that it is very visually unpleasant to see.

In order to reduce the fluctuation of the raster width,
Is it possible to consider measures such as adding a high-voltage capacitor or a high-voltage stabilizing circuit, or because the control time constant of the high-voltage generating circuit is long?
There is a problem that it is difficult to get a quick response.

The present invention has been made to solve the above problems, and is a television for performing at least horizontal underscan display (underscan by deflection, underscan by signal time axis compression, etc.). An object of the present invention is to obtain a blanking signal generating circuit in which the vertical lines on the left and right of the apparent image area displayed on the display surface of the CRT do not appear to be bent even if the raster width changes due to high voltage fluctuations in the receiver. I am trying.

Further, a blanking signal generation circuit in which the left and right vertical lines of the apparent image area do not appear to be bent even when the horizontal linearity correction circuit and the left and right pincushion distortion correction circuits have left and right imbalances is obtained. Is intended.

[0007]

A horizontal blanking signal generating circuit according to the present invention comprises means for detecting a variation amount of a high voltage applied to a CRT, and means for changing a width of a horizontal blanking signal to be generated. A means for adjusting the width of the horizontal blanking signal generated so that the left and right vertical lines of the raster displayed on the CRT become straight lines based on the detected high voltage fluctuation amount is provided.

Further, there is provided means for adjusting the phase and width of the horizontal blanking signal generated so that the position of the raster displayed on the CRT and the left and right vertical lines become straight lines in accordance with the deflection characteristics of the CRT. Is.

[0009]

According to the present invention, the width of the horizontal blanking signal generated according to the variation of the high voltage applied to the CRT is adjusted so that the vertical lines on the left and right of the raster displayed on the CRT become straight lines. Therefore, the apparent shape of the image area does not change.

Further, even if the amount of change in the left and right widths of the raster displayed on the CRT differs due to the fluctuation of the high voltage applied to the CRT, the vertical lines on the left and right of the raster width displayed on the CRT are displayed. Since the positions of the starting point and the ending point of the horizontal blanking signal are adjusted so that the line becomes a straight line, the apparent shape of the image area does not change.

[0011]

EXAMPLES Example 1. Embodiment 1 of the present invention will be described below with reference to FIG.
4 will be described. In FIG. 1, 8 is a CRT, 9
Is a flyback transformer for applying a DC high voltage to the CRT 8, and 10 is a first high voltage fluctuation amount detecting means which is composed of a voltage dividing circuit of a high resistance R1 and a low resistance R2, and detects a low frequency component of the high voltage fluctuation. Reference numeral 11 is a second high pressure fluctuation amount detecting means,
It is composed of a voltage dividing circuit of capacitors C1 and C2, and detects a high frequency component of high voltage fluctuation. 12 is an adder, which is the first
The detection signals of the second high-voltage fluctuation amount detecting means 10 and 11 are added to output a high-voltage fluctuation amount detecting signal including a DC component to a frequency component, and 10 to 12 constitute the high-voltage fluctuation amount detecting means 13. . Reference numeral 14 denotes a horizontal blanking signal generation circuit, which is composed of a triangular wave generation circuit 15, a slice circuit 16 and a waveform shaping circuit 17.

FIG. 2 is a block circuit diagram showing an example of the configuration of the triangular wave generating circuit 15, in which 18 is a one-shot multivibrator and 19 is an integrator composed of an operational amplifier.

Next, the operation will be described. When the horizontal sync signal shown in FIG. 3A is input to the positive trigger input terminal of the one-shot multivibrator 18, the inverted Q output terminal of FIG.
Inverted Q signal which is at L level for a period of time constant τ determined by R4 <C4 and one-shot multivibrator 18 therein is output. Since the values of R3 and C3 are set so that the time constant τ is exactly ½ of the horizontal scanning period H, a square wave signal having a horizontal cycle with a duty of 50% as shown in FIG. 3B. Occurs and is input to the integrator 19 via Tr. The integrator 19 integrates this square wave signal with a time constant determined by R4 and C4, and slices a triangular waveform signal having a horizontal period as shown in FIG.
Output to.

The slice circuit 16 receives the high-voltage fluctuation detection signal from the adder 13, and the level at which the input triangular waveform signal is sliced is determined according to the value. That is, if the high voltage of the CRT is lowered, the slice level shown in FIG. 3C is increased, and if the high voltage is increased, the slice level is lowered, and the sliced rectangular waveform signal is shaped by the waveform shaping circuit 17.
Output to.

The waveform shaping circuit 17 shapes the input rectangular waveform signal into a rectangular waveform and outputs it as a horizontal blanking signal shown in FIG. 3 (d). The width of the output horizontal blanking signal is as shown in FIG.
If the slice level shown in (c) is increased to widen the width B of the horizontal blanking signal, and if the high voltage returns to the steady state, the slice level is returned to the original level and the width of the horizontal blanking signal is restored to the original width. Adjusted to return, CRT
The left and right borders of the raster displayed in are adjusted to be straight.

The horizontal blanking signal thus created is added to the vertical blanking signal as shown in FIG. 7 and applied to the CRT to blank the video signal.

FIG. 4 is a diagram showing a display surface of a CRT in which the present embodiment is applied to a wide aspect television receiver, and a horizontal aspect is used for displaying a 4: 3 image on the wide aspect television receiver. By reducing the deflection width to 3/4, the circularity of the image is maintained and displayed.
In this example, even if the raster width fluctuates due to the high voltage fluctuation, the left and right vertical lines in the image display area are displayed straight.

In particular, in a wide aspect television receiver, when displaying a 4: 3 image, it is not necessary to provide a time axis compression circuit, and the weakness of the high voltage circuit when the horizontal deflection width is reduced is displayed. It is possible to obtain the effect of inexpensively compensating for the symptom that the vertical line at the boundary of the image display area that is generated is bent.

Further, in the first embodiment, the high voltage is directly divided to detect the fluctuation of the raster width. However, the high voltage fluctuation is indirectly high voltage by observing the inflow currents of the A, B and L terminals of the flyback transformer. It could be any other way of looking at fluctuations.

Example 2. Further, in the first embodiment, the high voltage fluctuation component is supplied as it is to the slice circuit for determining the width of the horizontal blanking signal. However, when the raster width correction circuit for correcting the raster width in accordance with the high voltage fluctuation is provided, A configuration may be adopted in which only the components having a relatively high frequency, which the raster width correction circuit cannot follow, are given to the second high-voltage fluctuation amount detection means blanking signal circuit to correct. That is, the high voltage fluctuation may be differentiated and given to the horizontal blanking pulse generation circuit 14 of the first embodiment, and the blanking pulse generation circuit may be used while compensating for the high frequency component of the raster width correction circuit.

Example 3. In the circuit for correcting the width B of the horizontal blanking signal shown in the first embodiment evenly in the left and right directions, the circuit having the horizontal linearity correction circuit and the left and right pincushion distortion correction circuits is used.
In an RT device, the left and right imbalances of the correction characteristics of these circuits may cause the left and right variations in the positions of the start and end points of the video area to differ. In the third embodiment, in order to compensate for such a left-right unbalance, the triangular wave generation circuit 15 of the horizontal blanking signal generation circuit 14 is provided with a phase changing means.

FIG. 5 is a block circuit diagram showing a triangular wave generation circuit of the third embodiment, and FIG. 6 is a timing diagram of the third embodiment. Since the overall configuration is the same as that of FIG. 2, its explanation is omitted.

The third embodiment is different from the triangular wave generating circuit of the first embodiment shown in FIG. 2 in that the time constant τ that determines the L period of the inverted output Q of the one-shot multivibrator 18 is variable, so that the variable resistance is changed. In addition to using the resistor VR1, the integration amount of the integrator 19 is also variable using the variable resistor VR2.

Now, when the resistance value of VR1 is made small, the time constant becomes short as τ ', and as shown in FIG. 6 (b), the one-shot multivibrator 18 outputs an inverted Q output signal having a short L period to the integrator. It is output to 19. Integrator 19
Adjusts the resistance value of VR2 according to the time constant τ 'so that the amplitude of the output triangular wave signal becomes constant. As a result, the waveform of the output triangular wave signal of the integrator 19 becomes the waveform shown by the broken line in FIG. This triangular waveform signal is used as a slice circuit 16
Waveform shaping circuit 1
The waveform is shaped in 7 and output as the horizontal blanking signal indicated by the broken line in FIG. On the display surface of the CRT, the right side has a larger response amount to the high pressure fluctuation.

By properly selecting the circuit constant,
It goes without saying that the left and right response amounts can be set to desired ratios.

[0026]

As described above, according to the present invention, the width of the horizontal blanking signal is changed so as to correct the fluctuation of the raster width caused by the fluctuation of the high voltage.
In a television receiver that underscans in the horizontal direction to display an image, the left and right vertical lines of the apparent image area can be displayed straight.

Further, since the phase and width of the generated horizontal blanking signal are changed, even if the amount of change in the left and right positions of the raster width is different due to the high voltage change, the left and right vertical lines of the apparent image area are changed. Can be displayed in a straight line.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a horizontal blanking generation circuit according to a first embodiment of the present invention and a diagram showing a high generation circuit of a CRT.

FIG. 2 is a diagram showing an example of the configuration of a triangular wave generation circuit that constitutes the horizontal blanking generation circuit of the first embodiment.

FIG. 3 is a timing diagram of the first embodiment.

FIG. 4 is a diagram showing a display surface of a wide aspect television receiver using the horizontal blanking generation circuit of the first embodiment.

FIG. 5 is a diagram showing a triangular wave generation circuit which constitutes a horizontal blanking generation circuit according to a second embodiment of the present invention.

FIG. 6 is a timing diagram of the second embodiment.

FIG. 7 is a diagram showing a conventional blanking signal generation circuit.

FIG. 8 is a waveform diagram of a conventional example.

FIG. 9 is a diagram showing an underscan display surface of a television receiver using a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CRT 9 Flyback transformer 10 1st high-voltage fluctuation amount detection means 11 2nd high-voltage fluctuation amount detection means 12 Adder 13 High-voltage fluctuation amount detection means 14 Horizontal blanking signal generation circuit 15 Triangular wave generation circuit 16 Slice circuit 17 Waveform shaping Circuit 18 One-shot multivibrator 19 Integrator

Claims (2)

[Claims] 1. A means for detecting a fluctuation amount of a high voltage applied to a cathode ray tube, and vertical lines at the left and right ends of a raster projected on the display surface of the cathode ray tube based on the detection signal are straight lines. A horizontal blanking signal generating circuit having means for adjusting the width of the horizontal blanking signal applied to the cathode ray tube. 2. A means for detecting a fluctuation amount of a high voltage applied to the cathode ray tube, and vertical lines at the left and right ends of the raster imaged on the display surface of the cathode ray tube based on the detection signal are straight lines, and A horizontal blanking signal generation circuit having means for adjusting the width and phase of a horizontal blanking signal applied to the cathode ray tube so that its position is not displaced.