JPH04324761A - Picture display device - Google Patents

Abstract

PURPOSE:To suppress picture distortion due to a white peak with simple circuit constitution by providing a means to detect the white peak of picture information and a means controlling fluctuation in a horizontal size with a detection signal of the white peak detection means in the display device. CONSTITUTION:After a video signal is amplified by a video amplifier circuit 1, a chroma clamp circuit 2 eliminates an undesired color signal, black levels are arranged through a pedestal clamp circuit 3, and a white peak detection circuit 4 slices a white peak depending on a slice level decided by a slice level adjustment circuit 8. The sliced signal is amplified by an amplifier circuit 5, a peak correction circuit 9 adjusts the level and gives the result as a bias of a horizontal size control circuit 11, an output of the circuit 11 is fed to a control amplifier 12 as a control signal for the horizontal size. Through the constitution above, a horizontal size change due to an increase in a beam current resulting from the short time increase in the white level is corrected at a high speed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a cathode ray tube (hereinafter referred to as "CR").
Related to image display devices using C (referred to as "T"), especially C used as terminals for television receivers and various electronic devices.
The present invention relates to an image display device such as an RT display.

0002

2. Description of the Related Art When image information such as a video signal having a white peak is input to an image display device such as a television receiver using a CRT, the beam current of the CRT increases.
The high voltage applied to the CRT is reduced by regulation, the screen size increases, and a distortion occurs in which a square image becomes a trapezoidal image.

Conventionally, in order to deal with the above problem, a high voltage regulator or the like was used to improve the regulation so that even if the beam current flowing through the CRT increased, the high voltage did not drop, thereby preventing image distortion. To improve the high voltage transformer (flyback transformer) top load method (FOCUS SCREE from high voltage)
(method of dividing the N voltage and extracting it and flowing a bleeder current from the high voltage to improve regulation),
Methods such as adding a high-voltage capacitor to the high-voltage output of the FBT were used to improve instantaneous high-voltage regulation.

0004

[Problem to be solved by the invention] In the above conventional method,
FBT (flyback transformer) is expensive, and there are problems such as ineffectiveness when the white peak signal period is long, and the response to instantaneous changes can be responded to by increasing the capacity of the high-voltage capacitor. There was a drawback that the FBT was large. In view of these problems, an object of the present invention is to prevent image distortion from occurring whether the period of the white peak is instantaneous or long.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a CRT for displaying image information, a white peak detection circuit for detecting the white peak of the image information, and a white peak detection circuit for detecting the white peak of the image information. The configuration includes a horizontal size control circuit that controls the horizontal size variation of the CRT using a peak signal.

In addition to the above configuration, an integrating circuit is provided to integrate the white peak signal detected by the white peak detecting circuit, and the above C
The configuration includes a horizontal size control circuit that suppresses fluctuations in the horizontal size of RT.

Furthermore, the configuration includes the white peak detection circuit, a horizontal size correction coil, and a control circuit for controlling the current to the horizontal size correction coil based on the white peak signal from the white peak detection circuit.

[0008] Furthermore, the configuration includes the white peak detection circuit, a horizontal resonant circuit provided in the horizontal output circuit, and a control circuit for controlling the capacitance of the horizontal resonant circuit based on the white peak signal detected by the white peak detection circuit. do.

[0009]

[Operation] According to the above configuration, when a white peak appears in the image information, the white peak detection means detects it, and the detection signal causes the horizontal size adjustment means to suppress the horizontal size fluctuation caused by the white peak. Therefore, even if a white peak occurs, fluctuations in the horizontal size of the display screen can be suppressed. In addition, when a white peak suddenly occurs, the white peak detection signal controls the horizontal size adjustment means, and when the white peak fluctuates gradually, the horizontal size adjustment means uses the output signal from the integrating means to suppress the horizontal size fluctuation caused by the white peak. CR is controlled so that no matter how white peaks occur, CR
Fluctuations in the T display screen can be effectively suppressed.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, the circuit within the dotted line frame is a control circuit forming the essential part of the present invention, and the other parts are conventionally known CRT deflection circuits.

In the figure, 1 is a video amplification circuit that amplifies the video signal introduced from the input terminal, 2 is a chroma trap circuit that removes the color signal from the video signal, and 3 is a pedestal clamp circuit that makes the black level of the luminance signal constant. , 4 is a white peak detection circuit that detects a white peak from the luminance signal, 5 is an amplifier that amplifies the signal detected by the white peak detection circuit, and 6 is an integration circuit that integrates the output of the amplifier 5.

7 is a DC amplifier for amplifying the output of the integration circuit 6; 8 is a slice level adjustment circuit for adjusting the slice level of the white level detection circuit 4; 9 is a peak correction circuit for correcting the horizontal size adjustment amount. The circuit 10 is a control level adjustment circuit for adjusting the output of the DC amplifier circuit 7, and each of the circuits 2 to 10 above constitutes a control circuit which is a main part of the present invention. Further, 11 is a horizontal size adjustment circuit that adjusts the size in the horizontal direction, 12 is a control amplifier, Q1 is a transistor that amplifies the control signal, and Q2
is the horizontal output transistor.

One embodiment of the present invention has the above configuration, and its operation will be explained below. The video signal led to the video amplification circuit 1 is amplified by the circuit 1, and then led to the chroma clamp circuit 2, where unnecessary color signals (chroma signals) are removed.
remove. A white peak signal is extracted from the video signal from which this color signal has been removed, but in order to make the level to be extracted constant, it is passed through a pedestal clamp circuit 3 to equalize the black level of the video signal, and its output is led to a white peak detection circuit 4. ,
The white peak detection circuit 4 slices the white peak. The slice level of this white peak is determined by the slice level adjustment circuit 8.
Adjusted by.

The signal sliced at the slice level determined by the slice level adjustment circuit 8 is amplified by the next-stage amplifier circuit 5, level-adjusted by the peak correction circuit 9, and then added as a bias to the horizontal size control circuit 11. The output of the control circuit 11 is supplied to the control amplifier 12 as a horizontal size control signal. The purpose of directly applying the output signal from the amplifier circuit 5 to the horizontal size adjustment circuit 11 to control the horizontal size is to quickly correct horizontal size changes due to increases in beam current caused by short-term white level increases. , this correction amount is adjusted by the peak correction circuit 9. In addition, for changes in the horizontal size due to an increase in beam current caused by a long-term increase in the white peak, the output of the amplifier circuit 5 is integrated by an integrator circuit 6, this output is amplified by a DC amplifier 7, and then horizontal This is done by adding it to the size adjustment circuit 11. The amount of correction at this time is adjusted by the control level adjustment circuit 10.

The correction signal thus applied to the horizontal size adjustment circuit 11 is amplified together with the horizontal side pin correction signal by the control amplifier 12, and is applied to the base of the transistor Q1. The correction signal amplified by the transistor Q1 is applied to a capacitor 14 connected in series with the horizontal size correction coil 13.
The electric potential of the horizontal size correction coil 13 is increased as the value of the white peak becomes higher, thereby reducing the current of the horizontal size correction coil 13 and suppressing an increase in the horizontal size due to the white peak.

That is, when the white peak signal increases, the horizontal size control signal from the horizontal size adjustment circuit 11 input to the control amplifier 12 increases, and since the control amplifier 12 is an inverting amplifier, the transistor Q1 is turned off. The current of the horizontal size correction coil 13 is reduced to suppress an increase in the horizontal size due to the white peak.

As described above, when a white peak video signal comes in, the high voltage decreases due to the increase in the beam current of the CRT, and the horizontal size of the CRT screen tends to increase.
On the other hand, the detection of a white peak generates a control signal to reduce the horizontal size, and it is possible to suppress fluctuations in the motion screen size so as to compensate for the expansion of the horizontal size due to a drop in the high voltage of the CRT. Further, rapid fluctuations in the white level are quickly controlled by the output of the amplifier circuit 5, and long-term fluctuations in the white level are controlled by the signal averaged by the integrating circuit 6. In this case, it is also possible to effectively suppress variations in the CRT screen size due to variations in the white level.

FIG. 2 is a block diagram of another embodiment of the present invention, and parts corresponding to those in FIG. 1 are designated by the same reference numerals and their explanation will be omitted. The embodiment shown in FIG. 2 is a further improvement of the embodiment shown in FIG. That is, in the embodiment shown in FIG. 1, the high voltage of the CRT decreases due to the white peak, and when the image size increases, it is corrected by the horizontal size control signal, but in this case, the high voltage of the CRT remains decreased. The focus voltage also decreases at the same time, and since the screen voltage is also divided and taken out from the same high-voltage power supply circuit, the cutoff of the CRT also changes. Therefore, in addition to image distortion, a shift in focus or a shift in black level occurs. The embodiment shown in FIG. 2 solves the above-mentioned problems of the embodiment shown in FIG.

In FIG. 2, 20 is a signal level setting device, 21 is a control amplifier consisting of an IC, and C1, C2.
, C3 and C4 are horizontal output resonant capacitors, and C
A series circuit of C1 and C2 and a series circuit of C3 and C4 are respectively connected between the collector of the horizontal output transistor Q2 and ground, and the connection point of the capacitors C1 and C2 is connected to the collector of the transistor Q1. 22 is an ABL circuit that generates an automatic brightness adjustment control signal for automatically adjusting brightness.

Next, the operation of FIG. 2 will be explained. Similar to the embodiment shown in FIG. It will be destroyed.

ABL circuit 2 is connected to control amplifier 21.
An automatic brightness adjustment control signal is simultaneously supplied from No. 2, but this automatic brightness adjustment control signal is a DC signal and is sufficiently integrated by the capacitor C5. On the other hand, since the white peak signal supplied from the amplifier 5 is a pulsed signal, it is necessary to prevent interference with the automatic brightness adjustment control signal. The resistors R1 and R2 are provided for this purpose, and the white peak signal from the amplifier 5 is divided by the resistors R1 and R2, mixed with the automatic brightness adjustment control signal, and supplied to the control amplifier 21.

The white peak signal amplified by the control amplifier 21 is applied to the base of the transistor Q1 to turn on and off the transistor Q1. When the white peak signal increases and transistor Q1 turns on, capacitor C2, which forms part of the horizontal resonant capacitor, is grounded, and the capacitance of the series circuit of capacitors C1 and C2 increases to C1,
The capacitance of the horizontal resonant capacitors C1 to C4 increases, and the high voltage of the horizontal output becomes lower. In other words, the rise (or fall) of the white peak signal applied to the third pin of the control amplifier 21 turns on (or turns off) the transistor Q1.
As a result, the high voltage of the horizontal output decreases (or increases).

On the other hand, when the current flowing through the CRT increases, the automatic brightness adjustment control signal from the ABL circuit 22 operates in the negative direction to suppress the current, turning off the transistor Q1 and changing the horizontal output voltage of the CRT. However, since this is a DC operation, the response to white peaks is very slow. Therefore, the pulsed negative white peak signal from the amplifier circuit 5 that detects the white peak is applied to the third pin of the control amplifier 21, but the CR signal is not affected by the automatic brightness adjustment control signal.
The high voltage of the horizontal output of T can be controlled at high speed.

As described above, according to this embodiment, since the resonance capacitance of the horizontal output circuit is controlled and the change in the high voltage is controlled, image distortion can be corrected. It is also possible to suppress changes in focus and screen voltage, and at the same time, it is possible to suppress a shift toward black, where the white peak shifts slightly toward a darker direction due to a focus shift or a change in cutoff.

[0025]

[Effects of the Invention] Since the present invention has the above configuration,
With a simple circuit configuration, image distortion caused by expansion of a CRT display screen due to white peaks can be corrected, and an image display device with excellent image display quality can be provided at a low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing main parts of an embodiment of the present invention.

FIG. 2 is a block diagram showing main parts of another embodiment of the present invention.

[Explanation of symbols]

4 White peak detection circuit 6 Integral circuit 12, 21 Control amplifier 13 Horizontal size correction coil Q2 Horizontal output transistor

Claims (4)

[Claims] 1. An image display device equipped with a cathode ray tube for displaying image information, including a white peak detection circuit that detects a white peak of the image information, and a white peak signal from the white peak detection circuit that determines the horizontal size of the cathode ray tube. An image display device comprising: a horizontal size control circuit for controlling variation. 2. An image display device equipped with a cathode ray tube for displaying image information, comprising: a white peak detection circuit for detecting a white peak of image information; and an integrating circuit for integrating a white peak signal detected by the white peak detection circuit. An image display device comprising: a horizontal size control circuit that suppresses fluctuations in the horizontal size of the cathode ray tube using both signals from the white peak detection circuit and the integration circuit. 3. An image display device equipped with a cathode ray tube for displaying image information, comprising: a white peak detection circuit for detecting a white peak of image information; a horizontal size correction coil provided in a horizontal output circuit; and the white peak detection circuit. An image display device comprising: a control circuit that controls current to the horizontal size correction coil based on a white peak signal from the horizontal size correction coil so that fluctuations in screen size due to the white peak are suppressed. 4. An image display device equipped with a cathode ray tube for displaying image information, comprising: a white peak detection circuit for detecting a white peak of image information; a horizontal resonant circuit provided in a horizontal output circuit; An image display device comprising: a control circuit that controls the capacitance of the horizontal resonant circuit using a white peak signal such that fluctuations in screen size due to the white peak are suppressed.