JPH0695637A - Display control circuit - Google Patents

Abstract

PURPOSE:To suppress a contrast and a peak brightness when the brightness is raised by interlocking electrically the contrast of a display image with the brightness. CONSTITUTION:A brightness controlled voltage is supplied the control input terminal BRT of a video preamplifier 4 via an interlocking circuit 2. A contrast controlled voltage Vcont fed from user controller is also applied at a control input terminal CONT of the video preamplifier 4 via the interlocking circuit 2. The interlocking circuit 2 is activated in one direction from the brightness to the contrast since the contrast of the display image on a CRT interlocked electrically to the brightness in the circuit. The video pre-amplifier 4 outputs a RGB video signal to a wire 4A according to the brightness control voltage inputted to the control input terminal BRT and the control voltage Vcont inputted to the control input terminal CONT. The signal of the wire 4A is supplied to the cathode of the CRT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display control circuit suitable for controlling a display image on an RGB display monitor, for example.

[0002]

2. Description of the Related Art In order to meet the German ZH-1 standard, it is necessary to secure the brightness of the back cluster at least 6 nit at the maximum brightness control voltage. Under such conditions, if the contrast is not corrected in any way, the maximum luminance standard of the CRT is exceeded when both the contrast and the brightness are maximum, and the life of the CRT is deteriorated. In order to prevent this, conventionally, AB
The contrast is linked to the beam current of the CRT by the L circuit.

[0003]

The conventional technique using the above-mentioned ABL circuit has the following problems. (1) When the brightness is pushed up, the peak luminance is pushed up by a character pattern of black letters and white letters, which deteriorates the focus and causes blooming. (2) Since the beam current is concentrated in a window pattern or the like, image distortion occurs. (3) When the beam current is detected, an integrator circuit is always required, so that the circuit response has a certain time constant and the tracking is delayed.

It is an object of the present invention to provide a display control circuit capable of suppressing the contrast and suppressing the peak luminance when the brightness is raised, without causing the above-mentioned problems of the prior art.

[0005]

A display control circuit according to claim 1 is provided with interlocking means (for example, interlocking circuit 2 in FIG. 1) for electrically interlocking contrast of a display image with brightness. To do.

According to another aspect of the display control circuit of the present invention, when the interlocking means increases the portion of the video signal which is controlled by the brightness control voltage (for example, Vb in FIG. 2), the interlocking means operates by the contrast control voltage of the video signal. It is characterized in that the controlled portion (for example, Vc in FIG. 2) is reduced (for example, the characteristic in FIG. 3).

According to another aspect of the display control circuit of the present invention, the interlocking means does not depend on a change in a portion of the video signal controlled by the contrast control voltage (for example, Vc in FIG. 2).
The video signal is characterized in that the portion controlled by the brightness control voltage (for example, Vb in FIG. 2) is kept constant (for example, the characteristic in FIG. 4).

In the display control circuit according to the fourth aspect, the interlocking means changes the contrast control voltage according to the change of the brightness control voltage and does not change the brightness control voltage depending on the change of the contrast control voltage. For example, the voltage follower V of FIG. 5 or FIG.
F) is provided.

[0009]

In the display control circuit having the structure of the first aspect, the contrast of the display image is electrically linked to the brightness. Therefore, it becomes possible to suppress the contrast and the peak luminance when pushing up the brightness.

In the display control circuit of the second aspect, when the portion of the video signal controlled by the brightness control voltage becomes large, the portion of the video signal controlled by the contrast control voltage becomes small. Therefore, when pushing up the brightness, the contrast can be suppressed and the peak luminance can be suppressed.

According to another aspect of the display control circuit of the present invention, the portion of the video signal controlled by the brightness control voltage is constant regardless of the change in the portion of the video signal controlled by the contrast control voltage. To be done.
Therefore, even if the contrast and the brightness are electrically linked, the brightness control voltage is not affected by the contrast control voltage.

According to another aspect of the display control circuit of the present invention, the contrast control voltage changes according to the change of the brightness control voltage, but the brightness control voltage does not change according to the change of the contrast control voltage. Therefore, the brightness control voltage is not affected by the contrast control voltage, and when the brightness is pushed up, the contrast can be suppressed and the peak luminance can be suppressed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of a display control circuit of the present invention. This embodiment is an example in which the present invention is applied to an RGB display monitor. The brightness control voltage Vrbt from the user control is supplied to the control input terminal RBT of the video preamplifier 4 via the interlocking circuit 2.
Further, the contrast control voltage Vcont from the user control is supplied to the control input terminal CONT of the video preamplifier 4 via the interlocking circuit 2. Interlocking circuit 2
Is for electrically connecting the contrast of the image displayed on the CRT monitor to the brightness, and acts in one direction from the brightness to the contrast. Video preamplifier 4
According to the brightness control voltage Vrbt input to the control input terminal BRT and the contrast control voltage Vcont input to the control input terminal CONT, the RGB video signal is amplified and output to the line 4A. The video signal on the line 4A is further amplified by the video amplifier 6 to obtain C
It is supplied to the cathode of RT.

FIG. 2 shows an example of a video signal output from the video preamplifier 4 of FIG. In the illustrated video signal, the part Vc controlled by the contrast control voltage Vcont is a part in the positive direction from the pedestal level, that is, the part of the video amplitude level, and the part Vb controlled by the brightness control voltage Vrbt is the pedestal level. This is the more negative portion, that is, the blanking level portion.

When the brightness variable resistance of the user control is changed while the contrast variable resistance of the user control is fixed at an appropriate position, the interlock circuit 2 outputs from the video preamplifier 4 as shown in FIG. When the portion Vb of the video signal to be reproduced becomes large, it acts so as to reduce the portion Vc. Therefore, as the back cluster floats, the picture level decreases, and the peak brightness can be suppressed when both the contrast control voltage and the brightness control voltage of the user control are maximum.

When the contrast variable resistance of the user control is changed while the brightness variable resistance of the user control is fixed at an appropriate position, the interlocking circuit 2 outputs the video preamplifier 4 as shown in FIG. It acts so that the portion Vb is kept constant irrespective of the change in the portion Vc of the video signal output from.
Therefore, the picture level is controlled, but the back cluster does not change.

FIG. 5 shows a first configuration example of the interlocking circuit 2 of FIG. As shown in FIG. 6, in the interlocking circuit having the configuration of FIG. 5, when the contrast control voltage Vcont increases, a part of the video signal voltage controlled by the contrast control voltage, that is, the video signal amplitude level Vc increases, and the brightness control voltage is increased. As Vbrt increases, the portion of the video signal voltage controlled by it, ie, the blanking level Vb.
It is suitable for the case of decreasing. Referring to FIG. 5, the brightness follower voltage Vbrt from the user control is supplied to the input of the voltage follower VF.
The output terminal of the voltage follower VF is connected to the control input terminal BRT of the video preamplifier 4 via the resistor R1. The contrast control voltage Vcont from the user control is input to the resistor R2. The resistor R2 is connected in series to the resistor R3 connected to the control input terminal CONT of the video preamplifier 4, and the resistor R4 is provided between the connection point between the resistors R2 and R3 and the output terminal of the voltage follower VF.
Are connected.

In the example shown in FIG. 5, the brightness control voltage Vbrt output from the voltage follower VF.
And the contrast control voltage Vcont are combined (that is, added) by the resistors R4 and R2 to obtain the resistor R
3 is supplied as a contrast control voltage Vcont to the control input terminal CONT of the video preamplifier 4. Therefore, since the contrast control voltage Vcont changes in conjunction with the change in the brightness control voltage Vbrt, the output characteristic of the preamplifier 4 can be made as shown in FIG. 3, so that the peak luminance can be suppressed when the brightness is pushed up. it can. Even if the user changes the contrast control voltage Vcont, the voltage follower VF
Of the brightness control voltage Vbr supplied to the control input terminal BRT of the video preamplifier 4
Since there is no change in t, the output characteristics of the preamplifier 4 are shown in FIG.
Can be like

FIG. 7 shows a second configuration example of the interlocking circuit 2 of FIG. As shown in FIG. 8, when the contrast control voltage Vcont increases, the interlocking circuit having the configuration of FIG. As Vbrt increases, the portion of the video signal voltage controlled by it, ie, the blanking level Vb.
Is preferable when is increased. Referring to FIG. 7, the brightness control voltage Vbrt from the user control is supplied to the input of the inverting amplifier INV.
The output terminal of the inverting amplifier VF is connected to the input terminal of the voltage follower VF. Also, the brightness control voltage V
The brt is connected to the control input terminal BRT of the video preamplifier 4 via the resistor T5. The contrast control voltage Vcont from the user control is the resistance R
Entered in 2. The resistor R2 is connected in series with the resistor R3 connected to the control input terminal CONT of the video preamplifier 4, and has a connection point between the resistors R2 and R3 and a voltage follower VF.
A resistor R4 is connected between the output terminal and the output terminal.

In the example shown in FIG. 8, the brightness control voltage Vbrt output from the voltage follower VF.
And the contrast control voltage Vcont are combined (that is, added) by the resistors R4 and R2 to obtain the resistor R
3 is supplied as a contrast control voltage Vcont to the control input terminal CONT of the video preamplifier 4. Therefore, since the contrast control voltage Vcont changes in conjunction with the change in the brightness control voltage Vbrt, the output characteristic of the preamplifier 4 can be made as shown in FIG. 3, so that the peak brightness can be suppressed when the brightness is pushed up. it can. Even if the user changes the contrast control voltage Vcont, the voltage follower VF
Of the brightness control voltage Vbr supplied to the control input terminal BRT of the video preamplifier 4
Since there is no change in t, the output characteristics of the preamplifier 4 are shown in FIG.
Can be like

FIG. 9 is a circuit diagram showing a third configuration example of the interlocking circuit 2 of FIG. The brightness control voltage Vbrt from the user control is input to the voltage follower 8 (including an inverting amplifier in the case of the characteristic shown in FIG. 8).
Is supplied. The output terminal of the voltage follower VF is a resistor R
Control input terminal BRT of the video preamplifier 4 via
It is connected to the. The contrast control voltage Vcont from the user control is input to the resistor R2.
The resistor R2 is a control input terminal CON of the video preamplifier 4.
A series circuit of the voltage detection and switch circuit 10 and the resistor R4 is connected in series with the resistor R3 connected to T, and between the connection point of the resistors R2 and R3 and the output terminal of the voltage follower VF. It

In the example shown in FIG. 9, when the brightness control voltage Vbrt output from the voltage follower 8 exceeds a predetermined value, the voltage detection / switch circuit 10 is short-circuited and the brightness control voltage Vbrt , The contrast control voltage Vcont depends on the resistors R4 and R2.
Are combined (that is, added) and supplied as a contrast control voltage to the control input terminal CONT of the video preamplifier 4 via the resistor R3. Therefore, when the brightness variable resistance of the user control is changed while the contrast variable resistance of the user control is fixed at an appropriate position, the brightness control voltage Vbr is changed.
When t exceeds a predetermined value, the brightness control voltage Vbrt
Since the contrast control voltage Vcont changes in association with the change of Vb, the output characteristic of the preamplifier 4 can be made to decrease Vc with an increase in Vb when Vb exceeds a predetermined value as shown in FIG. The peak brightness can be suppressed when pushing up the brightness. Further, even if the user changes the contrast control voltage Vcont, the brightness control voltage Vbrt supplied to the control input terminal BRT of the video preamplifier 4 does not change due to the buffer action of the voltage follower VF. Fig. 1 shows the output characteristics of the preamplifier 4 when the contrast variable resistance of the user control is changed with the resistance fixed at an appropriate position.
Vb can be made constant like 1.

[0023]

According to the display control circuit of the first aspect, since the contrast of the display image is electrically linked to the brightness, it is possible to suppress the contrast and the peak brightness when pushing up the bright eggplant. become.

According to the display control circuit of the second aspect, when the portion of the video signal controlled by the brightness control voltage becomes large, the portion of the video signal controlled by the contrast control voltage becomes small. Without the drawbacks of conventional ABL circuits,
With a simple configuration, when pushing up the brightness, it is possible to suppress the contrast and the peak brightness, improve the quality of the CRT monitor, and reduce the CR.
The deterioration of T can be prevented.

According to the display control circuit of the third aspect, the portion of the video signal controlled by the brightness control voltage is made constant regardless of the change of the portion controlled by the contrast control voltage. Therefore, even if the contrast and the brightness are electrically linked, the brightness control voltage is not affected by the contrast control voltage.

According to the display control circuit of the fourth aspect, the voltage tracking means for changing the contrast control voltage according to the change of the brightness control voltage and not changing the brightness control voltage depending on the change of the contrast control voltage is provided. It is possible to suppress the contrast and the peak brightness at the time of pushing up the brightness, with a simple configuration without the drawbacks of the conventional ABL circuit and without the influence of the contrast control voltage on the brightness control voltage. The quality of the monitor can be improved and the deterioration of the CRT can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a display control circuit of the present invention.

2 is a waveform diagram showing an example of a video signal output from the video preamplifier 4 of FIG.

FIG. 3 shows an example of characteristics obtained by the interlocking circuit 2 of FIG. 1 in the video preamplifier 4 when the brightness variable resistance of the user control is changed with the contrast variable resistance of the user control fixed at an appropriate position. It is a characteristic diagram.

4 shows an example of characteristics obtained by the interlocking circuit 2 of FIG. 1 in the video preamplifier 4 when the contrast variable resistance of the user control is changed while the brightness variable resistance of the user control is fixed at an appropriate position. It is a characteristic diagram.

5 is a circuit diagram showing a first configuration example of the interlocking circuit 2 of FIG.

6 shows the relationship between the contrast control voltage Vcont and the part of the video signal voltage controlled by the contrast control voltage Vcont, that is, the video signal amplitude level Vc, and the brightness control voltage Vbrt, which is controlled by the interlocking circuit of FIG. It is a characteristic view which shows an example of a part of a video signal voltage, ie, a blanking level Vb.

7 is a circuit diagram showing a second configuration example of the interlocking circuit 2 of FIG.

8 is a relationship between a contrast control voltage Vcont and a portion of a video signal voltage controlled by the contrast control voltage Vcont, that is, a video signal amplitude level Vc, and a brightness control voltage Vbrt, which are controlled by the interlocking circuit of FIG. It is a characteristic view which shows an example of a part of a video signal voltage, ie, a blanking level Vb.

9 is a circuit diagram showing a third configuration example of the interlocking circuit 2 of FIG.

10 is a characteristic showing an example of characteristics obtained by the interlocking circuit of FIG. 9 in the video preamplifier 4 when the brightness variable resistance of the user control is changed while the contrast variable resistance of the user control is fixed at an appropriate position. It is a figure.

11 is a characteristic showing an example of a characteristic obtained by the video preamplifier 4 by the interlocking circuit of FIG. 9 when the contrast variable resistance of the user control is changed while the brightness variable resistance of the user control is fixed at an appropriate position. It is a figure.

[Explanation of symbols]

 2 interlocking circuit 4 video preamplifier 6 video amplifier 10 voltage detection and switch circuit R1, R2, R3, R4, R5 VF voltage follower INV inverting amplifier

Claims (4)

[Claims] 1. A display control circuit comprising interlocking means for electrically interlocking contrast of a display image with brightness. 2. The interlocking means reduces the portion of the image signal controlled by the contrast control voltage when the portion of the video signal controlled by the brightness control voltage increases.
Display control circuit described. 3. The interlocking means keeps the portion of the video signal controlled by the brightness control voltage constant regardless of the change of the portion of the video signal controlled by the contrast control voltage. The display control circuit according to claim 1 or 2. 4. The interlocking means includes a voltage follow-up means that changes the contrast control voltage according to the change of the brightness control voltage and does not change the brightness control voltage depending on the change of the contrast control voltage. The display control circuit according to claim 1.