JPS6032199B2 - Color brightness adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color brightness adjustment device in which the white balance does not change even if the brightness is changed.

As is well known, in a display device using a cathode ray tube (hereinafter referred to as CRT), which is used as a display section of computer terminal equipment, the video signal applied to the CRT is displayed in a binary display, that is, whether the display screen lights up or not. In many cases, it is sufficient to simply indicate whether or not the light is shining. Therefore, so-called switching type video amplifying circuits that perform only binary amplification are often used as video amplifying circuits. The advantage of configuring a video amplifier circuit using this switching method is that power consumption can be reduced and the mounting area can be reduced. Furthermore, when a color CRT is used, interference between red (hereinafter referred to as R), green (hereinafter referred to as G), and blue (hereinafter referred to as B) video amplifiers can be avoided. An example of a brightness adjustment device using a conventional switching method will be described below with reference to FIG. 1st
In the figure, terminal 1 is a DC voltage regenerative power supply (approximately 1100V)
is connected, terminal 2 is connected to the amplifier power supply (approximately 150V) that determines the peak value of the video signal, terminal 3 is the video signal input, and terminal 4 is the horizontal planking signal input for direct current reproduction. At the same time, the terminal 26 is connected to the power source for the brightness amplification circuit (approximately 20 V), and the terminal 27 is connected to the power source for the brightness amplification circuit (approximately 200 V).

Circuit 5 is the basic configuration of a video amplification circuit. Circuit 6 is
If the output of the video amplifier circuit 5 is directly applied to the CRT cathode 22, the Takagi characteristics will deteriorate due to the capacitance of the cathode, and the impedance of the load resistor 9 must be lowered. It is for performing conversion. Circuit 7 is a well-known pulse clamp circuit, and is a DC reproduction circuit that generates a DC applied voltage for reproduction, that is, a clamp voltage, for balancing each color (R, G, B) in the Karoo CRT, as described later. . Here, the transistor 18 is used to prevent the clamp level from varying due to the display content of the video signal and the current of the cathode 22. The circuit 28 controls the first grid of the CRT 21 (
This is a brightness circuit that changes the brightness of the display screen by changing the brightness adjustment voltage applied to the GI (hereinafter referred to as GI) 25. Although not shown in the figure, in the color CRT, a voltage is also applied to the cathodes 23 and 24 by a circuit configuration similar to that of the video amplification circuit configurations 5, 6, and 7 applied to the cathode 22. However, in color CRT, as shown in Figure 2, G
Due to the IH cathode voltage VG, -K, K,,K2,K
As shown in Figure 3, the magnitude of the cathode current IK differs depending on the color, so the DC level of each color is changed by the volume 14 of the DC reproduction circuit 7 in Figure 1, as in the brightness 1 state in Figure 2, and the I try to find a balance.

In Figure 2, each cathode current is 1 to simplify the diagram.
, it is assumed that white balance is achieved when they are equal. In the configuration of FIG. 1, when the brightness volume 30 is changed, the voltage of GI changes by the same value for each cathode, so that the cathode currents IK and V of FIG.
Due to the relationship K, , K2, and K3 between the G and -K voltages, when the brightness is changed, the color balance changes.

Normally, this change in white balance is ignored, but when several CRT display devices are used side by side, the difference in white balance is very noticeable. The present invention aims to provide a color brightness adjustment device for a CRT display device in which the white balance does not change even when the brightness is changed, and the embodiment shown in FIG. 3 will be described below.

In FIG. 3, parts having the same functions as those in FIG. 1 are given the same reference numerals.

The circuit 40 is a circuit added in the present invention, and the circuit 47,
Since the circuit 48 has the same configuration as the circuits 6 and 7, it is omitted in the figure. When the luminance is at its lowest, that is, when the display is at its darkest, the transistor 32 is cut off by the luminance polyum 30. Assuming that the brightness is 1 in FIG. 2 at this time, the transistor 4
1, 42, and 43 are also cut off in the same way.
Therefore, first, the white balance is adjusted to 1 by using the polyurethane 14 and the equivalent of the volume 14 in the circuits 47 and 48.
It can be adjusted to the state of Next, when the brightness is increased to a high level, that is, when the collector current of the transistor 32 reaches its maximum, adjust the volumes 44, 45, and 46 so that the brightness is 2 as shown in FIG. At this time, the voltage V in FIG. 2 is the change range of the voltage applied to the GI25, and the change in the voltage between the GI power swords of each color is V, , V2,
It is adjusted by the volume controllers 44, 45, and 46 so that the voltage becomes V3, and the cathode current 12 can be made the same for each cathode.
This means that V,. V2 and V3 are each cathode 22, 23,
AVK, AVK2,A
This means that it is the sum of VK3 and voltage V. In a state where the brightness is 1, the transistors 41, 42, and 43 are cut off, so the adjusters 44, 45, and 46 do not affect the brightness 1. Furthermore, the third
As is clear from the diagram, the change in the color balance correction voltage from luminance 1 to luminance 2 is linear, and the color balance in the intermediate luminance state can be corrected to an almost negligible extent. That is, although the curves K, , K2, and K3 of the characteristics shown in FIG. 2 are actually somewhat curved, this does not pose any practical problem. Although the present invention has been described above with reference to an example of a cathode ray tube display device that handles 200 million display video signals, the color brightness adjustment device of the present invention is not limited to this, and can be applied to well-known home television receivers, etc. It is applicable even to analog video signals that are handled.

That is, in the DC component regeneration circuit 7 of FIG.
In other words, the darkest level is also clamped by the pulse input from terminal 4, so it is not limited to cases in which the video signal takes only two values, but also displays multi-values. Even analog video signals from home television receivers can be handled in the same way.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional color brightness adjustment device, FIG. 2 is a cathode current vs. first grid-cathode voltage characteristic diagram, and FIG. 3 is a circuit diagram showing an example of a device according to the present invention. It is. 7...DC regeneration circuit, 28...Brightness circuit, 14...First variable resistor group, 41, 42,
43... Active rotation, 44, 45, 46...
...Second variable resistor group. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 DC component regeneration circuits that apply video signals to each cathode of the color cathode ray tube and adjust the white balance, and a brightness circuit that applies a manually adjustable brightness adjustment voltage to the first grid of the color cathode ray tube. A color cathode ray tube display device comprising: a color cathode ray tube display device configured to change each DC applied voltage for reproduction in the DC component regeneration circuit in proportion to a change in the brightness adjustment voltage; In response to the output of the brightness circuit, which maintains the mutual values of the cathode currents of the color cathode ray tubes at the same value, which are about to change, with respect to the brightness on the screen of the color cathode ray tube, A color brightness adjustment device equipped with a compensation circuit that controls the DC applied voltage for reproduction.