JPS605674Y2 - White color control circuit for color television receivers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a white color control circuit for a color television receiver, and more particularly to a white color control circuit that is improved so as to change the white balance in accordance with the luminance signal level.

In the NTSC television broadcasting system, the entire system is currently designed and configured with the reference white color of color television receivers as C light (color temperature 6774°K), so faithful color reproduction is achieved using the above C light. It is appropriate to use this as a standard.

However, in actual home color television receivers, the color is much more bluish than C light (the color temperature is around 10,000' or higher).

) is reproduced as the reference white color.

This is thought to be influenced by the human preference for white, and this preference is one of the reasons for hindering faithful color reproduction.

On the other hand, from the perspective of human vision, the preferred white color is a color density of 1.
If you ask me if it is sufficient to have a color temperature of about 15,000 to 20,000'', it is not sufficient, and especially for high-luminance white, the preferred color temperature is around 15,000 to 20,000''.

In other words, in actual home color television receivers, a compromise between faithful color reproduction and preferred standard white settings is selected as the standard white, so it is possible to achieve both faithful color reproduction and preferred white reproduction. The drawback was that it could not be done.

The present invention was developed in view of the above circumstances, and automatically sets a relatively low color temperature for signals with a low brightness level, and increases the color temperature of signals with a high brightness level according to the brightness level. The present invention provides a white color control circuit for a color television receiver that can achieve both faithful color reproduction and preferable white color reproduction by controlling the color television receiver.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, Q is a video signal amplification transistor, the video signal is guided to its base, the collector is grounded via a resistor R1, and the emitter is a resistor R3.
1. It is connected to the power supply 1B□.

On the other hand, Q39 Q49 Q5 are color difference signals (R-Y), (
B=Y) and (G-Y) are the video output 1 to transistor for the R-axis, B-axis, and G-axis.

The base of the transistor Q is connected to the (RY) input terminal via the resistor R27, and the emitter is connected to the resistor R1.
7, and its collector is connected to the power supply 1B2 via a resistor R11.

Similarly, the transistor Q4 has a base connected to the (B-Y) input terminal via a resistor R28, an emitter grounded via a resistor R18, and a collector connected via a resistor R1° to the (B-Y) input terminal. The power supply is connected to 1,000 yen.

Similarly, the transistor Q3 has a base connected to the (G-Y) input terminal via a resistor R29, a collector grounded via a resistor R19, and a collector connected to the power supply B2 via a resistor R13. .

7.The emitter of the transistor Q1 is connected to the resistor R3.
Through 1. It is then connected to the emitter of the transistor Q3 via a resistor R6 and a capacitor C□ in parallel, and similarly connected to L7 via a variable resistor R7, then a resistor R8 and a capacitor C2.
is connected in parallel to the emitter of the transistor Q1, and similarly connected to the emitter of the 1-transistor Q5 through a variable resistor R9 and then through a resistor RIO and a capacitor C3 in parallel.

Furthermore, the emitter of the transistor Q3 is connected to a resistor R2o.
The variable resistor A is connected to the sliding end of the variable resistor R23 through the variable resistor R23.

3 is grounded at one end, and connected to the power supply B3 at the other end.

Similarly, the emitter of the transistor Q4 is connected to the resistor R21.
The variable resistor R24 is connected to the sliding end of the variable resistor R24 through the resistor R24, and the variable resistor R24 has one end grounded and the other end connected to the power supply B3.

Similarly, the emitter of the transistor Q5 is connected to the resistor R22.
The variable resistor R25 is connected to the sliding end of the variable resistor R25 through the resistor R25, and the variable resistor R25 has one end grounded and the other end connected to the power source Togarasu.

On the other hand, 1 is a color cathode ray tube, and R9G is connected to each cathode via resistors R14, R15, R1 from each of the transistors Qst Q49 and Q5.
A primary color signal of B is applied.

Furthermore, the connection point of the resistor Bzt R3 is the transistor Q.
2 base, the emitter of this transistor Q2 is connected to the emitter of said transistor Q through the lower part, - the collector of said transistor Q2 is connected to the resistor R
26 through 1. and is connected to the base of the transistor Q.

The additional circuit 2 consisting of the transistor Q2 and resistors R4 and R26 is newly added to the conventional white control circuit according to the present invention.

Next, the operation shown in FIG. 1 will be explained.

The transistor Q□ amplifies the video signal input, and the emitter potential of the transistors Q3tQ, Q, changes according to the output of the transistor Q1, and the primary color signals of R, B, and G are amplified with the amplification degree according to this emitter potential. Cathode ray tube 1
Supplied to the R-axis, B-axis, and G-axis cathodes.

In this case, variable resistors R, , R9 are connected to transistors Q4, .
Q.

There is a device ζ゛ for adjusting the degree of amplification.

In addition, capacitors C, C2, and C3 are for frequency characteristic correction, and variable resistor R239R24q R25 adjusts the cutoff of R axis, B axis, and G@ by adjusting the emitter potential of transistors Q, Ql, and Q. It is for adjusting the voltage.

By the way, when the luminance level of the video signal input to the transistor Q1 is low, the base potential of the transistor Q1 rises, and therefore the emitter potential also rises, and since the potential difference between both ends of the resistor R2 is small, the 1-transistor Q2 becomes non-conductive.

On the other hand, when the luminance level of the video signal input is high, the base potential of the transistor Q is lowered, and therefore the lower limiter potential is also lowered, and since the potential difference between both ends of the resistor R2 is large, the transistor Q2 becomes conductive.

This transistor Q2 becomes saturated and becomes conductive (
The current flowing from the R-Y) signal input terminal through the resistor "27* R26 to the transistor Q2 increases, and the voltage drop across the low loss B27 increases.

As a result, the base potential of transistor Q3 decreases and the amplification degree of transistor q decreases, so the G-knee voltage vs. R-axis beam current characteristic of cathode ray v1 is as shown in Figure 2. The B-axis and G narrow beam currents decrease.

In other words, according to the white control circuit shown in FIG. 1, voltage changes caused by changes in the current flowing through the video amplification transistor Q□ change the pace-emitter voltage of the transistor Q2, thereby changing its conductivity. The current path is connected to the color difference signal input terminal of the video output transistor q, and the amplification degree of the video output transistor Q3 is changed by changing the conductivity of the transistor Q2, and when the brightness of the video signal is low. (Regardless of chromatic or achromatic colors.

), it performs faithful color reproduction with a relatively low color temperature using conventional control, and controls the color temperature of achromatic video signals with high brightness levels to increase according to the brightness level. It is possible to reproduce a preferable white color.

In this case, since the color temperature changes in the direction in which the beam current decreases, the effect of improving white peak collapse can also be obtained.

Note that in the above embodiment, the transistor Q is adjusted according to the brightness level.
2, the amplification degree of only the R-axis transistor Q3 was changed, but as shown in FIG. 3, compared to FIG.
For example, by connecting the transistor Q5 to the base of the G-axis transistor Q5 through Q5, the amplification degree of this transistor Q5 may be reduced to reduce the G-axis current.

That is, equivalently, as shown in FIG. 4, the B-axis beam current can be increased relative to the R- and G-axis beam currents.

In addition, in order to obtain an operation in which the degree of conductivity of the transistor Q2 is changed based on the current change of the video amplification transistor Q1, and the degree of amplification of the video output transistor (for example, q) is changed in accordance with this change, the above embodiment is used. However, a circuit as shown in FIG. 5 may be used.

That is, in FIG. 5, the video amplification transistor Q
1's collector is grounded via resistors R3, , R, and its emitter is connected to the power supply 1B0 via resistors TP, and the connection point of the resistors R3 and R3□ is connected to the base of transistor Q2, The emitters of transistors 1 to Q2 are grounded via a resistor R4, and the collectors are connected to the base of a transistor Q3 via a resistor 26.

This idea is based on the transistor Q that senses the change in current flowing through the video signal amplification transistor Q between the base and emitter in order to capture information on changes in the luminance signal level as described above.
2 is provided, and this is used as an information detection section.

This information detection transistor Q2 is a common detection means for controlling each of the R, G, and B axes.

In this way, the reason for using a common unified detection means is that white color is determined by the 1-tal of each output of the R, G, and B axes, so if you monitor only the 17 bells of each axis, you will not be able to see if it is really white. This is because it becomes difficult to determine whether the

Further, if a luminance 1/bell detection means is added to each axis, variations between parts and variations in adjustment are more likely to occur.

As described above, the present invention can provide a white color control circuit for a color television receiver that can achieve both faithful color reproduction and preferable white color reproduction.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the white control circuit of a color television receiver according to the present invention, FIG. 2 is a characteristic diagram shown to explain the operation of FIG. 1, and FIGS. The figures are circuit diagrams showing essential parts of other embodiments of the present invention, and FIG. 4 is a characteristic diagram shown to explain the operation of the circuit of FIG. 3. Q□・・・Video amplification transistor, Q3~Q,
...Video output 1 to transistor, Q2...
・Transistor.

Claims (1)

[Scope of utility model registration request] M signal amplification transistor, video signal amplified by this transistor and (RY), (B-Y), (G-
R-axis, B-axis, and G-axis video output transistors to which each color difference signal of Y) is supplied, a color cathode ray tube to which the output of the video output transistor is supplied, and the video amplification]-
A transistor whose conductivity changes as the pace-emitter voltage changes due to a voltage change caused by a change in the current flowing through the transistor; 1. A white control circuit for a color television receiver, comprising: a transistor connected to an input terminal for supplying the white color.