JPS6143786A - Color signal processing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color signal processing circuit used in a color television receiver, and particularly relates to a GB interface circuit.

(Prior Art) The output formats of color demodulation ICs used in TV receivers, etc. include a method of outputting primary color signals of red (printed, green 0. blue (B)), (R-Y), The color difference signals (G-Y) and (B-Y) and the luminance signal Y are output and processed by the matrix circuit in the subsequent stage.
There are two types of methods for generating G and H primary color signals. The current G and B interface circuits, especially integrated circuits (hereinafter referred to as ICs), are connected after the color demodulation IC.
It is desirable that the integrated G, B interface circuit be able to handle both primary color signals and color difference signals.

The present invention relates to a color signal processing circuit that is often used in 几, G, B interface ICs, etc., and has a simple circuit configuration, commonization of primary color signal input terminals and color difference signal input terminals, and primary color signal and color difference signal processing circuits. This makes it possible to share the switching terminal with the luminance signal input terminal.

Figure 3 shows a conventionally used color signal processing circuit.
The color difference signal applied to the color difference signal input terminal 21C and the luminance signal applied to the luminance signal input terminal 3 are connected to the matrix circuit 6.
The primary color signal obtained by matrixing the primary color signal and the primary color signal applied to the primary color signal input terminal 1 are switched by the switch circuit 7 under the control of the switching signal applied to the 7 primary color color difference switching terminal 4.

(Problem to be Solved by the Invention) In this case, four terminals are used as input terminals: primary color signal input terminal 1, color difference signal input terminal 2, luminance signal input terminal 3, and primary color/color difference switching terminal 4. As a result, when integrated into an IC, there is a problem that the number of external connection terminals increases, and there are also problems that the circuit configuration is fl or sloppy and the number of elements increases.

(Means for Solving the Problems) According to the color signal processing circuit of the present invention, the primary color signal input terminal and the color difference signal input terminal are made common, and the primary color 7 color difference switching terminal and the luminance signal input terminal are made common. , a primary color signal or a color difference signal is inputted, the IJx circuit is selectively driven by a luminance signal or a constant bias voltage, thereby reducing the number of input terminals, simplifying the circuit configuration, and reducing the number of elements.

(Example) Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a block diagram illustrating the present invention, in which the luminance signal input to the input terminal 8 and the constant bias voltage output from the bias circuit 12 are switched by a switch circuit 11, and one of them is connected to the matrix. added to circuit 13. The primary color or color difference signal input from input terminal 9 is
In the case of primary color signals, they are outputted to the output terminal 10 through the matrix circuit 13 as they are, but in the case of color difference signals,
In the matrix circuit 13, the signal is mixed with the luminance signal applied from the input terminal 8 and output as a primary color signal to the output terminal IO.

The threshold voltage of the switch circuit 11 (Et-V+
h, and when a luminance signal Y below the threshold voltage V+h is input to the input terminal 8, the luminance signal Y is input to the matrix circuit 1311'c via the switch circuit 11, and on the other hand, the threshold voltage is input to the input terminal 8. EEV+
When a constant voltage of h or more is applied, bias circuit 1
A constant bias voltage outputted from the circuit 2 is input to the matrix circuit 13 via the switch 11.

When a color difference signal is input to input terminal 9, input terminal 8
The luminance signal Yt- below the threshold voltage V+h
If done manually, the color difference signal and the luminance signal Y are matrixed by the matrix circuit 13 and outputted to the output terminal 10 as primary color signals.

Next, when a primary color signal is input to the input terminal 9, by applying a constant voltage equal to or higher than the threshold voltage V+h to the input terminal 8, the primary color signal and the constant bias voltage output from the bias circuit 12 are connected to the matrix circuit 13. Since the matrix circuit 13 operates with a constant bias voltage instead of the luminance signal Y, the primary color signal is outputted as it is from the output terminal 10g.

That is, according to the present invention, it is possible to use the primary color signal input terminal and the color difference signal input terminal in common, and to make it possible to use the 7 primary colors color difference switching terminal and the Y input terminal in common, thereby reducing the number of input terminals.

Above, we have explained only one block, Rin, G, or B, but in reality, Rin, G.

Three blocks of B are required, and each block requires a primary color signal terminal and a color difference signal terminal, so eight input terminals are required. According to the present invention, these eight input terminals are reduced to four input terminals. In this way, whereas the conventional example required eight input terminals, the present invention can reduce the number of input terminals to four, thereby reducing the number of pins when integrated into an IC.

This has the effect of simplifying the circuit configuration and reducing the number of elements.

Diagram N2 shows an embodiment of the present invention that embodies the block diagram shown in FIG. 1. zener diode 3
The anode 6 corresponds to one end of the resistor 19, and the cando corresponds to the input terminal 8, which also serves as a 4-degree signal input terminal and a 7-color difference switching terminal for primary colors. It is connected to the input terminal 15, and the resistors 19 and 20 are connected in series between the anode of the Zener diode 36 and the reference potential. The emitter of the transistor 29 is connected to a common connection point between the base of the transistor 34 and one end of the resistor 21, the base is connected to the input terminal 15, and the collector is connected to a reference potential. One end of the resistor 21 is a transistor 29
The other end is connected to the common connection point between the emitter of the transistor 340 and the base of the transistor 340, and the other end is connected to the common connection point of the resistors 22 and 23. Resistors 22 and 23 are connected in series between the 1kc voltage supply terminal and the reference potential. The emitter of the transistor 31 is connected to the reference potential, the base is connected to the common connection point of the resistors 19 and 20, and the collector is connected to one end of the resistor 24. One end of the resistor 24 is connected to the collector of the transistor 31, and the other end is connected to a common connection point between the resistor 25, 26 and the base of the transistor 30.

Resistors 25 and 26 are connected in series between the power supply voltage supply terminal and the reference potential. The collector of the transistor 32 is connected to the power supply voltage supply terminal, the base is connected to the input terminal 16 corresponding to the input terminal 9 which serves as both the primary color signal input terminal and the color difference signal input terminal, and the emitter is connected to one end of the resistor 27. One end of the resistor 27 is connected to the emitter of the transistor 32, and the other end is connected to the emitter of the transistor 30. The emitter of the transistor 30 is connected to one end of the resistor 27, the base is connected to the common connection point of the resistors 24, 25, and 26, and the collector is connected to the base and the collector of the transistor 33.
It is connected to the common connection point with the base of 5. The collector and base of transistor 33 are short-circuited and connected to a common connection point between the collector of transistor 30 and the base of transistor 35, and the emitter is connected to a reference potential. The collector of the transistor 34 is connected to the power supply voltage supply terminal K.
, the base is connected to a common connection point between one end of the resistor 21 and the emitter of the transistor 29, and the emitter is connected to one end of the resistor 28. One end of the resistor 28 is connected to the emitter of the transistor 34, and the other end is connected to the output terminal 18. The collector of the transistor 35 is connected to the output terminal, the base is connected to a common connection point between the collector and base of the transistor 33, and the collector of the transistor 30, and the emitter is connected to a reference potential. Terminals 14, 17, and 18 are a power supply voltage supply terminal, a reference potential, and an output terminal, respectively.

The potential at the common connection point A of the resistors 21, 22, and 23 is VA, and the Zener voltage of the Zener diode 36 is Vz.

Resistance 24°25 when transistor 31 is off and on
．． The potential of 26 common connection points B is turned off.

VON (VOFF > VON).

Below, the operation will be explained separately for inputting primary color signals and inputting color difference signals.

1) When a primary color signal is input When a constant voltage higher than the potential VA or higher than the Zener voltage Vz is applied to the input terminal 15, the Zener diode 36fi turns off and the Zener diode 36fi becomes conductive. If the value of the resistor 20 is determined so that the voltage generated across the resistor 200 by the current flowing through the Zener diode 36 is equal to or higher than the base-to-emitter threshold value WEE of the transistor 31, the transistor 31 is turned on, and the voltage at point B is It becomes VON. The AC gain for the primary color signal input from terminal 16 and output from terminal 18 is determined by the resistance 27.28.
The DC potential at output terminal 18 is determined by the value of input terminal 1.
Assuming that the DC potential of transistor 30 is constant,
Determined by the °340 base bias.

1i) When inputting a color difference signal When a luminance signal below (VA-Va!+) and below the Zener voltage Vz is applied to the input terminal 15, the luminance signal is applied to the base of the transistor 34 through the emitter-follower type transistor 29. However, Yes is the base-emitter threshold voltage of the transistor 29. Since the voltage at the input terminal 15 is lower than Vz, the Zener diode 36 becomes non-conductive and the transistor 31 is turned off, so the potential at point B becomes VOFF.

The color difference signal is applied to input terminal 16 and transistor 34
It is matrixed with the luminance signal transmitted to the base of the primary color signal and output to the output terminal 18 as a primary color signal. The AC gain for the color difference signal is determined by the resistors 27 and 28, and the DC potential of the output is determined by the pace bias of the transistor 300 and the DC potential of the luminance signal.

As explained in 1) if), the reason why the base bias of the transistor 30 is changed depending on whether the primary color signal is input or the color difference signal is input is because the primary color signal is generally placed on the low potential side and the color difference signal is placed on the high potential side. This is because there is.

1) As explained in 11), the input terminal 15 also serves as the luminance signal input terminal and the 7 primary colors color difference switching terminal, and the input terminal L6ii also serves as the primary color signal input terminal and the color difference signal input terminal, so the two The input terminal forms a color signal processing circuit that supports seven primary colors.

Above, we have explained only one of the circuits of 几, G, and B, but in reality, three circuits of 几, G, and B are required, so the number of input terminals is reduced from 8 to 4. It turns out.

(Effects of the Invention) As explained above, while the conventional example requires eight input terminals, the present invention requires only four input terminals, so it can be used in TV receivers, etc. Iru Rin, G
, B When converting the interface circuit into an IC, the effect of reducing the number of pins, reducing the number of elements, and simplifying the circuit is brought about.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the color signal processing circuit of the present invention.
The figure is a circuit diagram showing one embodiment of the present invention. FIG. 3 is a block diagram of a conventional color signal processing circuit. L, 2, 3, 4, 8, 9, 15.16... Input terminal, 5, 10.18... Output terminal, 6, 13
・・・・・・Ma) IJ circuit, 7.11・・・・・・
・Switch circuit, 12...Bias circuit, 14
. . . Power supply voltage supply terminal, 17 . . . Reference potential, 19. 20. 21. 22゜23.24,2
5, 26, 27. 28... Resistance. 29', 30...PNP transistor, 31,
32゜33.34.35...NPN) transistor, 36...Zener diode. Australia 1 possible' + 3 autopsy Vz mouth

Claims (1)

[Claims] a first input terminal to which a luminance signal or a constant voltage is applied; a switch circuit that switches between the luminance signal and constant bias input from the first input terminal; and a second input terminal to which a color difference signal or a primary color signal is applied. A color signal processing circuit comprising: an input terminal; and a matrix circuit that matrixes a signal input from the second input terminal and an output of the switch circuit to output a primary color signal.