JPH0426474B2 - - Google Patents

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 to an RGB 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 (R), green (G), and blue (B); Y), (G-Y), (B-Y)
There are two methods of outputting a color difference signal and a luminance signal Y and generating R, G, and B primary color signals in a subsequent matrix circuit. The R, G, B interface circuit connected after the color demodulation IC, especially the integrated circuit (hereinafter referred to as IC) R, G, B interface circuit, is compatible with both primary color signals and color difference signals. It is desirable to be able to do so.

The present invention relates to a color signal processing circuit that is often used in R, 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 processing of primary color signals and color difference signals. This makes it possible to share the switching terminal with the luminance signal input terminal.

FIG. 3 shows a conventionally used color signal processing circuit in which a matrix circuit 6 matrixes the color difference signal applied to the color difference signal input terminal 2 and the luminance signal applied to the luminance signal input terminal 3. The primary color signal thus obtained 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 primary color/color difference switching terminal 4.

(Problem to be Solved by the Invention) In this case, there are four 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 was a problem that the number of external connection terminals increased, the circuit configuration became complicated, and the number of elements increased.

(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/color difference switching terminal and the luminance signal input terminal are made common. By selectively driving a matrix circuit to which a primary color signal or a color difference signal is input with a luminance signal or a constant bias voltage, the number of input terminals can be reduced, the circuit configuration can be simplified, and the number of elements can be reduced.

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

FIG. 1 is a block diagram illustrating the present invention, showing a luminance signal input to an input terminal 8 and a bias circuit 12.
A switch circuit 11 switches between the fixed bias voltages outputted from the matrix circuit 13, and one of them is applied to the matrix circuit 13. In the case of a primary color signal, the primary color or color difference signal inputted from the input terminal 9 is outputted to the output terminal 10 through the matrix circuit 13 as it is, but in the case of a color difference signal,
In the matrix circuit 13, the signal is matrixed with the luminance signal applied from the input terminal 8 and output as a primary color signal to the output terminal 10.

The threshold voltage of switch circuit 11 is
V _+h , and the threshold voltage is applied to input terminal 8.
When a luminance signal Y below V _+h is input, the luminance signal Y is input to the matrix circuit 13 via the switch circuit 11, while a constant voltage above the threshold voltage V _+h is applied to the input terminal 8. If so, the constant bias voltage output from the bias circuit 12 is input to the matrix circuit 13 via the switch 11.

When a color difference signal is input to the input terminal 9, if a luminance signal Y below the threshold voltage V _+h is input to the input terminal 8, the color difference signal and the luminance signal Y are matrixed in the matrix circuit 13, and the primary colors are The signal is output to the output terminal 10 as a signal.

Next, when a primary color signal is input to the input terminal 9, by applying a constant voltage 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. added to matrix circuit 13, matrix circuit 1
3 performs matrix operation using a constant bias voltage instead of the luminance signal Y, so the primary color signal is output to the output terminal 10 as is.

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 primary color/color difference switching terminal and the Y input terminal in common, thereby reducing the number of input terminals.

Above, only one block of R, G, or B was explained, but in reality, R,
Three blocks, G and 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 8 input terminals, the present invention can reduce the number of input terminals to 4, which reduces the number of pins when integrated into an IC, simplifies the circuit configuration, and reduces the number of input terminals. This has the effect of reducing the number of

FIG. 2 shows an embodiment of the present invention which embodies the block diagram shown in FIG. The anode of the Zener diode 36 corresponds to one end of the resistor 19, and the cathode corresponds to the input terminal 8, which also serves as a luminance signal input terminal and a primary color/color difference switching terminal. 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 to the input terminal 15, and the collector to the reference potential. One end of the resistor 21 is connected to the emitter of the transistor 29 and the transistor 3.
At the common connection point with the base of 4, the other end is a resistor 22,
It is connected to 23 common connection points. resistance 22,
23 is connected in series between the power supply 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 selector 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 the resistors 25, 26 and the transistor 3.
It is connected to the common connection point with the base of 0. 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 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 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 a common connection point between the resistors 24, 25, and 26, and the collector is connected to a common connection point between the collector and base of the transistor 33 and the base of the transistor 35. 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,
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 the collector of the transistor 33 and a common connection point between the base 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 resistors 21, 22, and 23 is
V _A is the Zener voltage of Zener diode 36.
V _Z , the potentials at the common connection point B of the resistors 24, 25, and 26 when the transistor 31 is off and on are V _OFF and V _ON (V _OFF >V _ON ), respectively.

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

) When a primary color signal is input, when a constant voltage higher than the potential V _A and higher than the Zener voltage V _Z is applied to the input terminal 15, the transistor 29 is turned off and the Zener diode 36 is turned off.
becomes conductive. When the value of the resistor 20 is determined so that the voltage generated across the resistor 20 by the current flowing through the Zener diode 36 is equal to or higher than the threshold voltage between the base and emitter of the transistor 31, the transistor 31 is turned on and the voltage at point B is reached. The voltage at is V _ON . The AC gain for the primary color signal input from the terminal 16 and output to the terminal 18 is determined by the values of the resistors 27 and 28, and the DC potential at the output terminal 18 is determined by the transistor 3, assuming that the DC potential at the input terminal 16 is constant.
Determined by a base bias of 0.34.

) When a color difference signal is input When a luminance signal below (V _A −V _BE ) and below the Zener voltage V _Z 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, V _BE 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 V _OFF .
The color difference signal is applied to the input terminal 16, matrixed with the luminance signal transmitted to the base of the transistor 34, and outputted to the output terminal 18 as a primary color signal. AC gain for color difference signal is resistor 2
7 and 28, and the output DC potential is determined by the base bias of the transistor 30 and the DC potential of the luminance signal.

)) The reason why the base bias of the transistor 30 is changed when the primary color signal is input and when the color difference signal is input is because the primary color signal is generally on the low potential side and the color difference signal is on the high potential side. It is.

)), the input terminal 15 serves both as the luminance signal input terminal and the primary color/color difference switching terminal, and the input terminal 16 serves as the primary color signal input terminal and the color difference signal input terminal, so there are two input terminals. The terminals form a color signal processing circuit that supports primary colors/color differences.

In the above, only one circuit of R, G, or B was explained, but in reality, three circuits of R, G, and B are required, so the number of input terminals is 8 to 4.
It will be reduced to 1.

(Effect of the invention) As explained above, the conventional example has an input terminal of 8
In contrast, the present invention requires only four input terminals, so the IC of the R, G, B interface circuit used in TV receivers etc.
This has the effect of reducing the number of pins, reducing the number of elements, and simplifying the circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a color signal processing circuit according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is a block diagram of a conventional color signal processing circuit. 1, 2, 3, 4, 8, 9, 15, 16... Input terminal, 5, 10, 18... Output terminal, 6, 13...
...Matrix circuit, 7,11...Switch circuit,
12...Bias circuit, 14...Power supply voltage supply terminal, 17...Reference potential, 19, 20, 21, 2
2, 23, 24, 25, 26, 27, 28...Resistor, 29, 30...PNP transistor, 31,
32, 33, 34, 35...NPN transistor,
36... Zener diode.

Claims (1)

[Claims] 1 A first input terminal into which a primary color signal or a color difference signal is input, and when the primary color signal is input to the first input terminal, a predetermined voltage is input, and when the color difference signal is input, a luminance signal is input. A second input terminal is inputted, a bias circuit outputs a constant bias voltage, and the brightness signal is output to the second input terminal by comparing the voltage of the second input terminal and the constant bias voltage. A switch that detects which of the predetermined voltages is input, outputs a signal corresponding to the luminance signal when the luminance signal is input, and outputs a DC bias voltage when the predetermined voltage is input. 1. A color signal processing circuit comprising: a matrix circuit that matrixes the output from the switch circuit and the signal input to the first input terminal and outputs the matrix.