JPH0563076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color signal switching device, and particularly to a switching device between a television color signal and an external RGB signal.

[Conventional technology]

For example, new media compatible television receivers have conventionally used IC-based color signal switching devices, but as they become more multi-functional and high-performance, on-screen and shadow functions are becoming necessary. In this case, control terminals are required for each function, and the circuit configuration becomes complicated.
Reliability was declining.

Figure 3 shows an example of a conventionally used color signal switching circuit.
Y), (B-Y) and luminance signal Y are respectively connected to terminal 7.
Matrix circuit 67 from 3, 74, 75, 79,
The signals are input to 68 and 69, matrixed, and then output as TV primary color signals RGB. The TV primary color signal RGB output from the matrix circuit and the external RGB signal input from terminals 80, 81, and 82 are both input to switch circuits 70, 71, and 72, and are switched by the control signal input from terminal 83. Connect the TV to terminals 76, 77, and 78.
Output as RGB signal or external RGB signal.

[Problem that the invention seeks to solve]

The conventional color signal switching device described above is used for TV R.
Since a control signal is required to switch between the GB signal and the external RGB signal, a control signal input terminal is required, and there is a problem in that the number of pins increases when integrated into an IC.

[Means for solving problems]

The color signal switching device of the present invention solves the above-mentioned problems and achieves multifunctionality with a smaller number of terminals, by using at least one of the external RGB signals to switch between the external RGB signal and the TV RGB signal. It is characterized by switching.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing a color signal switching device according to an embodiment of the present invention.

In Fig. 3, switching between the external RGB signal and the TV RGB signal was performed using a control signal input from the terminal 83, but in Fig. 1, the control signal was input by using the external RGB signal itself as a control signal. The terminal 83 is intended to be deleted.

That is, the external RGB signals inputted from the terminals 12, 13, and 14 also serve as control signals for the switch circuits 1, 2, and 3 and the luminance signal processing circuit 8. The switch circuits 1, 2, and 3 output only the external RGB signal when the external RGB signal is input, and output the television color difference signal when the external RGB signal is not input.

The OR circuit 7 is configured to output a control signal when any one of the external RGB signals is input.

The luminance signal processing circuit 8 conducts the luminance signal Y input from the terminal 15 when no control signal is input from the OR circuit 7, and connects it to the outputs of the matrix circuits 4, 5, and 6 when the control signal is input. Outputs a control signal that outputs only external RGB signals. Therefore, external RGB signal input terminal 1
When an external RGB signal is input to any one of 2, 13, and 14, it is input to matrix circuits 4, 5, and 6 through switch circuits 1, 2, and 3, while a control signal is input from OR circuit 7. Since the luminance signal processing circuit 8 outputs a control signal that outputs only the external RGB signal to the outputs of the matrix circuits 4, 5, and 6, the RGB output terminals 16, 1
7, 18 are external RGB signal input terminals 12, 1
Only the signals input to 3 and 14 will be output.

Next, a specific circuit example of the present invention will be explained with reference to FIG.

The emitter of the transistor 19 is connected to the power supply voltage supply terminal 65 via the resistor 38, the base is connected to the luminance signal input terminal 55, and the collector is connected to the reference voltage 66.
The emitter of transistor 20 is transistor 19
The base of the transistor 29 is connected to the common connection point between the emitter of the transistor 29 and the resistor 38, and the collector is connected to the reference potential 66 to the common connection point of the resistors 41 and 42, and the base of the transistor 29 is connected to the common emitter of the transistor 22 via the resistor 39. The collectors of the common emitters of the resistors 19 and 20 are connected to the power supply voltage supply terminal 65, and one end of the resistor 40 is connected to the reference potential 66 and the other end is connected to the R
The output terminal 56 is connected to the common collector of the transistors 21 and 22, the base of the transistor 21 is connected to the (RY) input terminal, and the transistor 2
The base of transistor 3 is connected to the common connection point between the collector of transistor 30 and resistor 42, and the base of transistor 3
The base of the transistor 30, which is the negative phase input terminal of a differential amplifier composed of 0, 31, resistors 41, 42, and a constant current source 51, is connected to an external R signal input terminal 59.
Transistor 3, which is connected to
The base of 1 is biased with a voltage source 54.

In Fig. 2, G block 85 and B block 8
Since the circuit connection of block 6 is similar to that of R block 84, the circuit operation of R block 84 will be explained as a representative. The case where a digital signal is input as an external RGB signal will be described below.

When the external R signal is not input to the terminal 59, the base potential of the transistor 30 is on the lower potential side compared to the base potential of the transistor 31, so the transistor 30 is cut off, and the bases of the transistors 20 and 22 are connected to the power supply. A voltage potential is applied, and the base potentials of the transistors 20 and 22 are on the high potential side with respect to the base potential of the transistors 19 and 21, so that the transistors 20 and 22 are in a cut-off state. The luminance signal Y input from the terminal 55 passes through an emitter follower circuit composed of a transistor 19 and a resistor 38 to the base of the transistor 29, which is one input terminal of a matrix circuit composed of transistors 29, 21 and resistors 39, 40. The color difference signal (R-Y) input from the terminal 62 is input to the base of the transistor 21, which is the other input terminal, and the television primary color R signal is output to the output terminal 56 of the matrix circuit.

Next, when an external R signal is input to the terminal 59, the base of the transistor 30 becomes a high potential side with respect to the base of the transistor 31, so the transistor 30
is turned on, and at this time, the base potentials of the transistors 20 and 22 are set to be on the low potential side with respect to the operating levels of the luminance signal Y and the color difference signal (RY) input to the terminals 55 and 62. resistance 41,
42. When the value of the constant current source 51 is set, the transistors 19 and 21 are cut off, so that the luminance signal Y and the color difference signal (R-Y) are no longer input to the matrix circuit. Further, since the common connection point of the resistors 41 and 42 and the emitter of the transistor 29 are at almost the same potential, the potential difference between the both ends of the resistor 42 and the potential difference between the emitter of the transistor 29 and the base of the transistor 22 are equal, and the potential difference between the emitter of the transistor 29 and the base of the transistor 22 becomes equal. An external R signal having a level corresponding to the relative ratio is output from the terminal 56.

When the external R signal is input, the emitter potential of the transistor 29, that is, the potential at the common connection point of the resistors 41 and 42 is lowered to such an extent that the transistor 21 does not become conductive even if the color difference signal (R-Y) is input to the terminal 62. When the values of the resistors 41, 42 and constant current source 51 are set, the transistors 20, 23, 26 form an OR circuit, so if any one of the external RGB signals is input, the brightness signal of the TV will be changed. Both the and color difference signals are blocked, and only the external RGB signal is output.

In the above embodiment, the case where the external RGB input signal is digital is explained, but the constant current source 5
Analog support can also be realized by replacing resistors 1, 52, and 53 with resistors, and by replacing resistors 41, 45, and 49 with appropriate constant voltage elements as necessary.

〔Effect of the invention〕

As explained above, the present invention uses an external RGB signal as a control signal for switching between a television signal and an external RGB signal.
Eliminates the need for a control signal input terminal for switching between RGB signals, reducing the number of pins when converting to an IC.
This has the effect of reducing costs and simplifying the circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit connection diagram showing a specific embodiment of the block diagram in FIG. 1, and FIG. 3 is a block diagram showing a conventional example. 9,62,73...Color difference signal (R-Y) input terminal, 10,63,74...Color difference signal (G-Y) input terminal, 11,64,75...Color difference signal (B-
Y) Input terminal, 12, 59, 80... External R signal input terminal, 13, 60, 81... External G signal input terminal, 14, 61, 82... External B signal input terminal, 15, 55, 79... ...Brightness signal input terminal, 1
6, 56, 76...R output terminal, 17, 57, 7
7...G output terminal, 18, 58, 78...B output terminal, 54...constant voltage source, 65...power supply voltage supply terminal, 66...reference potential supply terminal, 83...control signal input terminal, 84 ...R block, 85...G
Block, 86...B block.

Claims (1)

[Claims] 1. A matrix circuit that matrixes a color difference signal and a luminance signal to output a primary color signal, and a switch circuit that switches between the color difference signal and an external RGB signal, detects the presence or absence of the external RGB signal with an OR circuit, A color signal switching device characterized in that a luminance signal is turned on and off using the output of the OR circuit as a control signal.