JPH06205319A - Rgb interface circuit - Google Patents

Abstract

PURPOSE:To adopt a mall sized and simple circuit configuration for an RGB interface circuit for a color television receiver or the like having an on-screen display function and other RGB signal display function inexpensively with high performance. CONSTITUTION:A TV signal from input terminals 1, 2 is given to a signal processing circuit 3, in which a primary color signal is obtained, an external analog RGB signal from an input terminal 10 is processed by a signal processing circuit 9, an on-screen signal from an input terminal 11 is processed by an on-screen signal processing circuit 12 and the outputs of the circuits 11, 12 are fed to a changeover circuit 4 respectively. The changeover circuit 4 is subjected to switching control by a control signal from a changeover control circuit 5 and selects an on-screen signal when an on-screen switching control signal B is inputted from an input terminal 8 at least, and selects an RGB signal when an analog RGB switching control signal A is inputted from an input terminal 7, and selects a primary color signal in the TV signal when no input comes from the input terminals 7, 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RGB interface circuit of a color television receiver, and more particularly to an RGB interface circuit having an on-screen function for displaying a channel number and other RGB signal display functions. .

[0002]

2. Description of the Related Art Currently, color television (hereinafter referred to as TV
Most of the receivers have an on-screen display function for displaying information indicating the channel number, volume, etc. on the screen. In addition, character multiplex decoders and game devices Display an image with analog or digital RGB signals from external equipment such as
An increasing number of TV receivers have a function of displaying a desired image on a TV screen by using an analog RGB signal for a child screen obtained by signal processing in the TV receiver itself.
The V receiver has been required to have a function as a display device having an RGB interface for displaying information such as characters and figures as well as simply reproducing an image of a TV signal.

FIG. 8 is a block diagram showing an example of a conventional RGB interface circuit described in Japanese Patent Laid-Open No. 1-93281, wherein 1 and 2 are input terminals, 3 is a TV primary color signal processing circuit, and 9 is analog. RGB signal processing circuit, 1
0 and 11 are input terminals, 13 is an output terminal, 26 is a digital RGB signal processing circuit, 27 is an input terminal, 61 is a TV signal / external RGB signal switching circuit, 62 is an on-screen signal switching circuit, and 63 is an analog RGB signal. / Digital R
GB signal switching circuits 64 and 65 are switching control terminals.

In the figure, in this RGB interface circuit, in addition to the input terminal 11 for the on-screen signal, the input terminals for the two systems of RGB signals, that is, the analog R
A GB signal input terminal 10 and a digital RGB signal input terminal 27 are provided.

The analog RGB signal and the digital RGB signal input from the input terminals 10 and 27 are processed by the analog RGB signal processing circuit 9 and the digital RGB signal processing circuit 26, respectively, and then the analog RGB signal / digital RGB signal switching circuit. Either 63 is selected by 63 according to the analog RGB / digital RGB switching control signal input from the switching control terminal 65, and the TV signal /
It is supplied to the external RGB signal switching circuit 61. Further, the luminance signal of the TV signal is input from the input terminal 1 and the color difference signal of the TV signal is input from the input terminal 2 and supplied to the TV primary color signal processing circuit 3 where they are converted into primary color signals and the TV signal is converted. / Supplied to the external RGB signal switching circuit 61.

The TV signal / external RGB signal switching circuit 61 is controlled by the TV / external RGB switching control signal inputted from the switching control terminal 64, and the TV primary color signal from the TV primary color signal processing circuit 3 and the analog RGB signal / digital R signal.
One of the external RGB signals (analog RGB signal or digital RGB signal) from the GB signal switching circuit 63 is selected and supplied to the on-screen signal switching circuit 62. When an on-screen signal is input from the input terminal 11, the on-screen signal is subjected to an appropriate level conversion processing (not shown in this figure), and then the on-screen signal switching circuit 62. Is supplied to. In the on-screen signal switching circuit 62, the on-screen signal is RG from the TV signal / external RGB signal switching circuit 61.
The signal is inserted into the B signal and output from the output terminal 13.

By the way, most of the luminance signal / chroma signal processing ICs currently used in TV receivers have an on-screen display function, and therefore, the RGB interface used in TV receivers of such specifications. A circuit is generally configured by combining such a luminance signal / chroma signal processing IC and an RGB signal processing IC for switching between the output signal of this IC and an external RGB signal.

FIG. 9 shows an example of such an RGB interface circuit, which has an on-screen display function and one system of RGB input. However, in FIG.
Reference numerals 7 and 8 are input terminals, 12 is an on-screen signal processing circuit, 28 is a luminance signal processing circuit, 29 is a DC (direct current) signal generating circuit, 30 is a color difference signal processing circuit, and 33 is an output terminal.
34 is an output terminal, 64 is a switching control terminal, 66 is a luminance signal / on-screen DC signal switching circuit, and 67 is external RGB.
Black level control circuit, 68 is an input terminal, 69 is a luminance signal /
External RGB / DC signal switching circuit, 70 AND circuit, 7
Reference numeral 1 denotes an inverter circuit, parts corresponding to those in FIG.

In FIG. 9, A surrounded by a one-dot chain line on the left side
This section corresponds to the part related to the on-screen display function of the luminance signal / chroma signal processing IC, and here is the "Hitachi Consumer IC Data Book Video IC Edition", September 991 edition.
p. 103, -Y signal / color difference signal output type video / chroma / deflection processing ICH with screen display function
A11511 CNT is quoted. Further, the portion B surrounded by the broken line on the right side of FIG. 9 corresponds to the RGB signal processing IC,
1st edition “Panasonic Semiconductor Handbook Semiconductor Integrated Circuits (Linear IC for video)” p. 216 character / graphic interface IC AN5352N
Is simplified and quoted.

In this example, luminance signal / chroma signal processing I
Since C is a type that outputs a color difference signal and a -Y signal (inverted luminance signal) instead of the primary color signal,
The color difference signal of the TV signal, the on-screen signal and the RGB signal are switched, and the -Y signal of the TV signal and the DC signal corresponding to the black level of each of the on-screen signal and the RGB signal are switched in parallel. Become.

In FIG. 9, the color difference signal of the TV signal input from the input terminal 2 is processed by the color difference signal processing circuit 30 and supplied to the on-screen signal switching circuit 62, and
The on-screen signal input from the input terminal 11 is processed by the on-screen signal processing circuit 12 to be on-screen.
To the signal switching circuit 62. In the on-screen signal switching circuit 62, the on-screen switching control signal input from the switching control terminal 8 inserts the on-screen signal into the color difference signal and supplies it to the TV signal / external RGB signal switching circuit 61. . On the other hand, the external analog RGB signal input from the input terminal 10 is also processed by the analog RGB signal processing circuit 9, supplied to the TV signal / external RGB signal switching circuit 61, and input from the switching control terminal 64.
V / external RGB switching control signal, color difference signal, external R
One of the GB signals is selected and output from the output terminal 34.

On the other hand, the -Y signal of the TV signal input from the input terminal 1 is processed by the brightness signal processing circuit 28 and supplied to the DC signal generating circuit 29 and the brightness signal / on-screen DC signal switching circuit 66. The DC signal generating circuit 29 is-
A DC signal for switching the on-screen signal according to the Y signal is generated and supplied to the luminance signal / on-screen DC signal switching circuit 66. The two input signals of the brightness signal / on-screen DC signal switching circuit 66 are selected in accordance with the on-screen switching control signal input from the switching control terminal 8 as in the on-screen signal switching circuit 62, and the brightness is selected. It is supplied to the signal / external RGB / DC signal switching circuit 69.
This luminance signal / external RGB / DC signal switching circuit 69 is
Further, the external RGB / DC signals from the external RGB black level control circuit 67 controlled by the external RGB black level control signal from the control terminal 68 are also supplied, and like the TV signal / external RGB signal switching circuit 61, switching control is performed. 2 according to the TV / external RGB switching control signal input from the terminal 64
One of the two input signals is selected and the output terminal 33
Is output from.

Since the on-screen signal display is given the highest priority in a general TV receiver, in this example, the TV / external RGB input from the switching control terminal 64 is input.
The switching control signal is obtained by inverting the on-screen switching control signal input from the switching control terminal 8 by the inverter circuit 71,
The output signal and the switching control signal input from the analog RGB input terminal 7 which is an external RGB input are connected to the AND circuit 7
The external RGB signals can be switched only when the on-screen signal is not displayed.

FIG. 10 shows a T having an on-screen display function and one system of RGB input, as in the conventional example shown in FIG.
FIG. 10 is a block diagram showing still another conventional example of the RGB interface circuit of the V receiver, in which parts corresponding to those in FIG. 9 are designated by the same reference numerals.

In this example, the color difference signal and -Y signal output of the conventional example shown in FIG. 9 are of primary color signal processing type.

In FIG. 10, input terminal 1 and input terminal 2
The TV signal input from the above is converted into a primary color signal by the TV primary color signal processing circuit 3 and then supplied to the on-screen signal switching circuit 62. The on-screen signal input from the input terminal 11 is After being processed by the on-screen signal processing circuit 12, the on-screen signal switching circuit 62
To the TV signal / external RGB signal switching circuit 61 by inserting the on-screen signal into the primary color signal in accordance with the on-screen switching control signal supplied from the switching control terminal 8.
Is supplied to. On the other hand, the external analog RGB signal input from the input terminal 10 is the analog RGB signal processing circuit 9
After being processed by the TV signal / external RGB signal switching circuit 6
1 is supplied. In the TV signal / external RGB signal switching circuit 61, a TV primary color signal and an external RG signal are generated by the TV / external RGB switching control signal input from the switching control terminal 64.
Any one of the B signal is selected and output from the output terminal 13.

Also in this example, the TV / external RGB switching control signal for controlling the TV signal / external RGB signal switching circuit 61 is the same as in the conventional example shown in FIG.
The on-screen switching control signal input from the switching control terminal 8 is inverted by the inverter circuit 71, and its output signal and the switching control signal input from the analog RGB input terminal 7 which is an external RGB input are supplied to the AND circuit 70. Then, it is obtained by performing a logical operation.

[0018]

However, the above-mentioned conventional RGB interface circuit has the following problems. That is, first of all, first, FIG. 9 and FIG.
In the conventional example shown in 0, the on-screen signal switching circuit 6
2 and the TV signal / external RGB signal switching circuit 61, and there are two stages of signal switching. In the conventional example shown in FIG. 8, the analog RGB / digital RGB signal switching circuit 63, T is used.
V signal / external RGB signal switching circuit 61 and on-screen
The signal switching circuit 62 has three stages of signal switching, and the number of stages of signal switching increases as the number of input RGB signals increases, resulting in a large circuit scale and inferior cost and reliability. There is.

Secondly, since the signal switching is multi-staged, frequency characteristics of each signal switching circuit, signal delay, DC offset between input and output signals, etc. are added, and a through signal such as RGB signal or on-screen signal is transmitted. -The image quality is apt to deteriorate due to the deterioration of the image quality and the black level fluctuation.

Third, in the conventional example shown in FIGS. 9 and 10 which is actually adopted in many TV receivers, first, the TV
The on-screen signal is inserted into the signal, and after that, switching to the external RGB signal is performed.Therefore, in order to insert the on-screen signal into the external RGB signal, another control is required in addition to the normal control. It becomes necessary to manage the switching timing between the two signal switching circuits, and the quality of the on-screen display characters is likely to deteriorate.

Fourth, in each of the above conventional examples, external RGB
Signals and on-screen signals can be switched, but the operation of forcibly selecting a TV signal cannot be performed, so an external RG can be used during the horizontal blanking period or vertical blanking period.
When the B signal or the on-screen signal is input, there may be a problem such as a bright line appearing on the display screen of the TV receiver.

An object of the present invention is to provide an inexpensive and high-performance RGB interface circuit by solving such problems, reducing the circuit scale, and obtaining a high quality display image.

[0023]

In order to achieve the above object, the present invention is directed to a primary color signal of a color television signal, an on-screen signal, and the other RGB signals, of which one system is provided. A signal switching circuit that selects and outputs signals, and a switching control circuit that is supplied with a control signal for selecting these signals and that performs selective switching control of the signal switching circuit are provided. Set the priority of selection of these signals in the switching circuit.

Further, according to the present invention, the selection priority of the primary color signals of the color television signals in the signal switching circuit is minimized, and further, the switching control circuit inputs the color television signal switching control signal. A terminal is provided to forcibly select the primary color signal of the color television signal by the signal switching circuit.

[0025]

With a single-stage signal switching operation, it is possible to switch between a television signal and other RGB signals, and to insert an on-screen signal into these signals, and an image such as an RGB signal or an on-screen signal can be displayed. It is possible to suppress image quality deterioration, increase in circuit scale, and cost increase. Moreover, since priority is provided for selection of each signal in the signal switching circuit, selection of each signal is facilitated. For example, by giving top priority to the on-screen signal, the television signal during the insertion of the screen signal. Even if there is a switch between the RGB signal and the RGB signal, the quality of the on-screen display character does not deteriorate.

Further, since the television signal of the lowest priority can be forcibly selected by the signal switching circuit, the television receiver can be operated by making such selection by the horizontal blanking pulse or the vertical blanking pulse. It is possible to avoid the adverse effects such as the appearance of bright lines on the display screen.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an RGB interface circuit according to the present invention, wherein 1 and 2 are input terminals, 3 is a TV primary color signal processing circuit, and 4 is TV signal / RGB.
A signal / on-screen signal switching circuit, 5 is a switching control circuit, 6 is a switching control terminal, 7 and 8 are input terminals, 9 is an analog RGB signal processing circuit, 10 and 11 are input terminals, and 13 is an output terminal. Circuits having the same reference numerals as those in FIGS. 8 to 10 have the same functions.

In FIG. 1, TV signals input from the input terminals 1 and 2 are converted into primary color signals by the TV primary color signal processing circuit 3, and analog RGB signals input from the input terminal 10 are processed by analog RGB signal processing. The circuit 9 performs signal processing, and the on-screen signal input from the input terminal 11 is further processed by the on-screen signal processing circuit 12 and supplied to the TV signal / RGB signal / on-screen signal switching circuit 4, respectively. To be done.

On the other hand, the analog RGB switching control signal A and the on-screen switching control signal B are supplied to the switching control terminal 7 and the on-screen switching control signal B, respectively.
The signals are input from the switching control terminal 8 and supplied to the switching control circuit 5, which are selected with priority, and are selected as the switching control signal C from the switching control terminal 6 to the TV signal / RGB signal / on-screen signal switching circuit 4. Supplied. This T
V signal / RGB signal / on-screen signal switching circuit 4
The switching control signal C selects one of the primary color signal from the TV primary color signal processing circuit 3, the external RGB signal from the analog RGB signal processing circuit 9, and the on-screen signal from the on-screen signal processing circuit 12. Output from the output terminal 13.

The portion of the TV signal / RGB signal / on-screen signal switching circuit 4 and the switching control circuit 5 enclosed by a broken line is characteristic of this embodiment.
In the other examples, similarly, the characteristic portion is surrounded by a broken line.

Now, the switching control circuit 5 sets the priority order of the on-screen switching control signal B and the analog RGB switching control signal A, and based on this, the TV signal / RGB signal / on-screen signal switching circuit 4 is set. The operation of this embodiment will be described below, assuming that the switching control is performed.

In this case, as the signal output from the TV signal / RGB signal / on-screen signal switching circuit 4 and obtained at the output terminal 13, both the on-screen switching control signal B and the analog RGB switching control signal A are input. And when only the on-screen switching control signal B is input, it is an on-screen signal, and when only the analog RGB switching control signal A is input,
It is an analog RGB signal and becomes a TV primary color signal only when neither the on-screen switching control signal B nor the analog RGB switching control signal A is input.

As described above, in this embodiment, since the three input signals are switched by the one-stage switching circuit 4, the circuit scale becomes small, which is advantageous in terms of cost and reliability. Further, it is possible to reduce the fluctuation of the frequency characteristic due to the switching circuit, the signal delay amount, and the DC offset amount between the input and output signals, and suppress the deterioration of the image quality.

Further, since the priority is set in the signal selection of the TV signal / RGB signal / on-screen signal switching circuit 4, for example, if the on-screen signal is set to the highest priority, the TV signal is set. , RGB signals, or switching from one of these to the other,
On-screen signals can be inserted correctly. Therefore, in particular, even if the TV signal or the RGB signal is switched from one to the other, the quality of the on-screen display characters can be maintained high.

FIG. 2 is a block diagram showing another embodiment of the RGB interface circuit according to the present invention, in which 14 is a switching control terminal, and the portions corresponding to those in FIG. Omit it.

In FIG. 2, the forced TV switching control signal D is input from the switching control terminal 14 and supplied to the switching control circuit 5. When the forced TV switching control signal D is input, the switching control circuit 5 forcibly sets the TV signal having the lowest switching priority in the TV signal / RGB signal / on-screen signal switching circuit 4 as the highest priority. select.

The forced TV switching control signal D is, for example,
Horizontal and vertical blanking signals, etc., and when the TV signal / RGB signal / on-screen signal switching circuit 4 selectively switches the TV signal from the RGB signal or the on-screen signal at this timing, this switching is horizontal, Since it is performed during the vertical blanking period, it is possible to avoid the adverse effects such as the appearance of bright lines on the display screen of the TV receiver.

Although the forced TV switching control terminal 14 is a single terminal here, it may be a plurality of terminals.

FIG. 3 is a circuit diagram showing a specific example of the switching control circuit 5 in FIG.
6, 17 are AND circuits, 18 and 19 are inverter circuits,
Reference numerals 20 and 21 are AND circuits, and 22 to 24 are output terminals, and the portions corresponding to FIG.

In the figure, the switching control terminal 6 of the switching control circuit 5 shown in FIG. 2 is actually composed of three terminals, output terminals 22, 23 and 24, as shown in the figure.

Forced TV input from the switching control terminal 14
The switching control signal D is inverted by the inverter circuit 15, and AN
It is supplied to the D circuits 16 and 17. Also, the switching control terminal 8
The on-screen switching control signal B input from
The analog RGB switching control signal A input from the switching control terminal 7 to the ND circuit 16 is supplied to the AND circuit 17, respectively. The output signal of the AND circuit 16 is the inverter circuit 1
It is inverted at 8 and supplied to the AND circuits 20 and 21, and also supplied as an on-screen mode switching control signal F from the output terminal 23 to the TV signal / RGB signal / on-screen signal switching circuit 4 (FIG. 2). . The output signal of the AND circuit 17 is supplied to the AND circuit 21 and also inverted by the inverter circuit 19 and supplied to the AND circuit 21. The output signal of the AND circuit 20 is used as the TV mode switching control signal E from the output terminal 22 to the TV signal / R.
The output signal of the AND circuit 21 supplied to the GB signal / on-screen signal switching circuit 4 (FIG. 2) is analog RGB.
The mode switching control signal G is supplied from the output terminal 24 to the TV signal / RGB signal / on-screen signal switching circuit 4 (FIG. 2).

Next, the operation of this specific example will be described. First, when the "H" (high level) forced TV switching control signal D is input from the control terminal 14, the output signal of the inverter circuit 15 becomes "L" (low level), so the switching control terminal 8 , 7 whether or not the switching control signal is input
The output signals of the AND circuits 16 and 17 are "L", and the output signals of the inverter circuits 18 and 19 are "H".
The output signal of the circuit 20 becomes "H" and the output signal of the AND circuit 21 becomes "L". Therefore, the TV mode switching control signal E
Only H becomes "H" and the on-screen mode switching control signal F and the analog RGB mode switching control signal G become "L". Therefore, the TV signal / RGB signal / on-screen signal switching circuit 4 (FIG. 2) is forced to
This is a mode for selecting the TV signal from the primary color signal processing circuit 3.

When the forced TV switching control signal D is not input from the switching control terminal 14, the output signal of the inverter circuit 15 becomes "H", so that the output signals of the AND circuits 16 and 17 are switched respectively. This depends on whether or not the on-screen switching control signal B and the analog RGB switching control signal A are input from the terminals 8 and 7.

Therefore, assuming that the on-screen switching control signal B of "H" is inputted from the switching control terminal 8,
The output signal of the AND circuit 16 becomes “H” and the output signal of the inverter circuit 18 becomes “L” regardless of whether or not the analog RGB switching control signal A is input from the switching control terminal 7. Therefore, the output signals of the AND circuits 20 and 21 become "L", and only the on-screen mode switching control signal F output from the output terminal 23 becomes "H".
Therefore, the TV signal / RGB signal / on-screen signal switching circuit 4 (FIG. 2) is equivalent to the on-screen signal processing circuit 12.
This is a mode for selecting the on-screen signal supplied from.

There is no signal of "H" input from the switching control terminals 14 and 8, and an analog RG signal of "H" is input from the switching control terminal 7.
When the B switching control signal A is input, the AND circuit 1
Since the output signal of 6 is "L" and the output signal of the AND circuit 17 and the output signal of the inverter circuit 18 are "H", A
Only the analog RGB mode switching control signal G output from the ND circuit 21 becomes "H", and the TV signal / RGB signal / on-screen signal switching circuit 4 (FIG. 2) is supplied from the analog RGB signal processing circuit 9. This is a mode for selecting an analog RGB signal that is used.

There is no "H" signal input from the switch control terminal 14, and the "H" on-screen switch control signal B and the analog RGB switch control signal A are "H" from the switch control terminals 8 and 7, respectively.
, The output signals of the AND circuits 16 and 17 both become "H", and the output signals of the inverter circuits 18 and 19 both become "L". Therefore, the output terminal 2
ON-SCREEN MODE switching control signal F output from 3
Only becomes "H". Therefore, TV signal / RGB signal /
The on-screen signal switching circuit 4 (FIG. 2) serves as a mode for selecting the on-screen signal supplied from the on-screen signal processing circuit 12.

"H" is output from both of the switching control terminals 8 and 7.
When the signal of is not input, the AND circuits 16 and 17
Output signals of both become "L" and the inverter circuit 1
The output signals of 8 and 19 are "H", and only the TV mode switching control signal E is "H". Therefore, TV signal / RG
The B signal / on-screen signal switching circuit 4 (FIG. 2) is
This is a mode for selecting the TV signal from the V primary color signal processing circuit 3.

As described above, since each switching control signal is given priority in the switching control circuit 5 and one switching control signal is selected to collectively control one signal switching circuit 4, the circuit scale is greatly increased. It is possible to reduce the size to 1, and there is no need for complicated control in multiple stages. It is also possible to forcibly set the mode for selecting the TV signal having the lowest priority.

At first glance, it seems that the control circuit has become complicated, but in reality, even when the control circuit has multiple stages, complicated control including the timing is required as in the conventional example. The circuit scale of the control circuit is not so large, and further, the multistage signal switching circuit of the prior art has only one stage in this embodiment, so that the circuit scale can be greatly reduced.

In the configuration of FIG. 3, the input terminal 1
4, the inverter circuit 15 and the AND circuits 16 and 17 are omitted, so that the switching control circuit 5 in FIG. 1 can be used.

FIG. 4 is a block diagram showing another embodiment of the RGB interface circuit according to the present invention.
The parts corresponding to those in FIG. 2 are designated by the same reference numerals.

In this embodiment, the control method in the embodiment shown in FIG. 2 is partially modified, and the on-screen signal input from the input terminal 11 is also supplied to the switching control circuit 5 to be input. Even an on-screen signal enables switching control of the TV signal / RGB signal / on-screen signal switching circuit 4. According to this, even when the on-screen switching control signal B is not input from the switching control terminal 8, the on-screen signal from the input terminal 11 acts as the on-screen switching control signal. This enables timing management, simplification of wiring, and output port of the on-screen microcomputer.
It is possible to reduce the number of pins (1 pin).

FIG. 5 is a block diagram showing another embodiment of the RGB interface circuit according to the present invention.
Reference numeral 25 is a switching control terminal, 26 is a digital RGB signal processing circuit, and 27 is an input terminal. The parts corresponding to those in FIG.

In this embodiment, a digital RGB signal input terminal 27, a digital RGB signal processing circuit 26 and a digital RGB switching control terminal 25 are added to the embodiment shown in FIG. 2 to switch TV signal / RGB signal / on-screen signal. The circuit 4 is configured so that the digital RGB signal from the digital RGB signal processing circuit 26 can be selected, and the input of the RGB signals other than the on-screen is made into two systems.

In this case, the selection priority of each input signal in the TV signal / RGB signal / on-screen signal switching circuit 4 is determined by, for example, the output signal from the TV primary color signal processing circuit 3 or the input from the input terminals 10 and 11. The signals can be appropriately set by making the digital RGB signal from the input terminal 27 the highest priority in the same manner as in the previous embodiment. The switching control circuit 5 in this case can also be easily realized by adding an AND circuit and an inverter circuit to the configuration shown in FIG. 3 and wiring them appropriately.

In this embodiment, TV signal / RGB
The number of input signals of the signal / on-screen signal switching circuit 4 and the number of control targets of the switching control circuit 5 are increased by one system, respectively.
Also, as in the embodiment shown in FIG. 2, the one-stage signal switching circuit 4 is sufficient, so that the circuit configuration is much simpler than the conventional one, the circuit scale can be reduced, and the reliability of the circuit is improved.

FIG. 6 is a block diagram showing still another embodiment of the RGB interface circuit according to the present invention, in which 28 is a luminance signal processing circuit, 29 is a DC signal generating circuit, 30 is a color difference signal processing circuit, and 31 is. TV-Y signal /
For RGB / on-screen-Y. DC signal switching circuit, 3
Reference numeral 2 is a TV color difference signal / RGB signal / on-screen signal switching circuit, and 33 and 34 are output terminals. The parts corresponding to those in FIG.

This embodiment corresponds to the -Y signal and color difference signal processing type of the RGB interface circuit corresponding to the primary color signal processing of the embodiment shown in FIG.

In FIG. 6, the color difference signal of the TV signal input from the input terminal 2 is processed by the color difference signal processing circuit 30, the RGB signal input from the input terminal 10 and processed by the analog RGB signal processing circuit 9, and the like. TV color difference signal / RGB together with the on-screen signal input from the input terminal 11 and processed by the on-screen signal processing circuit 12.
It is supplied to the signal / on-screen signal switching circuit 32.
Further, the −Y signal (reverse luminance signal) of the TV signal input from the input terminal 1 is processed by the luminance signal processing circuit 28,
TV-Y signal / RGB for on-screen-Y. DC
It is supplied to the signal switching circuit 31 and the DC signal generating circuit 29. In this DC signal generating circuit 29, the RGB signal and the on-screen signal of -Y. DC signal is formed, TV
-Y signal / for RGB on-screen-Y. It is supplied to the DC signal switching circuit 31.

Here, the reason why the DC signals are required for the RGB signal and the on-screen signal is to make these signals, which are primary color signals, correspond to -Y, the color difference signal processing type. The DC signal of the ON-SCREEN signal and the ON-SCREEN signal may be shared by one signal.

On the other hand, the analog RGB switching control signal A, the on-screen switching control signal B and the forced TV switching control signal D are input from the switching control terminals 7, 8 and 14, respectively, and prioritized by the switching control circuit 5. Are output to the switching control terminal 6 and the switching control signal obtained at the switching control terminal 6 causes the TV color difference signal / RGB signal / on-screen signal switching circuit 32 and the TV-Y signal / RGB / on-screen- Y. The DC signal switching circuit 31 and the DC signal switching circuit 31 simultaneously switch signals to output the color difference signal and the -Y signal from the output terminals 34 and 33, respectively.

As described above, in the -Y signal and color difference signal processing type, the -Y signal system and the color difference / RGB signal system are switched in parallel, but in this case also, the signal switching for each one stage is performed. Since only a circuit is needed, the circuit configuration is much simpler than the conventional one.

Further, in this embodiment, by deleting the forced TV switching control terminal 14, the -Y signal and the color difference signal processing of the RGB interface circuit corresponding to the primary color signal processing in the embodiment shown in FIG. 1 are performed. It can also be a type. In addition, similar to the embodiment shown in FIG.
It is also easy to correspond to B input.

FIG. 7 shows the TV signal / in the embodiment described above.
FIG. 3 is a circuit diagram showing one channel portion (one-third portion of the entire circuit) of a specific example of the RGB signal / on-screen signal switching circuit 4, wherein 35 is a voltage source, 36 and 37 are resistors,
8, 39 are PNP transistors, 40 are NPN transistors, 41-43 are input terminals, 44-49 are NPN transistors, 50-55 are resistors, 56-58 are NPN transistors, and 59, 60 are constant current sources. The same reference numerals are attached to the parts corresponding to the drawings.

In the figure, one primary color signal S1 of the TV signal is input from the input terminal 41, one primary color signal S2 of the on-screen signal is input from the input terminal 42, and one of the analog RGB signals is input from the input terminal 43. The primary color signal S3 is input and supplied to the bases of the NPN transistors 44, 46 and 48, respectively.

Here, the NPN transistors 44 and 45
And resistors 50, 51 connected to these emitters,
The NPN transistor 56 whose collector is connected to the emitters of the NPN transistors 44 and 45 through the resistors 50 and 51 constitutes a switching circuit for the primary color signal S1 of the TV signal, and the NPN transistor 46 and
47 and resistors 52, 53 connected to these emitters
And the NPN transistor 57 whose collector is connected to the emitters of the NPN transistors 46 and 47 through these resistors 52 and 53 are the primary color signal S of the on-screen signal.
2 and a switching circuit for NPN transistor 4
8,49 and resistors 54 connected to these emitters,
55 and the collector via these resistors 54, 55
NP connected to the emitters of N transistors 48 and 49
The N-transistor 58 constitutes a switching circuit for the primary color signal S3 of the analog RGB signal, respectively.

The base of the NPN transistor 56 is supplied with, for example, the TV mode switching control signal E output from the output terminal 22 of the switching control circuit 5 of FIG. 3, and the base of the NPN transistor 57 is also subjected to the switching control. The on-screen mode switching control signal F output from the output terminal 23 of the circuit 5 is supplied, and the analog RGB mode switching output from the output terminal 24 of the switching control circuit 5 is also supplied to the base of the NPN transistor 58. The control signal G is supplied.
The emitters of the NPN transistors 56, 57 and 58 are connected to the constant current source 59.

The collectors of the NPN transistors 44, 46 and 48 are connected to the voltage source 35 through the PNP transistor 38 and the resistor 36, and the NPN transistors 45 and 4 are connected.
The collectors of 7, 49 are connected to the base of the NPN transistor 40 and the PNP transistor 38.
In addition, it is connected to a voltage source 35 via a PNP transistor 39 and a resistor 37 that form a current mirror. Therefore, the PNP transistors 38 and 39, the NPN transistor 40, the resistors 36 and 37, and the current sources 59 and 60.
Is a common load of the above switch circuit,
Configure the follower circuit. The collector of the NPN transistor 40 is connected to the voltage source 35, and the emitter thereof is connected to the output terminal 13 and the constant current source 60. Also, NP
The bases of the N transistors 45, 47 and 49 are connected to the emitter of the NPN transistor 40.

Next, the operation of this specific example will be described by taking the case where the selection mode of the TV signal is set as an example.

In this case, only the TV mode switching control signal E inputted from the switching control terminal 22 is "H", and the on-screen mode switching control signal F inputted from the switching control terminal 23. The analog RGB mode switching control signal G input from the switching control terminal 24 is "L". This turns on the NPN transistor 56,
The NPN transistors 57 and 58 are turned off, current flows through the NPN transistors 44, 45 and 56 and the resistors 50 and 51, and the PNP transistors 38 and 39, the NPN transistor 40, the resistors 36 and 37, and the current sources 59 and 60 are connected to the voltage sources. -The follower circuit is constructed. Therefore, the input terminal 41
The primary color signal S1 input from the output terminal 13 is output from the output terminal 13 through the voltage follower circuit.

Thus, in this specific example, the signal switching operation is performed by turning on the NPN transistor connected to the switching control terminal 6.

Further, according to such a configuration, even if the number of input signals increases, it is sufficient to add three NPN transistors and two resistors each time one system is added, and the load on the circuit scale is small.

Further, since it is a non-saturation type switching circuit using a voltage follower circuit as a load, high speed switching is possible and the quality of the displayed characters of the on-screen signal and the analog RGB signal is not deteriorated.

[0074]

As described above, according to the present invention,
Since it is composed of a single-stage signal switching circuit and a switching control circuit, the circuit scale can be greatly reduced compared to the prior art, and the cost of the circuit can be expected to be low. And low current can be achieved.

Further, since the signal switching circuit need only be one stage, the reliability of the circuit is improved and the on-screen signal and the RGB signal can be displayed in high quality as compared with the conventional circuit having a multi-stage configuration.

Furthermore, since the priority order for each switching control signal can be freely set by changing the control circuit, the degree of freedom in circuit design is expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an RGB interface circuit according to the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the RGB interface circuit according to the present invention.

FIG. 3 is a circuit diagram showing a specific example of a switching control circuit in FIG.

FIG. 4 is a block diagram showing the configuration of still another embodiment of the RGB interface circuit according to the present invention.

FIG. 5 is a block diagram showing the configuration of still another embodiment of the RGB interface circuit according to the present invention.

FIG. 6 is a block diagram showing the configuration of still another embodiment of the RGB interface circuit according to the present invention.

FIG. 7 is a circuit diagram showing a part of a specific example of a signal switching circuit in each embodiment.

FIG. 8 is a block diagram showing an example of a conventional RGB interface circuit.

FIG. 9 is a block diagram showing another example of a conventional RGB interface circuit.

FIG. 10 is a block diagram showing still another example of a conventional RGB interface circuit.

[Explanation of symbols]

1, 2 TV signal input terminal 3 TV primary color signal processing circuit 4 TV signal / RGB signal / on-screen signal switching circuit 5 Switching control circuit 6, 7, 8 Switching control terminal 9 Analog RGB signal processing circuit 10 External analog RGB signal Input terminal 11 On-screen signal input terminal 12 On-screen signal processing circuit 13 Output terminal 14 Switching control terminal 22 TV mode switching control signal output terminal 23 On-screen mode switching control signal output terminal 24 Analog RGB Mode switching control signal output terminal 25 Switching control terminal 26 Digital RGB signal processing circuit 27 Digital RGB signal input terminal 28 Luminance signal processing circuit 29 DC signal generating circuit 30 Color difference signal processing circuit 31 TV-Y signal / RGB on-screen -For-
Y. DC signal switching circuit 32 TV color difference signal / RGB signal / on-screen signal switching circuit 33, 34 Output terminals

Claims (6)

[Claims] 1. An RGB on-screen signal display function,
RGB other than at least one or more on-screen signals
R of a color television receiver or the like having a signal display function
In the GB interface circuit, a signal switching circuit for inputting a primary color signal of a color television signal, an on-screen signal, and the other RGB signals, and selecting and outputting one of the signals, and selection of these signals. And a switching control circuit for performing selective switching control of the signal switching circuit, the switching control circuit setting the priority of selection of these signals in the signal switching circuit. Characteristic RGB interface circuit. 2. The R according to claim 1, wherein the selection priority order of the primary color signals of the color television signal in the signal switching circuit is the lowest.
GB interface circuit. 3. The switching control circuit according to claim 2, wherein the switching control circuit is provided with an input terminal for a switching control signal of a color television signal, and the signal switching circuit forcibly selects the primary color signal of the color television signal. RGB that is possible
Interface circuit. 4. An RGB on-screen signal display function,
RGB other than at least one or more on-screen signals
R of a color television receiver or the like having a signal display function
In the GB interface circuit, a first signal switching circuit for inputting a color difference signal of a color television signal, an on-screen signal and the other RGB signals, and selecting and outputting a signal of one system among them, An inverted luminance signal of a television signal, a DC signal for determining a black level of an on-screen signal, and other R signals
A second signal switching circuit for inputting a DC signal for determining the black level of the GB signal, or a DC signal common to the on-screen signal and the RGB signal, and selecting and outputting a signal of one system among them; A switching control circuit which is supplied with a control signal for selecting these signals and which performs selective switching control of the first and second signal switching circuits, the switching control circuit including the first and second signals. An RGB interface circuit characterized by setting the priority of selection of these signals in a switching circuit. 5. The selection priority order of color difference signals of the color television signal in the first signal switching circuit, and the inversion luminance signal of the color television signal in the second signal switching circuit according to claim 4. An RGB interface circuit having the lowest selection priority. 6. The switching control circuit according to claim 5, wherein the switching control circuit is provided with an input terminal for a switching control signal of a color television signal, and the first signal switching circuit outputs a color difference signal of the color television signal, An RGB interface circuit, wherein the first signal switching circuit can forcibly select the inversion luminance signal of the color television signal.