JP2759709B2 - Signal switching device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal switching device for inputting a plurality of video signals or audio signals and displaying a multi-screen or audio on a television receiver.

2. Description of the Related Art In recent years, the input sources of television receivers have been diversified, and TV video signals obtained by receiving television broadcasts, BS
It is necessary to input a large number of video signals, such as a BS video signal, a VTR video signal, and a laser disk video signal obtained by receiving a broadcast, and display them on a television receiver. Also, a function of selecting a plurality of these signals and displaying a multi-screen on a television receiver is becoming common.

FIG. 4 is an example of a two-screen display television receiver,
The signals of the main screen and the sub screen are displayed. for that purpose,
A multi-output signal switching device for inputting a large number of video signals and displaying a multi-screen on a television receiver is required.

Hereinafter, an example of the above-described conventional multi-output signal switching device will be described with reference to FIG.

In FIG. 3, a TV video signal is input from an input terminal 1, a BS video signal is input from an input terminal 2, a video 1 video signal is input from an input terminal 3, and a video 2 video signal is input from an input terminal 4. Input, each signal is a capacitor 5,6,7,8,2
The first switch circuit 9 and the second switch circuit 10 select one video signal from each of the four types of video signals via 2, 23, 24, and 25, and output the selected video signal from the output terminals 13 and 14. The selection of the video signal is controlled by the signal switching control circuit 12 via the control lines 11, 11 ', and is controlled by the binary-to-decimal conversion decoders 26, 27.
Is performed by switching the first switch circuit 9 and the second switch circuit 10. The video signals output from the output terminals 13 and 14 are supplied to the first and second signal demodulators 15 and 1.
The signal is demodulated into color signals 17 and 18 such as R, G, and B by 6. And
The two types of video signals 17, 18 such as R, G, B are switched by a switcher of a third switch circuit 19, and the output signals thereof are output.
By displaying 20 on the CRT 21, the color signal 1 is displayed as shown in FIG.
A display can be made in which one of 7 or 18 is set as a main screen and the other is set as a sub-screen.

Problems to be Solved by the Invention However, in the above-described configuration, in order to display signals of a main screen and a sub-screen in a dual-screen television receiver, (1) the first switch circuit 9 is configured. In this case, two ICs are required, ie, an integrated circuit and an IC constituting the second switch circuit 10, so that the cost is high and the IC mounting area is doubled.

(2) Two capacitors are required for one input video signal to the first and second switch circuits 9 and 10, respectively.
The cost is high.

(3) Two systems of video signal selection control lines 11, 11 'are required to control the first and second switch circuits 9, 10,
A large number of output terminals of the signal switching control circuit 12 are required, which complicates the control program.

And so on.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to provide a signal switching device capable of reducing the cost, reducing the mounting area by half, and simplifying the control.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first transistor in which a plurality of video signals or audio signals are respectively input to a base, and a base connected to an emitter of the first transistor. A multi-emitter transistor, a second transistor having an emitter connected to the first emitter of the multi-emitter transistor, a collector connected to a connection point between the emitters of the multi-emitter transistor and the second transistor, and a decoder connected to the base. And a third transistor having a third transistor which is controlled to be turned on and off when the output of the first transistor is input to the second transistor. Connecting a load between the power supplies and connecting the collector to the base of the first output transistor connected to the power supplies; Further, the bases of the second transistors of each first set are connected to each other, and the connection point is connected to the emitter of the first output transistor to form a first switching output. A fourth transistor having an emitter connected to the second emitter, a fifth transistor having a collector connected to the emitter of the fourth transistor, and having an output from the decoder input to the base to be turned on and off. And a collector connected to the power supply while connecting the collectors of the fourth transistors of the second set to each other and connecting a load between the connection point and the power supply. The bases of the second output transistors are connected, and the bases of the fourth transistors of each second set are connected to each other, and the connection point is connected to the emitter of the second output transistor. Te is obtained by the second switch output.

According to the present invention, a signal switching circuit for outputting two kinds of video signals and audio signals required for displaying a signal of a main screen and a signal of a sub-screen in a two-screen display television receiver is configured as one chip in the above-described configuration. It can be made into an IC, lowering the IC cost and halving the IC mounting area.

Also, only one capacitor is required for one input video signal, and the cost can be reduced by half. Further, the video signal selection control line can be controlled by one system, the number of output terminals of the circuit can be reduced, and the control program can be simplified.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram of a signal switching device according to one embodiment of the present invention, and the same reference numerals are given to the same elements as those in the conventional example shown in FIG. In FIG. 1, 1 is a TV
Input terminal for video signal, 2 for BS video signal, 3 for video 1 video signal, 4
Is an input terminal for a video signal of video 2. 5,6,7,
8, a capacitor; 9, a first switch circuit; 10, a second switch circuit; 11, a control line; 12, a signal switching control circuit;
Is an output terminal, 15 is a first signal demodulator, 16 is a second signal demodulator, 17 and 18 are color signals, 19 is a third switch circuit, 20 is an output signal, 21 is a CRT, 100 is a signal switching circuit, 200 Is a decoder.

Next, the operation of the above embodiment will be described. In FIG. 1, a TV video signal is input from an input terminal 1, a BS video signal is input from an input terminal 2, a video signal of video 1 is input from an input terminal 3, and a video signal of video 2 is input from an input terminal 4. input. Each of the signals is selected from the above four types of video signals by the first switch circuit 9 and the second switch circuit 10 via the capacitors 5, 6, 7, and 8, and the output terminal 1
Output from 3,14. The selection of the video signal is performed by decoding the control data from the signal switching control circuit 12 by the decoder 200 via the control line 11. The signals at the output terminals 13 and 14 that have selected the video signal are demodulated by the first and second signal demodulators 15 and 16 into color signals 17 and 18 such as R, G, and B. The two types of video signals 17, 18 of R, G, B, etc. are switched by a switcher of a third switch circuit 19, and the output signal 20 is displayed on a CRT 21 to obtain a color signal as shown in FIG. A display can be made in which one of the signals 17 or 18 is used as a main screen and the other is used as a sub-screen.

FIG. 2 shows a signal switching circuit 10 according to an embodiment of the present invention.
FIG. 3 is a detailed circuit diagram of 0. In FIG. 2, the first switch circuit 9 is configured by connecting transistors 31 to 45,
The selection result is output from the output terminal 13. The second switch circuit 10 is configured by connecting the transistors 33, 36, 41, 44, 48 to 56, and outputs the selection result from the output terminal 14. The selection of the signal is based on the control signal from the signal switching control circuit 12.
11 is turned on and off by the decoder 200, and each of the video signal selecting transistors 37,
This is performed by controlling on / off of 38, 46, 47 and 50, 51, 55, 56.

The signal switching circuit 100 shown in FIG. 2 will be described in further detail. The signal switching circuit 100 is based on a TV video signal, a BS video signal, a video 1 video signal, a video 2 video signal, or their audio signals. First transistors 32, 39, 40, and 45 for impedance conversion input to
Multi-emitter transistors 33, 36, 4 whose bases are connected to the emitters of these first transistors 32, 39, 40, 45
1,44 and these multi-emitter transistors 33,36,41,4
4, a second transistor 34, 35, 42, 43 having an emitter connected to the first emitter;
A video signal whose collector is connected to the connection point between the emitters of the transistors 3,36,41,44 and the second transistors 34,35,42,43 and whose base is supplied with the output from the decoder 200 and whose on / off control is performed A first plurality of sets including third transistors 37, 38, 46, 47 for selection are provided, and the collectors of the second transistors 34, 35, 42, 43 of each first set are connected to each other. A load resistor 89 is connected between the connection point and the power supply line 30a to which the collectors of the first transistors 32, 39, 40, and 45 to which the bias voltage 30 is applied are connected, and the collector is connected to the power supply line 30a. Connected first output transistor 31
And the bases of the second transistors 34, 35, 42, and 43 of the first set are connected to each other, and the connection point is connected to the emitter of the first output transistor 31 so that the output terminal 13 is connected. To the first switching output.

A fourth transistor 48, 49, 53, 54 having an emitter connected to the second emitter of each of the first set of multi-emitter transistors 33, 36, 41, 44; Collectors are connected to the emitters of the transistors 49, 53, 54, and the bases receive the output from the decoder 200, and have fifth transistors 50, 51, 55, 56 that are controlled to be on and off. The collectors of the fourth transistors 48, 49, 53, 54 of each of the second sets are connected to each other, and a load resistor 97 is connected between the connection point and the power supply line 30a. The base of the second output transistor 52 to which the collector is connected is connected,
The bases of the fourth transistors 48, 49, 53, 54 of each set are connected to each other, the emitter of the second output transistor 52 is connected to the connection point, and the connection is led to the output terminal 14, and as the second switching output I have.

Next, the operation of the signal switching circuit 100 will be described. T
A V video signal is input from an input terminal 1 and a bias voltage 30 is applied via a capacitor 5 to a base of a first transistor 32 for impedance conversion via a resistor 80. The emitter output is applied to the base of the multi-emitter transistor 33, and one multi-emitter output of the multi-emitter transistor 33 is input to a switch circuit composed of the second transistor 34, the third transistor 37, and the resistor 82,
The other multi-emitter output is input to another switch circuit including the fourth transistor 48, the fifth transistor 50, and the resistor 93.

Similarly, a BS video signal is input from the input terminal 2, and the bias voltage 30 is applied to the base of the first transistor 39 for impedance conversion via the capacitor 6 via the capacitor 6. The emitter output is multi-emitter transistor
In addition to the base of 36, one multi-emitter output of the multi-emitter transistor 36 is input to a switch circuit composed of a second transistor 35, a third transistor 38 and a resistor 83, and the other multi-emitter output is The signal is input to another switch circuit including the fourth transistor 49, the fifth transistor 51, and the resistor 94.

By the output of the decoder 200 to which the control signal 11 is input,
When the third transistor 37 for selecting the video signal is turned on and the third transistor 38 for selecting the other video signal is turned off, the TV video signal from the input terminal 1 appears on the load resistor 89, and the first output transistor A voltage follower is constituted by 31 and a TV video signal is output to the output terminal 13.

The video signal of video 1 from the input terminal 3 or the input terminal 4
Is also selected by the same circuit.

Since the second switch circuit 10 has the same configuration, the selected output is output from the output terminal 14.

With the above configuration, a signal switching circuit that outputs two types of video signals and audio signals necessary for displaying signals of a main screen and a sub-screen in a dual-screen display television receiver
100 and the control signal decoder 200 can be made into one chip IC, thereby reducing the IC cost and halving the IC mounting area. Conventionally, two capacitors are required for one input video signal to the first switch and the second switch circuit, but in this embodiment, only one capacitor is required for each, and the cost is reduced by half. . In addition, the video signal selection control line can be controlled by one system, so that the number of output terminals of the circuit can be reduced and the control program can be simplified.

Effects of the Invention As described above, according to the present invention, in a dual-screen television receiver, signals for outputting two types of video signals and audio signals necessary for displaying signals of a main screen and a sub-screen are provided. The switching circuit can be made into a single-chip IC.
The cost can be reduced and the IC mounting area can be halved. Also, only one capacitor is required for one input video signal,
Cost can be cut in half. Furthermore, since the video signal selection control line can be controlled by one system, the output terminals of the circuit can be reduced and the control program can be simplified.

[Brief description of the drawings]

1 is a block diagram of a signal switching device according to one embodiment of the present invention, FIG. 2 is a detailed circuit diagram of a signal switching circuit according to one embodiment of the present invention, FIG. 3 is a block diagram of a conventional signal switching device, FIG. 4 is a front view of a two-screen display television receiver showing a state where signals of a main screen and a sub-screen are displayed. 1 ... TV video signal input terminal, 2 ... BS video signal input terminal, 3 ... Video 1 video signal input terminal, 4 ... Video 2 video signal input terminal, 5, 6, 7, 8: Capacitor, 9: First switch circuit, 10: Second switch circuit, 11: Control line, 12: Signal switching control circuit, 13, 14, ...
... Output terminals, 15,16 ... Signal demodulator, 17,18 ... Color signals,
19: Third switch circuit, 20: Output signal, 21: CR
T, 100: Signal switching circuit, 200: Decoder. 30 ... bias voltage, 30a ... power line, 31 ... first
Output transistors, 32, 39, 40, 45... First transistors for impedance conversion, 33, 36, 41, 44... Multi-emitter transistors, 34, 35, 42, 43. , 38, 46, 47... Third transistor for selecting a video signal, 48, 49, 53, 54... Fourth transistor, 50, 5
1,55.56... Fifth transistor for selecting a video signal, 52
... Second output transistor, 89, 97... Load resistance.

Claims (1)

(57) [Claims] 1. A first transistor to which a plurality of video signals or audio signals are respectively input to a base, a multi-emitter transistor having a base connected to an emitter of the first transistor, and a first transistor of the multi-emitter transistor. A second transistor whose emitter is connected to the emitter of the second transistor, a collector is connected to a connection point between the emitters of the multi-emitter transistor and the second transistor, an output from the decoder is input to the base, and the second transistor is turned on;
A first plurality of sets each including a third transistor to be controlled to be turned off, a collector of the second transistors in each of the first sets being connected to each other, and a load being connected between the connection point and a power supply. And a collector connected to the base of a first output transistor whose power supply is connected to a power supply, and further connected to the bases of the second transistors of each first set, and connected at the connection point to the emitter of the first output transistor. To form a first switching output, a fourth transistor having an emitter connected to a second emitter of each of the first set of multi-emitter transistors, and a collector connected to an emitter of the fourth transistor. , A fifth transistor having an output from the decoder input to the base and being turned on and off.
, The collectors of the fourth transistors of each of the second sets are connected to each other, a load is connected between the connection point of the fourth transistors, and a second power supply whose collector is connected to the power supply.
, The bases of the fourth transistors in each of the second sets are connected to each other, and the connection point is connected to the emitter of the second output transistor to obtain a second switching output. Signal switching device.