JPS6328552B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is capable of receiving ordinary RF television signals, as well as a video input terminal to which an external video signal is input, and a video input terminal to which character/graphic information from the outside is input.
This relates to a television receiver equipped with an RGB input (8-pin input, 21-pin input) terminal.

Conventional configuration and its problems As mentioned above, in television receivers equipped with video input terminals and RGB input terminals, RGB
One way to switch between the 21-pin and 8-pin input terminals is to use a mechanical switch to switch each signal (R, G, B) system, control signals YM, Ys, and video signal. In this case, a large number of terminals are required for the changeover switch, which increases the cost of the switch, which is extremely disadvantageous in terms of cost. Therefore, if possible, switching can be done using a transistor switching circuit, which makes it possible to reduce the number of terminals of the switch, thereby reducing costs.

Hereinafter, the above-mentioned conventional example will be explained with reference to the drawings.

Figure 1 shows a conventional example in which a mechanical switch is used to switch between the 8-pin and 21-pin RGB input terminals.

In Figure 1, 1 is an 8-pin input terminal, 2 is an 8-pin input terminal
This circuit creates an input buffer and a composite synchronization signal of horizontal and vertical synchronization signals. 6 is
This is an 8pin input and 21pin input signal selection switch.
4 is a 21pin input terminal.

The signals being switched by the changeover switch 6 are R,
G and B signals, the YS signal which is the TV/RGB character switching signal, and the synchronization signal applied to the synchronization circuit.
For shadow control when superimposing
This is a six signal system of YM signals.

One input of the TV/RGB signal switching circuit 5 receives television signals R-Y/TV, G-Y/TV,
The BY/TVY signal is applied, and the R, G, and B signals of the RGB signal are applied to the other, and depending on the signal level of the YS control terminal [when "H"
When the RGB side is "L", it is the TV side, and when the YS signal is switched at a constant cycle (switching between high and low levels), it is superimposed] The input signal is switched between the television signal and the RGB signal and output. That's what I do.

Output R-Y/R of TV/RGB signal switching circuit 5,
The G-Y/G, B-Y/B, and Y/YBLK signals are applied to a video output amplification circuit (not shown).

Now, with the configuration as above, switch 6 is 6
This is a switch with two circuit contacts and a very large number of circuits, which increases the cost.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to reduce the number of circuits in a switch, thereby reducing costs.

Structure of the Invention The television receiver according to the present invention uses four circuits of mechanical switches, and three of the circuits control the red R, green G, and blue B signals from the 8-pin input terminal section and the 21-pin input terminal section. After switching, the remaining one circuit creates a first control signal that has different levels when 8 pins are selected and when 21 pins are selected, and a second control signal of the control voltage generation circuit that has different levels between RGB mode and TV/video mode. control signal and the first
control signal from the 21pin input terminal section to the TV.
Similarly to the first switching circuit that controls the TV/RGB character switching signal and shadow control signal supplied to the RGB signal switching circuit, the first control signal and second control signal are used to control the synchronization signal of the 8-pin input terminal section. The second switching circuit that controls the switching of the synchronization signal of the 21-pin input terminal section is used to switch the signals from the 8-pin input terminal section and the 21-pin input terminal section, and compared to the conventional configuration. This makes it possible to reduce costs, especially for the first and second
By making the switching circuit side of the device an integrated circuit, the effect becomes greater.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows an embodiment of the present invention. In the drawings, the same parts as those in FIG. 1 are given the same numbers and explained.

In FIG. 2, the switch 6 has four circuits and two contacts. Further, 7, 8, 9, 10, and 11 are switching transistors. The signal switching circuit 28 switches the 21-pin synchronization signals of video 1, video 2, video 3, and RGB. When the control terminal becomes high level, the switch closes. Signal switching circuit 2
The output of 8 is applied to the synchronization circuit and the video circuit through the next stage television signal and video signal switching circuit.

A resistor 1 is connected between the base of transistor 7 and ground.
7 is connected, and a resistor 16 is connected to the intersection of the resistor 17 and the base, and the other end of the resistor 16 is connected to the
A high level voltage is applied in RGB mode, and a low level voltage is applied otherwise. In the RGB mode, the base of transistor 7 is at high level, so transistor 7 is turned on, and the collector of transistor 7 is at low level, so transistors 9 and 10 are not turned on but turned off, and YM,
The YS terminal is not forced to ground and input is not prohibited. On the other hand, in TV mode or video mode, a low level is applied to the base of transistor 7, so transistor 7 is turned off, and the collector becomes high level, and a high level signal is sent to the transistor from +B (usually 12V) via resistor 18. Since the voltage is applied to the bases of transistors 9 and 10, transistors 9 and 10 are turned on, and the YM and YS control terminals are inhibited. Therefore, even if the 21pin terminal is connected in TV mode and video mode,
Since the YS and YM control terminals are low
The output of the TV/RGB signal switching circuit 5 becomes a television signal. Furthermore, when switch 6 is switched to 8pin input terminal 1 in RGB mode, transistor 7 is turned on and transistor 8 is turned off.
Since a high level voltage is applied from the +B voltage via the resistor 19 to the YS control terminal via the resistor 24 and the diode 14, the TV/RGB switching circuit 5 is forced to switch to RGB mode, and the 21pin input Superimpose signal (high/low level switching signal) from terminal 4
Even if is applied, the collector of transistor 10 and
Since the resistor 30 is inserted between the YS control terminals, the YS control terminal becomes high level and the TV/RGB switching circuit 5 becomes RGB mode.
The image from 8pin input terminal 1 is displayed. When the input switch 6 is set to the 21pin input terminal 4 side, the collector of the transistor 8 is forcibly grounded, and the other end connected to the resistor 24 and diode 14 is grounded, so the diode 14 is turned off, and the 21pin YS signal of input terminal 4 remains as is.
Joins the YS control terminal. Of course, the transistor 10 is off at this time.

In addition, the cathode of the diode 12 is connected to the intersection of the resistor 16 and the control voltage generation circuit that outputs "H" level voltage in RGB mode, the anode of the diode 12 is connected to the 8-pin synchronization signal output terminal, and the 8-pin synchronous Connect the signal output end to resistor 27,
Video signal switching circuit 28 via diode 15
Connect to the output terminal of At the same time, the output of the 8pin synchronization signal is connected to the midpoint of the 8pin and 21pin control terminals of the 8pin and 21pin changeover switch 6 via the diode 29. In addition, the video synchronization signal input of the 21-pin input terminal 4 is connected to one input terminal of the video signal switching circuit 28.
The control terminal of the 21-pin signal input terminal is connected to the collector of the transistor 11, and is also connected at the same time to the output terminal of a signal generating circuit (not shown) that becomes high level in the RGB mode.

When selecting 8pin in RGB mode, transistor 1
Since a high level voltage is applied to the base of 1,
Transistor 11 turns on and transistor 1
Since the collector of 1 is forced to low level, the 21pin signal input switch is turned off, and the 21pin signal input switch is turned off.
No synchronizing signal is output from the video signal switching circuit 28. At this time, the 8-pin synchronization signal is connected to the output terminal of the video signal switching circuit 28 via the resistor 27 and diode 15, so the TV is synchronized with the 8-pin synchronization signal and the screen appears normally.

Next, when in RGB mode and 21pin, transistor 1
1 is forcibly grounded, transistor 11 is turned off, and a high-level signal is output from the RGB "H" output control generation circuit, so the 21-pin synchronization signal input switch of video signal switching circuit 28 is It turns on, and the 21pin synchronization signal is output to the output of the video signal switching circuit 28.
As with 8pin, the 21pin synchronization signal controls the synchronization of the TV and the screen appears normally. At this time
Since the 8-pin synchronization signal is grounded via the diode 29, the diode 15 is in an open state.

In the television mode and video mode, the transistor 7 is turned off, so the transistor 11 is turned on, and the 21-pin synchronization signal input of the video signal switching circuit 28 is not output.

Effects of the Invention As explained above, according to the configuration of the present invention
Switching between RGB 8-pin mode and 21-pin mode can be done with a switch of 4 circuits instead of 6, making it possible to reduce circuit costs. Particularly when the periphery of the switching circuit is integrated into an integrated circuit, the effect of cost reduction is significant.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional television receiver, and FIG. 2 is a circuit diagram of a television receiver according to an embodiment of the present invention. 1... 8-pin input terminal section, 2... 8-pin input signal buffer/synchronization signal generation circuit, 4... 21-pin input terminal section, 5... TV signal/RGB signal switching circuit,
6...8pin/21pin changeover switch, 28...video signal switching circuit, 7,8,9,10,11...transistor, 12,13,14,15...diode.

Claims (1)

[Claims] 1 It has an 8-pin structure, and has an 8-pin input terminal section with output terminals for red R, green G, blue B signals, and sync signals, and a 21-pin structure, which has R, G, B signals, sync signals, and TV. /RGB character switching signal and shadow control signal during superimposition. A four-circuit changeover switch that selects R, G, and B signals and emits a first control signal with different levels when the 21st pin is selected and when the 8th pin is selected, and one of the R signals that is applied via the above changeover switch. ,
G, B signals and television signals as well as the above
A TV-RGB signal switching circuit that inputs the TV/RGB character switching signal and shadow control signal and switches between the television signal and the RGB signal according to the level of the TV/RGB character switching signal, and the RGB mode. It is controlled by the second control signal and the first control signal of the control voltage generation circuit, which have different levels depending on the time and TV/video mode, and in the TV/video mode, the supply of the shadow control signal is stopped, and
The level of the TV/RGB character switching signal is maintained to output the television signal, and the above changeover switch is used to
When 21 pin is selected, the above TV/RGB character switching signal and shadow control signal are connected to TV - RGB.
Connect to the signal switching circuit, and when selecting 8 pins, set at least the level of the above TV/RGB character switching signal.
It is controlled by a first switching circuit that holds the RGB signal to be output, and the first and second control signals, and when the selector switch selects 8 pins, it selects the synchronization signal of the 8 pin input terminal section. 21
A television receiver equipped with a second switching circuit that selects and outputs the synchronizing signal from the 21-pin input terminal section to the next stage when the pin is selected, and stops outputting any synchronizing signals when in video/television mode.