JPH06153098A - Signal change-over circuit - Google Patents

Abstract

PURPOSE:To enable facilitating the circuit configuration of a rear stage by corresponding to using conditions. CONSTITUTION:When a signal is outputted via the resistor R of 75OMEGA, a second change-over switch 31B is set on a terminal (a) side. Then, one volt(1V) being a attenuated portion by the resistor R is amplified by a 6dB amplifier 32 so that the circuit configuration of the rear stage is facilitated. When the multiple input signals SA-SD are changed-over, the second change-over switch 31B is set on the terminal (b) side. Then, the selected input signal SA is outputted by 1V as it is. Therefore, necessity for connecting an attenuator is eliminated so that circuit configuration is facilitated. Thus, a cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal switching circuit suitable for application to a video signal processing system.

[0002]

2. Description of the Related Art In TV receivers, VTRs (video tape recorders), etc., a plurality of external devices can be connected and signals supplied from these devices can be switched and processed. It is common.

FIG. 3 shows a system of a general TV receiver 10. In the figure, the broadcast radio wave input from the antenna 11 is converted into an intermediate frequency by the tuner 12, and this is demodulated by the video detection circuit 13 into a composite signal. This composite signal is supplied to the Y / C separation circuit 15 via the video signal switching circuit 14 and separated into a luminance signal Y and a chroma signal C therein.

The chroma signal C is a YC signal switching circuit 16
Is supplied to the color difference demodulation circuit 17 through the Y color difference demodulation circuit 17 and demodulated into the color difference signals BY and RY, and then supplied to the Y color difference matrix circuit 19 via the Y color difference signal switching circuit 18. Also, the luminance signal Y separated by the Y / C separation circuit 15
Is supplied to the Y color difference matrix circuit 19 via the YC signal switching circuit 16 and the Y color difference signal switching circuit 18.

In the Y color difference matrix circuit 19, primary color signals R, G and B are generated from the luminance signal Y and the color difference signals BY and RY, which are supplied to the cathode ray tube 21 through the primary color signal switching circuit 20. This causes the video of the selected channel to be displayed on the screen.

In this TV receiver 10, in the video signal switching circuit 14, the YC signal switching circuit 16, the Y color difference signal switching circuit 18 and the primary color signal switching circuit 20, signals supplied from the internal processing circuit and external signals are supplied. It is possible to switch between signals. That is, the video signal switching circuit 14 switches between the output signal of the video detection circuit 13 and the video signal supplied from, for example, a VTR (not shown).

In the YC signal switching circuit 16, Y
The signals Y and C supplied from the / C separation circuit 15 and the signals Y and C supplied from a VTR or the like are switched, and the Y color difference signal switching circuit 18 compares the Y color difference signal supplied from the YC signal switching circuit 16 with, for example, HDTV. For MUSE
A Y color difference signal supplied from a decoder (not shown) or the like is switched, and in the primary color signal switching circuit 20, the primary color signals R, G, B supplied from the Y color difference matrix circuit 19 and the primary color signals supplied from the MUSE decoder or the like. R, G,
It is designed to switch between B and.

These various switching circuits 14, 16,
The external input signal switched from the signal from the internal processing circuit at 18, 20 is processed in the subsequent circuits in the same manner as described above and supplied to the cathode ray tube 21. As a result, the image supplied from the external device is displayed on the screen.

[0009]

The various switching circuits 14, 16, 18 and 20 described above are classified into a type without a 6 dB amplifier and a type with a built-in 6 dB amplifier, which will be described below. There are problems with each.

That is, as shown in FIG. 4 (a), 6 dB
In the signal switching circuit 31 of the type without an amplifier, for example, two input signals SA and S of 1 V (volt) are provided.
When switching B and outputting to the outside, 75Ω resistor R
The signal must be output via the resistor R, but since the voltage of the signal is attenuated by the resistor R, the signal switching circuit 3
It is necessary to connect the 6 dB amplifier 32 after 1 and amplify the signal to 2V. In this case, the signal switching circuit 3
Since the 6 dB amplifier 32 must be connected to 1,
There is a problem that the work is troublesome and time-consuming, which increases the cost.

In addition, as shown in FIG. 2B, in the signal switching circuit 40 in which the changeover switch 31A and the 6 dB amplifier 32 are integrated, for example, four systems of input signals SA to SD are used.
There is a problem in that when the input signal of one system is selected, the attenuator 33 (attenuator) must be connected after the signal switching circuit 40. This is because in the signal switching circuit 40, the output signal is amplified to 2V, so it is necessary to return this to 1V by the attenuator 33 and then output it.

In this case as well, there is a problem that it takes time and effort to connect the attenuator 33, resulting in an increase in cost.
In this case, if a signal switching circuit 40 having a built-in 6 dB amplifier 32 and a single signal switching circuit 31 are mixed and used, a simpler circuit configuration is possible without using the attenuator 33. The circuit configuration shown in FIG. 4B is used because the same signal switching circuit 40 is used for the same device to reduce the cost.

As described above, in the conventional signal switching circuit 31 with the external 6 dB amplifier and the signal switching circuit 40 with the built-in 6 dB amplifier, the circuit configuration of the subsequent stage may be complicated depending on the use condition, which is costly. There was a problem of causing up.

Therefore, the present invention has solved the above-mentioned problems, and can simplify the circuit structure of the subsequent stage according to the use situation, thereby reducing the cost. Is proposed.

[0015]

In order to solve the above problems, in the first invention, a switching means for switching a plurality of input signals and an amplification means for amplifying an output signal of the switching means are provided, and the output of the switching means is provided. Also, the output of the amplifying means can be output.

Further, in the second invention, the first switching means for switching a plurality of input signals, the amplifying means for amplifying the output of the first switching means, the output of the first switching means and the output of the amplifying means. And a second switching means for switching between and.

[0017]

In FIG. 1, one of the two input signals SA and SB is selected by the first changeover switch 31A of the signal changeover circuit 50, this is amplified by the 6 dB amplifier 32, and the terminal a of the second changeover switch 31B is selected. Is supplied to. Further, both outputs of the first changeover switch 31A are directly supplied to the terminal b of the second changeover switch 31B.

Then, for example, as shown in FIG.
When outputting a signal through the 5Ω resistor R, the second changeover switch 31B is set to the terminal a side. As a result, 1 V that is attenuated by the resistor R is amplified by the 6 dB amplifier 32.

When switching a large number of input signals SA to SD as shown in FIG. 3B, the second changeover switch 31B is set to the terminal b side. As a result, of the input signals SA to SD, the input signal SA selected by the first changeover switch 31A of the signal changeover circuit 50 at the preceding stage,
SC is supplied as it is to the signal switching circuit 50 in the subsequent stage, where, for example, the input signal SA is selected and output as it is at 1V. Therefore, the attenuator 33
Since it is not necessary to connect (FIG. 4B), the circuit configuration becomes simple.

[0020]

Next, an embodiment of a signal switching circuit according to the present invention will be described in detail with reference to the drawings. The same parts as those described above are designated by the same reference numerals and detailed description thereof is omitted.

FIG. 1 shows a signal switching circuit 50 according to the present invention.
Shows the system of. This signal switching circuit 50 is the various signal switching circuits 14, 1 of the TV receiver 10 shown in FIG.
It is applicable to 6, 18, and 20. In FIG. 1, the input signals SA and SB are selected by the first changeover switch 31A. The output of the first changeover switch 31A is output to the second changeover switch 3 via the 6 dB amplifier 32.
It is supplied to the terminal a of 1B and directly to the terminal b of the second changeover switch 31B.

Here, the first changeover switch 31A is changed over by a selection signal KA supplied from, for example, a remote controller of the TV receiver 10 (FIG. 3). Also, the second
The changeover switch 31B is also changed over by the amplification presence / absence selection signal KB supplied from the remote controller. The switching signal KA and the amplification presence / absence selection signal KB are 1-bit signals and can be switched between “high” and “low”. Thus, in the signal switching circuit 50 of the present invention, 1
V input signals SA and SB are switched to 1 as it is.
It becomes possible to output at V or amplify to 2V and output.

FIG. 2 shows a usage example of the signal switching circuit 50. FIG. 3A shows the case of outputting a signal to the outside. For example, one input signal SA of the two 1V input signals SA and SB is selected by the first changeover switch 31A, which is passed through the 6 dB amplifier 32. 2V
It is supplied to the terminal a of the changeover switch 31B. Also,
The output signal SA of the first changeover switch 31A is directly the second signal
It is supplied to the terminal b of the changeover switch. Here, the second changeover switch 31B is set to the terminal a side, so that the signal amplified to 2V is set to 1 by the resistor R of 75Ω.
Attenuated to V and output.

In this case, only the resistor R is connected to the signal switching circuit 50, and it is not necessary to connect the 6 dB amplifier 32 as in the conventional case. Therefore, the circuit structure in the subsequent stage is simplified, which reduces the cost. It will be possible.

FIG. 2B shows a case where a large number of signals are switched by using the signal switching circuit 50. For example, when switching and outputting four input signals SA to SD,
First, of the two systems of input signals SA and SB, for example, the input signal SA is selected by the first changeover switch 31A of the signal changeover circuit 50. In addition, the remaining two input signals S
For example, the input signal SC of C and SD is selected by the first changeover switch 31A of another signal changeover circuit 50.

Here, the second changeover switch 31B of both signal changeover circuits 50 is set to the terminal b side. Therefore, the signals SA and SC output from both the first changeover switches 31A are output without passing through the 6 dB amplifier 32. These output signals SA and SC are input to the signal switch 50 at the subsequent stage, and the signal SA, for example, is selected by the switch 31B. The second changeover switch 31B of the signal changeover circuit 50 is also set to the terminal b side, so that the signal SA is output at 1V.

In this case, the circuit can be constructed without connecting the attenuator 33 (FIG. 4 (b)) as in the prior art, so that the circuit configuration in the subsequent stage is simplified, thereby reducing the cost. It will be possible.

In the above embodiment, the case where the input signals of two systems are switched has been described, but the present invention can be applied to the case of switching the input signals of two or more systems. Further, the present invention can be configured not only as a signal switching circuit independently, but also incorporated in an IC such as the Y / C separation circuit 15 (FIG. 3) or the color difference demodulation circuit 17. In addition to the TV receiver 10, the present invention is not limited to V
A such as TR (video tape recorder) and AV switch
It can be applied to V equipment.

[0029]

As described above, according to the present invention, the first switching means for switching a plurality of input signals, the amplifying means for amplifying the output signal of the first switching means, and the output signal of the first switching means. And a second switching means for switching between the output signal of the amplifying means and the output signal of the amplifying means.

Therefore, according to the present invention, when the switched signal is output to the outside through the 75Ω resistor, the second signal is output.
6d by setting the switching means of the
When it is not necessary to attach a B amplifier externally and a large number of input signals are switched, the second switching means is used as a first switch.
By setting it on the switching means side, it is not necessary to connect an attenuator, and in any situation, the circuit configuration of the latter stage is simple and the connection work is simple, which results in cost reduction. is there.

[Brief description of drawings]

FIG. 1 is a system diagram of a signal switching circuit according to the present invention.

FIG. 2 is a diagram illustrating a usage example of a signal switching circuit according to the present invention.

FIG. 3 is a system diagram of a general TV receiver.

FIG. 4 is a diagram illustrating a usage example of a signal switching circuit according to a conventional example.

[Explanation of symbols]

 10 TV receiver 12 tuner 14 video signal switching circuit 16 YC signal switching circuit 18 Y color difference signal switching circuit 20 primary color signal switching circuit 31A first switching switch 31B second switching switch 32 6 dB amplifier 33 attenuator 31, 40, 50 signal switching circuit

Claims (3)

[Claims] 1. A switching means for switching a plurality of input signals, and an amplifying means for amplifying an output of the switching means, wherein the output of the switching means and the output of the amplifying means can be output to the outside. Signal switching circuit. 2. A first switching means for switching a plurality of input signals, an amplifying means for amplifying an output of the first switching means, and an output of the first switching means and an output of the amplifying means. A signal switching circuit comprising a second switching means. 3. The signal switching circuit according to claim 1, wherein the amplifying means is a 6 dB amplifier.