JP2597420Y2 - Signal switching circuit - Google Patents

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, and in particular, detects a squeeze identification signal as in a wide aspect television receiver having an S video input terminal (separate input terminal for luminance signal and color signal). The present invention relates to a signal switching circuit in a television receiver having the function of performing

[0002]

2. Description of the Related Art In recent years, high-definition television broadcasting (HDT)
V broadcast) and second-generation EDTV broadcasts are being studied and are being implemented. In such broadcasting, the current NTSC
The aspect ratio of the screen is different from that of the
Wide aspect television receivers wider than TSC television receivers are employed.

On the other hand, as a receiver for easily viewing HDTV broadcasts of Japan (aspect ratio: 16: 9, 1125 scanning lines), an aspect ratio of 16: 9, the number of scanning lines is 52.
So-called landscape television receivers that perform five sequential scans have appeared. The second generation EDTV broadcast is also a horizontally long screen broadcast in which an aspect ratio of 16: 9 and 525 scanning lines are sequentially scanned.

A wide aspect television receiver having 525 scanning lines and an aspect ratio of 16: 9 has an aspect ratio of
A function of compressing the horizontal amplitude of a 4: 3 conventional NTSC signal and displaying it in an aspect ratio of 4: 3, and an aspect ratio
It has both the function of expanding the 4: 3 squeeze signal (vertical image) and increasing the horizontal amplitude to display the entire screen with an aspect ratio of 16: 9. As the latter video source, MUS
There are E-NTSC converters, VTRs, video discs and the like.

When a signal from the S video output terminal of these video equipment is connected to a wide aspect television receiver for display, the S video output terminal is automatically switched so that the screen size is changed according to the signal mode. The signal mode detection signal is superimposed on the color signal output of. The signal mode detection signal is a DC voltage of 0 V or 5 V, and is sent out with the DC output impedance of the video source device being 10 ± 3 kΩ. At this time, the color input of the wide aspect television receiver is set to an input DC impedance of 100 kΩ or more, the DC voltage is detected, and the aspect ratio is automatically changed to 4: 3 for 0 V and 16: 9 for 5 V. I do.

FIG. 2 shows a signal mode discriminating circuit in a wide aspect television receiver having an S video input terminal.

In FIG. 2, the television receiver has an S video input terminal S1, and the S video input terminal S1 is composed of a chrominance signal input terminal C1 and a luminance signal input terminal Y1.

A color signal and a luminance signal from the S input terminal S1 and a color signal and a luminance signal (ie, a TV signal) inside the television receiver are inputted to an AV input switching circuit 1, where either one of them is inputted. Is selected and subjected to video processing by the video processing circuit 2 at the next stage, and then supplied to a cathode ray tube (CRT) 3 having an aspect ratio of 16: 9. The CRT 3 is driven by the deflection circuit 6 for deflection. The color signal input terminal C1 of the S video input terminal S1 is connected to a squeeze determination terminal 5a of the control microcomputer 5 via a low-pass filter 4 for detecting a signal mode by a resistor R11 and a capacitor C11. The control microcomputer 5 controls to switch the AV input switching circuit 1 based on a key input operation (not shown), and controls the video processing of the video processing circuit 2 and the deflection operation of the deflection circuit 6 according to the signal mode. ing.

With this arrangement, when the input video source is connected to the S video input terminal S1 and the signal mode of the input of the input terminal S1 is the squeeze mode, the squeeze mode discrimination superimposed on the color signal is determined. Is supplied to the control microcomputer 5 through the low-pass filter 4. Here, the control microcomputer 5
If the S1 input is selected by switching the AV input switching circuit 1 with the control signal a1 based on the key designation, and if there is a squeezed DC voltage at the squeeze determination terminal 5a, the deflection signal 6 is controlled by the control signal a2. And controls the video processing circuit 2 to support the squeeze mode. As a result, the image of the 4: 3 squeeze mode shown in FIG.
As shown in FIG. 7, the horizontal amplitude is enlarged and the image is fully displayed on a CRT screen having a 16: 9 wide aspect ratio.

Next, as shown in FIG. 4, S video terminals S2 and S1 are provided on the front and back of the wide aspect television receiver 10, respectively, and the terminals S2 and S1 on the front and back are connected to a direct current. Suppose you are connected to An S video terminal S1 has a video device 2 as a video source.
The S video signal from S0 is supplied, and the S video signal from the S video terminal S2 is supplied to the video device 30 to be dubbed. The circuit shown in FIG. 4 shows a case where the squeeze mode discriminating means 4 is not provided, shows only the connection of the color signal input, and omits the connection line of the luminance signal input. The color signal terminals C2 and C1 on the front and rear terminals S2 and S1 are connected in common, and the signal line is connected to a capacitor C12, a dubbing changeover switch 11, and a resistor R2.
13 are connected in series to a reference potential point. Z1 is the output impedance of the video device 20 on the back, and Z2 is the input impedance of the video device 30 on the front.

The S video terminal S2 on the front is used not only for dubbing output of the video equipment 30 connected to the back but also for inputting an S video signal from the video equipment 30. When used for dubbing, the dubbing changeover switch 11 is short-circuited and the input is terminated at 75Ω. When used for dubbing output, the dubbing changeover switch 11 is opened, and the input impedance of the television device 10 from the video device 20 on the rear side becomes the input impedance Z2 of the front device 30 as it is. Therefore, when the front terminal S2 is used for input, the dubbing switch 11 is short-circuited, and the device 20 is not connected to the rear terminal S1.

Here, when the S video terminals S2 and S1 are provided with a function of detecting a squeeze signal, a circuit shown in FIG. 5 can be considered. That is, a squeeze mode detection low-pass filter 4 including resistors R11 and R12 and a capacitor C11 is connected to a signal line connecting the S video terminal S1 and the S video terminal 2, so that a squeeze detection output is obtained. At this time, when one of the front and rear S video terminals is used for inputting an S video signal, since both terminals are connected in a DC manner, an input device is connected to either S video terminal. Also, the detection signal is supplied to the signal mode detection circuit 4 without any particular problem.

On the other hand, the rear terminal S1 is used for input and the front terminal S
When 2 is used for dubbing, the color output including the DC voltage for squeeze detection is directly input to the front device 30 through the front terminal S2. At this time, the DC impedance of the rear terminal S1 is a parallel composite value of the original impedance of the television receiver and the input impedance Z2 of the front video equipment 30 connected to the front terminal S2. Specifically, when the DC impedance of the front video device 30 is 100 kΩ, the total DC impedance is a parallel composite value of the sum (R11 + R12) of the resistors R11 and R12 and the impedance Z2 (100 kΩ). There is a problem that the size becomes smaller and the standard for squeeze detection is not satisfied.

Further, in order to satisfy the squeeze detection standard, a DC blocking capacitor is inserted on the signal line connecting between the terminals S2 and S1 and near the terminal S2, and the terminal S2 is separated DC. However, when the S video terminal S2 on the front is used as an input terminal, the external equipment 30
There is a problem that the DC component from the squeeze is cut off, and squeeze detection cannot be performed.

[0015]

[Problems to be Solved by the Invention] As described above, two S video terminals, in which the color terminals on the front and back sides are directly connected to DC,
When the front terminal is used for dubbing output when squeeze detection is supported, the input impedance of the rear terminal is damped by the input impedance of the video equipment connected to the front terminal, and in the worst case, it does not satisfy the squeeze detection standard There was a problem.

Therefore, the present invention is to solve the above-mentioned problem, and it is an object of the present invention to provide a signal switching circuit which can be used for input and dubbing output and which can realize an S video terminal capable of detecting squeeze. It is the purpose.

[0017]

According to the present invention, a first S-video terminal capable of inputting an S-video output on which a signal mode discriminating DC voltage is superimposed from a first video device; An S-video output on which a signal mode discriminating DC voltage is superimposed can be input, and the S-video output input from the first S-video input terminal is used as a dubbing signal by the second S-video output.
A signal switching circuit of a television receiver having a second S video terminal capable of outputting to a second video device, wherein the insertion of a damping resistor is turned on and off according to the use of the second S video terminal. When using the second S video terminal for input, turn on the insertion of the damping resistor,
When the second S video terminal is used for dubbing, a first switch for turning off the insertion of the damping resistor and a signal line connecting the first S video terminal and the second S video terminal are provided. A signal mode detection circuit for detecting a specific signal mode; and a signal mode detection circuit provided on a signal line connecting the first S video terminal and the second S video terminal and on the second S video terminal side. A changeover switch having first and second two input terminals and one output terminal which are switched in association with ON / OFF of the first switch,
The input signal from the first S video terminal is branched into two, one input is directly connected to the first input terminal, and the other input is connected to the second input terminal via a DC blocking capacitor. ,
The output terminal is connected to the second S-video terminal, and selects the first input terminal when the first switch is on, and selects the second input terminal when the first switch is off. A second switch for selecting an input terminal of the second input terminal, when the second switch selects the second input terminal to perform dubbing, and when the signal mode detection circuit detects a specific signal mode, A DC superimposing circuit for supplying a mode detection DC voltage corresponding to the specific mode to the second S video terminal and superimposing the DC voltage on the dubbing signal.

[0018]

According to the present invention, when the second video terminal is used for input, each color signal terminal at the first and second video terminals is operated by a second switch interlocked with the first switch for dubbing switching. Are directly connected to each other in a DC manner, and at this time, the signal mode detection circuit can be operated by the S video signal input to the second video terminal to detect a specific signal mode (squeeze mode). Also, when the second video terminal is used for dubbing,
Since the DC cutoff capacitor is inserted between the first and second video terminals by switching the second switch, the input impedance of the first video terminal is reduced by the second video device connected to the second video terminal. And the DC voltage for detecting the specific signal mode can be superimposed on the second video device connected to the second video terminal.

[0019]

An embodiment will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a signal switching circuit according to one embodiment of the present invention.

In FIG. 1, a television receiver 10 receives or outputs an S video signal in the same manner as an S video terminal S1 on the rear side to which an S video signal (separate video signal) can be input or output. A front S-video terminal S2 is provided. Each of the S video terminals S1 and S2 has a color signal terminal and a luminance signal terminal.
The connection line of the luminance signal terminal is omitted for each terminal. In the figure, an external video equipment 20 such as a VTR is connected to the rear terminal S1, and a VT is connected to the front terminal S2.
This shows a state where an external video device 30 such as R is connected and an S video signal from the device 20 is supplied to the device 30 during dubbing. A signal line connecting the color signal terminal C1 of the rear terminal S1 and the color signal terminal C2 of the front terminal S2 includes a capacitor C12, a dubbing changeover switch 11, and a resistor R1.
3 is connected in series to a reference potential point. The color signal input to the signal line is a capacitor C1.
Is supplied to a video circuit (not shown) in the receiver 10 via a squeeze mode detection circuit, and is supplied to a squeeze mode detection low-pass filter 4 composed of resistors R11 and R12 and a capacitor C11 to extract a DC voltage and output it as a squeeze detection output. It has become so. Further, a switch 12 having two input terminals a and b and one output terminal is inserted on the signal line connecting the terminals S2 and S1 and on the front terminal S2 side. Branched color signals are input to the two input terminals a and b of the switch 12. One of the branched lines is directly connected to the input terminal a, and the other line is connected to the input terminal b via the capacitor C13. doing. The output terminal of the switch 12 is connected to the color signal terminal C2 of the front terminal S2. The switch 12 is adapted to be switched in conjunction with the dubbing switch 11. Between the output terminal of the squeeze mode detection low-pass filter 4 and the input terminal b of the switch 12, there is provided a DC superimposing circuit 13 for superimposing a squeeze detection signal on the dubbing output during dubbing. In the DC superimposing circuit 13, the squeeze detection output from the low-pass filter 4 is connected to the base of the switching transistor Q1, the emitter of the transistor Q1 is connected to the reference potential point, and the collector is connected to the DC power supply Vcc via the resistor R14. On the other hand, it is connected to the base of the switching transistor Q2. The emitter of the switching transistor Q2 is connected to the reference potential point, and its collector is connected to the DC power supply Vcc via the resistor R15 while being connected to the input terminal b of the switch 12. The output impedance of the external video device 20 is 10 kΩ, and the input impedance of the external video device 30 is 100 kΩ.

In the above configuration, a squeeze mode signal having an aspect ratio of 4: 3 is supplied as an S image signal, and a DC voltage for squeeze mode discrimination is used for a color signal in the S image signal. Are superimposed. The color input supplied to the color signal terminal C1 of the rear terminal S1 branches into four, one of which is input to a video circuit (not shown) in the receiver 10 via the capacitor C1 for display, and the other is resistors R11, R12 and capacitors. The DC component is extracted by the squeezed mode detection filter 4 composed of C11, and becomes a squeezed detection output. The other two-branch color inputs are connected to two input terminals a and b of a two-input one-output switch 12, one of which is supplied to the input terminal a as it is, and the other is input via a capacitor C13. b. The input terminal b via the capacitor C13 is connected to switching transistors Q1, Q2, a resistor R14,
A DC output from a DC superimposing circuit 13 comprising R15 is supplied. The DC superimposing circuit 13 is switched by the squeeze detection output. When a DC voltage of 5 V is output as the squeeze detection output, the transistor Q1 is turned on, the transistor Q2 is turned off, and the DC power supply Vcc (5 V) is supplied to the input terminal b of the switch 12. The dubbing changeover switch 11 is switched according to the use of the front terminal S2, and the switch 13 is also switched in conjunction with the switch 11. That is, switch 1
1 is a short circuit when the front terminal S2 is used for input. At this time, the interlock switch 12 is switched to the a side,
The switch 11 is open when the front terminal S2 is used for dubbing output, and the interlock switch 13 is switched to the b side.

Any one of the front terminal S2 and the rear terminal S1
When one of them is used as an input terminal, the switch 12 is switched to the a side, so that the color signal input of the terminal S2 or S1 is directly connected to the filter 4 for extracting the squeezed detection signal.

When the rear terminal S1 is used as an input terminal and the front terminal S2 is used as a dubbing output terminal, the interlocking switch 12 is switched to the b side, so that the rear terminal S1 is used.
Since the DC component is cut off by the DC blocking capacitor C13 between the color signal input of the front terminal S2 and the color signal output of the front terminal S2, the DC input impedance of the color signal input on the rear side is changed by the video equipment 30 connected to the front terminal S2. No dumping. Therefore, if the sum of the resistance values of the resistors R11 and R12 (R11 + R12) is set to 100 kΩ or more,
Even during dubbing, the squeeze detection standard can be satisfied. Further, at the time of this dubbing, the collector output of the transistor Q2, which is the output of the DC superimposing circuit 13, is
DC output in the same mode as squeeze detection output,
The DC superimposed signal supplied to the color signal terminal C2 of the front terminal S2 has the same signal mode as the color signal input to the rear terminal S1.

[0024]

As described above, according to the present invention, the detection and superimposition of the squeeze identification signal can be sufficiently performed on the S video terminal which is used for both input and dubbing output with a simple circuit by using the squeeze mode standard. Can be applied satisfactorily.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a wide aspect television receiver having an S video input terminal.

FIG. 3 is a view for explaining processing for projecting a squeeze mode video input having an aspect ratio of 4: 3 on a wide aspect television screen having an aspect ratio of 16: 9.

FIG. 4 is a circuit diagram showing a conventional signal switching circuit.

FIG. 5 is a circuit diagram showing a conventional signal switching circuit having a squeeze detection function.

[Explanation of symbols]

Reference Signs List 4 Low-pass filter for detecting squeeze mode (signal mode detection circuit) 10 Television receiver 11 Dubbing changeover switch (first switch) 12 Switch (second switch) 13 DC superimposing circuit 20, 30 Video equipment S1 Rear terminal (No. 1st video terminal) S2 Front terminal (2nd video terminal)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/38-5/46 H04N 5/91 H04N 7/00-7/088

Claims (1)

(57) [Scope of request for utility model registration] A first S video terminal capable of inputting an S video output on which a signal mode discrimination DC voltage is superimposed from a first video device, and a signal mode discrimination DC voltage from a second video device are superimposed. And the first S
A second S that enables the S video output input from the video input terminal to be output to the second video device as a dubbing signal;
A signal switching circuit for a television receiver having a video terminal, for turning on and off the insertion of a damping resistor in accordance with the use of the second S video terminal. A first switch for turning on the insertion of the damping resistor when using the first S video terminal, and turning off the insertion of the damping resistor when using the second S video terminal for dubbing; A signal mode detection circuit for detecting a specific signal mode, provided on a signal line connecting between the first S video terminal and the second S video terminal; and a signal connecting the first S video terminal and the second S video terminal. On the line and on the side of the second S video terminal,
A changeover switch having two first and second input terminals and one output terminal that are switched in conjunction with turning on and off of the first switch, wherein an input signal from the first S video terminal is The input is directly connected to the first input terminal, the other input is connected to the second input terminal via a DC blocking capacitor, and the output terminal is connected to the second S video terminal. A second switch that selects the first input terminal when the first switch is on, and selects the second input terminal when the first switch is off. When the second switch selects the second input terminal to perform dubbing, and when the signal mode detection circuit detects a specific signal mode, a DC voltage for mode detection corresponding to the specific mode. Is supplied to the second S video terminal and the dubbing is performed. And a direct current superimposing circuit for superimposing the superimposed signal on a signal for use.