JPH0648282U - Signal switching circuit - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To realize an S-video terminal that is used both for input and for dubbing output and is capable of squeeze detection. [Structure] Filter 4 for squeeze mode detection, dubbing switch 11 for turning on insertion of damping resistor R13 when front terminal S2 is for input, and for turning off for front side terminal S2, and input from rear terminal S1 Signal 2
One branch is connected to the first input end a and the other is connected to the second input end b via the DC blocking capacitor C13. When the dubbing changeover switch is on, the first input end is off. The second switch 12 that switches to the second input terminal when
And when this is switched to the second input terminal b and the squeeze mode detection filter detects the squeeze mode, a DC voltage for corresponding signal mode detection is supplied to the front terminal to be superimposed on the dubbing signal. Superimposing circuit 13
And.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a signal switching circuit, and in particular, has a function of detecting a squeeze discrimination signal like a wide aspect television receiver having an S video input terminal (separate input terminal for luminance signal and color signal). Signal switching circuit for television receivers.

[0002]

[Prior art]

 In recent years, high-definition television broadcasting (HDTV broadcasting) and second-generation EDTV broadcasting have been studied and are about to be implemented. In such broadcasting, the aspect ratio of the screen is different from that of the current NTSC system, and a wide aspect television receiver, which is wider than a general NTSC television receiver, is adopted.

On the other hand, as a receiver for easily viewing high-definition broadcasting (16: 9 aspect ratio, 1125 scanning lines), which is HDTV broadcasting in Japan, it performs sequential scanning with an aspect ratio of 16: 9 and 525 scanning lines. The so-called horizontal television receiver has appeared. The second generation EDTV broadcast is also a landscape screen broadcast with an aspect ratio of 16: 9 and progressive scanning of 525 scanning lines.

A wide aspect television receiver with 525 scanning lines and an aspect ratio of 16: 9 displays a conventional NTSC signal with an aspect ratio of 4: 3 in the aspect ratio of 4: 3 by compressing the horizontal amplitude. And a function to display a squeeze signal with an aspect ratio of 4: 3 (vertical image) on the full screen with an aspect ratio of 16: 9 by expanding the horizontal amplitude. The latter video source sources include MUSE-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 and displayed, the screen size is automatically switched according to the signal mode. The signal mode detection signal is superimposed on the color signal output of the video output terminal. 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 sets the input DC impedance to 100 kΩ or more and detects the DC voltage. When 0V, the aspect ratio is 4: 3, and when 5V, the aspect ratio is 16: 9. Automatically switch.

FIG. 2 shows a signal mode discrimination 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 color 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 (that is, a TV signal) inside the television receiver are input to the AV input switching circuit 1. One input is selected, and after being image-processed by the image-processing circuit 2 in the next stage, it is supplied to a cathode ray tube (CRT) 3 having an aspect ratio of 16: 9. The CRT 3 is deflected by the deflection circuit 6. The color signal input terminal C1 of the S image input terminal S1 is connected to the squeeze discrimination terminal 5a of the control microcomputer 5 through the low-pass filter 4 for detecting the signal mode by the resistor R11 and the capacitor C11. The control microcomputer 5 controls the switching of 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. Has become.

With this configuration, in the case where the input video source source is connected to the S video input terminal S1 and the signal mode of the input terminal S1 input is the squeeze mode, the squeeze mode superimposed on the color signal is obtained. Only the DC voltage 5V for discrimination is supplied to the control microcomputer 5 through the low-pass filter 4. Here, if the control microcomputer 5 selects the S1 input by switching the AV input switching circuit 1 with the control signal a1 based on the key designation, if there is a squeeze DC voltage at the squeeze discrimination terminal 5a, The deflection circuit 6 and the video processing circuit 2 are controlled by the control signal a2 so as to correspond to the squeeze mode. As a result, the image in the 4: 3 squeeze mode of FIG. 3 (a) is enlarged in horizontal amplitude as shown in FIG. 3 (b) and is fully displayed on the 16: 9 wide aspect ratio CRT screen.

By the way, 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 the back are connected to direct current. Consider the case where they are physically connected. The S video signal from the video device 20 which is the video source is supplied to the S video terminal S1, 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 discrimination means 4 is not provided, and shows only the connection of the color signal input, and the connection line of the luminance signal input is omitted. The color signal terminals C2 and C1 at the front and rear terminals S2 and S1 are commonly connected, and the signal line is connected to a reference potential point through a capacitor C12, a dubbing changeover switch 11 and a resistor R13 in series. There is. Z1 is the output impedance of the rear video equipment 20, and Z2 is the input impedance of the front video equipment 30.

The S-video terminal S2 on the front side is used not only for the dubbing output of the video equipment 30 connected to the rear surface but also for the input for inputting the S-video signal from the video equipment 30. When used as an input, the dubbing selector switch 11 is short-circuited and the input is terminated with 75Ω. When used for dubbing output, the dubbing changeover switch 11 is opened, and the input impedance of the television receiver 10 from the rear image device 20 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 changeover 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 squeeze signal detection function, a circuit shown in FIG. 5 is conceivable. That is, a squeeze detection output is obtained by connecting a squeeze mode detection low-pass filter 4 composed of resistors R11, R12 and a capacitor C11 to the signal line connecting the S video terminal S1 and the S video terminal 2. At this time, when using either the S-video terminal on the front or the back for inputting the S-video signal, since both terminals are connected in DC, connect the input device to either S-video terminal. However, the detection signal is supplied to the signal mode detection circuit 4, and there is no particular problem.

On the other hand, when the rear terminal S1 is used for input and the front terminal S2 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 becomes 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 equipment 30 is 100 kΩ, the total DC impedance is the parallel combined value of the sum of the resistors R11 and R12 (R11 + R12) and the impedance Z2 (100 kΩ). There is a problem that the size becomes smaller and the squeeze detection standard is not satisfied.

In order to satisfy the squeeze detection standard, a DC blocking capacitor is inserted on the signal line connecting the terminals S2 and S1 and near the terminal S2 to separate the terminal S2 in terms of DC. However, there is a problem that when the front S-video terminal S2 is used as an input terminal, the DC component from the external device 30 is cut off and squeeze detection cannot be performed.

[0015]

[Problems to be solved by the device]

 As mentioned above, when the two S-video terminals that directly connect the color terminals on the front and the back are squeeze detection and the front terminals are used for dubbing output, the input impedance of the back terminals becomes the front terminals. There is a problem in that the input impedance of the connected video equipment causes damping, and in the worst case, the squeeze detection standard is not satisfied.

Therefore, the present invention is to solve the above problems, and to provide a signal switching circuit that can be used for both input and dubbing output, and can realize an S-video terminal capable of squeeze detection. The purpose is.

[0017]

[Means for Solving the Problems]

 According to the present invention, a first S-video terminal capable of inputting an S-video output on which a DC voltage for signal mode discrimination is superimposed from a first video equipment and a DC voltage for signal mode discrimination from a second video equipment are superimposed. A second S-video terminal capable of inputting an S-video output that is input from the first S-video input terminal to the second video device as a dubbing signal. A signal switching circuit of a television receiver having a switch for turning on / off the insertion of a damping resistor according to the use of the second S video terminal, and using the second S video terminal for input. A first switch for turning on the insertion of the damping resistor and a second switch for turning off the insertion of the damping resistor when the second S video terminal is used for dubbing; The second S projection A signal mode detection circuit provided on a signal line connecting between the image terminals to detect a specific signal mode; and a signal line connecting the first S video terminal and the second S video terminal on the signal line. A changeover switch which is provided on the S video terminal side of No. 2 and has two first and second input terminals and one output terminal which are switched in conjunction 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 end, and the other input is connected to the second input end via a DC blocking capacitor. The output terminal is connected to the second S-video terminal, the first input terminal is selected when the first switch is on, and the first input terminal is selected when the first switch is off. A second switch for selecting the second input end, and the second switch When the second input terminal is selected for dubbing and the signal mode detection circuit detects a specific signal mode, the DC voltage for mode detection corresponding to the specific mode is applied to the second mode. And a direct current superimposing circuit for superimposing it on the dubbing signal by supplying it to the S video terminal.

[0018]

[Action]

 In the present invention, when the second video terminal is used for input, the second switch interlocking with the first switch for switching the dubbing causes the respective color signal terminals of the first and second video terminals to be connected to each other. Since the DC signal is directly connected, 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). In addition, when the second video terminal is used for dubbing, a DC blocking capacitor is inserted between the first and second video terminals by switching the second switch, so that the first video terminal is connected. The force impedance is not damped by the second video device connected to the second video terminal, and the DC voltage for detecting the specific signal mode is applied to the second video device connected to the second video terminal. It can be superimposed.

[0019]

【Example】

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

In FIG. 1, the television receiver 10 has a rear S video terminal S1 capable of inputting or outputting an S video signal (separate video signal) and an S video signal input or output similarly. A front S video terminal S2 capable of outputting is provided. Each of the S video terminals S1 and S2 has a color signal terminal and a luminance signal terminal, but the connection line of the luminance signal terminal for each S terminal is omitted. In the figure, an external video device 20 such as a VTR is connected to the rear terminal S1 and an external video device 30 such as a VTR is connected to the front terminal S2, so that the S video signal from the device 20 is transmitted during dubbing. The state of being supplied to the device 30 is shown. The signal line connecting the color signal terminal C1 of the rear terminal S1 and the color signal terminal C2 of the front terminal S2 is connected to the reference potential point via the capacitor C12, the dubbing changeover switch 11 and the resistor R13 in series. . The color signal input output to the signal line is supplied to a video circuit (not shown) in the receiver 10 via a capacitor C13, while it is supplied to a squeeze mode detecting low pass filter 4 including resistors R11, R12 and a capacitor C11. The supplied DC voltage is extracted and output as squeeze detection output. 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. The 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. Connected. The output terminal of the switch 12 is connected to the color signal terminal C 2 of the front terminal S 2. The switch 12 can be switched in conjunction with the dubbing switch 11. Between the output terminal of the low-pass filter 4 for detecting the squeeze mode and the input terminal b of the switch 12, there is provided a DC superimposing circuit 13 for superimposing the squeeze detection signal on the output for dubbing. This direct current superimposing circuit 13 connects the squeeze detection output from the low-pass filter 4 to the base of the switching transistor Q1, the emitter of the transistor Q1 is connected to the reference potential point, and the collector thereof is connected to the DC power source via the resistor R14. While connected to Vcc, it is connected to the base of switching transistor Q2. The emitter of the switching transistor Q2 is connected to the reference potential point, and the collector of the switching transistor Q2 is connected to the DC power source Vcc via the resistor R15, while being connected to the input terminal b of the switch 12. The output impedance of the external image device 20 is 10 kΩ, and the input impedance of the external image device 30 is 100 kΩ.

In the above configuration, a squeeze mode signal having an aspect ratio of 4: 3 is supplied as the S video signal, and a DC signal for determining the squeeze mode is included in the color signal of the S video signal. It is assumed that the voltages are superimposed. The color input supplied to the color signal terminal C1 of the rear terminal S1 is branched into four, one of which is input to a video circuit (not shown) in the receiver 10 through a capacitor C13 for display, and one of which is a resistor R11, R12. , The DC component is extracted by the squeeze mode detection filter 4 including the capacitor C11 and becomes a squeeze detection output. The other two branched color inputs are connected to the two input terminals a and b of the 2-input 1-output switch 12, one of which is supplied to the input terminal a as it is, and the other of which is connected via the capacitor C13. It is supplied to the input terminal b. The DC output from the DC superimposing circuit 13 including the switching transistors Q1 and Q2 and the resistors R14 and R15 is supplied to the input terminal b via the capacitor C13. The DC superposition circuit 13 is switched by the squeeze detection output described above. When the DC voltage 5V is output as the squeeze detection output, the transistor Q1 is turned on, the transistor Q2 is turned off, and the direct current power supply Vcc (5V) is supplied to the input end b of the switch 12. The dubbing changeover switch 11 can be changed over depending on the use of the front terminal S 2, and the switch 13 can also be changed over in conjunction with this switch 11. That is, the switch 11 is short-circuited when the front terminal S2 is used for input. At this time, the interlocking switch 12 is switched to the a side, and the switch 11 is used when the front terminal S2 is used for dubbing output. When open, the interlocking switch 13 is switched to the b side.

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

When the rear terminal S1 is used as the input terminal and the front terminal S2 is used as the dubbing output terminal, since the interlock switch 12 is switched to the b side, the color signal input of the rear terminal S1 and the color of the front terminal S2 are changed. Since the DC component is blocked by the DC blocking capacitor C13 between the signal outputs, the DC input impedance of the color signal input on the rear side is not damped by the video equipment 30 connected to the front terminal S2. Therefore, if the sum of the resistance values of the resistors R11 and R12 (R11 + R12) is set to 100 kΩ or more, the squeeze detection standard can be satisfied even during dubbing. Further, at the time of this dubbing, the collector output of the transistor Q2, which is the output of the DC superimposing circuit 13, outputs DC in the same mode as the squeeze detection output, so that the DC superimposing signal supplied to the color signal terminal C2 of the front terminal S2. Is the same as the signal mode of the color signal input to the rear terminal S1.

[0024]

[Effect of device]

 As described above, according to the present invention, the detection and superimposition of the squeeze discrimination signal is applied to the S video terminal which is used both for input and for dubbing, with a simple circuit, sufficiently satisfying the standard of squeeze mode. be able to.

[Brief description of 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 diagram for explaining a process for displaying a squeeze mode video input with an aspect ratio of 4: 3 on a wide aspect television screen with 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]

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 (first) 1 video terminal) S2 front terminal (second video terminal)

Claims (1)

[Scope of utility model registration request] 1. A first S video terminal capable of inputting an S video output on which a DC voltage for signal mode discrimination is superimposed from a first video device, and a DC voltage for signal mode discrimination superimposed from a second video device. The input S video output, 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 of a television receiver having a video terminal for turning on / off the insertion of a damping resistor according to the use of the second S video terminal for inputting the second S video terminal. A first switch for turning on the insertion of the damping resistor when used as a second S video terminal and a second switch for turning off the insertion of the damping resistor when using the second S video terminal for dubbing. And a signal line connecting between the second S video terminal and a signal line detecting circuit for detecting a specific signal mode, and a signal connecting the first S video terminal and the second S video terminal. Provided on the line and on the side of the second S image terminal,
A changeover switch having two input terminals, a first input terminal and a second output terminal, and one output terminal, which are switched in conjunction with turning on and off of the first switch, wherein an input signal from the first S video terminal is received. It is branched into two, one input is directly connected to the first input end, the other input is connected to the second input end via a DC blocking capacitor, and the output end is the second S video terminal. And 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 end for dubbing and the signal mode detection circuit detects a specific signal mode, a DC voltage for mode detection corresponding to the specific mode To the second S-video terminal to supply the dubbing A signal switching circuit, comprising: a DC superimposing circuit for superimposing the signal on a use signal.