JP3159205B2 - Automatic input signal path 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 display device having a plurality of signal input connection terminals.

[0002]

In recent years, the diversification of the computer, the input signal of the display device, Sync plus synchronizing signal of the horizontal and vertical green signal Film image signal On G
A reen signal (hereinafter, referred to as a three-wire signal because of three signal inputs of red, green, and blue), an H / V Mixed Sync signal obtained by adding a vertical synchronizing signal to a horizontal synchronizing signal (other than three video signals) Since there are four signal inputs of a synchronization signal obtained by adding a vertical synchronization signal to a horizontal synchronization signal,
H / V Separated signals in which the horizontal and vertical synchronization signals are independent of each other (because there are five signals of a horizontal synchronization signal and a vertical synchronization signal in addition to three video signals, Signal). Further, the shape of the signal input connection terminal is also various, such as a BNC plug and a D-SUB connector.

Hereinafter, a conventional input signal path switching circuit will be described. FIGS. 6 and 7 show the configuration of a conventional input signal path switching circuit.

In FIG. 6, reference numeral 1 denotes a signal input connection terminal;
Is another signal input connection terminal, 4 is an input signal path switching circuit, 5 is a synchronization signal separation circuit, 10 is a manual switch, 9 is a switch state detecting means for detecting and determining the state of the switch, and 7 is a signal path switching control means. in Ru Oh. The operation of the input signal path switching circuit configured as shown in FIG. 6 will be described. First, the on / off state of the manual switch 10 is detected by the switch state detecting means 9, a determination is made as to which of the input signal paths of the signal input connection terminals 1 and 2 is to be switched, and the signal path switching control means 7. Based on the determination of the signal path to be switched, a control signal for switching the signal path is output to the input signal path switching circuit 4. A control signal for switching the signal paths in the input signal path switching circuit 4 switches the input signal path of the signal input connection 1, an input signal of the input signal path is switched, the 3-wire signals and 4-wire signal In such a case, the signal is input to a synchronizing signal separating circuit 5 for separating the video signal, the horizontal synchronizing signal and the vertical synchronizing signal, and the input signal path is manually switched.

In FIG. 7, reference numeral 1 denotes a signal input connection terminal;
Other signal input connection terminal 11 is a manual switch, 5 Ru Oh by the synchronization signal separation circuit. In the input signal path switching circuit configured as shown in FIG. 7, the input signal path of the signal input connection terminals 1 and 2 is switched by the manual switch 11 to output the input signal to the synchronization signal separation circuit 5. The signal path was manually switched.

[0006]

However, in the above configuration, the input signal path is switched by the manual switch. Therefore, there is a trouble that the manual switch is switched, and a signal path having no input signal is selected. And
Problem signals to a display device is not input has occurred.

The present invention solves the above-mentioned conventional problems. A display capable of automatically switching an input signal path by detecting a synchronization signal frequency of an input signal and controlling an input signal path switching circuit. An object of the present invention is to provide an input signal path automatic switching circuit of a device.

[0008]

[MEANS FOR SOLVING THE PROBLEMS] To achieve this object
The automatic input signal path switching circuit of the present invention
An input video signal is transmitted through a plurality of signal input connection terminals 1 and 2
Input signal path switching circuit 4 (here,
Input to at least one of the signal input connection terminals 1 and 2
The input video signals are red, green, and blue
A video signal and one of the three video signals
Such as horizontal and vertical sync signals superimposed on the signal
And the input signal path switching time
One input video signal is input from the path 4 and
If the input video signal is a three-wire signal,
To separate the horizontal and vertical synchronization signals from the
Separated by the synchronization signal separation circuit 5 and the synchronization signal separation circuit 5.
Synchronization signal for detecting the synchronized horizontal and vertical synchronization signals
The horizontal synchronizing signal and the vertical synchronizing signal are detected by the detecting means 6 and the synchronizing signal detecting means 6.
Detects the absence of at least one of the direct sync signal
Input video signal output to the synchronization signal separation circuit 5
Signal path switching circuit 4
The horizontal synchronization signal and the vertical synchronization signal are
When at least one of the direct synchronization signal is detected
Input video signal to be output to the synchronization signal separation circuit 5 in order.
Stop the next switching operation, and
Video input signal for which at least one of
Signal path control means 7 for controlling the output of the signal
I have. Further, in order to achieve the above object, another embodiment of the present invention is described.
The input signal path automatic switching circuit
Is input through a plurality of signal input connection terminals 1 and 2.
Input signal path switching circuit 4 (here, signal input connection terminal
Input video signal input to at least one of the children 1 and 2
Are three video signals of red, green and blue, and 3
It consists of a synchronization signal different from the video signal of the book, and the synchronization signal is
One consisting of a superimposed horizontal synchronization signal and vertical synchronization signal
And the input signal path
One input video signal is input from the path switching circuit 4
And if the input video signal is a 4-wire signal
In this case, the horizontal synchronizing signal and the vertical synchronizing signal
Synchronizing signal separating circuit 5 and synchronizing signal separating circuit 5
Detects horizontal and vertical sync signals separated by
Synchronization signal detection means 6 and the synchronization signal detection means 6
It is at least one of the synchronizing signal and the vertical synchronizing signal
If it is detected that there is no such signal, it is output to the synchronization signal separation circuit 5.
Turn off the input signal path
Switching circuit 4 and the synchronization signal detecting means 6
At least one of the synchronization signal and the vertical synchronization signal
When it is detected, the input to the synchronization signal separation circuit 5
Stop the operation of sequentially switching the video signal, and
And / or vertical sync signal is detected.
Signal path control means for controlling output of a video input signal
7 is provided. In order to achieve the above object, the present invention
Still another input signal path automatic switching circuit includes a plurality of input signal path automatic switching circuits.
An input video signal is transmitted through a plurality of signal input connection terminals 1 and 2
Input signal path switching circuit 4 (here, the signal
Signal input to at least one of the signal input connection terminals 1 and 2.
The power image signal is three images of red, green and blue
Signal, three horizontal video signals, and another video signal.
And the input signal path.
Horizontal synchronization signal and vertical synchronization input from the switching circuit 4
Synchronizing signal detecting means 6 for detecting a signal and a synchronizing signal
In the means 6, at least one of the horizontal synchronizing signal and the vertical synchronizing signal
If it detects that there is no deviation,
Switching the input video signal output from the switching circuit 4 sequentially
Control for the input signal path switching circuit 4 and
The period signal detection means 6 detects the difference between the horizontal synchronization signal and the vertical synchronization signal.
At least one of them is detected.
Stops the operation of sequentially switching signals, and
Video in which at least one of the synchronization signal is detected
Signal path control means 7 for performing control for outputting an input signal;
Have. The synchronizing signal detecting means 6 outputs water
Counts the pulses of flat sync signal and vertical sync signal respectively
If the frequency is below the preset frequency
It is preferable to determine that there is no signal at.

With this configuration, even when a plurality of signal input connection terminals are provided, the synchronization signal frequency of the input signal is increased.
By detecting the number and controlling to sequentially switch the input signal path switching circuit, the input signal path can be automatically switched.

[0010]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a signal input connection terminal;
Is another signal input connection terminal, 4 is an input signal path switching circuit, 5 is a synchronization signal separation circuit, 6 is a synchronization signal detection means, 7
Denotes signal path switching control means.

The synchronizing signal separating circuit 5 separates the Sync On Green signal into a green signal, a horizontal synchronizing signal and a vertical synchronizing signal in the case of a three-wire signal, and outputs the separated signal. In the case of a four-wire signal, the H / V Mixed Sync signal is used. The signal is separated into a horizontal synchronizing signal and a vertical synchronizing signal and output. In the case of a 5-wire signal, a horizontal synchronizing signal and a vertical synchronizing signal are output.

The operation of the input signal path automatic switching circuit configured as described above will be described below. First, in the initial state of the input signal path automatic switching circuit, the input signal path switching circuit 4 is used as the signal path of the signal input connection terminal 1. When the display device is turned on,
Input signal path switching circuit 4, because that is the signal path of the signal input connection 1, becomes as follows.

When an input signal is present at the signal input connection terminal 1, the above operation is performed by the synchronization signal separation circuit 5, and a horizontal synchronization signal appears at the output terminal. This horizontal synchronizing signal is detected by the synchronizing signal detecting means 6, and there is a horizontal synchronizing signal.

When there is no signal at the signal input connection terminal 1, it is determined that there is no input signal because there is no horizontal synchronizing signal at the output terminal, and the signal path switching control means 7 sends a control signal to the input signal path switching circuit 4. The signal path is switched to the signal input connection terminal 2. If an input signal is present at the signal input connection terminal 2, a horizontal synchronization signal appears at the output terminal. The horizontal synchronization signal is determined by the synchronization signal detection means 6 to have an input signal, and the input signal path is connected to the signal input connection terminal 2. Control so that it remains as it is.

[0016] Here, shown concrete examples of the input signal path switching circuit 4 of FIG. 1 in FIG. 4.

This circuit is a capacitor C for separating a DC component.
, C2, C3, C4, DC level switching transistors Tr1, Tr2 and signal switching diode D
1 and D2. From the signal path switching control means 7 of FIG. 1, when the Hi signal is outputted Trang
The transistor Tr2 is turned off, no DC voltage is superimposed on the point b of the input signal 2, the switching diode D2 is cut off, and the input signal 2 is electrically disconnected from the output. On the other hand, the Hi signal output from the signal path switching control means 7 is converted to a Low signal via the NOT gate and reaches the transistor Tr1. At this time, the transistor T
r1 turns ON, and a DC voltage is superimposed on the point a of the input signal 1.
The diode D1 conducts, and the input signal 1 is output. Similarly, when a Low signal is output from the signal path switching control means 7 , the input signal 2 is output and the input signal 1 is electrically disconnected from the output.

As described above, if there is an input signal in the connected input signal path, the connection of that path is maintained, and if there is no input signal, the path is switched to the next input signal path. Here, the synchronizing signal separating circuit 5 separates the synchronizing signal from the video signal and outputs a horizontal synchronizing signal at an output terminal, not only for a 5-wire signal but also for a 3-wire signal or a 4-wire signal. Signal detection means 6
, The presence or absence of an input signal is determined based on the presence or absence of the synchronization signal, and the input signal path automatic switching circuit can automatically switch the input signal path.

[0019] (Embodiment 2) will be described with reference to the drawings a second embodiment of the present invention in the following.

In FIG. 2, reference numeral 1 denotes a signal input connection terminal;
Is another signal input connection terminal, 3 is another signal input connection terminal,
4 is an input signal path switching circuit, 5 is a synchronization signal separation circuit, 6 is a synchronization signal detection means, and 7 is a signal path switching control means .

The difference from the configuration of FIG. 1 is that another signal input connection terminal 3 is added. Operation of the configuration input signal path automatic switching circuit as shown in Figure 2, and the same operation as that in FIG. 1, the presence judgment of the input synchronizing signal, the absence of the horizontal sync signal is sequential signal input connection Are switched to 1, 2, and 3, and control is performed such that the connection remains unchanged on the input signal path determined to have the horizontal synchronization signal. Here, FIG.
Specific examples of the input signal path switching circuit 4 in FIG. 2 will be described.

This circuit comprises a capacitor C for separating a DC component.
1, C2, C3, C4, C5, C6, DC level switching transistors Tr1, Tr2, Tr3 and signal switching diodes D1, D2, D3. From the signal path switching control means 7 in FIG. 2, the control signal Low signal to 1, control the signal 2,3 the Hi signal is output transistor Tr2, Tr3 is OFF, ON input signal 2 b points and the input signal 3 DC voltage is not superimposed on the c point, diodes D2, D3 becomes a cut-off state, the input signal 2 is disconnected the output electrically. On the other hand, Trang by Low signal output from the control signal 1
The transistor Tr1 is turned on, a DC voltage is superimposed on the point a of the input signal 1, the diode D1 is turned on, and the input signal 1 is output. Similarly, when a Low signal is output as the control signal 2 and a Hi signal is output as the control signals 1 and 3, the input signal 2 is output and the input signals 1 and 3 are electrically disconnected from the output. Further, when a Low signal is output as the control signal 3 and a Hi signal is output as the control signals 1 and 2, the input signal 3
And the input signals 1 and 2 are electrically separated from the output. In this way, in FIG. 2 configuration, the signal input connection terminals 2
Even when the number is increased from three to three, the input signal path automatic switching circuit can automatically switch the input signal path.

Embodiment 3 Next, Embodiment 3 of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 1 denotes a signal input connection terminal;
Is another signal input connection terminal, 3 is another signal input connection terminal,
4 the input signal path switching circuit, the synchronization signal detection means 6, 7 is a signal path switching control means.

The difference from the configuration of FIG. 2 is that the synchronization signal detected by the synchronization signal detecting means 6 is supplied to the input signal path switching circuit 4.
Output. Therefore, there is no function to separate the input signal into the video signal, horizontal sync signal, and vertical sync signal.
A video signal input signal, a horizontal synchronizing signal, it is effective in the case of No. 5 Senshikishin which are independent of the vertical synchronizing signal. In the case of a five-wire signal, the input signal path can be automatically switched by the input signal path automatic switching circuit.

The operation of the thus configured input signal path automatic switching circuit as shown in Figure 3, and the same operation as that in FIG. 2, the presence judgment of the input synchronizing signal when the synchronizing signal is not sequentially input terminal Switch between 1 , 2, and 3.

It should be noted, first embodiment, second embodiment, in the third embodiment, a state in which an input signal path switching circuit 4 and the signal path of the signal input connection 1, the input signal path <br/> automatic switching Although the circuit is in the initial state, it goes without saying that the signal path of the signal input connection terminal 2 or the signal path of the signal input connection terminal 3 (excluding the first embodiment) may be used.

Further, in the first, second embodiment, third embodiment of the embodiment, although the signal input connections terminals 1 and 3, it is needless to say further may be a number of signal input connections terminals .

Although the horizontal synchronizing signal is detected by the synchronizing signal detecting means 6, it goes without saying that the vertical synchronizing signal may be detected.

Further, as a method of the synchronization signal detecting means 6, a method of judging the presence or absence of a synchronization signal at the rising and falling edges of the synchronization signal pulse, and a method of determining the number of synchronization signal pulses within a certain time by setting the synchronization signal frequency to a predetermined value. , The frequency may be detected, and when the frequency is zero, it may be determined that there is no synchronization signal.

[0031]

As described above, according to the input signal path automatic switching circuit of the present invention, if the input signal has a synchronizing signal, the input signal path of the display device can be automatically switched. An automatic path switching circuit can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an input signal path automatic switching circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an input signal path automatic switching circuit according to a second embodiment of the present invention;

FIG. 3 is a block diagram of an input signal path automatic switching circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of an input signal path switching circuit according to the first embodiment of the present invention;

FIG. 5 is a circuit diagram of an input signal path switching circuit according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a conventional input signal path switching circuit.

FIG. 7 is a block diagram of another conventional input signal path switching circuit example .
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[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal input connection terminal 1 2 Signal input connection terminal 2 3 Signal input connection terminal 3 4 Input signal path switching circuit 5 Synchronous signal separation circuit 6 Synchronous signal detection means 7 Signal path switching control means 8 Function realization means achieved by microcomputer 9 Switch status detecting means 10 Manual switch 11 Manual switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09G 5/00 G06F 3/00 H03K 17/00 H04N 5/04 H04N 5/66

Claims (4)

(57) [Claims] 1. A method according to claim 1, wherein the plurality of input video signals are a plurality of input video signals.
Input signal path input via input terminals (1, 2)
A switching circuit (4) , wherein at least one of the signal input connection terminals (1, 2)
The input video signals input to one are red, green,
Three blue video signals and any of the three video signals
Horizontal sync signal superimposed on one video signal
A three-wire signal composed of a direct synchronization signal and one input video signal from the input signal path switching circuit (4).
The image signal is input and the input video signal is
When the signal is a three-wire signal, the water signal is output from the three-wire signal.
A synchronization signal for separating the flat synchronization signal and the vertical synchronization signal.
Separation circuit (5) and the horizontal synchronization separated by the synchronization signal separation circuit (5).
Synchronization signal detecting means for detecting a signal and a vertical synchronization signal
(6) The horizontal synchronizing signal and the vertical synchronizing signal are synchronized by the synchronizing signal detecting means (6).
When it is detected that there is no signal
The input video signal to be output to the synchronization signal separation circuit (5)
The input signal path switching circuit
(4), and the synchronization signal detecting means (6)
At least one of flat sync signal and vertical sync signal
Is output to the synchronizing signal separation circuit (5).
Stops the operation of sequentially switching the input video signals
At least one of flat sync signal and vertical sync signal
The signal path for controlling the output of the detected video input signal
Automatic switching of input signal path provided with path control means (7)
Circuit . 2. A method according to claim 1, wherein the plurality of input video signals are a plurality of signal input signals.
Input signal path input via input terminals (1, 2)
A switching circuit (4) , wherein at least one of the signal input connection terminals (1, 2)
The input video signals input to one are red, green,
The three blue video signals are different from the three video signals
And the synchronizing signal is a superimposed horizontal signal.
From one synchronization signal consisting of a synchronization signal and a vertical synchronization signal
And a single input video signal from the input signal path switching circuit (4).
The image signal is input and the input video signal is
When the signal is a four-wire signal, the water signal is output from the four-wire signal.
A synchronization signal for separating the flat synchronization signal and the vertical synchronization signal.
Separation circuit (5) and the horizontal synchronization separated by the synchronization signal separation circuit (5).
Synchronization signal detecting means for detecting a signal and a vertical synchronization signal
(6) The horizontal synchronizing signal and the vertical synchronizing signal are synchronized by the synchronizing signal detecting means (6).
When it is detected that there is no signal
The input video signal to be output to the synchronization signal separation circuit (5)
The input signal path switching circuit
(4), and the synchronization signal detecting means (6)
At least one of flat sync signal and vertical sync signal
Is output to the synchronizing signal separation circuit (5).
Stops the operation of sequentially switching the input video signals
At least one of flat sync signal and vertical sync signal
The signal path for controlling the output of the detected video input signal
Automatic switching of input signal path provided with path control means (7)
Circuit . 3. A method according to claim 2, wherein the plurality of input video signals are a plurality of signal input signals.
Input signal path input via input terminals (1, 2)
A switching circuit (4) , wherein at least one of the signal input connection terminals (1, 2)
The input video signals input to one are red, green,
The three blue video signals are different from the three video signals
5-wire signal consisting of horizontal and vertical sync signals
And water input from the input signal path switching circuit (4).
Synchronization signal detection method for detecting flat synchronization signal and vertical synchronization signal
A horizontal synchronizing signal and a vertical synchronizing signal at the stage (6) and the synchronizing signal detecting means (6);
When it is detected that there is no signal
Output from the input signal path switching circuit (4).
Control for sequentially switching the input video signals
The synchronization signal detection is performed for the path switching circuit (4).
By means (6), at least the horizontal synchronizing signal and the vertical synchronizing signal
When either one is detected, the input video signal is
The next switching operation is stopped, and the horizontal synchronization signal is
Period signal and a video input for at least one hand has been detected
Signal path control means (7) for controlling output of a force signal;
Input signal path automatic switching circuit provided with . 4. The apparatus according to claim 1, wherein said synchronization signal detecting means is provided for a period of time.
Between the horizontal and vertical sync pulses.
And counting, the frequency is below the preset frequency.
4. When there is no signal, it is determined that there is no signal.
Input signal path automatic switching circuit
Road .