JPH0651730A - Mixed synchronizing signal selecting circuit - Google Patents

Abstract

PURPOSE:To provide circuit which detects the frequency of the synchronizing signal of an input signal and automatically switches input signal paths. CONSTITUTION:The mixed synchronizing signal selecting circuit consisting of an input signal path switching circuit 4 equipped with plural signal input terminals, a synchronizing signal separating circuit 5, a synchronizing signal detecting means 6, and a signal path switching control means 7 which operates according to the detection state of the synchronizing signal detecting means 6 switches the input signal paths in order by the signal path switching control means 7 when the synchronizing signal detecting means 6 detects the absence of the synchronizing signal or stops the sequential input switching operation when the synchronizing signal detecting means 6 detects the presence of the synchronizing signal.

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 signal input connection terminal.

[0002]

2. Description of the Related Art In recent years, due to the diversification of computers, a sync signal is an input signal of a display device, which is a green signal of a video signal plus a horizontal / vertical sync signal.
c On Green signal (hereinafter referred to as 3-wire type signal because three signals of red, green and blue are input), H / V Mixed in which vertical synchronizing signal is added to horizontal synchronizing signal
Sync signal (Because there are four signal inputs of a composite synchronizing signal obtained by adding the vertical synchronizing signal to the horizontal synchronizing signal in addition to the three signals, it will be referred to as a four-wire type signal hereinafter.) Horizontal and vertical synchronizing signals are independent H / V Separated signal (Because there is a horizontal sync signal and a vertical sync signal in addition to the three video signals,
There is a wide variety.

A conventional mixed sync signal selection circuit will be described below. 6 and 7 show the configuration of a conventional mixed sync signal selection circuit.

In FIG. 6, 1 is a signal input terminal, 2 is another signal input terminal, 4 is an input signal path switching circuit, 5 is a synchronizing signal separation circuit, 10 is a manual switch, and 9 is a state of the manual switch 10. Switch state detecting means for detecting and determining, 7 is constituted by signal path switching control means. The operation of the input signal path switching circuit configured as shown in FIG. 6 will be described.

First, the switch state detecting means 9 detects the on / off state of the manual switch 10 to determine which of the input signal paths of the signal input terminals 1 and 2 should be switched, and the signal path switching control means. At 7, the control signal for switching the signal path is output to the input signal path switching circuit 4 according to the determination of the signal path to be switched. The other input signal path of the signal input terminals 1 and 2 is switched by the control signal for switching the signal path in the input signal path switching circuit 4, and the input signal of the switched input signal path is switched between the 3-wire signal and the 4-wire signal. In this case, the video signal, the horizontal sync signal, and the vertical sync signal are input to the sync signal separation circuit 5, and the input signal path is manually switched.

An example of the configuration of the input signal path switching circuit 4 will be described with reference to FIG. Reference numeral 1 is a signal input terminal, 2 is another signal input terminal, 11 is a manual switch, and 5 is a sync signal separation circuit. In the input signal path switching circuit configured as shown in FIG. 7, the input signal path of the signal input terminals 1 and 2 is switched by the manual switch 11 to output the input signal to the sync signal separation circuit 5. The route was switched manually.

[0007]

However, in the above-mentioned configuration, since the input signal path is switched by the manual switch, there is the trouble of switching the manual switch, and the signal path with no input signal is selected. Then
Since no signal was input to the display, there was a synchronization flow problem.

The present invention solves the above-mentioned conventional problems, and a display capable of automatically switching the input signal path by detecting the synchronizing signal frequency of the input signal and controlling the input signal path switching circuit. It is an object to provide a mixed sync signal selection circuit for a device.

Further, the present invention provides a circuit for automatically outputting a sync signal according to the type of the input signal by detecting the sync signal frequency of the input signal depending on the type of the input signal and controlling the circuit. .

[0010]

In order to achieve this object, a mixed sync signal selection circuit of the present invention inputs an input signal switching circuit having a plurality of signal input terminals and a signal from the input signal switching circuit. And a signal path control unit that operates in the detection state of the synchronization signal detection unit. The mixed synchronization signal selection circuit switches the signal when the synchronization signal detection unit detects that there is no synchronization signal. One kind of input signal characterized by controlling the sequential input signal paths to be switched by the control means and stopping the sequential input signal path switching operation when the synchronization detecting means detects that there is a synchronization signal. It has a circuit configuration for automatically selecting a route.

Further, a mixed sync signal selection circuit as another invention has a circuit structure for automatically selecting one kind of sync signal in addition to the above structure.

[0012]

With this configuration, even when a plurality of signal input terminals are provided, the input signal synchronization signal is detected and the input signal paths are automatically switched by controlling the sequential switching of the mixed synchronization signal selection circuit. be able to.

Further, since the input signal is discriminated based on the presence or absence of the input signal and the synchronizing signal, the input signal path can be automatically switched regardless of the type of the input signal.

[0014]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 and 2 are signal input terminals,
Reference numeral 4 is an input signal path switching circuit, 5 is a synchronization signal separation circuit, 6 is a synchronization signal detecting means, and 7 is a signal path switching control means.

In the case of a 3-wire type signal, the sync signal separating circuit 5 separates the Sync On Green signal into a green signal, a horizontal sync signal and a vertical sync signal and outputs a horizontal sync signal and a vertical sync signal to output a 4-wire type signal. H / V Mi for signals
The xed Sync signal is separated into a horizontal sync signal and a vertical sync signal to output the horizontal sync signal and the vertical sync signal, and in the case of a 5-wire type signal, the horizontal sync signal and the vertical sync 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 terminal 1. When the display device is powered on (not shown in the figure), the input signal path switching circuit 4 serves as the signal circuit of the signal input connection terminal 1 and is as follows.

When there is an input signal at the signal input terminal 1, it is input to the sync signal separation circuit 5 through the input signal path switching circuit, where the sync signal is separated, and the horizontal sync signal appears at the output terminal. This horizontal synchronizing signal is detected by the synchronizing signal detecting means 6, and when there is a horizontal synchronizing signal, the input state of the input signal path switching circuit 4 is the signal input terminal 1
Leave as it is.

When no signal is input to the signal input terminal 1, it is judged that there is no signal input to the input signal path switching circuit 4 because the signal output from the synchronization signal separation circuit 5 has no horizontal synchronization signal. The signal path switching control means 7 sends a control signal for switching the signal input terminal to the input signal path switching circuit 4 to switch the signal path to the signal input terminal 2. If an input signal is input to the signal input terminal 2, a horizontal sync signal appears at the output terminal of the sync signal separation circuit. By detecting this horizontal sync signal by the sync signal detection means 6, the horizontal sync signal is input to the input signal path switching circuit 4. It is judged that there is an input signal, and the input signal path is controlled so as to remain connected to the signal input terminal.

As described above, if there is an input signal in the connected input signal path, the connection of that path is left as it is, and if there is no input signal, it is switched to the next input signal path. Here, in the sync signal separation circuit 5, not only in the 5-wire type signal but also in the 3-wire type signal and the 4-wire type signal, the sync signal is separated from the video signal, and the horizontal sync signal appears at the output terminal to synchronize. Signal detecting means 6
It is possible to detect a sync signal with, and determine the presence or absence of an input signal based on the presence or absence of a sync signal, and the mixed sync signal selection circuit can automatically switch the input signal path.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, 1 is a signal input terminal, 2 is another signal input terminal, 3 is another signal input terminal, 4 is an input signal path switching circuit, 5 is a sync signal separation circuit, and 6 is a sync signal detection means. , 7 are signal path switching control means. The above is the same as the configuration of FIG.

The difference from the configuration of FIG. 1 is that another signal input connection terminal 3 is added. The input signal path automatic switching circuit configured as shown in FIG. 2 operates in the same manner as in FIG. 1 to determine the presence or absence of an input synchronizing signal. When there is no horizontal synchronizing signal, the signal input terminals are sequentially turned on. It is switched to 1, 2 and 3 and is controlled so that the connection remains as it is in the input signal path determined to have the horizontal synchronizing signal. As described above, in the configuration of FIG. 2, even if the number of signal input terminals is increased from two to three, the input signal path automatic switching circuit can automatically switch the input signal path.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings.

In FIG. 3, 1 is a signal input terminal, 2 is another signal input terminal, 3 is another signal input terminal, 4 is an input signal path switching circuit, 6 is a synchronizing signal detecting means, and 7 is a signal path switching control. It consists of means. The above is the same as the configuration of FIG.

The difference from the configuration of FIG. 2 is that the sync signal detected by the sync signal detecting means 6 is input signal path switching circuit 4
Is the output. Therefore, there is no function to separate the input signal into video signal, horizontal sync signal and vertical sync signal,
This is effective when the input signal is a 5-wire type signal which is independent of the video signal, the horizontal synchronizing signal and the vertical synchronizing signal. If the signal is a 5-wire type signal, the input signal path automatic switching circuit can automatically switch the input signal path.

The operation of the input signal path automatic switching circuit configured as shown in FIG. 3 is the same as that of FIG. 2, and the presence / absence of an input synchronizing signal is determined. When there is no synchronizing signal, the sequential signal input terminal 1 , 2, 3 is switched.

The first embodiment, the second embodiment, the third embodiment
In the embodiment, the signal path of the signal input terminal 1 in the input signal path switching circuit 4 is set to the initial state of the mixed sync signal selection circuit, but the signal path of the signal input terminal 3 is also used as the signal path of the signal input terminal 2. It goes without saying that it may be (except for the second embodiment).

Further, the first embodiment, the second embodiment, the third embodiment
Needless to say, in the embodiment, the number of signal input terminals is set to 1 to 3, but more signal input terminals may be used.

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 the method of the synchronizing signal detecting means 6, there is a method of judging the presence or absence of the synchronizing signal at the rising and falling edges of the synchronizing signal pulse, and how many times the synchronizing signal frequency is within a fixed time. It is also possible to use a method of detecting the frequency by counting and determining that there is no synchronizing signal when the frequency is zero.

(Embodiment 4) Next, a first embodiment of the second invention will be described with reference to the drawings. In FIG. 4, 1 is a signal input terminal, 20 is a synchronization selection circuit, 5 is a synchronization signal separation circuit, 6 is a synchronization signal detection means, and 21 is a synchronization selection control means.

The operation of the mixed sync signal selection circuit configured as shown in FIG. 4 will be described. First, in the initial state of the mixed sync signal selection circuit, the sync selection circuit 20 is set to the 5-wire signal selection state. When the power supply of the display device is turned on, the synchronization selection circuit 20 is in the state of selecting the 5-wire type signal, and therefore the following is performed. When the signal input terminal 1 has a 5-wire type signal, the synchronization selection circuit 20 does not output the horizontal synchronization signal and the vertical synchronization signal input from the signal input terminal 1 to the synchronization signal separation circuit 5. The sync signal separation circuit 5 receives the horizontal sync signal and the vertical sync signal input to the signal input terminal 1, and the horizontal sync signal and the vertical sync signal appear at the output terminal as they are. This horizontal synchronizing signal is detected by the synchronizing signal detecting means 6, and when there is a horizontal synchronizing signal, the input state of the synchronizing selection circuit 20 is set to the 5-wire type signal input state.

When there is no horizontal synchronizing signal, there is no horizontal synchronizing signal in the signal output from the synchronizing signal separating circuit 5, so there is no signal input to the horizontal synchronizing signal terminal and the vertical synchronizing signal terminal of the signal input terminal 1. And the synchronization selection control means 2
At 1, the synchronization selection circuit 20 sends a control signal for selecting the 3-wire type signal to bring the synchronization selection circuit 20 into the 3-wire type signal selection state. The sync selection circuit 20 does not output the horizontal sync signal and the vertical sync signal input from the signal input terminal 1 to the sync signal separation circuit 5, but only the green signal.
Output to.

The sync signal separating circuit 5 separates the horizontal sync signal and the vertical sync signal from the green signal, and the horizontal sync signal and the vertical sync signal appear at the output terminal. This horizontal synchronizing signal is detected by the synchronizing signal detecting means 6, and when there is a horizontal synchronizing signal, the input state of the synchronizing selection circuit 20 is set to the 3-wire signal input state. When there is no horizontal sync signal, it is determined that there is no signal input to the sync signal terminal and the vertical sync signal terminal, and the sync selection control means 21 causes the sync selection circuit 20 to select the 5-wire type control signal. To send the synchronization selection circuit 2
0 is set to the 5-wire signal selection state.

As described above, if there is an input signal at the connected signal input connection terminal 1, it is possible to judge the presence / absence of a sync signal and automatically bring the signal into a state suitable for the type of the input signal.

(Fifth Embodiment) Next, a second embodiment of the second invention will be described with reference to the drawings. In FIG. 5, 1 is a signal input terminal, 20 is a synchronization selection circuit, 5 is a synchronization signal separation circuit, 22 is a three-line selection circuit, 6 is a synchronization signal detection means, 2
Reference numeral 1 is a synchronization selection control means.

The operation of the mixed sync signal selection circuit configured as shown in FIG. 5 will be described. First, in the initial state of the mixed sync signal selection circuit, the sync selection circuit 20 is set to the 5-wire type signal selection state, and the 3-line selection circuit 22 is set to the output end state of the sync signal separation circuit. When you turn on the display device,
The synchronization selection circuit 20 is in the following state because it is in the state of selecting the 5-wire type signal.

When the signal input terminal 1 has a 5-wire type signal,
The synchronization selection circuit 20 does not output the horizontal synchronization signal and the vertical synchronization signal input from the signal input terminal 1 to the synchronization signal separation circuit 5. The sync signal separation circuit 5 receives the horizontal sync signal and the vertical sync signal input to the signal input terminal 1, and the horizontal sync signal and the vertical sync signal appear at the output terminal as they are. Three
Since the line selection circuit 22 is in the output state of the synchronization signal separation circuit, the output horizontal synchronization signal of the synchronization signal separation circuit 5 is detected by the synchronization signal detection means 6, and if there is a horizontal synchronization signal, the synchronization selection circuit 20 outputs the same. The state is set to a 5-line signal input state, and the state of the 3-line selection circuit 22 is set to a synchronization signal separation circuit selection state.

When there is no horizontal sync signal output from the sync signal separation circuit 5, the signal output from the sync signal separation circuit 5 does not include a horizontal sync signal. Therefore, the horizontal sync signal terminal and the vertical sync signal terminal of the signal input terminal 1 It is determined that there is no signal to be input to the synchronous selection control means 21, and the synchronous selection control means 21 sends a control signal for the synchronous selection circuit 20 to select the 3-wire type signal to put the synchronous selection circuit 20 into the 3-wire type signal selected state.

The sync selection circuit 20 does not output the horizontal sync signal and the vertical sync signal input from the signal input terminal 1 to the sync signal separation circuit 5, but outputs only the green signal to the sync signal separation circuit 5. The sync signal separation circuit 5 separates the horizontal sync signal and the vertical sync signal from the green signal, and the horizontal sync signal and the vertical sync signal appear at the output terminal. 3-line selection circuit 22
Is in the output state of the synchronization signal separation circuit, the output horizontal synchronization signal of the synchronization signal separation circuit 5 is the synchronization signal detection means 6
Detected by.

When there is an output horizontal sync signal from the sync signal separation circuit 5, the three-line selection circuit 22 is set to the sync selection circuit selected state. Since the 3-line selection circuit 22 is in the synchronization selection circuit selection state, the output horizontal synchronization signal of the synchronization selection circuit 20 is detected by the synchronization signal detection means 6. When there is no output horizontal sync signal from the sync selection circuit 20, the sync selection circuit 20
Is set to a 3-wire type signal input state, and the synchronization selection circuit is set to a synchronization signal separation circuit selection state. When there is no output horizontal sync signal from the sync signal separation circuit 5, the 3-line selection circuit 22 is set to the sync signal separation circuit selected state, and the sync selection circuit 20 is set to the 5-wire type signal input state.

The signal input terminal 1 connected as described above
If there is an input signal, it is possible to determine the presence or absence of the synchronization signal and automatically set the state suitable for the type of the input signal.

[0045]

As described above, according to the mixed synchronizing signal selection 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. The automatic switching circuit can be realized.

Further, since the input signal path can be automatically switched depending on the difference in the input signal, it is possible to reduce manual work and avoid misunderstanding such as failure.

[Brief description of drawings]

FIG. 1 is a block diagram of a mixed sync signal selection circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a mixed sync signal selection circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a mixed sync signal selection circuit according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a mixed sync signal selection circuit according to the first embodiment of the second invention.

FIG. 5 is a block diagram of a mixed sync signal selection circuit according to a second embodiment of the second invention.

FIG. 6 is a block diagram of a conventional mixed sync signal selection circuit.

FIG. 7 is an explanatory diagram showing a conventional mixed sync signal selection circuit.

[Explanation of symbols]

 1 signal input terminal 1 2 signal input terminal 2 3 signal input terminal 3 4 input signal path switching circuit 5 sync signal separation circuit 6 sync signal detecting means 7 signal path switching control means 8 function realizing means by a microcomputer 9 switch state detection Means 10 Manual switch 11 Manual switch 16 Sync signal detection means 20 Sync selection circuit 21 Sync selection control means

Claims (2)

[Claims] 1. A mixed sync signal selection circuit comprising: a sync signal detecting means for inputting a signal from a signal input terminal; and a signal path control means operating in a detection state of the sync signal detecting means. When it is detected that there is no sync signal, the signal path control means controls the input signal paths to be sequentially switched, and when the sync signal detection means detects that there is a sync signal, the sequential input signal path switching operation is performed. A mixed sync signal selection circuit characterized by controlling so as to stop. 2. A sync separation circuit which receives a signal from a signal input terminal and outputs a sync signal, a sync signal detection means which determines the presence or absence of a sync signal from the sync signal separation circuit, and the sync signal. A mixed sync signal selection circuit comprising: a sync selection control means for outputting a control signal based on the discrimination of the detection means; and a sync selection circuit for selecting the type of the sync signal of the input signal based on the control signal.