JP3157757B2 - Digital signal switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal switching device for selectively switching digital control signals output from a plurality of PCs and outputting the signals to a display.
The present invention relates to a digital signal switching device suitable for use when one liquid crystal display is shared by a plurality of PCs.

[0002]

2. Description of the Related Art Conventionally, in a display such as a CRT display or a part of a liquid crystal display which inputs and displays an analog display signal, a display switch is used to share one display with a plurality of PCs. there were. This display switching device inputs display signals from a plurality of PCs, switches contacts using a rotary switch or the like, and selectively outputs a display signal of one PC to the display side.

[0003]

The above-mentioned prior art has the following problems.

[0004] High-speed digital signal lines cannot be switched by a method of switching contacts such as a rotary switch. Therefore, the conventional display switch cannot be applied to a display switch for a liquid crystal display which inputs and displays a digital display signal.

The present invention has been made in view of the above problems, and has as its object to provide a digital signal switching device capable of selectively connecting a display for inputting a digital control signal to a plurality of PCs. .

[0006]

According to one aspect of the present invention, there is provided a digital signal switching device for selectively connecting a display for inputting a digital control signal to a plurality of PCs. , The plurality of PCs
And a plurality of digital signal receivers capable of receiving the digital control signal output by
A DDC line switching circuit for selectively connecting a DC signal line to the plurality of PCs; and activating any one of the plurality of digital signal receivers, and synchronizing the switching of the digital signal receivers with the DDC line switching circuit. A switching control means for controlling switching of the line switching circuit; and a digital signal driver for outputting a digital control signal received by the digital signal receiver instructed by the switching control means to the display. is there.

In the invention according to claim 1 configured as described above, the plurality of digital signal receivers are connected to the plurality of PCs, respectively, and can receive digital control signals output from each PC. The switching control means instructs one of the plurality of digital signal receivers to operate. Then, only the selected digital signal receiver operates, and the digital signal driver outputs the digital control signal received by the digital signal receiver to the display.

Thus, a plurality of PCs that output digital control signals can share a display for inputting the same digital control signals. The displays to be shared are various and not particularly limited, but a system configuration in which a plurality of PCs share one display has been conventionally adopted. The plurality of PCs output digital control signals for image display. As described above, the switching control means switches the digital signal receiver, receives the digital control signal output from one PC, and displays the digital control signal. The DDC signal line of the PC is connected to the display by controlling the switching of the DDC line switching circuit in synchronization with the switching of the digital signal receiver. The display displays an image based on the input digital control signal and transmits / receives a DDC signal to / from a connected PC.

As an example thereof, the invention according to claim 2 is the digital signal switching device according to claim 1, wherein the display includes a dot matrix-like pixel constituting a display image and disposes the pixel in a horizontal direction. The configuration is a liquid crystal display that displays an image by sub-scanning in the vertical direction while performing main scanning.

The liquid crystal display is broadly divided into a so-called TFT liquid crystal display panel and a DSTN liquid crystal display panel. Since the means for color reproduction are different from each other, the liquid crystal display is provided with the means for connecting the liquid crystal display to the PC. It was common to install an interface board and compatibility was low. In view of such low compatibility, the present applicant has proposed a configuration in which a display image generated on the PC side is transmitted as it is to the display side as a digital control signal as it is, and the liquid crystal display side has means for color reproduction. . That is, the digital display signal output from the PC is standardized without depending on the type of the liquid crystal display connected to the PC.

[0011] Further, with the recent increase in the number of functions of the operating system, a PC monitors the peripheral device by exchanging signals with the peripheral device. As an example, a PC is a so-called D
Sending and receiving DC signals. This DDC signal contains information about the liquid crystal display, and the PC
The liquid crystal display is monitored using the C signal, and information on the liquid crystal display is acquired as necessary.

In the liquid crystal display according to the second aspect of the present invention, the liquid crystal display vertically scans the pixels in the dot matrix forming the display image in the horizontal direction based on the input digital control signal while performing the main scanning in the horizontal direction. The image is displayed by sub-scanning in the direction, and a DDC signal is transmitted / received to / from a connected PC.

As another example of the configuration for switching the signal line in synchronization with the switching of the digital signal receiver, the invention according to claim 3 is the digital signal switching device according to claim 1 or 2. USB signal lines for connecting to USB standard external devices
A USB line switching circuit selectively connected to the
The switching control means controls switching of the USB line switching circuit in synchronization with switching of the digital signal receiver.

In the third aspect of the present invention, the switching control means controls the switching of the USB line switching circuit in synchronization with the switching of the digital signal receiver in the same manner as the switching of the DDC signal line. Control switching,
A USB signal line to be connected to a USB standard external device is selectively connected to the plurality of PCs. Therefore, the US connected to the digital signal switching device as an external device
The data can be input to the PC selected by the switching control means using a B-standard keyboard or mouse.

The conditions such as the transmission medium and transmission speed of the digital control signal from the plurality of PCs to the plurality of digital signal receivers are not particularly limited, but the transmission speed is high because a liquid crystal display or the like is used as a peripheral device. Is more preferable.

According to a fourth aspect of the present invention, in the digital signal switching apparatus according to any one of the first to third aspects, the plurality of PCs transmit the digital control signal at high speed in accordance with a predetermined transmission standard. There is a configuration to do.

That is, when a PC transmits a digital control signal, it transmits at a high speed in accordance with a transmission standard such as the TMDS standard.

In selecting a digital signal receiver to be actually operated, a user interface such as a changeover switch or a changeover button may be provided as a changeover control means, and selection may be made based on an input through the user interface. Of course, the selection may be made by other means.

[0019]

[0020]

[0021]

As described above, according to the present invention, a plurality of P
C selectively outputs a digital control signal output to the display side, and outputs a digital control signal to and from a connected PC.
A digital signal switching device capable of transmitting and receiving DC signals can be provided.

According to the second aspect of the present invention, a single liquid crystal display can be shared by a plurality of PCs.

Further, according to the third aspect of the present invention,
A plurality of PCs can share USB standard external devices.

Further, according to the invention according to claim 4,
Since the digital control signal is transmitted from the PC at a high speed, the processing speed is improved as a whole.

[0025]

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a digital signal switching device according to an embodiment of the present invention, and a system including a plurality of PCs and a liquid crystal display constructed using the digital signal switching device.

In FIG. 1, PC1, PC2, and PC3 each have slots (not shown), and board portions B1, B2, and B3 are mounted in the respective slots. The board units B1, B2, and B3 are digital signal switching devices 1 respectively.
The input ports 20, 30, and 40 of the digital signal switching device 10 are connected to the input port 20, 30, and 40 by a predetermined cable.

Each of the board sections B1, B2, and B3 is provided with a graphic board (not shown) including a graphic chip for generating image data by a display driver executed on the PC body side.
Although the image memory and the interface are not shown in the drawings, they are naturally provided.
Each graphic board of the board part B1, B2, B3,
A digital signal (Y signal in the figure) representing the luminance information for each pixel while performing main scanning in the horizontal direction and sub-scanning in the vertical direction for each pixel constituting the dot matrix image to be displayed by the graphic chip. Generate

This digital signal represents each pixel with 8-bit or 6-bit luminance information RGB for each color of red, green and blue, and is composed of a synchronizing signal for digital signal transmission and the like. Then, the generated digital signal is transmitted at a high speed by reducing 28 signal lines to four lines based on the TMDS standard. In the present embodiment, the TMDS standard is adopted. However, various conditions such as the transmission speed of the digital signal are arbitrary, and other standards,
For example, the LVDS standard can be adopted.

Digital signals input to the input ports 20, 30, and 40 are received by receivers 21, 31, and 41, respectively.
Is received at. Each of the receivers 21, 31, and 41 is provided with four FETs so as to correspond to the four signal lines described above. For convenience, the receivers 21, 31, and 41 are provided as shown in the schematic circuit diagram of FIG. , 41 for each
It is assumed that the FETs 21a, 31a, and 41a are provided. In the figure, FETs 21a, 31a, 41
a are input ports 20, 3 on the source (S) side, respectively.
0 and 40 are connected, and the drain (D) side is connected to a driver 70 described later. Therefore, although the digital signals are received by the receivers 21, 31, and 41, the receivers that actually receive the signals are limited to the receivers to which the gate (G) voltage is applied.

The decoder 60 applies a gate voltage to the FETs 21a, 31a and 41a. The decoder 60 includes a switching button 61 corresponding to PC1, PC2, and PC3, and applies a gate voltage to any one of the FETs 21a, 31a, and 41a according to the button input of the switching button 61. In this sense,
The decoder 60 and the switching button 61 constitute switching control means.

For example, when PC1 is used, when PC1 is selected by the switching button 61, the decoder 60 detects and applies a gate voltage to the FET 21a. Then, the source-drain of the FET 21a conducts, and the input digital signal is output to the driver 70. The driver 70 transmits the digital signal to the liquid crystal display LCD via the output port 50.

The decoder 60 is connected to the input ports 20, 3
In each of 0 and 40, the signal input status of the digital signal is monitored, and the receiver corresponding to the input port having the signal input is preferentially operated. For example, PC
When only PC1 is operated from the state where PC1, PC2 and PC3 are not operated, the digital signal is input only to the input port 20. Then, the decoder 60 detects and activates the receiver 21 to receive the digital signal from the PC 1. At this time, the flag is set and the PC
The fact that the digital signal from 1 is being received is stored, and the digital signal of the same PC is not received even if another PC is operated thereafter.

What has been described above includes the receivers 21 and 3.
One FET 21a, 31a, 4
1a, but the same is true even when four FETs are provided. However, it goes without saying that the gate voltage is applied to the four FETs in the same receiver in synchronization.

The board units B1, B2, and B3 and a liquid crystal display LCD described later are provided with a DDC (not shown) for transmitting and receiving a DDC signal indicating a vendor ID of the liquid crystal display LCD, a manufacturing date, and the like. It transmits / receives format data of a predetermined standard having a length of 256 bytes via the number of DDC signal lines.

As shown in FIG. 1, PC1, PC2, PC
3 is a DDC line switching circuit 80.
The output side is connected to a liquid crystal display LCD via an output port 50. This DDC
The line switching circuit 80 selectively connects one DDC signal line from the input side DDC signal lines to the output side based on a predetermined control signal from the decoder 60. Specifically, the decoder 60 instructs the operation of one receiver as described above, and the DD corresponding to the instructed receiver.
A control signal is transmitted to select the C signal line. Therefore, the switching of the receiver and the switching of the DDC signal line are performed in synchronization, and at least the liquid crystal display LCD and the P using the liquid crystal display LCD are used.
The transmission and reception of the DDC signal with C are possible, and the information of the liquid crystal display LCD can be obtained.

The liquid crystal display LCD receives a digital signal transmitted at a high speed with a reduced number of signal lines as described above, generates a predetermined drive signal based on the digital signal, and drives a liquid crystal display panel (not shown). . In general, a liquid crystal display panel is roughly classified into a TFT system and a DSTN system, and has different driving systems.
A driving signal for driving the liquid crystal display panel is generated by the interface board on the C side and transmitted to the liquid crystal display, and the liquid crystal display drives the liquid crystal display panel based on the driving signal. On the other hand, in the present embodiment, the PC generates a digital signal representing the luminance information and transmits it to the liquid crystal display LCD.
The liquid crystal display LCD converts the drive signal into a drive signal corresponding to the liquid crystal display panel.

That is, since the low compatibility of the type of liquid crystal display panel is absorbed on the liquid crystal display LCD side, even if the liquid crystal display panel used is of the TFT type, the liquid crystal display panel has a D type.
The STN system may be used, and there is no need to change the interface board on the PC side according to the type of the liquid crystal display panel.

In the present embodiment, one PC is used for three PCs.
Although the two liquid crystal displays are configured to be shared, the number of PCs is, of course, arbitrary, and the number of input ports and receivers may be increased or decreased, and the operation may be controlled by a decoder. In the present embodiment,
Although the DDC line is switched in synchronization with the switching of the receiver, other signal lines may be switched in synchronization with the switching of the receiver.

As an example, in the apparatus shown in FIG. 3, the digital signal switching device 10
1, 31, 41, a decoder 60, and a switch button 61
And a main circuit unit 90 including a driver 70 and a DDC line switching circuit 80, and a USB line switching circuit 100. USB of PC1, PC2, PC3
The ports are connected to the USB line switching circuit 100 via the USB ports 22, 32, and 42 on the digital signal switching device 10, respectively, and the keyboard K and the mouse M are connected in a daisy chain via the USB port 52. Have been. The USB line switching circuit 100 performs the above-described receivers 21 and 3 based on an instruction from the decoder 60.
USB of PC corresponding to operation switching of 1,41
The signal line and the USB line on the USB port 52 side are connected.

That is, the USB line of the PC for displaying an image on the liquid crystal display LCD is connected to the USB lines of the keyboard K and the mouse M.
In C, a keyboard K and a mouse M can be used as input devices. Therefore, PC1, PC2,
There is no need to provide a dedicated keyboard and mouse for each of the PCs 3, and the system configuration is reduced as a whole.

Further, in the present embodiment, the present invention is applied to a system including a PC for generating a digital signal representing luminance information, but in the case of a PC for generating an analog signal,
The configuration shown in FIG. 4 is also possible. In the figure, a digital signal switching device 210 is connected to an input port 22.
0, 230, and 240, respectively.
An RGB analog signal generated by the PC 6 is input and connected to a liquid crystal display LCD via an output port 250. One of the analog signals input from PC4, PC5, and PC6 is selected by the rotary switch 260, and the A / D converter 27
After being output to 0 and converted to a digital signal by the A / D converter 270, the signal is output to the liquid crystal display LCD via the output port 250.

Next, the operation of the present embodiment configured as described above will be described.

A graphic board (not shown) in each of the board sections B1, B2, and B3 performs main scanning in the horizontal direction for each pixel constituting a dot matrix image to be displayed by a display driver executed on the PC body side. While performing vertical scanning in the vertical direction, a digital signal representing luminance information of 8 bits or 6 bits for each of R, G, and B is generated for each pixel. Then, the generated digital signals are transmitted at high speed by reducing 28 signal lines to four lines based on the TMDS standard.

The digital signals transmitted from PC1, PC2, and PC3 are converted into digital signal switching devices 10 respectively.
2 via the input ports 20, 30, 40 on the side
1, 31, and 41 are input. The user selects the PC by inputting a button with the switch button 61 to display a desired PC image. Then, the decoder 60 applies and operates the voltage signal to the receiver corresponding to the PC detected and selected, and the receiver starts receiving the digital signal.

The decoder 60 is connected to the input ports 20, 3
At 0 and 40, the signal input status of the digital signal is constantly monitored, and the receiver corresponding to the input port having the signal input is preferentially operated. For example, PC1, P
When only PC1 is operated in a state where C2 and PC3 are not operated, the digital signal is input only to the input port 20. Then, the decoder 60 detects and activates the receiver 21 to receive the digital signal from the PC 1. At this time, since the fact that the digital signal is being received from the PC 1 is stored by setting a flag or the like, the digital signal of the same PC is not received even if another PC is operated thereafter.

The decoder 60 sends a predetermined control signal to the DDC line switching circuit 80 in synchronization with the switching of the receiver as described above, and upon receiving the control signal, the DDC line switching circuit 80 receives the DDC signal of the corresponding PC. The line is connected to the DDC signal line of the liquid crystal display LCD. As a result, D between the PC and the liquid crystal display
Transmission and reception of DC signals become possible, and information such as a vendor ID relating to the liquid crystal display LCD is acquired by the PC.

The digital signal received by the receiver is output by the driver 70 to the liquid crystal display LCD via the output port 50. Then, the liquid crystal display LCD generates a drive signal corresponding to the type of the liquid crystal display panel (not shown) based on the digital signal transmitted at high speed as described above, and drives the liquid crystal display panel using the drive signal. In the present embodiment, the digital signal switching device is applied to a system in which a plurality of PCs share one liquid crystal display. However, digital signals output from a plurality of PCs are switched to peripheral devices. It goes without saying that the present invention can be widely applied when outputting.

As described above, the input ports 20, 30, 40
, Digital signals representing the luminance information generated by PC1, PC2 and PC3, respectively, and
When receiving the digital signal at 1, 31, 41, only one receiver is operated according to the instruction of the decoder 60 to receive the digital signal, and the received digital signal is transmitted to the liquid crystal display LC via the driver 70.
D, so that the liquid crystal display LCD
, A digital signal switching device that can be shared by a plurality of PCs.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing the configuration of a digital signal switching device according to an embodiment of the present invention, and a system including a plurality of PCs and a liquid crystal display constructed using the digital signal switching device.

FIG. 2 is a schematic circuit diagram for explaining an operation state of a receiver.

FIG. 3 is a schematic block diagram illustrating a configuration of a system to which a digital signal switching device according to a modification is applied.

FIG. 4 is a schematic block diagram illustrating a configuration of a system in which a plurality of PCs that output analog RGB signals share one liquid crystal display.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Digital signal switching device 20, 30, 40 ... Input port 21, 31, 41 ... Receiver 50 ... Output port 60 ... Decoder 61 ... Switching button 70 ... Driver 80 ... DDC line switching circuit

Claims (4)

(57) [Claims] 1. A digital signal switching device for selectively connecting a display for inputting a digital control signal to a plurality of PCs, said plurality of digital signals being capable of receiving digital control signals output from said plurality of PCs. A receiver; a DDC line switching circuit for selectively connecting a DDC signal line connected to the display to the plurality of PCs; and operating one of the plurality of digital signal receivers; Switching control means for controlling the switching of the DDC line switching circuit in synchronization with the switching of the digital signal line; and a digital signal for outputting a digital control signal received by the digital signal receiver instructed by the switching control means to the display. A digital signal switching device, comprising: a signal driver. . 2. The digital signal switching device according to claim 1, wherein the display includes a dot matrix pixel forming a display image, and performs main scanning in the horizontal direction and sub-scanning in the vertical direction. A digital signal switching device, which is a liquid crystal display for displaying an image. 3. The digital signal switching device according to claim 1, wherein a USB signal line connected to a USB standard external device is connected to the plurality of PCs.
A digital signal switching device, wherein the switching control means controls the switching of the USB line switching circuit in synchronization with the switching of the digital signal receiver. . 4. The digital signal switching device according to claim 1, wherein said plurality of PCs
A digital signal switching device for transmitting said digital control signal at a high speed in accordance with a predetermined transmission standard.