Patent Application
20080259060
The present invention relates to a video connection line and particularly to a video connection line to integrate analog and digital signals.
On display devices and the peripheral devices thereof VGA connector (namely D-Sub, DB-15) is most widely used in the earlier period. As hardware technology advances, demands for dedicated digital is higher. A new DVI specification is introduced on the market. Simply speaking, D-Sub aims at transmitting analog signals. In the era in which CRT (cathode ray tube) was the main stream, digital signals in the VGA card have to be converted to analog signals before being displayed on the screen. In the conversion process the signals attenuate and are distorted. DVI specification can solve this problem. It is a totally digital transmission method. The signals are sent out from the VGA card in a digital format. The display end directly receives the digital format without the conversion process. As a result display quality improves.
DVI data format is based on the technology of PanelLink developed by Silicon Image Co. of USA (initially adopted on notebook computers). It employs the technology of Transition Minimized Differential Signaling (TMDS) to maintain the stability of high speed data stream transmission. In the newer version of DVI specification an extra set of DVI link channel is provided. When two sets of the links are used at the same time, an extra transmission bandwidth can be provided, called Dual-link DVI operation mode. In the DVI specification 165 MHz is the boundary of bandwidth. When the requirement of the display mode is lower than such a bandwidth, a single link operation is used. For the bandwidth higher than 165 MHz automatic switching to the dual-link is done. The second link may also transmit data of color pixels exceeding 24 bits. In addition, a DVI connector also has pins conforming to DDC-2 protocol same as the VGA interface to enable the VGA card to read EDID data on the screen and help the VGA card to determine possible output resolution.
There are two types of common DVI connectors on the market at present, namely DVI-Digital (DVI-D) and DVI-Integrated (DVI-I). DVI-D supports only digital display devices. DVI-I supports both digital and analog display. While DVI was a standard developed for liquid crystal display to perform digital transmission without lowering picture quality, conversion of analog signals still has to be taken into account. The DVI-D and DVI-I connectors are developed to meet those requirements. DVI-I can support DVI-D devices (including connection lines). But DVI-D connector cannot be coupled with DVI-I connection line. This is because DVI-I signal line has four more pins to transmit the analog signals. But the DVI-D connector does not have the pin holes. Thus they cannot be matched and coupled. As a result, on the market there are DVI-D connectors for liquid crystal screens while the connection line adopts DVI-I connector and the VGA card also adopts DVI-I connector.
The connectors of new and old specifications now on the market often make users confused. To make the VGA card compatible with the old CRT screen, D-Sub is still available on the market. The back panel of the computer has to provide different video output ports to meet the requirement of compatibility. As shrinking the size of computers is a prevailing trend, to provide different types of video output ports creates configuration problem in the limited space of the personal computer. Moreover, although the VGA cards now on the market provide the DVI-I connector to transmit digital and analog signals, only one type of signal can be transmitted at a given time. Two transmit two types of signals at the same time through one DVI-I connector is not allowed. And to display two types of signals through one DVI-I connector at the same time (dual view, the vista operation system of Microsoft Co. allows one computer to display pictures on different display devices) also is not possible. There are still rooms for improvement.
The primary object of the present invention is to provide a video connection line to integrate analog and digital signals. It includes a first video connection port to support digital and analog video signals. After being connected to a computer or VGA card, the digital and analog signals can be output at the same time to be used by a second video connection port and a third video connection port, and be displayed respectively on different display devices.
To achieve the forgoing object, an embodiment of the invention includes a first video connection port to transmit digital and analog video signals (may be DVI-I specification), that is divided through a connection line to form a second video connection port (may be a DVI-D specification) to transmit the digital video signals and a third video connection port (may be VGA, D-Sub specifications) to transmit the analog signals.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Please refer to
Referring to
DVI is the abbreviation of Digital Visual Interface. It is a video interface standard aims to improve picture quality of display devices of personal computers through digital transmission. It is now widely used on display devices such as LCD digital projectors. The second video connection port 20 conforms to DVI-D specifications and has a pin layout different from DVI-I. The second video connection port 20 (DVI-D) does not have pin positions of C1, C2, C3 and C4 for analog signals that are existed on the first video connection port 10 (DVI-I). It can be easily understood, hence no table is presented.
Refer to
The first connection line 11 and the second connection line 12 are split to connect respectively to the second video connection port 20 (may be DVI-D specification) to transmit digital video signals and the third video connection port 30 (may be VGA, D-SUB specifications) to transmit analog signals.
Table 3 indicates that the first video connection port 10 has a first digital pin to transmit the digital signals, a first analog pin to transmit the analog video signals, a first power pin to transmit power signals and a first ground pin to be grounded.
The second video connection port 20 to transmit the digital video signals includes at least a second digital pin, a second power pin and a second ground pin corresponding respectively to the pin positions of the first digital pin, first power pin and first ground pin. The first connection line 11 connects the corresponding first and second digital pins, first and second power pins and first and second ground pins.
The third video connection port 30 to transmit the analog signals includes at least a third analog pin, a third power pin and a third ground pin corresponding to the pin positions of the first analog pin, first power pin and first ground pin. The second connection line 12 connects the corresponding first and third analog pins, first and third power pins, and first and third ground pins.
The second video connection port 20 has a plurality of second ground pins (Pins 5, 6, 7, 8 and 10) that are jointly connected to the single first ground pin (Pin C5) of the first video connection port 10 through the first connection line 11.
The first, second and third video connection ports 10, 20 and 30 have respectively a vertical synchronous signal pin (V-sync). The second video connection port 20 has a vertical synchronous signal pin (Pin 8) and the third video connection port 30 has a vertical synchronous signal pin (Pin 14) jointly connected to a vertical synchronous signal pin (Pin 8) of the first video connection port 10 through the first and second connection lines 11 and 12.
In addition, the first, second and third video connection ports 10, 20 and 30 have respectively a power pin. The power pins (pin 14 and 9) of the second video connection port 20 and the third video connection port 30 are jointly connected to a single power pin (Pin 14) of the first video connection port 10 through the first and second connection lines 11 and 12.
The invention provides a video connection line to integrate analog and digital signals. It has the first video connection port 10 to support digital and analog signals and is connected to a computer or VGA card to output digital and analog signals at the same time to be used by the second and third video connection ports 20 and 30, and to display the signals on different display devices.
While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
