BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given herein below for illustration only for, and thus are not limitative of the present invention, and wherein:
FIG. 1 is a schematic view showing the connection relationships of the video output system of the prior art;
FIG. 2 is a schematic view showing the connection relationships of the video output system in the first embodiment of the present invention;
FIG. 3 is a schematic view showing the connection relationships of the video output system in the second embodiment of the present invention; and
FIG. 4 is a schematic view showing the connection relationships of the switches with the control unit of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The preferable embodiment of the present invention is described in details below with reference to the accompanying drawings.
Referring to FIG. 2, it shows a video output system in the first embodiment of the present invention. Similar to the video output system of the prior art shown in FIG. 1, the video output system comprises an internal VGA interface 301, an external VGA interface 303, and a video output interface 305. The internal VGA interface 301 and the external VGA interface 303 are connected to the video output interface 305 respectively in the way of being connected to a connection point A 300 through individual leads respectively, and then to the video output interface 305 at the connection point A 300 through a common lead. The internal VGA interface 301 and the external VGA interface 303 are built-to-order, realizing a more flexible arrangement. What is different from the video output system of the prior art shown in FIG. 1 is that switches 21, 23 are respectively added on the leads through which the internal VGA interface 301 and the external interface VGA 303 are connected to the connection point A 300.
The operating principle of the video output system of the present invention shown in FIG. 2 is described as follows. When a PC sends an instruction, a VGA interface (for example, the internal VGA interface 301) delivers signals in response to the instruction of the PC (herein, only one VGA interface will operate). Before delivery of signals to the video output interface 305 by the internal VGA interface 301, the switch 21 between the internal VGA interface 301 and the connection point A 300 is turned on, and the switch 23 between the non-operative VGA interface (i.e. the external VGA interface 303) and the connection point A 300 is turned off, such that the signals are delivered to the video output interface from the internal VGA interface, and meanwhile a small portion of the signal stub is prevented from remaining in the lead between the external VGA interface 303 and the switch 23. In the same way, when the external VGA interface 303 receives an instruction sent by the PC, it delivers signals according to the method described above.
The present invention employs the technique of respectively adding switches 21, 23 on the leads through which the internal VGA interface 301 and the external VGA interface 303 are connected to the connection point A 300. When the internal VGA interface 301 operates, the switch 21 between the internal VGA interface 301 and the connection point A 300 is turned on, and the switch 23 between the non-operative external VGA interface 303 and the connection point A 300 is turned off, such that the operative internal VGA interface 301 can transmit signals to the video output interface 305 successfully. Also, after the signal transmission is completed, since the switch 23 between the non-operative external VGA interface 303 and the connection point A 300 is turned off, the signal stub remains only in the lead between the connection point A 300 and the switch 23. Compared with the prior art in which the signal stub remains in the lead between the connection point A 100 and the non-operative VGA interface, the signal stub in the lead between the non-operative VGA interface and the switch is reduced according to the invention, i.e. the length of the lead with signal stub is reduced (by the length of the lead between the non-operative external VGA interface 303 and the switch 23), and thus the amount of signal stub remaining in this part of lead is reduced. Therefore, when the external VGA interface 303, which did not operate this time, transmits signals upon receiving its next instruction, the influence of the previous signal stub to this signal transmission is reduced, thereby improving signal quality.
The switches 21, 23 can be disposed as close to connection point A 300 as possible. But obviously, there should be a certain distance, thus ensuring that the least possible signal stub remains in the leads between the switches 21, 23 and the connection point A 300. The switches 21, 23 can be switchable on and off, and the purpose of blocking signal flow direction can be achieved by the on and off of the switches.
In the first embodiment of the present invention, all elements can be formed on the same substrate, which is well known as a co-layout.
Referring to FIG. 3, it shows a video output system in the second embodiment of the present invention, which is similar to the video output system shown in the first embodiment, except that a switch control unit 40 is additionally connected to the two switches 31, 33 respectively. The switch control unit 40 further comprises an ID control pin, so as to select modes freely. When the external VGA interface 503 transmits signals to the video output interface 505 through a connection point A 500 upon receiving an instruction of the PC, the switch control unit 40 may turn off the switch 31 connected with the internal VGA interface 501 and turn on the switch 33 connected with the external VGA interface 503 automatically or manually by the user, thereby realizing the signal transmission, and vice versa.
Referring to FIG. 4, it shows the connection relationships of the switches with a control unit of the present invention. The switch can be a zero ohm resistor. When the switch is a zero ohm resistor, the control unit 50 must be disposed inside or outside for fusing the resistor to cut off the connection thoroughly, thus blocking the flow direction of the signal. However, in this method, once the resistor is fused, the VGA interface cannot operate any more. Furthermore, the switch can be any combination of the zero ohm resistor and common switch as desired.
The video output system described in the present invention is suitable for greatly reducing signal stub by adding switches between the internal VGA interface and the connection point A and between the external VGA interface and the connection point A respectively, thus avoiding the reflection caused by signal stub as much as possible, enhancing signal quality and improving the graphic display. Especially, the disposed switch control unit allows the user to select modes freely, thus improving convenience. Moreover, all elements including switches can be formed on the same substrate. The process is simple, reducing the increased costs of using multiple substrates, and increasing productivity.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Patent Application
20080001955
