Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
1999-01-25
2001-12-11
Chow, Dennis-Doon (Department: 2775)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C345S001300, C345S003100
Reexamination Certificate
active
06329983
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 87117560, filed Oct. 23, 1998, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to computer video display technology, and more particularly, to a method and apparatus for automatically detecting whether a video output port on a computer video display adapter is currently externally connected or disconnected. In practice, the invention can be utilized, for example, on a video display adapter having an S output port and an AV Output port to detect which one of them is currently externally connected for video transmission to the video display unit.
2. Description of Related Art
A video display adapter for a personal computer (PC) is typically included with a television (TV) function that allows the PC monitor or a TV set to display digital video programs. This kind of video display card includes two different kinds of video output ports—an S output port and an AV output port—for connection to a PC monitor or a TV set. Conventionally, the use of the S output port or the AV output port is selectively set by jumper means or through software means by the operating, system (OS) of the computer. These setting methods, however, are both inconvenient to carry out.
If the video display card is set to use the AV output port, when the S output port on the TV set is connected via a cable to the S output port on the video display card, the video signal from the video display card is almost impossible to display on the TV screen. This is because the output video signal from the S output port is coded in a non-composite format, while the output video signal from the AV output port is coded in a composite format.
One drawback to the S/AV setting by the OS is that it can be carried out only after the computer is powered on and booted up, and the video image that is displayed after power-on and prior to entering the OS cannot be changed.
One drawback to the use of jumper means to set the S/AV option is that it is quite inconvenient to carry out since it requires the user to dismantle the PC case each time the jumper setting is to be changed.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for use on a video display adapter having an S output port and an AV output port. Either of the S output port or the AV output is currently externally connected for video transmission can be detected thereby. The detected result can be subsequently used to set S/AV option of the video display adapter.
In accordance with the foregoing, and other objectives of the present invention, a new method and apparatus that can achieve the foregoing objective is provided.
Broadly speaking, the method and apparatus of the invention can be utilized on a video display adapter having two video output ports including a first video output port and a second video output port to detect which one of the two video output ports is currently externally connected. In practice, for example, the two video output ports can be an S output port and an AV output port. The method and apparatus are characterized by the provision of a microswitch on one of the video output ports, for example the S output port. The microswitch is set to a first state when the S output port is externally disconnected (i.e., no insertion connector is inserted therein), and will be actuated to a second state when the S output port is externally connected (i.e., the insertion connector of a cable is inserted therein). Accordingly, when the microswitch is in a connected state, it indicates that the other port, i.e., the AV output port, is currently externally connected for video transmission; whereas when the microswitch is in a disconnected state, it indicates that the S output port is currently externally connected. Therefore, the video display adapter can discern which one of the two video output ports is currently externally connected simply by detecting the connected/disconnected state of the microswitch.
Three preferred embodiments of the invention are disclosed in accordance with the foregoing concept.
In the first preferred embodiment, the apparatus of the invention comprises: (a) a microswitch mounted on the video output port and having a first end connected to a setting signal output port and a second end connected to a ground voltage representing a low-voltage logic state, the microswitch actuated to a connected state when the video output port is externally disconnected and to a disconnected state when the video output port is externally connected; and (b) a resistor having a first end connected to the setting signal output port and a second end connected to a system voltage representing a high-voltage logic state. When the microswitch is in a connected state, the setting signal output port takes on the ground voltage and thus outputs a LOW-state logic signal serving to indicate that the video output port is currently externally disconnected; and whereas when the microswitch is in a disconnected state, the setting signal output port takes on the system voltage via the resistor and thus outputs a HIGH-state logic signal serving to indicate that the video output port is currently externally connected.
In the second preferred embodiment, the apparatus of the invention comprises: (a) a microswitch mounted on the video output port and having a first end connected to a first node and a second end connected to a ground voltage representing a low-voltage logic state, the microswitch actuated to a connected state when the video output port is externally disconnected and to a disconnected state when the video output port is externally connected; (b) a diode whose positive end is connected to a bias voltage representing a high-voltage logic state; (c) a resistor having a first end connected to the first node and a second end connected to the negative end of the diode; (d) an inverter whose input end s is connected to the first node and whose output end is connected to a second node; and (f) a setting signal output port connected to the second node. When the microswitch is in a connected state, the setting signal output port takes on the inverted version of the ground voltage and thus outputs a HIGH-state logic signal serving to indicate that the video output port is currently externally disconnected; and whereas when the microswitch is in a disconnected state, the setting signal output port takes on the inverted version of the bias voltage via the resistor and the diode and thus outputs a LOW-state logic signal serving to indicate that the video output port is currently externally connected.
In the third preferred embodiment, the apparatus of the invention comprises: (a) a microswitch mounted on the video output port and having a first end connected to a first node and a second end connected to a ground voltage representing a low-voltage logic state, the microswitch actuated to a connected state when the video output port is externally disconnected and to a disconnected state when the video output port is externally connected; (b) a diode whose positive end is connected to a bias voltage representing a high-voltage logic state; (c) a first resistor having a first end connected to the first node and a second end connected to the negative end of the diode; (d) a BJT whose base is connected to the first node, whose emitter is connected to the ground, and whose collector is connected to a second node; (e) a second resistor having a first end connected to a system voltage representing a high-voltage logic state and a second end connected to the second node, and (f) a setting signal output port connected to the second node.
When the microswitch is in a connected state, the BJT is switched off, causing the setting signal output port to take on the system voltage via the second resistor and thus output a HIGH-state logic signal serving to indicate that the video output port is currently externally disconnected; whereas when the microswit
Chow Dennis-Doon
Huang Jiawei
J. C. Patents
Winbond Electronics Corp.
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