Abstract:
A transmitter includes an output module coupled to an output port for outputting an output signal to the output port according to a detection signal, and a detect module for detecting the output port to generate the detect signal.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to signal output devices and, more particularly, to signal transmitters and driving methods thereof.  
         [0003]     2. Description of the Prior Art  
         [0004]      FIG. 1  is the block diagram of a prior art signal output device  10 . The signal output device  10  comprises a signal transmitter  12  and a display device  14 . The signal transmitter  12  comprises a signal processing circuit  16 , an output circuit  18 , and a connection port  20 . The data processing circuit  16  decodes the signal DATA inputted to the signal processing circuit  16  and outputs an image signal DATA′. The output circuit  18  transforms the digital signal DATA′ into an analog signal DATA″, and the signal DATA″ is transmitted to the display device  14  through the connection port  20  and a connecting line  22 . The display device  14  then displays the image corresponding to the signal DATA″.  
         [0005]     If the signal transmitter  12  is not connected to the display device  14 , the signal transmitter  12  is not able to drive the display device  14  when the signal transmitter is powered on because the connection between the signal transmitter  12  and the display device  14  is broken. However, the signal processing circuit  16  and the output circuit  18  begin to dissipate power when they are powered on, and this results in an unnecessary waste of power in the signal transmitter  12 . If such a signal transmitter is used in portable electronic devices, such as a notebook, it will definitely shorten the time the battery is able to supply power.  
       SUMMARY OF INVENTION  
       [0006]     It is one of the objectives of the present invention to provide a signal transmitter for determining whether or not to output a signal by detecting the connection of the load device and a driving method thereof.  
         [0007]     According to the claimed invention, a signal transmitter is disclosed comprising an output module for determining whether to stop outputting an output signal to an output port according to a detect signal; and a detect module coupled to the output port for detecting the output port in order to generate the detect signal.  
         [0008]     According to the claimed invention, a method is disclosed for controlling outputting an output signal, the method comprising determining whether to stop outputting an output signal according to a detect signal; and detecting the output port to generate the detect signal.  
         [0009]     These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  is a block diagram of a prior art output device system.  
         [0011]      FIG. 2  is a block diagram of a signal transmitter according to the present invention.  
         [0012]      FIG. 3  is a flowchart of the signal transmitter of  FIG. 2 .  
         [0013]      FIG. 4  is another flowchart of the signal transmitter of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0014]      FIG. 2  is a block diagram of a signal transmitter  100  according to the present invention. The signal transmitter  100  comprises an output module  110 , a switch module  120 , a signal generating module  130 , a detect module  140 , and a connection port  142 . The detect module  140  comprises a detect unit  150  and a resistor unit  160 . The signal transmitter  100  receives a working voltage when beginning to operate. The output module  110  is used for generating an output signal. The switch module  120  is intervened between the signal generating module  130  and the connection port  142 . The signal generating module  130  is used for providing a current signal or a voltage signal. The detect module  140  is used for detecting whether the connection port  142  is connected to an external load. For example, if the signal transmitter  100  is a DVD player, the connection port  142  is connected to a display through a connecting line. For another example, if the signal transmitter  100  is an audio amplifier, the connection port  142  is connected to a speaker through the connecting line. Note that the signal transmitter  100  may be any device with an output port, or which outputs an output signal to another device.  
         [0015]     Please refer to  FIG. 3 .  FIG. 3  is an operational flowchart of the signal transmitter in  FIG. 2 , and the signal transmitter works as follows: 
        Step  200 : The output module  110  generates an output signal So;     Step  202 : The detect module  140  detects the voltage value Vout of the connection port  142 ;     Step  204 : The detect module  140  compares the voltage value Vout and a predetermined value. If the voltage value Vout is greater than the predetermined value, operation proceeds to step  206 ; otherwise, operation proceeds to step  200 ;     Step  206 : The detect module  140  generates a control signal Sc to switch the output module  110  off;     Step  208 : Activate the function of hot-plug-and-play. In another embodiment of the present invention, the signal transmitter  100  may stop operations and begin a stand-by mode (power-saving mode) while the input data DATA is still being inputted. When the detect module  140  detects that the connection port  142  is connected to the external load, the output module  110  is informed by the control signal Sc to switch to normal operation. In anther embodiment of the present invention, the control signal Sc may directly cut off the working voltage of the output module  110  so as to save power.        
 
         [0021]     In this embodiment of the present invention, the output module  110  operates in current mode, meaning that the output module  110  is capable of generating an output signal So with a specific current value when the output module  110  is processing a predetermined signal (step  200 ). The detect unit  150  of the detect module  140  detects the voltage value of the connection port  142  ( 202 ). Additionally, the resistor unit  160  is used for assisting the detect module  150  to detect the connection status between the connection port  142  and the external load. The steps of the operation are described as follows.  
         [0022]     Assume that the input resistance of the external load, such as a display, is 75-ohm, which is equal to the resistance of the resistor unit  160 . When an external load is connected to the connection port  142  through a connecting line, if the resistance of the connecting line and the connection port  142  can be eliminated, the output resistance of the signal transmitter  100  is regarded as the parallel connection of the 75-ohm resistance and the resistor unit  160 , meaning that the voltage value Vout detected by the detect unit  150  is equal to the product of the current value I of the output signal So and the equivalent resistance of the parallel connection of the 75-ohm resistance and the resistor unit  160 , which is I*37.5. Conversely, if the external load is not connected to the connection port  142 , the voltage value detected by the detect unit  150  will be I*75. Therefore, the detect module  140  determines whether the connection port  142  is connected to an external load according to the voltage value Vout detected. In this embodiment of the present invention, the detect module  150  compares the voltage value Vout with a predetermined value (such as I*56.25) so as to determine the connection status of the connection port  142  (step  204 ). If the voltage value Vout is greater than the predetermined value, the external load is not connected to the connection port  142  and the operation of the output module  110  will be stopped so as to save power (step  206 ). In another embodiment of the present invention, the control signal Sc of the detect module  150  may also be capable of controlling the operation of the switch module  120 . Meanwhile, the switch module  142  is switched on in order to connect the signal generating module  130  to the connection port  142 . In the present embodiment, the signal generating module  130  may generate an additional steady current Iss so that when the output module  110  stops generating the output signal So, a voltage value of Iss*75 is generated at the connection port  142  while the additional steady current Iss runs through the resistor unit  160 . Thus the voltage of the connection port  142  is not zero although the operation of the output module  110  has been stopped. As long as the external load is connected to the connection port  142 , another voltage value Iss*37.5 is generated at the connection port  142 . Therefore the detect unit  150  outputs the control signal Sc to reactivate the output module  110 , the switch module  142  is switched off, and the output module  110  outputs the output signal So to drive the display. Generally speaking, the signal generating module  130  is used for generating an output voltage at the connection port  142  when the output module  110  is switched off, and the signal transmitter  110  may thus have the function of hot-plug-and-play (step  208 ).  
         [0023]     On the other hand, if the voltage value Vout is not greater than the predetermined value, meaning that the external load is connected to the connection port  142 . In this situation, the output module  110  generates the output signal So to drive the display. Moreover, steps  200 ,  202 , and  204  will keep detecting the connection between the external load and the signal transmitter  100 .  
         [0024]     In another embodiment of the present invention, the resistor unit  160  may comprises a plurality of resistor so as to form the value of resistance needed and the operation of the detect module  140  can be illustrated by an example of a signal transmitter  100  driving a display. The output signal is of the CVBS, S-Video, YPbPr or RGB specification. The signal transmitter  100  may also drive other kinds of loads (such as a speaker). Accordingly, the resistance value of the resistor unit  160  depends on the external load and the detect module  140  uses an appropriate predetermined value in step  204 . In other words, the signal transmitter  100  may detect the connection status through appropriately arranged detect module  140  in different situations.  
         [0025]     In another embodiment of the present invention, the output module  110  may operate in voltage mode. When the output module  110  is processing a signal so as to generate an output signal So, the output signal So corresponds to a voltage value, meaning that different signals processed by the output module  110  results in the corresponding output signal So of different voltage values. Meanwhile, the detect module  140  of the present invention detects the connection status of an external connecting line. Please refer to  FIG. 4 .  FIG. 4  is another operational flowchart of the signal transmitter  100  in  FIG. 2 , and the operation comprises the following steps: 
        Step  300 : The output module  110  generates an output signal So.     Step  302 : The detect module  140  detects the current value lout of the connection port  142 .     Step  304 : The detect module  140  compares the current value lout and a predetermined value, if the current value lout is less than the predetermined value, operation proceeds to step  306 ; otherwise, operation proceeds to step  300 .     Step  306 : The detect module  140  generates a control signal Sc to switch off the output module  110 .     Step  308 : Activate the function of hot-plug-and-play.        
 
         [0031]     The output module  110  may generate an output signal of a specific voltage value V when it processes a signal (step  300 ). The detect unit  150  of the detect module  140  detects the current value lout at the connection port  142  (step  302 ), and the resistor unit  160  is also used for assisting the detect unit  150  to determine the connection status between the connection port  142  and the external load. The operation is illustrated as follows.  
         [0032]     If the external load of the signal transmitter  100  is a display, when the display is connected to the connection port  142 , the output resistance of the signal transmitter  100  may be regarded as a parallel connection of a 75-ohm resistor and the resistor unit  160 , wherein the resistance value of the resistor unit  160  is 75-ohm. In other words, the current value detected by the detect unit  150  is V/37.5. Conversely, when the display is not connected to the connection port  142 , the output resistance of the signal transmitter  100  is the resistance value of the resistor unit  160 , meaning that the current value lout detected by the detect unit  150  is equal to V/75.  
         [0033]     Therefore, the detect unit  150  determines whether the connection port  142  is connected to an external load according to the current value lout. In this embodiment, the detect unit  150  compares the current value lout with a predetermined value (such as V/56.25) to determine the connection status of the connection port  142  (step  304 ). If the current value lout is smaller than the predetermined value, the display is not connected to the connection port  142  so the detect unit  150  will output the control signal Sc to stop the operation of the output module  110  so as to save power (step  306 ). When the display is not connected to the connection port  142 , the output module  110  enters power-saving mode either actively or passively.  
         [0034]     On the contrary, if the current value lout is not less than the predetermined value, the display is connected to the connection port  142  of the signal transmitter  100  through a connecting line.  
         [0035]     From the above two exemplary embodiments, whether the output module  110  operates in current mode or voltage mode, the detect module  140  is capable of determining whether the connection port  142  is connected to an external load, and thus the performance of the signal transmitter  100  is greatly improved.  
         [0036]     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.