Patent Publication Number: US-6984990-B2

Title: Apparatus for detecting connection state between stereo earphone plug and corresponding jack of mobile communication terminal

Description:
PRIORITY 
     This application claims priority to an application entitled “APPARATUS FOR DETECTING CONNECTION STATE BETWEEN STEREO EARPHONE PLUG AND CORRESPONDING JACK OF MOBILE COMMUNICATION TERMINAL”, filed in the Korean Intellectual Property Office on Aug. 24, 2002 and assigned Serial No. 2002-50355, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal, and more particularly to an apparatus for detecting a connection state between a stereo earphone plug and a corresponding jack of a mobile communication terminal. 
     2. Description of the Related Art 
     Various methods for detecting a connection state between an earphone plug and a corresponding jack of a GSM mobile terminal are well known in the art. However, with the development of audio/video technology, the need for reproducing moving images has been rapidly increasing in recent times. Thus, stereo reproduction needs to be readily performed by such a mobile communication terminal. 
       FIG. 1  illustrates a block diagram of a general mobile communication terminal. Referring to  FIG. 1 , a mobile communication terminal includes a RF (Radio Frequency) signal processor  100 , an IF (Intermediate Frequency) signal processor  102 , a controller  104 , a storage unit  106 , a display  108 , an input unit  110 , and a voice processor  112 , which is connected to a microphone and speaker. An apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal is positioned in the voice processor  112 . The voice processor  112  transmits a signal for indicating a connection state between the earphone plug and the corresponding jack to the controller  104 . The controller  104  outputs an acoustic signal to an earphone according to the signal received from the voice processor  112 . 
       FIG. 2  illustrates a schematic diagram of a conventional apparatus for detecting a connection state between an earphone plug and a corresponding jack  200  of a mobile communication terminal. Referring to  FIG. 2 , the apparatus shifts a level of a signal entered into the controller  104  using a microphone bias and a comparator  210  in order to determine whether an earphone plug is connected to a corresponding jack of a mobile communication terminal. But, this method has a disadvantage in that it is available for only a mono signal. In other words, the above method is applicable to a mobile communication terminal whereby a voltage difference exists between an output voltage of a microphone&#39;s positive terminal (+) and the other output voltage of a microphone&#39;s negative terminal (−). Earphone jacks can be divided into a mono type as shown in  FIG. 2  and a stereo type as shown in  FIG. 3 . Table 1, below, shows the terminal layouts of conventional mono and stereo earphone jacks corresponding to conventional mono and stereo earphone plugs, respectively. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 MONO 
                 STEREO 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Terminal 1 
                 MIC− 
                 SPEAKER-LEFT 
               
               
                   
                 Terminal 2 
                 MIC+ 
                 MIC 
               
               
                   
                 Terminal 3 
                 Plug Inserting 
                 Plug Inserting 
               
               
                   
                   
                 Detection 
                 Detection 
               
               
                   
                 Terminal 4 
                 X 
                 X 
               
               
                   
                 Terminal 5 
                 SPEAKER 
                 SPEAKER-RIGHT 
               
               
                   
                 Terminal 6 
                 GROUND 
                 GROUND 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 1, a mono earphone jack has polarized terminals MIC+ (positive terminal) and MIC− (negative terminal), which create the voltage difference that the conventional apparatus uses to detect a connection state of a mono earphone plug. However, the stereo earphone jack has only an unpolarized MIC terminal. Therefore, if a user wants to implement a stereo mode in his or her mobile communication terminal, it is impossible for the above method to detect a connection state between a stereo earphone plug and a corresponding jack of such a mobile communication terminal because a stereo audio signal is a one side ended signal. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an apparatus for detecting a stereo signal without increasing the number of earphone jack terminals in a conventional apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile terminal. 
     In accordance with the present invention, the above and other objects can be accomplished by the provision of an apparatus for detecting a connection state between a stereo earphone plug and a corresponding jack of a mobile communication terminal including: an earphone jack having two terminals which are disconnected from each other when an earphone plug is inserted into the jack; a switching unit connected to one of the two terminals, and driven when the two terminals are connected to each other; a comparator connected to the switching unit, for generating a first state signal when the switching unit is driven, and generating a second state signal when the switching unit is not driven; and a controller for receiving the first or second state signal from the comparator, and determining whether the earphone plug is connected to the jack according to the first or second state signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a block diagram of a general mobile communication terminal; 
         FIG. 2  illustrates a schematic diagram of a conventional apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal; and 
         FIG. 3  illustrates a schematic diagram of an apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal in accordance with a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear. 
     An apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal in accordance with a preferred embodiment of the present invention is applicable to the mobile communication terminal shown in  FIG. 1 . Referring to  FIG. 1 , the apparatus is positioned in voice processor  112 . Voice processor  112  transmits a signal for indicating a connection state between an earphone plug and a corresponding jack of a mobile communication terminal to controller  104 . Controller  104  outputs an acoustic signal to an earphone according to the signal received from voice processor  112 . 
       FIG. 3  illustrates a schematic diagram of an apparatus for detecting a connection state between an earphone plug and a corresponding jack of a mobile communication terminal in accordance with a preferred embodiment of the present invention. 
     Referring to  FIG. 3 , the apparatus includes a four-pole stereo earphone jack  300  for use with an external earphone plug, a comparator  310  for transmitting a detected signal to the controller  104 , a plurality of resistors R 1 ˜R 5 , and an NMOSFET (NMOS Field Effect Transistor) Q 1  for performing a switching operation. 
     Operation of the apparatus shown in  FIG. 3  will hereinafter be described in the following description. 
     Firstly, provided that an earphone plug is not connected to a corresponding jack  300  of a mobile communication terminal, the apparatus operates as follows. 
     Resistors R 4  and R 5  distribute voltage. More particularly, referring to  FIG. 3 , the resistors R 4  and R 5  are used to apply a voltage to the negative terminal (−) of comparator  310 , both when NMOSFET Q 1  is turned on, and when NMOSFET Q 1  is turned off. The applied voltage equals the voltage received by the positive terminal (+) of comparator  310  when NMOSFET Q 1  is turned off, multiplied by ½. 
     In the case where the earphone plug is not inserted into the jack  300 , second and third terminals  2 ˜ 3  of the jack  300  are connected to each other such that the NMOSFET Q 1  is turned on by a pull-up resistor R 1 . Since a positive terminal (+) of comparator  310  is connected to a ground terminal through Q 1 , the comparator  310  generates a first state signal, for example, a logic low signal. That is, voice processor  112 , shown in  FIG. 1 , transmits the logic low signal generated from the comparator  310  to the controller  104 . Upon receiving the logic low signal from the voice processor  112 , the controller  104  determines that the earphone plug is not connected to the jack  300 . 
     Secondly, provided that the earphone plug is connected to the jack  300 , the apparatus operates as follows. 
     In the case where the earphone plug is inserted into the jack  300 , second and third terminals  2 ˜ 3  of the jack  300  are disconnected from each other such that the NMOSFET Q 1  is turned off by a pull-down resistor R 2 . As a result, the comparator  310  generates a second state signal, for example, a logic high signal, by a pull-up resistor R 3 . That is, voice processor  112  shown in  FIG. 1  transmits the logic high signal generated from the comparator  310  to the controller  104 . Upon receiving the logic high signal from voice processor  112 , the controller  104  determines that the earphone plug is connected to the jack  300 . Then, the controller  104  recognizing the connection state between the earphone plug and the jack  300  may generate a signal via the jack  300 . 
     Thirdly, provided that the earphone plug in such a connection state is released (i.e., disconnected) from the jack  300 , the apparatus operates as follows. 
     In the case where the earphone plug is released from the jack  300 , second and third terminals  2 ˜ 3  of the jack  300  are connected again to each other such that the NMOSFET Q 1  is turned on by the pull-up resistor R 1 . Since the positive terminal (+) of the comparator  310  is connected to a ground terminal, the comparator  310  generates a logic low signal. That is, the voice processor  112  shown in  FIG. 1  transmits the logic low signal generated from the comparator  310  to the controller  104 . Upon receiving the logic low signal from the voice processor  112 , the controller  104  determines that the earphone plug is not connected to the jack  300 . 
     As apparent from the above description, the apparatus using the NMOSFET according to the present invention detects a connection state between a stereo earphone plug and a corresponding jack of a mobile communication terminal without increasing the number of the jack&#39;s terminals. 
     Also, the apparatus makes a stereo earphone plug and a corresponding jack available for a mobile communication terminal, detects a connection signal between the earphone plug and the corresponding jack while maintaining the number of conventional four-pole terminals, and is applicable even to a single ended signal differently from the conventional apparatus applicable to a double ended signal only. 
     Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.