Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Divisional of co-pending application Ser. No. 11/755,043, filed on May 30, 2007, and for which priority is claimed under 35 U.S.C. §120, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to audio interface, and in particular to an audio interface device and method to selectively connect a three-wire analog or digital microphone through a three-wire analog audio jack connector. 
     2. Description of the Related Art 
     An analog microphone has a three-wire audio plug, requiring a three-wire (or three-contact) audio jack connector, and a digital microphone generally has a four-wire audio plug, requiring a four-wire (or four-contact) audio jack connector. Conventionally, both the three-wire audio jack connector and the four-wire audio jack connector are simultaneously provided to an electronic system to meet requirements of either analog or digital microphone. Such configuration of audio jack connectors inevitably increases dimensions and production costs of the electronic system. 
     Accordingly, it is desirable to provide an audio interface requiring only a single connector for both analog and digital microphones. 
     BRIEF SUMMARY OF INVENTION 
     An exemplary embodiment of the invention is directed to an audio interface for three-wire microphone. The audio interface comprises an audio jack connector having first to third contacts electronically connected with the three-wire microphone plugged thereinto; and an audio processing device, detecting a type of the three-wire microphone plugged into the audio jack connector, outputting a clock signal to the three-wire microphone and receiving a digital audio signal from the three-wire microphone when the microphone is digital; or receiving analog audio signals from the three-wire microphone when the microphone is analog. 
     Further provided is a three-wire digital microphone for the disclosed audio interface. The three-wire digital microphone comprises a digital microphone circuit having a power terminal to receive a power signal, a clock terminal to receive the clock signal from the audio interface, a data terminal and a ground terminal; and a conversion device to convert the clock signal from the audio interface into the power signal for the power terminal. It is noted that the digital microphone circuit is activated by the power signal and the clock signal to output the digital audio signal through the data terminal to the second contact of the audio jack connector plugged into by the three-wire digital microphone. 
     Also provided is an interface method for a three-wire microphone. The interface method comprises providing an audio jack connector with first to third contacts electronically connected with the three-wire microphone plugged thereinto; detecting a type of the three-wire microphone plugged into the audio jack connector; and outputting a clock signal to the three-wire microphone and receiving a digital audio signal from the three-wire microphone when the microphone is digital, or receiving analog audio signals from the three-wire microphone when the microphone is analog. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIGS. 1 and 2  show an audio interface  100  for a three-wire microphone, according to a first exemplary embodiment of the invention. 
         FIG. 3  is a flowchart of an audio interfacing method according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIGS. 1 and 2  show an audio interface  100  for a three-wire microphone, according to an embodiment of the invention. In  FIG. 1 , the three-wire microphone  130  is a digital microphone. In  FIG. 2  the three-wire microphone  150  is an analog microphone. 
     The audio interface  100  comprises an audio jack connector  102 , an audio processing device  104  and a bias device  106 . The audio jack connector  102  has first to third contacts  102   a ,  102   b  and  102   c  electronically connected with the three-wire microphone ( 130  or  150 ) plugged thereinto and the third contact  102   c  is connected to a reference ground. The audio jack connector  102  may be an analog audio jack connector of three wires (contacts). 
     In addition to receiving signals from the three-wire microphone  130  or  150 , the audio processing device  104  also detects the type of the three-wire microphone plugged into the audio jack connector  102 , and operates in response thereto. Referring to  FIG. 1 , when the microphone is digital, the audio processing device  104  outputs a clock signal CLK to the three-wire digital microphone  130 , then receives a digital audio signal DATA from the three-wire digital microphone  130 . Referring to  FIG. 2 , when the microphone is analog, the audio processing device  104  receives analog audio signals from the three-wire analog microphone  150  and drives the bias device  106  to bias the first and second contacts  102   a  and  102   b.    
     The audio processing device  104  has a first terminal T 1  connected to the first contact  102   a  to output the clock signal CLK, a second terminal T 2  connected to the second contact  102   b  to receive the digital audio signal DATA, a third terminal T 3  coupled to the first contact  102   a  through capacitor C 1  to receive a left-channel signal L_ch of the analog audio signals, and a fourth terminal T 4  coupled to the second contact  102   b  through capacitor C 2  to receive a right-channel signal R_ch of the analog audio signals. 
     When the three-wire digital microphone  130 , is plugged into the audio jack connector  102 , the audio processing device  104  outputs a clock signal CLK from the first terminal T 1  to activate the three-wire microphone  130  and subsequently receives a digital audio signal DATA from the three-wire digital microphone  130  through the second contact  102   b  to a second terminal T 2 . The audio processing device  104  further disables the bias device  106 . 
     In  FIG. 2 , the three-wire analog microphone  150  may comprise an analog microphone circuit  152  and a plug unit  134  as depicted in  FIG. 1 . The analog microphone circuit  152  comprises a microphone unit  152   a  and an analog microphone unit  152   b  to convert the analog audio signals from the microphone unit  152   a  to the right-channel and left-channel signals R_ch and L_ch. When the three-wire analog microphone  150  is plugged into the audio jack connector  102 , the audio processing device  104  merely receives the analog audio signals of the left-channel signal L_ch and right-channel signal R_ch from the three-wire analog microphone  150  through the first and second contacts  102   a  and  102   b  to the third and fourth terminals T 3  and T 4  respectively. The audio processing device  104  further drives the bias device  106  to bias the first and second contacts  102   a  and  102   b . Also, the audio processing device  104  disables the first and second terminals T 1  and T 2 , for example by setting T 1  and T 2  to high impedance states. 
     An exemplary embodiment of a three-wire digital microphone applicable with the disclosed audio interface is also provided. Referring to  FIG. 1 , the three-wire digital microphone  130  comprises a microphone unit  132  and a plug unit  134 . The microphone unit  132  comprises a microphone  132   a , a digital microphone circuit  132   b  to convert an analog audio signal from the microphone  132   a  into the digital audio signal DATA, and a conversion device  132   c  to convert the clock signal CLK from the audio interface  100  into a power signal SP for the digital microphone circuit  132   b.    
     The conversion device  132   c  such as a rectifier receives and rectifies the clock signal CLK to generate a DC voltage as the power signal SP. The rectifier can be implemented by half-bridge, full-bridge rectifiers and the likes which can convert AC signal to DC signal. 
     The digital microphone circuit  132   b  such as an analog-to-digital converter (ADC) has a power terminal to receive the power signal SP, a clock terminal to receive the clock signal CLK from the audio interface  100 , a data terminal to output the digital audio signal DATA and a ground terminal connected to reference ground. The digital microphone circuit  132   b  is activated by the power signal SP and the clock signal CLK to output the digital audio signal DATA through the data terminal to the second contact  102   b  of the audio jack connector  102 . 
     The plug unit  134  is a three-wire plug with a tip portion  134   a  connected to the clock terminal C, a ring portion  134   b  connected to the data terminal D and a sleeve portion  134   c  connected to the ground terminal G. The tip, ring and sleeve portions  134   a  to  134   c  respectively are electrically connected to the first, second and third contacts  102   a  to  102   c  of the audio jack connector  102  when the three-wire digital microphone  130  is plugged into the audio interface  100 . 
     As shown in  FIGS. 1 and 2 , the bias device may be implemented by transistors M 1  and M 2  and resistors R 1  and R 2 , but is not limited thereto. The audio processing device  104  may output a logic control signal SC signal to control the bias device. For example, the audio processing device  104  may output the control signal SC with logic “High” to turn on the transistors M 1  and M 2  (i.e., enables the bias device  106 ) such that bias voltage Vb is provided to the first and second terminals  102   a  and  102   b  when the three-wire microphone plugged into the audio interface  100  is analog type. Otherwise, the audio processing device  104  outputs the control signal SC with logic “Low” to turn off the transistors M 1  and M 2  thereby turning off the transistors M 1  and M 2  and disabling the bias device  106 . 
     To detect type of the three-wire microphone plugged into the audio interface  100 , the audio processing device  104  may first assume the microphone is digital, then output the clock signal CLK to the three-wire microphone and disables the bias device  106 . Then, the audio processing device  104  awaits response of the digital audio signal DATA from the three-wire microphone. If the microphone is digital, the audio processing device  104  receives response of the digital audio signal DATA and functions accordingly. Otherwise, the audio processing device  104 , not receiving an appropriate response of the digital audio signal DATA, enables the bias device  106  and sets the first and second terminals T 1  and T 2  to high impedance states, thereby receiving and processing analog audio signals form the three-wire analog microphone. It is noted that the type detection as described above is proposed as an example and the disclosure is not limited thereto. 
       FIG. 3  is a flowchart showing an audio interface method applying the disclosed audio interface, in which an audio jack connector is first provided to electronically connect with a three-wire microphone plugged thereinto, and further a three-wire digital microphone is configured to comprise a digital microphone circuit and a conversion device (Step S 1 ). The type of the three-wire microphone plugged into the audio jack connector is determined (step S 2 ). Finally, a clock signal is output to the three-wire microphone and a digital audio signal outputted from the three-wire microphone is received when the microphone is digital, or analog audio signals outputted from the three-wire microphone are received when the microphone is analog (Step S 3 ). 
     In Step S 1 , the digital microphone circuit of the three-wire digital microphone comprises a power terminal to receive a power signal, a clock terminal to receive the clock signal from the audio interface, a data terminal and a ground terminal, activated by the power signal and the clock signal to output the digital audio signal through the data terminal to the second contact of the audio jack connector into which the three-wire digital microphone is connected. The three-wire digital microphone is also configured to comprise a three-wire plug with a tip portion connected to the clock terminal, a ring portion connected to the data terminal and a sleeve portion connected to the ground terminal. In addition, the conversion device converts the clock signal from the audio interface into the power signal for the power terminal. 
     The audio interface disclosed can use a common audio jack connector for plugging into a three-wire analog microphone or a three-wire digital microphone, and thus any electronic system such as notebook computer, cell phone, handheld devices, portable communication apparatus or other can utilize the audio interface to reduce dimension and production costs. Also, the three-wire digital microphone according to the disclosure described above has a simpler configuration than conventional four-wire digital microphone. 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Technology Category: 5