Patent Publication Number: US-11399250-B2

Title: Digital audio array circuit

Description:
FIELD OF INVENTION 
     The present invention relates to the field of an audio circuit, and in particular, to a digital audio array circuit. 
     BACKGROUND OF INVENTION 
     Currently, there are a variety of audio transmission interfaces for digital microphones (DMICs) on the market. Common audio transmission interfaces include inter-chip audio transmission (Inter-IC Sound, I2S), time division multiplexing (TDM), and other DMIC audio transmission interfaces. 
     An I2S audio transmission protocol uses two audio chips to divide audio data into two sets of left and right channels for data transmission in a sequence. Because the two audio chips receive a word selection signal at a same time, sound wave sampling of the two audio chips can be synchronized, which is conducive to subsequent noise reduction processing and other procedures. However, if more audio chips need to be set to achieve better audio reception, the I2S audio transmission protocol must configure a processing unit or a decoder for every two audio chips to provide word selection signals, which causes costs and volume increase. 
     With a TDM audio transmission protocol, multiple audio chips can be connected in series, making it easier to form an audio chip array circuit. There is no need to set up multiple processing units or decoders like the I2S audio transmission protocol. However, each audio chip of the TDM audio transmission protocol is sampled with a time offset, which is not conducive to the subsequent processing of the signal by noise reduction algorithms. 
     TECHNICAL SOLUTION 
     In order to solve the above technical problem, an objective of the present invention is to provide a digital audio array circuit to solve the time offset problem of TDM audio sampling. 
     In order to achieve the above objective, the present invention provides a digital audio array circuit comprising at least two digital audio units and a system master unit. Each of the digital audio units is adapted to convert a received sound wave into a digital audio signal, and each of the digital audio units comprises a left/right channel configuration input terminal. The system master unit is connected to the at least two digital audio units and configured to control the at least two digital audio units and to receive the digital audio signals of the at least two digital audio units. Wherein the system master unit is connected to the at least two digital audio units in time division multiplexing, and the left/right channel configuration input terminal of each of the digital audio units is configured to receive a same synchronization signal. 
     In the digital audio array circuit of an embodiment of the present invention, further comprises a synchronization signal line, wherein the system master unit further comprises a synchronization signal output terminal, and the synchronization signal line is electrically connected to the synchronization signal output terminal and the left/right channel configuration input terminal of each of the digital audio units. 
     In the digital audio array circuit of the embodiment of the present invention, wherein the system master unit further comprises a word selection signal terminal, and each of the digital audio units comprises a word selection signal input terminal and a word selection signal output terminal. 
     In the digital audio array circuit of the embodiment of the present invention, wherein the word selection signal terminal of the system master unit is electrically connected to the word selection signal input terminal of one of the digital audio units, and the word selection signal output terminal of the digital audio unit is electrically connected to the word selection signal input terminal of another one of the digital audio units. 
     In the digital audio array circuit of the embodiment of the present invention, wherein each of the digital audio units comprises a program to recognize whether a signal received by the left/right channel configuration input terminal is the synchronization signal. 
     In the digital audio array circuit of the embodiment of the present invention, wherein if each of the digital audio units recognizes that the signal received by the left/right channel configuration input terminal is the synchronous signal, each of the digital audio units performs sound wave sampling synchronously; if not, each of the digital audio units performs sound wave sampling according to the signal received by its word selection signal input terminal 
     In the digital audio array circuit of the embodiment of the present invention, wherein the synchronization signal output terminal is a word selection signal terminal of the system master unit, and each of the digital audio units comprises a word selection signal input terminal and a word selection signal output terminal. 
     In the digital audio array circuit of the embodiment of the present invention, wherein the word selection signal terminal of the system master unit is electrically connected to the word selection signal input terminal of one of the digital audio units, the word selection signal output terminal of the digital audio unit is electrically connected to the word selection signal input terminal of another one of the digital audio units, and the synchronization signal line is electrically connected to the word selection signal terminal and the left/right channel configuration input terminal of each of the digital audio units. 
     In the digital audio array circuit of the embodiment of the present invention, wherein each of the digital audio units comprises a program to recognize whether a signal received by the left/right channel configuration input terminal is the synchronization signal. 
     In the digital audio array circuit of the embodiment of the present invention, wherein if each of the digital audio units recognizes that the signal received by the left/right channel configuration input terminal is the synchronous signal, each of the digital audio units performs sound wave sampling synchronously; if not, each of the digital audio units performs sound wave sampling according to the signal received by its word selection signal input terminal. 
     In the digital audio array circuit of the embodiment of the present invention, the left/right channel configuration input terminal of each of the digital audio units is configured to receive the same synchronization signal, and if each of the digital audio units recognizes that the signal received by the left/right channel configuration input terminal is the synchronous signal, each of the digital audio units performs sound wave sampling synchronously, which can reduce costs and circuit volume, and solve the time offset problem of TDM audio sampling. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic structural view of a digital audio array circuit according to an embodiment of the present invention. 
         FIG. 2  is a schematic view of signal timing of the digital audio array circuit according to the embodiment of the present invention. 
         FIG. 3  is a flow chart of steps of identifying a synchronization signal according to the embodiment of the present invention. 
         FIG. 4  is a schematic structural view of a digital audio array circuit according to another embodiment of the present invention. 
         FIG. 5  is a schematic view of signal timing of the digital audio array circuit according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In order to make the above and other objectives, features, and advantages of the present invention more obvious and understandable, the following will specifically cite the preferred embodiments of the present invention, together with the accompanying drawings, and describe in detail as follows. Further, directional terms, such as upper, lower, top, bottom, front, rear, left, right, inner, outer, side, around, central, horizontal, vertical, axial, radial, uppermost, or lowermost, mentioned in the present invention are only for reference. Therefore, the directional terms are used for describing and understanding rather than limiting the present invention. 
     Referring to  FIG. 1 , the present invention provides a digital audio array circuit  100 , which comprises at least two digital audio units  20 ,  22  and a system master unit SMU. Each of the digital audio units is adapted to convert a received sound wave into a digital audio signal, and each of the digital audio units comprises a left/right channel configuration input terminal LR. The system master unit SMU is connected to the at least two digital audio units  20 ,  22  and is configured to control the at least two digital audio units  20 ,  22  and to receive the digital audio signals of the at least two digital audio units  20 ,  22 . Wherein, the system master unit SMU is connected to the at least two digital audio units in time division multiplexing, and the left/right channel configuration input terminal LR of each of the digital audio units is configured to receive a same synchronization signal. 
     Specifically, each of the digital audio units further comprises an audio signal output terminal SD for transmitting the digital audio signal back to the system master unit SMU, a transmission method is, for example, in time division multiplexing (TDM) mode. 
     The digital audio array circuit  100  of an embodiment of the present invention further comprises a synchronization signal line  10 . Wherein, the system master unit SMU further comprises a synchronization signal output terminal SYN, and the synchronization signal line  10  is electrically connected to the synchronization signal output terminal SYN and the left/right channel configuration input terminal LR of each of the digital audio units. 
     Specifically, the digital audio units  20 ,  22  can be TDM protocol audio chips, which comprise sound wave sensing components  30 ,  32 , sampling components, analog-digital components (not shown), etc., to convert the received sound wave into digital audio signal. A number of the digital audio units range from 2 to 16. 
     Referring to  FIG. 1 , in the digital audio array circuit  100  of the embodiment of the present invention, the system master unit SMU further comprises a word selection signal terminal WSS, and each of the digital audio units comprises a word selection signal input terminal WS and a word selection signal output terminal WSO. 
     In the digital audio array circuit of the embodiment of the present invention, the word selection signal terminal WSS of the system master unit SMU is electrically connected to the word selection signal input terminal WS of one of the digital audio units  20 , and the word selection signal output terminal WSO of the digital audio unit  20  is electrically connected to the word selection signal input terminal WS of another one of the digital audio units  22 . 
     Referring to  FIG. 2 , specifically, a signal in which four digital audio units are connected in series is taken as an example. The system master unit will provide a clock signal SCK for each digital audio unit, and the synchronization signal is SYNC. A word selection signal of a first digital audio unit is WS 1 , and a sampling clock signal of pulse code modulation (PCM) is PCM CK 1 . A word selection signal of a second digital audio unit is WS 2 , and a sampling clock signal of PCM is PCM CK 2 . A word selection signal of a third digital audio unit is WS 3 , and a sampling clock signal of PCM is PCM CK 3 . A word selection signal of a fourth digital audio unit is WS 4 , and a sampling clock signal of PCM is PCM CK 4 . It can be seen from  FIG. 2  that the word selection signals of different digital audio units have a time offset because the word selection signals are transmitted from one digital audio unit to another digital audio unit in order. If the sampling clock signal is triggered according to the word selection signal, there will be a problem of sampling time offset. As shown in  FIG. 2 , the present invention additionally disposes a synchronization signal SYNC to synchronize the sampling clock signals PCM CK 1  to PCM CK 4 . Specifically, when the digital audio unit receives the first pulse of the synchronization signal SYNC, it starts a state machine. When the digital audio unit receives the second pulse of the synchronization signal SYNC, it synchronously starts the sampling clock signals PCM CK 1  to PCM CK 4 . 
     Specifically, after the audio signal output terminal SD of each of the digital audio units receives a pulse signal at the word selection signal input terminal WS of the digital audio unit, it transmits the digital audio signal back to the system master unit SMU, and the transmission method is, for example, in TDM mode. 
     In the digital audio array circuit of the embodiment of the present invention, each of the digital audio units comprises a program to recognize whether a signal received by the left/right channel configuration input terminal is the synchronization signal. Specifically, when the signal received by the left/right channel configuration input terminal is high, it means that the digital audio unit is set to a right channel. When the signal received by the left/right channel configuration input terminal is low, it means that the digital audio unit is set to a left channel. Or when the signal received by the left/right channel configuration input terminal is high, it means that the digital audio unit is set to the left channel. When the signal received by the left/right channel configuration input terminal is low, it means that the digital audio unit is set to a right channel. The present invention is not limited thereof. 
     In the digital audio array circuit of the embodiment of the present invention, if each of the digital audio units recognizes that the signal received by the left/right channel configuration input terminal is the synchronous signal, each of the digital audio units performs sound wave sampling synchronously; if not, each of the digital audio units performs sound wave sampling according to the signal received by its word selection signal input terminal. Specifically, if the signal received by the left/right channel configuration input terminal is the pulse signal, an identification procedure of the digital audio unit will start to perform a synchronization operation of the sampling clock signal PCM CK. 
     Specifically, referring to  FIG. 3 , steps of identifying the synchronization signal include: Step S 10 : Reset the digital audio units; Step S 20 : Detect the signal from the left/right channel configuration input terminal; Step S 30 : Determine whether the signal is the pulse signal; If the signal is the pulse signal, perform step S 40 : Start the state machine and synchronize the sampling clock signals PCM CK of all digital audio units. If not, perform step S 50 : Determine the digital audio channel according to a signal level of the left/right channel configuration input terminal. 
     Referring to  FIG. 4 , in a digital audio array circuit  100 ′ of an embodiment of the present invention, the synchronization signal output terminal is a word selection signal terminal WSS′ of a system master unit SMU′, and each of the digital audio units comprises a word selection signal input terminal WS and a word selection signal output terminal WSO. 
     In the digital audio array circuit  100 ′ of the embodiment of the present invention, the word selection signal terminal WSS′ of the system master unit SMU′ is electrically connected to the word selection signal input terminal WS of one of the digital audio units  20 , a word selection signal output terminal WSO of the digital audio unit  20  is electrically connected to a word selection signal input terminal WS of another one of the digital audio units  22 , and a synchronization signal line  10 ′ is electrically connected to the word selection signal terminal WSS′ and the left/right channel configuration input terminal LR of each of the digital audio units. 
     Referring to  FIG. 5 , specifically, a signal in which four digital audio units are connected in series is taken as an example. The system master unit will provide a clock signal SCK for each digital audio unit, and provide a word selection signal WS 1  for a first digital audio unit. Meanwhile, the word selection signal WS 1  is also used as the synchronization signal for all digital audio units. A word selection signal of the first digital audio unit is WS 1 , and a sampling clock signal of PCM is PCM CK 1 . A word selection signal of a second digital audio unit is WS 2 , and a sampling clock signal of PCM is PCM CK 2 . A word selection signal of a third digital audio unit is WS 3 , and a sampling clock signal of PCM is PCM CK 3 . A word selection signal of a fourth digital audio unit is WS 4 , and a sampling clock signal of PCM is PCM CK 4 . It can be seen from  FIG. 5  that the word selection signals of different digital audio units have a time offset because the word selection signals are transmitted from one digital audio unit to another digital audio unit in order. If the sampling clock signal is triggered according to the word selection signal, there will be a problem of sampling time offset. As shown in  FIG. 5 , the present invention uses the synchronization signal line  10 ′ to provide the word selection signal WS 1  to the left/right channel configuration input terminal LR of all audio units as the synchronization signal of all digital audio units, which can synchronize the sampling clock signals PCM CK 1  to PCM CK 4 . Specifically, when the digital audio unit receives the first pulse of the word selection signal WS 1 , it starts a state machine. When the digital audio unit receives the second pulse of the word selection signal WS 1 , it synchronously starts the sampling clock signals PCM CK 1  to PCM CK 4 . 
     In the digital audio array circuit of the embodiment of the present invention, wherein each of the digital audio units comprises a program to recognize whether a signal received by the left/right channel configuration input terminal is the synchronization signal. Specifically, steps of identifying the synchronization signal are similar to the above-mentioned embodiment. Please refer to  FIG. 3  and the above description, and the steps will not be repeated here. 
     In the digital audio array circuit of the embodiment of the present invention, the left/right channel configuration input terminal of each of the digital audio units is configured to receive the same synchronization signal, and if each of the digital audio units recognizes that the signal received by the left/right channel configuration input terminal is the synchronous signal, each of the digital audio units performs sound wave sampling synchronously, which can reduce costs and circuit volume, and solve the time offset problem of TDM audio sampling. 
     Although the present invention has been disclosed in preferred embodiments, it is not intended to limit the present invention. People skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of the claims. 
     REFERENCE NUMERALS 
       10 ,  10 ′ synchronization signal line 
       20  digital audio unit 
       22  digital audio unit 
       30  sound wave sensing component 
       32  sound wave sensing component 
       100 ,  100 ′ digital audio array circuit 
     SMU, SMU′ system master unit 
     SYN synchronization signal output terminal 
     LR left/right channel configuration input terminal 
     SD audio signal output terminal 
     WSS, WSS′ word selection signal terminal 
     WS word selection signal input terminal 
     WSO word selection signal output terminal 
     SCK clock signal 
     SYNC synchronization signal 
     WS 1 , WS 2 , WS 3 , WS 4  word selection signal 
     PCM CK 1 , PCM CK 2 , PCM CK 3 , PCM CK 4  sampling clock signal 
     S 10 -S 50  steps