Abstract:
A signal processing circuit with a pressure-sensitive sensor array includes a pressure-sensitive sensor array with M rows and N columns, and an excitation source adapted for outputting positive and negative excitation voltages, wherein: the positive output terminals of the sensing units at a same row of the pressure-sensitive sensor array are connected with each other and act as an output of the row; the negative output terminals of the sensing units at a same column of the pressure-sensitive sensor array are connected with each other and act as an output of the column; so that the whole pressure-sensitive sensor array has a positive excitation input end, a negative excitation input end, M row output signals and N column output signals. The signal processing circuit and method are capable of significantly decreasing an amount of output signal wires of the sensor, reducing connection areas, and improving reliability.

Description:
CROSS REFERENCE OF RELATED APPLICATION 
       [0001]    The present invention claims priority under 35 U.S.C. 119(a-d) to CN 201610006038.9, filed Jan. 1, 2016. 
       BACKGROUND OF THE PRESENT INVENTION 
       [0002]    Field of Invention 
         [0003]    The present invention relates to the field of signal processing, and more particularly to a signal processing circuit and method with a pressure-sensitive sensor array. 
         [0004]    Description of Related Arts 
         [0005]    The pressure-sensitive sensor is adapted for converting the externally applied pressure into electrical signals. It comprises resistive pressure-sensitive sensor, capacitive pressure-sensitive sensor and piezoelectric pressure-sensitive sensor. The resistive sensor is made from early metal sheet electric resistance strain gauges to existing composite materials and nano-materials (graphene). Correspondingly, the size becomes smaller and smaller. Therefore, the scope of application of the pressure-sensitive sensor is gradually expanded. 
         [0006]    For example, the touch key, comprising the conventional pressure-sensitive sensor made from composite materials, is applied to household electrical appliances and other fields, for replacing traditional mechanical key. It has some advantages such as long service life, good looking appearance, and multiple functions able to be realized. Generally, in order to obtain excellent signal quality, the pressure-sensitive sensor is in a bridge form on electrical properties, so as to convert the pressure signal to the differentially electrical signal. However, every bridge has a corresponding differential signal pair, so that for manufacturing a large press key array, connection wires of the signals become more. For example, the 4×3 keyboard has 24 signal wires and 2 excitation signals, so that the wire area is increased, which makes against reducing the product size, reduces reliability, and simultaneously needs subsequent signal processing chips to increase input channels, thereby increasing manufacturing cost. 
         [0007]    For example, Chinese Patent CN 200710087168.0 disclosed a method for constructing a fingerprint image input apparatus through a pressure-sensitive sensor, which comprises steps of: firstly respectively horizontally and vertically arranging multiple pressure-sensitive sensors, whose contact surface maximum radius is less than fingerprint single gully width, on an insulation board whose area is larger than a singer area, obtaining an array formed by the multiple pressure-sensitive sensors, wherein: every sensor produces a strongly electrical signal while being trigger by pressure, the sensors without pressure do not produce electrical signals; when a finger is placed on the sensor array, the protruding part of the finger fingerprint will trigger the sensor, the sensor produces the strongly electrical signals. Because every sensor in the sensor array represents one pixel point in a fingerprint image, the strong and weak signals produced by the sensor array form a binaryzation fingerprint image. In spite of resolving problems through the pressure-sensitive sensor array, the method do not treat the signal connection wires, so that the signal connection wires adopted by the pressure-sensitive sensor array are still more, thus the wire area is larger, which makes against reducing production size and simultaneously decreasing reliability of the wires, and increasing manufacturing cost. 
       SUMMARY OF THE PRESENT INVENTION 
       [0008]    An object of the present invention is to provide a signal processing circuit and method with a pressure-sensitive sensor array for resolving the above problems, which are capable of effectively decreasing an amount of signal wires, improving reliability and reducing cost. 
         [0009]    Another object of the present invention is to provide a signal processing circuit and method with a pressure-sensitive sensor array, which are capable of significantly decreasing an amount of output signal wires of the sensors, reducing connection areas, inputting channels of subsequent chips, conversion times from analog signals to digital signals, and manufacturing cost and volume of the whole system. 
         [0010]    Accordingly, in order to accomplish the above objects, technical solutions of the present invention are as follows. 
         [0011]    A signal processing circuit with a pressure-sensitive sensor array comprises: a pressure-sensitive sensor array with M rows and N columns (wherein at least one of M and N is larger than one), and an excitation source adapted for outputting positive and negative excitation voltages, wherein: 
         [0012]    the pressure-sensitive sensor array comprises M×N sensing units which are connected with each other through a bridge manner, wherein every sensing unit has a positive excitation input terminal, a negative excitation input terminal, a positive output terminal and a negative output terminal, the positive excitation input terminal of every sensing unit is connected with the positive excitation voltage, the negative excitation input terminal of every sensing unit is connected with the negative excitation voltage; 
         [0013]    the positive output terminals of the sensing units at a same row of the pressure-sensitive sensor array are connected with each other and act as an output of the row; 
         [0014]    the negative output terminals of the sensing units at a same column of the pressure-sensitive sensor array are connected with each other and act as an output of the column; 
         [0015]    the whole pressure-sensitive sensor array has a positive excitation input end, a negative excitation input end, M row output signals and N column output signals. 
         [0016]    The signal processing circuit further comprises an analog-digital convert circuit which comprises at least one analog-digital converter (ADC) for converting the row and column output signals of the sensor array to digital signals. 
         [0017]    The analog-digital convert circuit further comprises an instrument amplifier located before the analog-digital converter for amplifying the row and column output signals of the sensor array and then sending to the analog-digital converter for conversion. 
         [0018]    Any one of the row output signals and any one of the column output signals form a differential signal pair to be sent to the analog-digital converter for conversion. 
         [0019]    The signal processing circuit further comprises a pseudo half-bridge circuit which has a positive excitation input end and a negative excitation input end respectively connected with the positive and negative excitation voltages; wherein the pseudo half-bridge circuit has an output signal which is determined by the positive and negative excitation voltages of the excitation source and does not change with pressure; any one of the row and column output signals and the output signal of the pseudo half-bridge circuit form a signal pair to be sent to the analog-digital convert circuit for conversion. 
         [0020]    The present invention also provides a signal processing method of a signal processing circuit with a pressure-sensitive sensor array, comprising steps of: 
         [0021]    (1) combining M row output signals with N column output signals to form M×N differential signal pairs; 
         [0022]    (2) respectively sending the M×N differential signal pairs to an analog-digital convert circuit for conversion, and obtaining digital signals, wherein the conversion is made for M×N times; 
         [0023]    (3) arranging the digital signals in sequence; and 
         [0024]    (4) taking a maximum of the digital signals as a pressure signal which is applied to the pressure-sensitive sensor array. 
         [0025]    When M=1 or N=1, an average value, of former two digital signals of the digital signals arranged from big to small, is taken as the pressure signal which is applied to the pressure-sensitive sensor array; when M&gt;1 and N&gt;1, an average value, of former four digital signals of the digital signals arranged from big to small, is taken as the pressure signal which is applied to the pressure-sensitive sensor array. 
         [0026]    The average value is multiplied by a preset coefficient which is larger than one to obtain the pressure signal applied to the pressure-sensitive sensor array; and the preset coefficient is related to a structure of the sensor and characteristics of a deformation body. 
         [0027]    Furthermore, the present invention also provides a signal processing method of a signal processing circuit with a pressure-sensitive sensor array, comprising steps of: 
         [0028]    (1) respectively combining M row output signals and N column output signals with an output signal of the pseudo half-bridge circuit to form multiple signal pairs; 
         [0029]    (2) respectively converting the multiple signal pairs (assuming the output signal of the pseudo half-bridge circuit as a negative input) to an analog-digital convert circuit for conversion, and obtaining digital signal, wherein the conversion is made for M+N times; 
         [0030]    (3) respectively arranging the digital signals in sequence according to a row output signal combination and a column output signal combination; and 
         [0031]    (4) respectively taking a maximum of the digital signals in the row output signal combination and a maximum of digital signals in the column output signal combination, and taking a difference value between the two maximums as a pressure signal which is applied to the pressure-sensitive sensor array. 
         [0032]    When M=1 or N=1, an average value, of former two digital signals of the digital signals in the row (when N=1) or column (when M=1) output signal combination arranged from big to small, is taken as the pressure signal which is applied to the pressure-sensitive sensor array; when M&gt;1 and N&gt;1, the digital signals in the column output signal combination and the row output signal combination are respectively arranged from big to small, and then the former two digital signals of the digital signals in the row output signal combination arranged from big to small, and the former two digital signals of the digital signals in the column output signal combination arranged from big to small are taken, these four digital signals are subtracted from each other, so that four subtracted values are obtained, and then an average value of the four subtracted values is taken as the pressure signal which is applied to the pressure-sensitive sensor array. 
         [0033]    The average value is multiplied by a preset coefficient which is larger than one to obtain the pressure signal applied to the pressure-sensitive sensor array; and the preset coefficient is related to a structure of the sensor and characteristics of a deformation body. 
         [0034]    In spite that the row output signals are connected with the positive output terminal of the bridge of the sensing units, the column output signals are connected with the negative output terminal of the bridge of the sensing units; contrarily, the row output signals are connected with the negative output terminal of the bridge of the sensing units, the column output signals are connected with the positive output terminal of the bridge of the sensing units, which is feasible. 
         [0035]    The signal processing circuit and method with a pressure-sensitive sensor array, which are capable of significantly decreasing an amount of output signal wires of the sensor, reducing connection areas, improving reliability, reducing inputting channels of subsequent chips, conversion times from analog signals to digital signals, and manufacturing cost and volume of the whole system. 
         [0036]    These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a circuit diagram of a conventional signal processing circuit with a pressure-sensitive sensor array. 
           [0038]      FIG. 2  is a circuit diagram of a signal processing circuit with a pressure-sensitive sensor array according to a first preferred embodiment of the present invention. 
           [0039]      FIG. 3  is a circuit diagram of an analog-digital convert circuit  204  in the signal processing circuit shown in  FIG. 2 . 
           [0040]      FIG. 4  is a flow chart of the conventional signal processing circuit in  FIG. 2 . 
           [0041]      FIG. 5  is a circuit diagram of a signal processing circuit with a pressure-sensitive sensor array according to a second preferred embodiment of the present invention. 
           [0042]      FIG. 6  is a circuit diagram of an analog-digital convert circuit  305  in the signal processing circuit shown in  FIG. 5 . 
           [0043]      FIG. 7  is a flow chart of the signal processing circuit shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0044]    To more clearly understand objectives, technical solutions and advantages, the present invention is further explained in detail accompanying with drawings and embodiments as follows. It should be understood that the specific embodiments described herein are merely for illustrating the present invention and are not intended to limit the present invention. 
         [0045]    Referring to  FIG. 1 , a common signal processing circuit  100  with a pressure-sensitive sensor array is illustrated. There are two pressure-sensitive sensing units  101  and  102  which have the same structure. Take the pressure-sensitive sensing unit  101  for example, it has a bridge circuit and comprises two resistive sensors RS 100  and RS 103 , and two resistors RS 101  and RS 102 , wherein: one end of the RS 100  is connected with an excitation voltage positive terminal VREF, the other end of the RS 100  is connected with one end of the RS 102 , the other end of the RS 102  is connected with an excitation voltage negative terminal GND; one end of the RS 101  is connected with the excitation voltage positive terminal VREF, the other end of the RS 101  is connected with one end of the RS 103 , the other end of the RS 103  is connected with the excitation voltage negative terminal GND. A common node of the RS 101  and the RS 103  outputs a positive voltage signal VP 10 , and a common node of the RS 100  and the RS 102  outputs a negative voltage signal VN 10 . The VP 10  and VN 10  form a differential signal pair and then are sent to an analog-digital convert circuit  103  for conversion. Furthermore, the pressure-sensitive sensing unit  102  outputs a differential signal pair formed by VP 11  and VN 11  to the analog-digital convert circuit  103 . 
         [0046]    It is obvious that the differential signal pairs outputted by the sensing units are respectively sent to the analog-digital convert circuit for conversion. One sensing unit has a differential signal pair, so that K sensing units have corresponding (2×K) signals. A signal amount is significantly increased with an increase of an amount of the sensing units. 
         [0047]    Referring to  FIG. 2 , a signal processing circuit  200  with a pressure-sensitive sensor array according to a first preferred embodiment of the present invention is illustrated, which comprises: three pressure-sensitive sensing units  201 ,  202  and  203  which define an array with 1 row and 3 columns, and an analog-digital convert circuit  204 . All of the pressure-sensitive sensing units  201 ,  202  and  203  have the same structure with the pressure-sensitive sensing unit  101 , and however, have different connection modes of positive and negative output signals from those shown in  FIG. 1 . The positive output signals of the pressure-sensitive sensing units  201 ,  202  and  203  are connected with each other for forming a voltage signal VP 2 , and the negative output signals of the pressure-sensitive sensing units  201 ,  202  and  203  are respectively VN 20 , VN 21  and VN 22 . The signals VP 2 , VN 20 , VN 21  and VN 22  are sent to the analog-digital convert circuit for conversion. 
         [0048]    Referring to  FIG. 3 , a specific structure of the analog-digital convert circuit  204  in the signal processing circuit  200  for the pressure-sensitive sensor array is illustrated, which comprises a multiplexer  2041 , an instrument amplifier  2042  and an analog-digital converter  2043 . The signal VP 2 , which is outputted by the pressure-sensitive sensing units  201 - 203  and acts as a positive input signal INP 0 , is inputted to a positive input terminal of the instrument amplifier  2042  through the multiplexer  2041 . The signals VN 20 -VN 22  which act as a negative input signal INN 0  are respectively inputted to a negative input terminal of the instrument amplifier  2042  through the multiplexer  2041 . The signals INP 0  and INN 0  are amplified by the instrument amplifier  2042  amplifies and then sent to the analog-digital converter  2043 , and the analog-digital converter  2043  converts inputted analog signals to digital signals for outputting. 
         [0049]    Referring to  FIG. 4 , a signal processing method corresponding to the signal processing circuit  200  with the pressure-sensitive sensor array is illustrated, which comprises steps of: 
         [0050]    step (S 201 ): the multiplexer  2041  combining the input signals in turn to form three differential signal pairs (VP 2 , VN 20 ), (VP 2 , VN 21 ) and (VP 2 , VN 22 ), and outputting a differential signal pair (INP 0 , INN 0 ); 
         [0051]    step (S 202 ): then sending the three differential signal pairs (VP 2 , VN 20 ), (VP 2 , VN 21 ) and (VP 2 , VN 22 ) to the instrument amplifier  2042  and the analog-digital converter  2043  in sequence, and obtaining three digital signals, namely, a first digital signal, a second digital signal, and a third digital signal, wherein when the multiplexer  2041  combines one differential signal pair, the instrument amplifier  2042  and the analog-digital converter  2043  accordingly convert the differential signal pair; the combination and conversion are divided into two steps for further explanation; 
         [0052]    step (S 203 ): arranging the converted digital signals in sequence, wherein if a pressure application point is at the pressure-sensitive sensing unit  202  and nears the pressure-sensitive sensing unit  201 , the converted digital signals are arranged, from big to small, as the second digital signal, the first digital signal and the third digital signal; 
         [0053]    step (S 204 ): averaging former two digital signals, and obtaining a digital signal mean value 0 which is capable of representing a pressure value without correction; and 
         [0054]    step (S 205 ): multiplying the digital signal mean value 0, obtained in the step (S 204 ), by a preset correction factor 1.2, and obtaining a final digital signal mean value 1 which is capable of representing a corrected pressure value. 
         [0055]    Referring to  FIG. 5 , a signal processing circuit  300  with a pressure-sensitive sensor array according to a second preferred embodiment of the present invention is illustrated, which comprises: four pressure-sensitive sensing units  301 ,  302 ,  303  and  304  which define an array with 2 rows and 2 columns, and an analog-digital convert circuit  305 . All of the pressure-sensitive sensing units  301 - 304  have the same structure with the pressure-sensitive sensing unit  101 , and however, have different connection modes of positive and negative output signals from those shown in  FIG. 1 . The positive output signals of the pressure-sensitive sensing units  301  and  303  at the first row of the array are connected with each other for forming a row output signal VROW 0 ; the positive output signals of the pressure-sensitive sensing units  302  and  304  at the second row of the array are connected with each other for forming a row output signal VROW 1 ; the negative output signals of the pressure-sensitive sensing units  301  and  302  at the first column of the array are connected with each other for forming a column output signal VCOL 0 ; the positive output signals of the pressure-sensitive sensing units  303  and  304  at the second column of the array are connected with each other for forming a column output signal VCOL 1 . 
         [0056]    Furthermore, a pseudo half-bridge circuit comprises resistors RS 360  and RS 361 , wherein: an upper end of the resistor RS 360  is connected with an excitation voltage positive terminal VREF, a lower end thereof is connected with an upper end of the resistor RS 361 ; a lower end of the resistor RS 361  is connected with an excitation voltage negative terminal GND. A combination point of the resistor RS 360  and the resistor RS 361  outputs a common mode voltage signal VCM 0 . 
         [0057]    The above signals VROW 0 , VROW 1 , VCOL 0  and VCOL 1  are sent to the analog-digital convert circuit  305  for analog-to-digital conversion. 
         [0058]      FIG. 6  shows a specific structure of the analog-digital convert circuit  305  in the signal processing circuit  300  with the pressure-sensitive sensor array is illustrated, which comprises a multiplexer  3051 , an instrument amplifier  3052  and an analog-digital converter  3053 . The pressure-sensitive sensing units  301 - 304  output the row output signals VROW 0  and VROW 1 , the column output signals VCOL 0  and VCOL 1 , and the common mode voltage signal VCM 0  to the multiplexer  3051 , and then the multiplexer  3051  outputs signals INP 1  and INN 1  which act as a differential signal pair to the instrument amplifier  3052  for amplifying, and then the instrument amplifier  3052  sends the amplified signals to the analog-digital converter  3053 , and then the analog-digital converter  3053  converts inputted analog signals to digital signals for outputting. 
         [0059]    Referring to  FIG. 7 , a signal processing method corresponding to the signal processing circuit  300  with the pressure-sensitive sensor array is illustrated, which comprises steps of: 
         [0060]    step (S 301 ): the multiplexer  3051  combining input signals in turn to form four differential signal pairs (VROW 0 , VCM 0 ), (VROW 1 , VCM 0 ), (VCOL 0 , VCM 0 ) and (VCOL 1 , VCM 0 ), and outputting a differential signal pair (INP 1 , INN 1 ); 
         [0061]    step (S 302 ): converting the four differential signal pairs (VROW 0 , VCM 0 ), (VROW 1 , VCM 0 ), (VCOL 0 , VCM 0 ) and (VCOL 1 , VCM 0 ) by the instrument amplifier  3052  and the analog-digital converter  3053  in sequence, and obtaining four digital signals, namely, DR 0 , DR 1 , DC 0  and DC 1 , wherein when the multiplexer  3051  combines one differential signal pair, the instrument amplifier  3052  and the analog-digital converter  3053  accordingly convert the differential signal pair; the combination and conversion are divided into two steps for further explanation; 
         [0062]    step (S 303 ): arranging the converted digital signals in sequence, wherein an arrangement result, from big to small, is DC 0 , DR 0 , DR 1  and DC 1  in sequence; 
         [0063]    step (S 304 ): averaging former four digital signals, and obtaining a digital signal mean value 2 which is capable of representing a pressure value without correction; and 
         [0064]    step (S 305 ): multiplying the digital signal mean value 2, obtained in the step (S 304 ), by a preset correction factor 1.2, and obtaining a final digital signal mean value 3 which is capable of representing a corrected pressure value applied to the pressure-sensitive sensing units  301 - 304 . 
         [0065]    The above cited sensor array is 2×2, which has not obvious improvement on connection and conversion steps, compared with conventional solutions. However, if the sensor array is 4×4, an amount of connections of the output signals of the sensor array is decreased from 32 to 8, and a conversion time is decreased from original 32 to 8, which shows a very large decrease extent. 
         [0066]    Moreover, in spite that the resistive pressure-sensitive sensors are explained in above embodiments, the structure provided by the present invention is also adapted for the capacitive and piezoelectric pressure-sensitive sensors. 
         [0067]    One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting. 
         [0068]    It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.