TWI464662B

TWI464662B - Noise cancellation circuit for capacitive touch panel

Info

Publication number: TWI464662B
Application number: TW101119244A
Authority: TW
Inventors: Su Chen Chang
Priority date: 2012-05-30
Filing date: 2012-05-30
Publication date: 2014-12-11
Also published as: TW201349064A

Description

適用於電容式觸控面板之雜訊消除電路Noise for capacitive touch panels Elimination circuit

本發明有關於雜訊消除(noise cancelation)，尤有關於一種適用於電容式觸控面板(capacitive touch panel)之雜訊消除電路。The invention relates to noise cancelation, and more particularly to a noise cancellation circuit suitable for a capacitive touch panel.

在目前電容式觸控面板普遍遇到電源雜訊(power noise)干擾的問題，變成是量產的一個門檻。In the current capacitive touch panel, the problem of power noise interference is generally encountered, which becomes a threshold for mass production.

第1圖顯示一傳統電荷轉移量測(charge transfer measurement)電路之架構圖。第1圖是美國專利公告第6452514號之圖示，該專利文獻中主要是感測(sense)電荷消除電路405中電容器Cz之電容(capacitance)，透過感測電容器Cz的電流變化，來推算電容器Cz的電容變化。Figure 1 shows an architectural diagram of a conventional charge transfer measurement circuit. Figure 1 is a diagram of U.S. Patent Publication No. 6452514, which mainly senses the capacitance of the capacitor Cz in the sense charge eliminating circuit 405, and the current through the sensing capacitor Cz to estimate the capacitor. The capacitance of Cz changes.

一般傳統電路中，感測電流會比感測電壓有更好的訊號雜訊比(signal noise ratio)，但系統的電源雜訊能會從電荷消除電路405中的電源端點或/及接地端點耦合(couple)雜訊。In a conventional circuit, the sense current has a better signal noise ratio than the sense voltage, but the power noise of the system can be from the power supply terminal or/and the ground terminal in the charge elimination circuit 405. Point coupled noise.

為解決上述電源雜訊干擾問題，因此提出本發明。In order to solve the above problem of power supply noise interference, the present invention has been proposed.

本發明之目的之一，在於提供一種雜訊消除電路，以解決習知技術中的問題。One of the objects of the present invention is to provide a noise canceling circuit to solve the problems in the prior art.

根據本發明之一實施例，係提供一種雜訊消除電路，適用於一電容式觸控面板，包含：一訊號產生器、複數個感測電路以及一處理電路。該訊號產生器，產生一電壓訊號。每一感測電路包含：一感測電容器，其第一端接收該電壓訊號；一電流感測器，其輸入端耦接該感測電容器的第二端，用以感測該感測電容器的電容值以產生一感測電流量；一第一減法器，耦接該電流感測器，用以根據本身感測電路之電流感測器的感測電流量及一鄰近感測電路之電流感測器的感測電流量之差，產生一電流差訊號；一第一電流電壓轉換器，其第一端耦接該第一減法器的輸出端，其第二端接地，用以產生一第一類比電壓訊號；以及，一第一類比數位轉換器，用以將該第一類比電壓訊號，轉換為一第一數位訊號。該處理電路係用以接收該些感測電路產生之複數個第一數位訊號，以判斷是否有觸碰發生。According to an embodiment of the present invention, a noise cancellation circuit is provided, Suitable for a capacitive touch panel, comprising: a signal generator, a plurality of sensing circuits and a processing circuit. The signal generator generates a voltage signal. Each of the sensing circuits includes: a sensing capacitor, the first end of which receives the voltage signal; and a current sensor having an input coupled to the second end of the sensing capacitor for sensing the sensing capacitor The capacitance value is used to generate a sense current amount; a first subtractor coupled to the current sensor for sensing the current amount of the current sensor of the circuit and the current sense of a proximity sensing circuit a difference between the sensed currents of the detectors generates a current difference signal; a first current-to-voltage converter having a first end coupled to the output of the first subtractor and a second end grounded to generate a first a type of ratio voltage signal; and a first analog-to-digital converter for converting the first analog voltage signal into a first digital signal. The processing circuit is configured to receive a plurality of first digital signals generated by the sensing circuits to determine whether a touch occurs.

以下之說明將舉出本發明之數個較佳的示範實施例。熟悉本領域者應可理解，本發明可採用各種可能的方式實施，並不限於下列示範之實施例或實施例中的特徵。另外，眾所知悉之細節不再重覆顯示或贅述，以避免模糊本發明之重點。The following description will set forth several preferred exemplary embodiments of the invention. It will be appreciated by those skilled in the art that the present invention may be embodied in a variety of possible ways and is not limited to the features of the following exemplary embodiments or embodiments. In addition, details are not repeatedly shown or described in detail to avoid obscuring the invention.

第2圖為本發明雜訊消除電路之第一實施例的架構示意圖。請參考第2圖，本發明雜訊消除電路20，適用於一電容式觸控面板(圖未示)，包含一訊號產生器210、複數個感測電路21~2N(N>=2)以及一微處理器250。訊號產生器210用以產生一可調整週期或/及振幅的電壓訊號ps，例如一方波(square wave)。每一感測電路(21~2N)包含一感測電容器(C_Z1 ~C_ZN )、一電流感測器(221~22N)、一減法器(231~23N)、一電流電壓轉換器(211~21N)以及一類比數位轉換器(241~24N)。其中，各感測電容器(C_Z1 ~C_ZN )具實質上相同的電容值(capacitance)。一實施例中，電流電壓轉換器可利用電容器或電阻器來實現，但本發明不以此為限，目前現有或未來發展出之各種可由電流轉換成電壓的裝置或電路均可適用。FIG. 2 is a schematic structural diagram of a first embodiment of a noise cancellation circuit according to the present invention. Referring to FIG. 2, the noise cancellation circuit 20 of the present invention is applicable to a capacitive touch panel (not shown), including a signal generator 210, a plurality of sensing circuits 21~2N (N>=2), and A microprocessor 250. The signal generator 210 is configured to generate a voltage signal ps of an adjustable period or/and amplitude, such as a square wave. Each sensing circuit (21~2N) includes a sensing capacitor (C _Z1 ~ C _ZN ), a current sensor (221 ~ 22N), a subtractor (231 ~ 23N), a current voltage converter (211 ~21N) and an analog-to-digital converter (241~24N). Wherein, each of the sensing capacitors (C _Z1 ~ C _ZN ) has substantially the same capacitance value. In one embodiment, the current-to-voltage converter can be implemented by using a capacitor or a resistor, but the invention is not limited thereto, and various devices or circuits that can be converted into a voltage by current or in the future can be applied.

所有感測電路(21~2N)的運作方式皆類似，以下僅以感測電路21為例作說明。感測電容器C_Z1 之一端接收該可控制電壓訊號ps，而該感測電容器C_Z1 的另一端耦接電流感測器221之輸入端，用以感測該感測電容器C_Z1 的電容值以產生一相對應感測電流I₁ 。減法器231的二輸入端耦接該電流感測器221及222的輸出端，用以根據本身分支21之電流感測器221的感測電流I₁ 及鄰近分支22之電流感測器222的感測電流I₂ 之電流量差，產生一電流差訊號(I₁ -I₂ )。電流電壓轉換器211之一端耦接該減法器231的輸出端，另一端則接地，使該電流差訊號(I₁ -I₂ )對電流電壓轉換器211充電。於本發明中，電流電壓轉換器211之作用是將電流訊號轉換成電壓訊號。類比數位轉換器241的輸入端耦接該電流電壓轉換器211的輸出端，用以將類比電壓訊號a1，轉換為一數位訊號b1。All of the sensing circuits (21~2N) operate in a similar manner. Hereinafter, only the sensing circuit 21 will be described as an example. One end of the sensing capacitor C _Z1 receives the controllable voltage signal ps, and the other end of the sensing capacitor C _Z1 is coupled to the input end of the current sensor 221 for sensing the capacitance value of the sensing capacitor C _Z1 . A corresponding sense current I _{1 is} generated. The two input ends of the subtractor 231 are coupled to the output ends of the current sensors 221 and 222 for sensing the current I ₁ of the current sensor 221 of the branch 21 and the current sensor 222 of the adjacent branch 22 . The current amount difference of the current I ₂ is sensed to generate a current difference signal (I ₁ -I ₂ ). One end of the current-to-voltage converter 211 is coupled to the output of the subtractor 231, and the other end is grounded to cause the current difference signal (I ₁ -I ₂ ) to charge the current-to-voltage converter 211. In the present invention, the function of the current-to-voltage converter 211 is to convert the current signal into a voltage signal. The input end of the analog-to-digital converter 241 is coupled to the output of the current-to-voltage converter 211 for converting the analog voltage signal a1 into a digital signal b1.

當手指沒有觸碰該電容式觸控面板時，每一感測電容器(C_Z1 ~C_ZN )的電容值為C₁ 、C₂ 、.....、C_N ，而每一電流感測器(221~22N)產生相對應的感測電流為I₁ 、I₂ 、I₃ .....、I_N 。當手指觸碰該電容式觸控面板時，感測電容器(C_Z1 ~C_ZN )的電容值變化為(C₁ +dC₁ )、(C₂ +dC₂ )、.....、(C_N +dC_N )，導致電流感測器(221~22N)產生之感測電流變化為(I₁ +d I₁ )、(I₂ +d I₂ )、......、(I_N +dI_N )。這可由以下公式推導而出：I=C*dv/dt，其中由於dv、dt不變，故電流量(I)的變化會正比於電容值(C)的變化。When the finger does not touch the capacitive touch panel, the capacitance values of each of the sensing capacitors (C _Z1 ~ C _ZN ) are C ₁ , C ₂ , . . . , C _N , and each current sensing The corresponding sensing currents generated by the devices (221~22N) are I ₁ , I ₂ , I ₃ . . . , I _N . When the finger touches the capacitive touch panel, the capacitance values of the sensing capacitors (C _Z1 ~ C _ZN ) change to (C ₁ + dC ₁ ), (C ₂ + dC ₂ ), . . . , ( C _N +dC _N ), causing the sense currents generated by the current sensors (221~22N) to be (I ₁ +d I ₁ ), (I ₂ +d I ₂ ), ..., ( I _N +dI _N ). This can be derived from the following formula: I = C * dv / dt, where the change in current amount (I) is proportional to the change in capacitance value (C) because dv, dt are constant.

另外，電容值變化量(dC₁ ~dC_N )係與手指及該感測電容器之間的距離成反比，亦即，手指的觸碰位置與一感測電容器(C_Z1 ~C_ZN )的距離越接近，則電容值變化量(dC₁ ~dC_N )越大，故電流感測器(221~22N)產生之感測電流變化量(d I₁ ~dI_N )也越大，最後類比數位轉換器(241~24N)產生的數位訊號(b1~bN)也隨之變大。最後，微處理器250從整體數位訊號(b1~bN)的相對值大小，即可判斷是否有手指觸碰該電容式觸控面板，並從個別數位訊號(b1~bN)相對值的相對大小關係，即可判斷手指觸碰該電容式觸控面板之位置。一實施例中，微處理器250可由一微控制器來替代。In addition, the capacitance value change amount (dC ₁ ~dC _N ) is inversely proportional to the distance between the finger and the sensing capacitor, that is, the distance between the touch position of the finger and a sensing capacitor (C _Z1 ~ C _ZN ) The closer the capacitance is, the larger the change in capacitance value (dC ₁ ~dC _N ), so the amount of change in the sense current (d I ₁ ~dI _N ) generated by the current sensor (221~22N) is larger, and finally the analogous digit. The digital signals (b1~bN) generated by the converters (241~24N) also become larger. Finally, the microprocessor 250 can determine whether a finger touches the capacitive touch panel from the relative value of the overall digital signal (b1~bN), and the relative value of the relative value from the individual digital signal (b1~bN). The relationship can be used to determine the position of the finger touching the capacitive touch panel. In one embodiment, the microprocessor 250 can be replaced by a microcontroller.

一實施例中，當手指觸碰該電容式觸控面板時，感測電流為(I₁ +dI₁ )、(I₂ +dI₂ )、.....、(I_N +dI_N )，而通常電流量(I₁ 、I₂ 、...、I_N )是電流變化量(d I₁ 、d I₂ 、...、dI_N )的30~50倍大。In one embodiment, when the finger touches the capacitive touch panel, the sensing currents are (I ₁ +dI ₁ ), (I ₂ +dI ₂ ), . . . , (I _N +dI _N ). However, the amount of current (I ₁ , I ₂ , ..., I _N ) is usually 30 to 50 times larger than the amount of current change (d I ₁ , d I ₂ , ..., dI _N ).

當手指沒有觸碰該電容式觸控面板時，每一感測電容器(C_Z1 ~C_ZN )的電容值為C₁ 、C₂ 、.....、C_N ，而每一電流感測器(221~22N)產生相對應的感測電流為I₁ 、I₂ 、I₃ .....、I_N 。當手指觸碰該電容式觸控面板時，感測電容器(C_Z1 ~C_ZN )的電容值變化為(C₁ +dC₁ )、(C₂ +dC₂ )、.....、(C_N +dC_N )，導致電流感測器(221~22N)產生之感測電流變化為(I₁ +d I₁ )、(I₂ +d I₂ )、.....、(I_N +d_IN )。這可由以下公式推導而出：I=C^＊ dv/dt，其中由於dv、dt不變，故電流量(I)的變化會正比於電容值(C)的變化。When the finger does not touch the capacitive touch panel, the capacitance values of each of the sensing capacitors (C _Z1 ~ C _ZN ) are C ₁ , C ₂ , . . . , C _N , and each current sensing The corresponding sensing currents generated by the devices (221~22N) are I ₁ , I ₂ , I ₃ . . . , I _N . When the finger touches the capacitive touch panel, the capacitance values of the sensing capacitors (C _Z1 ~ C _ZN ) change to (C ₁ + dC ₁ ), (C ₂ + dC ₂ ), . . . , ( C _N +dC _N ), causing the sense currents generated by the current sensors (221~22N) to be (I ₁ +d I ₁ ), (I ₂ +d I ₂ ), ....., (I _N +d _IN ). This can be derived from the following formula: I = C ^* dv / dt, where the change in current amount (I) is proportional to the change in capacitance value (C) because dv, dt are constant.

另外，電容值變化量(dC₁ ~dC_N )係與手指及該感測電容器之間的距離成反比，亦即，手指的觸碰位置與一感測電容器(C_Z1 ~C_ZN )的距離越接近，則電容值變化量(dC₁ ~dC_N )越大，故電流感測器(221~22N)產生之感測電流變化量(dI₁ ~dI_N )也越大，最後類比數位轉換器(231~23N)產生的數位訊號(db1~bN)也隨之變大。最後，微處理器250從整體數位訊號(b1~bN)的相對值大小，即可判斷是否有手指觸碰該電容式觸控面板，並從個別數位訊號(b1~bN)相對值的相對大小關係，即可判斷手指觸碰該電容式觸控面板之位置。一實施例中，微處理器250可由一微控制器來替代。In addition, the capacitance value change amount (dC ₁ ~dC _N ) is inversely proportional to the distance between the finger and the sensing capacitor, that is, the distance between the touch position of the finger and a sensing capacitor (C _Z1 ~ C _ZN ) The closer the capacitance is, the larger the change in capacitance value (dC ₁ ~dC _N ), so the amount of change in the sense current (dI ₁ ~dI _N ) generated by the current sensor (221~22N) is larger, and finally the analog-to-digital conversion The digital signals (db1~bN) generated by the devices (231~23N) also become larger. Finally, the microprocessor 250 can determine whether a finger touches the capacitive touch panel from the relative value of the overall digital signal (b1~bN), and the relative value of the relative value from the individual digital signal (b1~bN). The relationship can be used to determine the position of the finger touching the capacitive touch panel. In one embodiment, the microprocessor 250 can be replaced by a microcontroller.

當手指沒有觸碰該電容式觸控面板時，每一感測電容器(C_Z1 ~C_ZN )的電容值為C₁ 、C₂ 、.....、C_N ，而每一電流感測器(221~22N)產生相對應的感測電流為I₁ 、I₂ 、I₃ .....、I_N 。因為感測電容器(C_Z1 ~C_ZN )具實質上相同的電容值，故電流感測器(221~22N)產生的感測電流幾乎相等，即I₁ ≒I₂ ≒....≒I_N 。因此，減法器(231~23N)進行減法運算後，得到電流差訊號幾乎等於0。此時，若電路產生電源雜訊，將導致電流感測器(221~22N)產生之感測電流為(I₁ +noise_1)、(I₂ +noise_2)、.....、(I_N +noise_N)，其中noise_1、noise_2、...、noise_N表示因電源雜訊而產生之電流變化量。因為noise_1、noise_2、...、noise_N是由於電源雜訊而同時發生的共模雜訊(common noise)，所以noise_1≒noise_2≒......≒noise_N。因此，在各減法器(231~23(N-1))進行減法運算後，得到電流差訊號將趨近於0。When the finger does not touch the capacitive touch panel, the capacitance values of each of the sensing capacitors (C _Z1 ~ C _ZN ) are C ₁ , C ₂ , . . . , C _N , and each current sensing The corresponding sensing currents generated by the devices (221~22N) are I ₁ , I ₂ , I ₃ . . . , I _N . Since the sensing capacitors (C _Z1 ~ C _ZN ) have substantially the same capacitance value, the sensing currents generated by the current sensors (221 to 22N) are almost equal, that is, I ₁ ≒I ₂ ≒....≒I _N. Therefore, after the subtractor (231~23N) performs the subtraction operation, the current difference signal is almost equal to zero. At this time, if the circuit generates power noise, the current sensed by the current sensor (221~22N) will be (I ₁ +noise_1), (I ₂ +noise_2), ....., (I _N +noise_N), where noise_1, noise_2, ..., noise_N indicates the amount of current change due to power supply noise. Because noise_1, noise_2, ..., noise_N are common noises that occur simultaneously due to power supply noise, noise_1≒noise_2≒...≒noise_N. Therefore, after the subtractors (231~23(N-1)) are subtracted, the current difference signal will be close to zero.

另一方面，在手指觸碰該電容式觸控面板時，若電路剛好產生電源雜訊，將導致電流感測器(221~22N)產生之感測電流(I₁ +dI₁ +noise_1)、(I₂ +dI₂ +noise_2)、.....、(I_N +dI_N +noise_N)。如上所述，I₁ ≒I₂ ≒....≒I_N 以及noise_1≒noise_2≒......≒noise_N，以減法器231為例，在進行減法運算後，得到電流差訊號等於(dI₁ -dI₂ )。因此，一旦電路產生電源雜訊，無論手指是否觸碰該電容式觸控面板，本發明雜訊消除電路都能有效防止電源雜訊的問題。On the other hand, when the finger touches the capacitive touch panel, if the circuit just generates power noise, it will cause the sensing current generated by the current sensor (221~22N) (I ₁ +dI ₁ +noise_1), (I ₂ +dI ₂ +noise_2), ....., (I _N +dI _N +noise_N). As described above, I ₁ ≒I ₂ ≒....≒I _N and noise_1≒noise_2≒...≒noise_N, taking the subtractor 231 as an example, after performing the subtraction operation, the current difference signal is equal to ( dI ₁ -dI ₂ ). Therefore, once the circuit generates power noise, the noise cancellation circuit of the present invention can effectively prevent the problem of power supply noise regardless of whether the finger touches the capacitive touch panel.

第3圖為本發明雜訊消除電路之第二實施例的架構示意圖。比較第2圖及第3圖，第二實施例與第一實施例的第一個差異在於，各電流電壓轉換器(211~21N)係利用取樣保持電容器(C_S1 ~C_SN )來實施。第二個差異在於：在每一感測電路(31~3N)中，新增一電流放大器(261~26N)，耦接在減法器(231~23N)以及取樣保持電容器(C_S1 ~C_SN )之間，以放大電流變化量。FIG. 3 is a schematic structural diagram of a second embodiment of the noise cancellation circuit of the present invention. Comparing Fig. 2 and Fig. 3, the first difference between the second embodiment and the first embodiment is that each of the current-voltage converters (211 to 21N) is implemented by the sample-and-hold capacitors (C _S1 to C _SN ). The second difference is that in each of the sensing circuits (31~3N), a current amplifier (261~26N) is added, which is coupled to the subtractor (231~23N) and the sample-and-hold capacitor (C _S1 ~C _SN). Between) to amplify the amount of current change.

當手指觸碰該電容式觸控面板時，若直接放大電流感測器(221~22N)的輸出電流，例如(I₁ +dI₁ )×K倍，並不能拉開電容變化量(dC₁ 、dC₂ 、....、dC_N )跟感測電容器(C_Z1 ~C_ZN )原本的電容值(C₁ 、C₂ 、.....、C_N )的比例。有鑑於此，本實施例利用電流放大器(261~26N)來放大減法器(231~23N)產生的電流差訊號(以減法器231為例，其電流差訊號等於(dI₁ -dI₂ )≒(I₁ +dI₁ )-(I₂ +dI₂ ))。因為僅放大電流變化量(相當於電容變化量)部分，故可以拉開電容變化量(dC₁ 、dC₂ 、....、dC_N )跟感測電容器(C_Z1 ~C_ZN )原本的電容值(C₁ 、C₂ 、.....、C_N )的比例，並進而放寬後級類比數位轉換器241的規格(specification)，以節省硬體成本。至於其他元件的運作方式與第2圖的第一實施例相同，於此不再贅述。When the finger touches the capacitive touch panel, if the output current of the current sensor (221~22N) is directly amplified, for example, (I ₁ +dI ₁ )×K times, the capacitance change amount cannot be pulled (dC ₁ , the ratio dC _2, ...., dC _N) with the sensing capacitor (C _Z1 ~ C _ZN) the original capacitance value _{_{(C 1, C 2, .....}} , C N) is. In view of this, the current amplifier (261~26N) is used to amplify the current difference signal generated by the subtractor (231~23N) (for example, the subtracter 231 has a current difference signal equal to (dI ₁ -dI ₂ )≒ (I ₁ +dI ₁ )-(I ₂ +dI ₂ )). Since only the amount of current change (corresponding to the amount of capacitance change) is amplified, the amount of capacitance change (dC ₁ , dC ₂ , . . . , dC _N ) and the original sense capacitor (C _Z1 to C _ZN ) can be pulled apart. The ratio of the capacitance values (C ₁ , C ₂ , . . . , C _N ), and then the specification of the latter analog converter 241 is relaxed to save hardware costs. The operation of the other components is the same as that of the first embodiment of FIG. 2 and will not be described again.

從上述實施例可以發現到，在邊緣的感測電路(2N或3N)的減法器23N會面臨沒有電流訊號可以減的問題。此時，通常微處理器250會選擇忽視chN的輸入值bN。為解決上述各感測電路之減法運算不一致的問題，因此進一步提出以下實施例。It can be seen from the above embodiment that the subtractor 23N of the sensing circuit (2N or 3N) at the edge faces the problem that no current signal can be reduced. At this point, typically microprocessor 250 will choose to ignore the input value bN of chN. In order to solve the problem of inconsistency in the subtraction of the above-described respective sensing circuits, the following embodiments are further proposed.

第4圖為本發明雜訊消除電路之第三實施例的架構示意圖。比較第2圖及第4圖，第三實施例與第一實施例的第一個差異在於，電流電壓轉換器(211~21N)係利用取樣保持電容器(C_S1 ~C_SN )來實施。第二個差異在於：對於在邊緣的感測電路2N，透過電流數位類比轉換器(I-DAC)421產生虛擬的電流信號I_R1 ，提供給邊緣的感測電路2N進行減法運算，使整體感測電路之減法運算更有一致性，並提高估算電路下方邊緣觸碰位置(或電容式觸控面板下方邊緣觸碰位置)的準確率。FIG. 4 is a schematic structural diagram of a third embodiment of the noise cancellation circuit of the present invention. Comparing the second and fourth figures, the first difference between the third embodiment and the first embodiment is that the current-to-voltage converters (211 to 21N) are implemented by the sample-and-hold capacitors (C _S1 to C _SN ). The second difference is that for the sensing circuit 2N at the edge, the virtual current signal I _{R1 is} generated by the current digital analog converter (I-DAC) 421, and the sensing circuit 2N provided to the edge is subtracted to make the overall sense. The subtraction of the measurement circuit is more consistent, and the accuracy of estimating the touch position of the lower edge of the circuit (or the touch position of the lower edge of the capacitive touch panel) is improved.

如上所述，當手指沒有觸碰該電容式觸控面板時，因為感測電容器(C_Z1 ~C_ZN )具實質上相同的電容值，故電流感測器(221~22N)產生的感測電流幾乎相等，即I₁ ≒I₂ ≒....≒I_N 。因此，減法器231~23(N-1)進行減法運算後，得到電流差訊號幾乎等於0。同理，邊緣的電路分支2N之減法器23N進行減法運算(I_N -I_R1 )後，得到電流差訊號也應趨近於0。據此，電路在電源開啟(turn-on)之後，微處理器250先對通道chN的數位訊號值bN設定一特定誤差範圍(係收斂且趨近於0，本實施例假設該特定誤差範圍為-3~+3)，並執行如下初始校正程序：微處理器450根據chN的數位訊號值bN大小調整數位控制訊號DS1值，而電流數位類比轉換器(I-DAC)421再根據該數位控制訊號DS1值調整輸出電流量I_R1 ，接著，減法器23N產生電流差訊號(I_N -I_R1 )、類比數位轉換器24N再更新數位訊號bN，如此周而復始，直到數位訊號值bN收斂在該特定誤差範圍內，才完成初始校正程序。至於其他元件的運作方式與第2圖的第一實施例相同，於此不再贅述。As described above, when the finger does not touch the capacitive touch panel, since the sensing capacitors (C _Z1 ~ C _ZN ) have substantially the same capacitance value, the sensing of the current sensor (221 22 22 N) is generated. The currents are almost equal, ie I ₁ ≒I ₂ ≒....≒I _N . Therefore, after the subtractors 231 to 23 (N-1) perform the subtraction operation, the current difference signal is almost equal to zero. Similarly, after the subtraction operation (I _N -I _R1 ) of the subtractor 23N of the edge circuit branch 2N, the current difference signal should also be close to zero. Accordingly, after the power is turned on, the microprocessor 250 first sets a specific error range for the digital signal value bN of the channel chN (which converges and approaches 0. This embodiment assumes that the specific error range is -3~+3), and perform the following initial calibration procedure: the microprocessor 450 adjusts the digital control signal DS1 value according to the digital signal value bN of the chN, and the current digital analog converter (I-DAC) 421 controls according to the digital position. The signal DS1 value adjusts the output current amount I _R1 , and then the subtractor 23N generates a current difference signal (I _N -I _R1 ), and the analog digital converter 24N re-updates the digital signal bN, so as to repeat until the digital signal value bN converges at the specific The initial calibration procedure is completed within the error range. The operation of the other components is the same as that of the first embodiment of FIG. 2 and will not be described again.

第5圖為本發明雜訊消除電路之第四實施例的架構示意圖。比較第3圖及第5圖，第四實施例與第二實施例之間有二個差異，第一個差異在於：在每一感測電路51~5N，新增一電流放大器(521~52N)。所有感測電路(51~5N)的運作方式皆類似，以下僅以感測電路51為例作說明。電流感測器221在感測該感測電容器C_Z1 的電容值以產生一相對應感測電流I₁ 之後，再利用電流放大器521以進一步放大感測電流I₁ 以產生放大電流I_C1 。本實施例係適用於電容值(C₁ 、C₂ 、.....、C_N )偏小或感測電流(I₁ 、I₂ 、I₃ .....、I_N )偏小的狀況，利用電流放大器(521~52N)放大感測電流後，可放寬後級減法器(231~23N)的規格，以節省硬體成本。FIG. 5 is a schematic structural diagram of a fourth embodiment of the noise cancellation circuit of the present invention. Comparing Figures 3 and 5, there are two differences between the fourth embodiment and the second embodiment. The first difference is that a current amplifier (521~52N) is added to each of the sensing circuits 51~5N. ). All of the sensing circuits (51~5N) operate in a similar manner. Hereinafter, only the sensing circuit 51 will be described as an example. After sensing the capacitance value of the sensing capacitor C _Z1 to generate a corresponding sensing current I ₁ , the current sensor 221 uses the current amplifier 521 to further amplify the sensing current I ₁ to generate an amplification current I _C1 . This embodiment is applicable to a small capacitance value (C ₁ , C ₂ , . . . , C _N ) or a small sense current (I ₁ , I ₂ , I ₃ ....., I _N ). In the case of using a current amplifier (521~52N) to amplify the sense current, the specifications of the post-stage subtractor (231~23N) can be relaxed to save hardware costs.

第二個差異在於：新增一電流數位類比轉換器(I-DAC)421及一虛擬感測電路5v。對於在邊緣的感測電路5N，透過電流數位類比轉換器(I-DAC)421產生虛擬的電流信號I_R1 ，提供給邊緣的感測電路5N進行減法運算。該虛擬感測電路5v包含一電流數位類比轉換器(I-DAC)422、一減法器230、一取樣保持電容器C_S0 以及一類比數位轉換器240。對於在邊緣的感測電路(5N、5v)，透過電流數位類比轉換器(I-DAC)421、422產生虛擬的電流信號I_R1 、I_R2 ，讓邊緣的電路分支5N、5v做減法運算，使整體感測電路之減法運算更有一致性，同時提高估算邊緣觸碰位置的準確性。因為在習知電容式觸控面板之感測電路中，手指觸碰的位置是由感測電容器的感測輸出值兩兩內插(interpolation)得到的，至於邊緣的觸碰位置則是利用外插得到，而外插誤差又比內插誤差大。有鑑於上述問題，本發明透過設置虛擬的感測電路5N、5v，使得上下方邊緣的觸碰位置也可以進行內插運算，以提高估算手指觸碰位置的準確率。相較於第三實施例(第4圖)，第四實施例多增加一虛擬的感測電路5v，使電路更具對稱性，增加估算電路上方邊緣觸碰位置(或電容式觸控面板上方邊緣觸碰位置)的準確率。至於第四實施例在電源啟動之後，微處理器550也需先對通道ch0及chN的數位訊號b0及bN值設定一特定誤差範圍(係收斂且趨近於0，本實施例假設該特定誤差範圍為-3~+3)，再執行與第三實施例相同的初始校正程序如下：微處理器550根據ch0及chN的數位訊號值b0及bN大小分別調整數位控制訊號DS2及DS1值，而電流數位類比轉換器(I-DAC)422及421再根據該數位控制訊號DS2及DS1值分別調整輸出電流量I_R2 及I_R1 ，接著，減法器230及23N分別產生電流差訊號(I_R2 -I_C1 )及(I_CN -I_R1 )，而電流放大器260及26N再分別放大該電流差訊號(I_R2 -I_C1 )及(I_CN -I_R1 )，之後，類比數位轉換器240及24N再分別更新數位訊號b0及bN，如此周而復始，直到數位訊號b0及bN值皆收斂在該特定誤差範圍內，才完成初始校正程序。The second difference is that a current digital analog converter (I-DAC) 421 and a virtual sensing circuit 5v are added. For the edge sensing circuit 5N, a virtual current signal I _{R1 is} generated by a current digital analog converter (I-DAC) 421, and the sensing circuit 5N supplied to the edge performs subtraction. The virtual sensing circuit 5v includes a current digital analog converter (I-DAC) 422, a subtractor 230, a sample and hold capacitor C _{S0 ,} and an analog digital converter 240. For the sensing circuits (5N, 5v) at the edges, the virtual current signals I _R1 and I _{R2 are} generated by the current digital analog converters (I-DAC) 421, 422, and the circuit branches 5N and 5v of the edges are subtracted. The overall sensing circuit is more consistent in subtraction, while improving the accuracy of estimating the edge touch position. Because in the sensing circuit of the conventional capacitive touch panel, the position of the finger touch is obtained by the interpolation of the sensing output value of the sensing capacitor, and the touch position of the edge is utilized. Inserted, and the extrapolation error is larger than the interpolation error. In view of the above problems, the present invention can perform an interpolation operation by setting the virtual sensing circuits 5N, 5v so that the touch position of the upper and lower edges can be improved to improve the accuracy of estimating the touch position of the finger. Compared with the third embodiment (Fig. 4), the fourth embodiment adds a dummy sensing circuit 5v to make the circuit more symmetrical, and increases the upper edge touch position of the estimating circuit (or above the capacitive touch panel). The accuracy of the edge touch position). As for the fourth embodiment, after the power is turned on, the microprocessor 550 also needs to set a specific error range for the digital signals b0 and bN of the channels ch0 and chN (converges and approaches 0, which is assumed in this embodiment). The range is -3 to +3), and the same initial calibration procedure as that of the third embodiment is performed as follows: The microprocessor 550 adjusts the digital control signals DS2 and DS1 according to the digital signal values b0 and bN of ch0 and chN, respectively. The current digital analog converters (I-DAC) 422 and 421 respectively adjust the output current amounts I _R2 and I _R1 according to the digital control signals DS2 and DS1 values, and then the subtractors 230 and 23N respectively generate current difference signals (I _R2 - I _C1 ) and (I _CN -I _R1 ), and current amplifiers 260 and 26N respectively amplify the current difference signals (I _R2 -I _C1 ) and (I _CN -I _R1 ), and then analog-to-digital converters 240 and 24N Then, the digital signals b0 and bN are updated separately, and then the cycle is repeated until the digital signals b0 and bN values converge within the specific error range, and the initial calibration procedure is completed.

須注意的是本發明不限定電流數位類比轉換器421、422的類型，任何能藉由控制數位輸入值調整輸出電流量的數位類比轉換器，皆屬本發明的範疇。It should be noted that the present invention does not limit the type of current digital analog converters 421, 422. Any digital analog converter capable of adjusting the amount of output current by controlling the digital input value is within the scope of the present invention.

本發明可有效解決電源雜訊的問題，同時能放寬類比數位轉換器與減法器的規格，並提高估算邊緣觸碰位置的準確性。The invention can effectively solve the problem of power noise and can relax the analogy The specifications of the digital converter and subtractor, and improve the accuracy of estimating the edge touch position.

以上雖以實施例說明本發明，但並不因此限定本發明之範圍，只要不脫離本發明之要旨，該行業者可進行各種變形或變更，均應落入本發明之申請專利範圍。The present invention has been described above by way of examples, and the scope of the present invention is not limited thereto, and various modifications and changes may be made by those skilled in the art without departing from the scope of the invention.

10‧‧‧感測元件10‧‧‧Sensor components

20、30、40、50‧‧‧雜訊消除電路20, 30, 40, 50‧‧‧ noise cancellation circuit

210、101‧‧‧訊號產生器210, 101‧‧‧ Signal Generator

100、104‧‧‧電極100, 104‧‧‧ electrodes

105‧‧‧耦合電容器105‧‧‧Coupling capacitor

5v‧‧‧虛擬感測電路5v‧‧‧Virtual sensing circuit

21~2N、31~3N、51~5N‧‧‧感測電路21~2N, 31~3N, 51~5N‧‧‧ sensing circuit

C_Z1 ~C_ZN ‧‧‧感測電容器C _Z1 ~C _ZN ‧‧‧Sense Capacitor

211~21N‧‧‧電流電壓轉換器211~21N‧‧‧current voltage converter

221~22N‧‧‧電流感測器221~22N‧‧‧ current sensor

230~23N‧‧‧減法器230~23N‧‧‧Subtractor

C_S1 ~C_SN ‧‧‧取樣保持電容器C _S1 ~C _SN ‧‧‧Sampling and Holding Capacitor

240~24N‧‧‧類比數位轉換器240~24N‧‧‧ Analog Digital Converter

260~26N‧‧‧電流放大器260~26N‧‧‧ current amplifier

250、450、550‧‧‧微處理器250, 450, 550‧‧‧ microprocessor

401‧‧‧取樣開關401‧‧‧Sampling switch

402‧‧‧電荷積分器402‧‧‧Charge integrator

403‧‧‧放大器403‧‧Amplifier

404‧‧‧重置開關404‧‧‧Reset switch

405‧‧‧電荷消除電路405‧‧‧Charge elimination circuit

407‧‧‧量測裝置407‧‧‧Measurement device

408‧‧‧控制器408‧‧‧ Controller

421、422‧‧‧電流數位類比轉換器421, 422‧‧‧ current digital analog converter

521~52N‧‧‧電流放大器521~52N‧‧‧ Current Amplifier

第1圖顯示一傳統電荷轉移量測電路之架構圖Figure 1 shows the architecture of a conventional charge transfer measurement circuit.

第2圖為本發明雜訊消除電路之第一實施例的架構示意圖。FIG. 2 is a schematic structural diagram of a first embodiment of a noise cancellation circuit according to the present invention.

第3圖為本發明雜訊消除電路之第二實施例的架構示意圖。FIG. 3 is a schematic structural diagram of a second embodiment of the noise cancellation circuit of the present invention.

第4圖為本發明雜訊消除電路之第三實施例的架構示意圖。FIG. 4 is a schematic structural diagram of a third embodiment of the noise cancellation circuit of the present invention.

第5圖為本發明雜訊消除電路之第四實施例的架構示意圖。FIG. 5 is a schematic structural diagram of a fourth embodiment of the noise cancellation circuit of the present invention.

20‧‧‧雜訊消除電路20‧‧‧ Noise Elimination Circuit

210‧‧‧訊號產生器210‧‧‧Signal Generator

21~2N‧‧‧感測電路21~2N‧‧‧Sensor circuit

C_Z1 ~C_ZN ‧‧‧感測電容器C _Z1 ~C _ZN ‧‧‧Sense Capacitor

221~22N‧‧‧電流感測器221~22N‧‧‧ current sensor

231~23N‧‧‧減法器231~23N‧‧‧Subtractor

211~21N‧‧‧電流電壓轉換器211~21N‧‧‧current voltage converter

241~24N‧‧‧類比數位轉換器241~24N‧‧‧ Analog Digital Converter

250‧‧‧微處理器250‧‧‧Microprocessor

Claims

一種雜訊消除電路，適用於一電容式觸控面板，包含：一訊號產生器，產生一電壓訊號；複數個感測電路，每一感測電路包含：一感測電容器，其第一端接收該電壓訊號；一電流感測器，其輸入端耦接該感測電容器的第二端，用以感測該感測電容器的電容值以產生一感測電流量；一第一減法器，耦接該電流感測器，用以根據本身感測電路之電流感測器的感測電流量及一鄰近感測電路之電流感測器的感測電流量之差，產生一第一電流差訊號；一第一電流電壓轉換器，其第一端耦接該第一減法器的輸出端，其第二端接地，用以產生一第一類比電壓訊號；以及一第一類比數位轉換器，用以將該第一類比電壓訊號，轉換為一第一數位訊號；一處理電路，用以接收該些感測電路產生之複數個第一數位訊號，以判斷是否有觸碰發生；以及一第一電流數位類比轉換器，用以根據該處理電路之第一數位控制訊號，產生一第一輸出電流量，以提供給該些感測電路之其一之第一減法器。 A noise cancellation circuit is applicable to a capacitive touch panel, comprising: a signal generator for generating a voltage signal; and a plurality of sensing circuits, each sensing circuit comprising: a sensing capacitor, the first end receiving The current signal is coupled to the second end of the sensing capacitor for sensing the capacitance of the sensing capacitor to generate a sensing current amount; a first subtractor coupled The current sensor is configured to generate a first current difference signal according to a difference between a sense current amount of the current sensor of the sensing circuit and a sense current amount of the current sensor adjacent to the sensing circuit. a first current-to-voltage converter having a first end coupled to the output of the first subtractor, a second end grounded to generate a first analog voltage signal, and a first analog-to-digital converter Converting the first analog voltage signal into a first digital signal; a processing circuit for receiving a plurality of first digital signals generated by the sensing circuits to determine whether a touch occurs; and a first Current digital analogy Device, according to a first digital control signal of the processing circuit to generate a first output current, to be supplied to a first subtractor one of the plurality of sensing circuits.

如申請專利範圍第1項所記載之雜訊消除電路，其中各該感測電路更包含：一第一電流放大器，耦接在該第一減法器及該第一電流電壓轉換器之間，用以放大該第一電流差訊號。 The noise cancellation circuit of claim 1, wherein each of the sensing circuits further comprises: a first current amplifier coupled between the first subtractor and the first current-to-voltage converter, To amplify the first current difference signal.

如申請專利範圍第1項所記載之雜訊消除電路，其中各該感測電路更包含：一第二電流放大器，耦接在該電流感測器及該第一減法器之間，用以放大該感測電流。 The noise cancellation circuit of claim 1, wherein each of the sensing circuits further comprises: a second current amplifier coupled between the current sensor and the first subtractor for amplifying The sense current.

如申請專利範圍第1項所記載之雜訊消除電路，其中在電源開啟時，該處理電路對耦接該第一電流數位類比轉換器之感測電路執行一初始校正程序，藉以使該感測電路之第一數位訊號收斂及趨近於0。 The noise cancellation circuit of claim 1, wherein the processing circuit performs an initial calibration procedure on the sensing circuit coupled to the first current digital analog converter when the power is turned on, so that the sensing is performed. The first digital signal of the circuit converges and approaches zero.

如申請專利範圍第4項所記載之雜訊消除電路，其中該處理電路更接收耦接該第一電流數位類比轉換器之感測電路之第一數位訊號，以進行內插運算，進而估計一邊緣觸碰位置。 The noise cancellation circuit of claim 4, wherein the processing circuit further receives a first digital signal coupled to the sensing circuit of the first current digital analog converter to perform an interpolation operation, thereby estimating one The edge touches the position.

如申請專利範圍第1項所記載之雜訊消除電路，其中各該感測電容器具實質上相同的電容值。 The noise cancellation circuit of claim 1, wherein each of the sensing capacitors has substantially the same capacitance value.

如申請專利範圍第6項所記載之雜訊消除電路，其中當手指沒有觸碰該電容式觸控面板時，無論電路是否產生一電源雜訊，各該電流差訊號皆趨近於0。 For example, in the noise cancellation circuit described in claim 6, wherein when the finger does not touch the capacitive touch panel, the current difference signal approaches zero regardless of whether the circuit generates a power supply noise.

如申請專利範圍第1項所記載之雜訊消除電路，其中當手指觸碰該電容式觸控面板時，該些感測電流之至少其一係變大。 The noise cancellation circuit of claim 1, wherein at least one of the sensing currents becomes larger when the finger touches the capacitive touch panel.

一種雜訊消除電路，適用於一電容式觸控面板，包含：一訊號產生器，產生一電壓訊號；複數個感測電路，每一感測電路包含：一感測電容器，其第一端接收該電壓訊號；一電流感測器，其輸入端耦接該感測電容器的第二端，用以感測該感測電容器的電容值以產生一感測電流量；一第一減法器，耦接該電流感測器，用以根據本身感測電路之電流感測器的感測電流量及一鄰近感測電路之電流感測器的感測電流量之差，產生一第一電流差訊號；一第一電流電壓轉換器，其第一端耦接該第一減法器的輸出端，其第二端接地，用以產生一第一類比電壓訊號；以及一第一類比數位轉換器，用以將該第一類比電壓訊號，轉換為一第一數位訊號；一處理電路，用以接收該些感測電路產生之複數個第一數位訊號，以判斷是否有觸碰發生；以及一虛擬感測電路，係位於該些感測電路的邊緣，該虛擬感測電路包含：一第二電流數位類比轉換器，用以根據該處理電路之第二數位控制訊號，產生一第二輸出電流量；一第二減法器，耦接該第二電流數位類比轉換器，用以根據第二輸出電流量及一鄰近感測電路之電流感測器的感測電流量之差，產生一第二電流差訊號；一第二電流電壓轉換器，其第一端耦接該第二減法器的輸出端，其第二端接地，用以產生一第二類比電壓訊號；以及一第二類比數位轉換器，其輸入端耦接該第二電流電壓轉換器的第一端，用以將該第二類比電壓訊號，轉換為一第二數位訊號；其中，該處理電路更接收該第二數位訊號，進行內插運算，進而估計一邊緣觸碰位置。 A noise cancellation circuit is applicable to a capacitive touch panel, comprising: a signal generator for generating a voltage signal; and a plurality of sensing circuits, each sensing circuit comprising: a sensing capacitor, the first end receiving The voltage signal is coupled to the second end of the sensing capacitor for sensing a capacitance value of the sensing capacitor to generate a sensing current amount; a first subtractor coupled to the current sensor for measuring a difference between a sensed current amount of a current sensor of the sensing circuit and a sensed current amount of a current sensor adjacent to the sensing circuit, Generating a first current difference signal; a first current-to-voltage converter having a first end coupled to the output of the first subtractor and a second end grounded to generate a first analog voltage signal; An analog-to-digital converter for converting the first analog voltage signal into a first digital signal; a processing circuit for receiving a plurality of first digital signals generated by the sensing circuits to determine whether there is a touch a virtual sensing circuit is disposed at an edge of the sensing circuit, the virtual sensing circuit includes: a second current digital analog converter for generating a second digital control signal according to the processing circuit a second output current amount; a second subtractor coupled to the second current digital analog converter for determining a difference between the second output current amount and the sense current amount of the current sensor of a proximity sensing circuit Produce one a second current-to-voltage converter, the first end of which is coupled to the output of the second subtractor, the second end of which is grounded to generate a second analog voltage signal; and a second analog digital a converter, the input end of which is coupled to the first end of the second current-to-voltage converter for converting the second analog voltage signal into a second digital signal; The processing circuit further receives the second digital signal, performs an interpolation operation, and further estimates an edge touch position.

如申請專利範圍第9項所記載之雜訊消除電路，其中在電源開啟時，該處理電路對該虛擬感測電路執行一初始校正程序，藉以使該虛擬感測電路之第二數位訊號收斂及趨近於0。 The noise cancellation circuit of claim 9, wherein the processing circuit performs an initial calibration procedure on the virtual sensing circuit when the power is turned on, so that the second digital signal of the virtual sensing circuit converges Approaching to zero.

如申請專利範圍第9項所記載之雜訊消除電路，其中該第一電流電壓轉換器以及該第二電流電壓轉換器分別為一電容器以及一電阻器之其一。The noise cancellation circuit of claim 9, wherein the first current voltage converter and the second current voltage converter are respectively a capacitor and a resistor.