CN101739186B - Image display system, capacitive touch panel and capacitance measuring device and method thereof - Google Patents
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Abstract
Description
技术领域technical field
本发明是有关于一种触控面板,特别是有关于一种影像显示系统、电容式触控面板及其电容测量装置与方法。The present invention relates to a touch panel, in particular to an image display system, a capacitive touch panel and a capacitance measuring device and method thereof.
背景技术Background technique
触控面板(touch panel)的应用非常广泛,例如自动柜员机、销售点终端机、工业控制系统等。随着便携式电子产品如智能型手机及个人数字助理(PDA)的普及,触控面板也提供对按键输入不熟的使用者更方便的输入方式,因此市场成长相当快速。Touch panels are widely used, such as automatic teller machines, point-of-sale terminals, industrial control systems, and the like. With the popularity of portable electronic products such as smart phones and personal digital assistants (PDAs), touch panels also provide a more convenient input method for users who are not familiar with key input, so the market is growing rapidly.
触控面板可依其检测触控点的物理原理,主要分为电阻式(resistive)触控面板及电容(capacitive)式触控面板两种。用手指或触控笔轻按电阻式触控面板就会产生电压;而电容式触控面板是以手指接触面板而吸取微小的电流方式操作。再者,电容式触控面板又可分为表面电容式(surface capacitive)触控面板及投射电容式(projected capacitive)触控面板,其中投射电容式触控面板由于可以达成多点触控(Multi-Touch)功能,因此更为吸引业界竞相研发。若将投射电容式触控面板整合至液晶荧幕,以形成内嵌式多点触控面板(In-CellMulti-Touch Panel),更可以维持原面板的薄度。在薄膜晶体管液晶显示器(TFTLCD)中常用透明电极(ITO)锁住保存电荷,同样原理反向操作,这层ITO也可当感测器,并可提供高密度检测。然而在TFT LCD中,由于TFT所导致的噪声很大,因此电容感测控制电路相当重要。According to the physical principle of detecting touch points, the touch panel is mainly divided into two types: resistive touch panel and capacitive touch panel. A resistive touch panel generates a voltage when lightly pressed with a finger or a stylus; while a capacitive touch panel operates by drawing a tiny current when a finger touches the panel. Moreover, the capacitive touch panel can be further divided into surface capacitive touch panel and projected capacitive touch panel. The projected capacitive touch panel can achieve multi-touch -Touch) function, so it is more attractive to the industry to compete for research and development. If the projected capacitive touch panel is integrated into the LCD screen to form an in-cell multi-touch panel (In-CellMulti-Touch Panel), the thinness of the original panel can be maintained. In thin film transistor liquid crystal displays (TFTLDs), transparent electrodes (ITO) are commonly used to lock and store charges. The same principle is reversed. This layer of ITO can also be used as a sensor and can provide high-density detection. However, in TFT LCD, since the noise caused by TFT is very large, the capacitive sensing control circuit is very important.
参见图1,为一现有技术投射电容式触控面板200A的示意图,如图所示,该投射电容式触控面板200A包含一电容式触控面板单元300A及一控制器30A。该电容式触控面板单元300A具有一绝缘基底(未标号)、垂直方向的条状电极32A、水平方向的条状电极34A,其中该条状电极32A及条状电极34A呈90度夹角。图1仅为一简化的示意图,须知垂直条状电极32A及水平条状电极34A在绝缘基底的不同平面上(如正面及反面),且数目分别为M条及N条。因此控制器30A的输入线路至少为(M+N)条。通过垂直条状电极32A及水平条状电极34A捕捉电极之间的电容变化,控制器30A可感知在该电容式触控面板单元300A上的一接触位置。Referring to FIG. 1 , it is a schematic diagram of a prior art projected
参见图2,为一相关技术(related art)电容式触控面板的感测电路100A,该感测电路100A例如可以内建于第一图所示的控制器30A内,以通过测量电容值变化而得知接触位置。假设Cs是手指接触第k条垂直条状电极32A所产生的接触电容,Cp为寄生电容(stray capacitance),则该感测电路100A会先由一充电电流源Ic将电荷Q充至接触电容Cs及寄生电容Cp。随后该感测电路100A会先经由一较大的第一电流源20A放电,再经由一较小的第二电流源22A放电。由公式Q=C×V可知若因手指接触电极造成电容C改变,则在连接点P的电压也会改变,因此通过一比较器50A比较连接点P的电压(和一参考电压比较),即可知道手指是否接触第k条电极条。Referring to FIG. 2 , it is a
更详细而言,若该控制器30A周期性地切换充电开关SW_C、第一放电开关SW_A、第二放电开关SW_B,则比较器50A输出为脉宽会随接触与否而变化的脉宽调变(PWM)信号。控制器30A通过读取感测电路100A的输出PWM信号,即可知道第k条垂直条状电极32A是否有手指接触及接触位置。感测电路100A可依序选择测量图1的垂直条状电极32A及水平条状电极34A,控制器30A即可知道在所述这些电极上的电容变化及在投射电容式触控面板的接触位置。In more detail, if the
然而在上述的相关技术电容式触控面板的感测电路100A有两个缺点:However, the
1.由于寄生电容Cp一般而言很大,约为触控面板的接触电容Cs的1000倍,因此若在寄生电容Cp上有噪声,则会影响检测精确度。再者,当该投射电容式触控面板使用于液晶显示器时,由于液晶显示器上板上的ITO电极(形成电极条)及直流共同电压(DCVCOM)电极很接近,因此会使寄生电容Cp变大,造成接触电容Cs测量困难。此外,位在下板上的感测电路100A常会有很大的噪声耦合到上板的寄生电容Cp,造成测量错误。1. Since the parasitic capacitance Cp is generally large, about 1000 times of the contact capacitance Cs of the touch panel, if there is noise on the parasitic capacitance Cp, it will affect the detection accuracy. Furthermore, when the projected capacitive touch panel is used in a liquid crystal display, since the ITO electrodes (forming electrode strips) on the upper panel of the liquid crystal display and the DC common voltage (DCVCOM) electrodes are very close, the parasitic capacitance Cp will increase. , making it difficult to measure the contact capacitance Cs. In addition, the
2.由于对于M条垂直条状电极32A及N条水平条状电极34A需要(M+N)条信号线导引到感测电路100A,因此配线较为复杂。2. Since the M
发明内容Contents of the invention
因此本发明的一目的即在提供一种可降低噪声的电容式触控面板的电容测量装置。Therefore, an object of the present invention is to provide a capacitance measurement device for a capacitive touch panel that can reduce noise.
因此本发明的另一目的即在提供一种可降低噪声的电容式触控面板。Therefore, another object of the present invention is to provide a capacitive touch panel capable of reducing noise.
为了达成上述目的,本发明提供一种电容式触控面板的电容测量装置,该电容测量装置包含:一第一放电电流源,电连接到该连接点以提供一第一放电电流;一第二放电电流源,电连接到该连接点以提供一第二放电电流,其中该第一放电电流大于该第二放电电流;一差动比较器具有一第一输入端及一第二输入端,该第一输入端电连接到该连接点;一参考电压源,电连接到该第二输入端,该参考电压源接收一参考电压及一液晶显示器的直流共同电压(DCVCOM)以产生与该直流共同电压相关的一修正参考电压,其中该液晶显示器的直流共同电压亦电连接到该触控面板。该差动比较器比对该连接点上的一输入电压及该修正参考电压以产生代表该接触电容值的一脉宽调变信号,藉此可降低在直流共同电压上的噪声干扰。In order to achieve the above object, the present invention provides a capacitance measuring device for a capacitive touch panel, the capacitance measuring device includes: a first discharge current source electrically connected to the connection point to provide a first discharge current; a second A discharge current source, electrically connected to the connection point to provide a second discharge current, wherein the first discharge current is greater than the second discharge current; a differential comparator has a first input terminal and a second input terminal, the first discharge current An input terminal is electrically connected to the connection point; a reference voltage source is electrically connected to the second input terminal, and the reference voltage source receives a reference voltage and a DC common voltage (DCVCOM) of a liquid crystal display to generate the DC common voltage A related modified reference voltage, wherein the DC common voltage of the liquid crystal display is also electrically connected to the touch panel. The differential comparator compares an input voltage on the connection point with the modified reference voltage to generate a pulse width modulation signal representing the contact capacitance, thereby reducing noise interference on the DC common voltage.
为了达成上述目的,本发明提供一种电容式触控面板,包含:在纵方向具有第一数目M的第一电极;在横方向具有第二数目N第二电极;及一电容测量装置。该电容测量装置包含:一第一放电电流源,电连接到该连接点以提供一第一放电电流;一第二放电电流源,电连接到该连接点以提供一第二放电电流,其中该第一放电电流大于该第二放电电流;一差动比较器具有一第一输入端及一第二输入端,该第一输入端电连接到该连接点;一参考电压源,电连接到该第二输入端,该参考电压源接收一参考电压及一液晶显示器的直流共同电压(DCVCOM)以产生与该直流共同电压相关的一修正参考电压,其中该直流共同电压亦电连接到该触控面板。该差动比较器比对该连接点上的一输入电压及该修正参考电压以产生代表该接触电容值的一脉宽调变信号,藉此可降低在直流共同电压上的噪声干扰。In order to achieve the above object, the present invention provides a capacitive touch panel, comprising: first electrodes having a first number M in the vertical direction; second electrodes having a second number N in the horizontal direction; and a capacitance measuring device. The capacitance measurement device includes: a first discharge current source, electrically connected to the connection point to provide a first discharge current; a second discharge current source, electrically connected to the connection point to provide a second discharge current, wherein the The first discharge current is greater than the second discharge current; a differential comparator has a first input terminal and a second input terminal, the first input terminal is electrically connected to the connection point; a reference voltage source is electrically connected to the first input terminal Two input terminals, the reference voltage source receives a reference voltage and a DC common voltage (DCVCOM) of a liquid crystal display to generate a modified reference voltage related to the DC common voltage, wherein the DC common voltage is also electrically connected to the touch panel . The differential comparator compares an input voltage on the connection point with the modified reference voltage to generate a pulse width modulation signal representing the contact capacitance, thereby reducing noise interference on the DC common voltage.
为了达成上述目的,本发明提供一种电容式触控面板的电容测量方法,所述电容测量方法测量所述电容式触控面板的一电极的一接触电容,所述电容测量方法包含:a.提供一第一放电电流源,电连接到一连接点以提供一第一放电电流,该连接点与该电极电连接;b提供一第二放电电流源,电连接到所述连接点以提供一第二放电电流,其中所述第一放电电流大于所述第二放电电流;c.提供一差动比较器具有一第一输入端及一第二输入端,所述第一输入端电连接到所述连接点;d提供一参考电压源,电连接到所述第二输入端,所述参考电压源迭加一参考电压及一液晶显示器的直流共同电压以产生与所述直流共同电压相关的一修正参考电压,其中所述直流共同电压亦电连接到所述触控面板;e.经由该连接点对于所述电极预充电后,对所述电极以该第一放电电流放电;f.对所述电极以该第二放电电流放电;g.在所述第二放电电流放电期间,比对所述修正参考电压及在所述连接点上的一输入电压,以判断所述接触电容。In order to achieve the above object, the present invention provides a capacitance measurement method of a capacitive touch panel, the capacitance measurement method measures a contact capacitance of an electrode of the capacitive touch panel, and the capacitance measurement method includes: a. providing a first discharge current source electrically connected to a connection point to provide a first discharge current, the connection point being electrically connected to the electrode; b providing a second discharge current source electrically connected to the connection point to provide a A second discharge current, wherein the first discharge current is greater than the second discharge current; c. providing a differential comparator with a first input and a second input, the first input is electrically connected to the The connection point; d provides a reference voltage source, electrically connected to the second input terminal, the reference voltage source superimposes a reference voltage and a DC common voltage of a liquid crystal display to generate a related to the DC common voltage modifying the reference voltage, wherein the DC common voltage is also electrically connected to the touch panel; e. after precharging the electrode via the connection point, discharging the electrode with the first discharge current; f. The electrode is discharged with the second discharge current; g. During the discharge period of the second discharge current, compare the modified reference voltage with an input voltage on the connection point to determine the contact capacitance.
再者依据本发明的一较佳具体实例,该电容式触控面板更具有一多工器,具有对应所述这些第一电极及所述这些第二电极的多数开关,且产生第三数目的控制信号,其中该第三数目为该第一数目及该第二数目的较大者加上一。该多工器通过所述这些控制信号控制所述这些开关,以选择所述这些第一电极及所述这些第二电极其中之一电连接到该电容测量装置,以测量被选择电极的接触电容,藉此可以降低信号线数目。Furthermore, according to a preferred embodiment of the present invention, the capacitive touch panel further has a multiplexer, which has a plurality of switches corresponding to the first electrodes and the second electrodes, and generates a third number of switches. A control signal, wherein the third number is the larger of the first number and the second number plus one. The multiplexer controls the switches through the control signals to select one of the first electrodes and the second electrodes to be electrically connected to the capacitance measuring device to measure the contact capacitance of the selected electrode , thereby reducing the number of signal lines.
附图说明Description of drawings
图1为一现有技术投射电容式触控面板的示意图。FIG. 1 is a schematic diagram of a prior art projected capacitive touch panel.
图2为一相关技术(related art)电容式触控面板的感测电路电路图。FIG. 2 is a circuit diagram of a sensing circuit of a related art capacitive touch panel.
图3为依据本发明一较佳具体实例的电容式触控面板的电容测量装置的电路图。FIG. 3 is a circuit diagram of a capacitance measuring device for a capacitive touch panel according to a preferred embodiment of the present invention.
图4A所示为本发明多工器的一方块图。FIG. 4A is a block diagram of the multiplexer of the present invention.
图4B所示为图4A中多工器的部分电路图。FIG. 4B is a partial circuit diagram of the multiplexer in FIG. 4A.
图5为依据本发明较佳具体实例的参考电压源的电路图。FIG. 5 is a circuit diagram of a reference voltage source according to a preferred embodiment of the present invention.
图6为依据本发明较佳具体实例的第一放电电流源的电路图。FIG. 6 is a circuit diagram of a first discharge current source according to a preferred embodiment of the present invention.
图7为依据本发明较佳具体实例的差动比较器的电路图。FIG. 7 is a circuit diagram of a differential comparator according to a preferred embodiment of the present invention.
图8为依据本发明较佳具体实例的第一低通滤波器的电路图。FIG. 8 is a circuit diagram of a first low-pass filter according to a preferred embodiment of the present invention.
图9为说明本发明较佳具体实例的电容测量装置操作波形图。Fig. 9 is a waveform diagram illustrating the operation of the capacitance measuring device of a preferred embodiment of the present invention.
图10为说明本发明的电容测量方法流程图。FIG. 10 is a flowchart illustrating the capacitance measurement method of the present invention.
图11为依据本发明另一具体实例的影像显示系统的方块示意图。FIG. 11 is a schematic block diagram of an image display system according to another embodiment of the present invention.
附图标号:Figure number:
触控面板200A 触控面板单元300A
控制器30A
条状电极32A、34A
感测电路100A 充电电流源Ic
第一电流源20A 第二电流源22AThe first
多工器10 电容测量装置100
充电电流源Ic 第一放电电流源20Charging current source Ic The first discharging current source 20
第二放电电流源22 参考电压源30The second discharge current source 22
第一低通滤波器40 第二低通滤波器42The first low-
差动比较器50 输出缓冲器60
充电开关SW_C第一放电开关SW_ACharge switch SW_C First discharge switch SW_A
第二放电开关SW_BThe second discharge switch SW_B
X方向开关SX1-SXM Y方向开关SY1-SYNX direction switch SX1-SXM Y direction switch SY1-SYN
XY控制信号SWXY 开关控制信号SW1-SWMXY control signal SWXY switch control signal SW1-SWM
电极X1-XMElectrode X1-XM
第一切换开关电容C11,C12,C13First switching capacitors C11, C12, C13
第二切换开关电容C21,C22 储存电容CxThe second switching capacitor C21, C22 storage capacitor Cx
薄膜晶体管对 A-F 晶体管Q1-Q7Thin film transistors to A-F transistors Q1-Q7
电容式触控面板200 显示模块300
输入模块400 影像显示系统500
步骤S100-S106Steps S100-S106
具体实施方式Detailed ways
请参见图3,为依据本发明一较佳具体实例的电容式触控面板的电容测量装置100的电路图,该电容测量装置100可以配合一多工器10使用,以选择性地测量如图1所示的投射电容式触控面板单元300A上的某一电极的接触电容Cs(详见后述)。为了简化说明,部分类似的元件使用与图1及图2类似的图号,虽未见于图面,但是须知多工器10及该电容测量装置100受到一控制器(未图示)所控制,以进行电极选择、提供操作时脉及判读接触位置工作。Please refer to FIG. 3 , which is a circuit diagram of a capacitance measuring device 100 of a capacitive touch panel according to a preferred embodiment of the present invention. The capacitance measuring device 100 can be used in conjunction with a
如图3所示,该电容测量装置100包含一差动比较器50、分别接于差动比较器50的第一输入端(例如为非反相输入端V+)及第二输入端(例如为反相输入端V-)的第一低通滤波器40及第二低通滤波器42、接于第二低通滤波器42的参考电压源30、与第一低通滤波器40及该多工器10的接点P电连接的充电电流源Ic、第一放电电流源20(提供第一放电电流IL)、第二放电电流源22(提供第二放电电流IS)。再者该充电电流源Ic、该第一放电电流源20及该第二放电电流源22分别由充电开关SW_C、第一放电开关SW_A、及第二放电开关SW_B所切换控制。该比较器50的输出连接至一输出缓冲器60,以进一步连到控制器分析。As shown in FIG. 3 , the capacitance measuring device 100 includes a
图4A所示为该多工器10的一方块图,该多工器10可用于如图1所示的投射电容式触控面板单元300A,因此图4A亦包含投射电容式触控面板单元300A以利说明。该多工器10包含对应M条垂直(纵方向)条状电极32A的M组开关SX1-SXM及对应于N条水平(横方向)条状电极34A的N组开关SY1-SYN。假设M>N,则多工器10仅需M+1组控制信号即可控制M组X方向开关SX1-SXM及N组Y方向开关SY1-SYN。更详细而言,若多工器10要选择第k组X方向开关,以将第k条电极信号输出至连接点P,则多工器10可由XY控制信号SWXY选择X方向开关,再通过开关控制信号SW1-SWM来选择第k组X方向电极输出至连接点P,且将其余未被选择的电极接地。再者,若多工器10要选择第k组Y方向开关,以将第k条电极信号输出至连接点P,则多工器10可由XY控制信号SWXY选择Y方向开关,再通过开关控制信号SW1-SWN来选择第k组Y方向电极输出至连接点P,且将其余未被选择的电极接地。因此该多工器10仅需要1+Max(M,N)条信号线(在此范例为1+M,因为M>N)及(M+N)组开关即可控制M组X方向开关SX1-SXM及N组Y方向开关SY1-SYN,大幅减少信号线使用数目。FIG. 4A is a block diagram of the
图4B所示为该多工器10的部分电路图,主要为对应M组X方向开关SX1-SXM的电路,而对应N组Y方向开关SY1-SYN的电路也可依此类推。如该图所示,每一开关包含四个晶体管,且通过控制信号SWk(k=1..M)及SWXY选择性地将所述这些开关接到连接点P或是接地。更具体而言,每一开关(SX1-SXM,SY1-SYN)具有四个晶体管,且其中两个晶体管串接于连接点P及一电极(X1-XM)之间,另两个晶体管并接于一接地及电极(X1-XM)之间。FIG. 4B is a partial circuit diagram of the
参见图5,为依据本发明一较佳具体实例的电容测量装置100所使用的参考电压源30的电路图。该参考电压源30包含一参考电压Vref、一直流共同电压(DCVCOM)、五个分别受到第一时脉及第二时脉控制的切换开关电容C11,C12,C13,C21,C22、及一个储存电容Cx。参见图9,该第一时脉CLK1及第二时脉CLK2为彼此在时间上不重叠的时脉,在第一时脉CLK1导通(第二时脉CLK2关闭)时,第一切换开关电容C11,C12,C13闭合而第二切换开关电容C21,C22打开,因此参考电压Vref可以储存在储存电容Cx内。在第二时脉CLK2导通(第一时脉CLK1关闭)时,第二切换开关电容C21,C22闭合而第一切换开关电容C11,C12,C13打开,因此可将参考电压Vref与直流共同电压(DCVCOM)叠加(superimposed)产生一修正参考电压Vref′,该修正参考电压Vref′送至差动比较器50的第二输入端处理。若直流共同电压(DCVCOM)有噪声,参考图3,噪声也会由寄生电容Cp而耦合至差动比较器50的第一输入端。通过本发明的参考电压源30,由于修正参考电压Vref′也有来自于直流共同电压(DCVCOM)的叠加成份,因此可以通过差动方式消除噪声,增加测量精密度。在该电容式触控面板用于液晶显示器的触控面板时,该参考电压源30可以消除来自直流共同电压的噪声。更具体而言,在液晶显示器中,须通过调整直流共同电压(DCVCOM)来减少闪烁现象,且上下板的共同电压的共电极(common electrode)通过阵列外的导电金胶连接。由于电容式触控面板用于液晶显示器的触控面板时是位于上板,因此电容式触控面板的电容测量装置须克服来自下板且透过共电极耦合至上板的噪声;通过产生叠加有直流共同电压(DCVCOM)噪声的修正参考电压Vref′及差动比较,即可降低来自下板的噪声干扰。Referring to FIG. 5 , it is a circuit diagram of the
参见图6,为依据本发明一较佳具体实例的电容测量装置100所使用的第一放电电流源20的电路图。该第一放电电流源20包含一个输入TFT晶体管及六个薄膜晶体管(TFT)对(A-F),以提供一个在连接点P电压由-5V到7V(或是更大)变化时皆可提供大放电电流的电流源。在连接点P电压为-5V时,六个TFT晶体管对(A-F)在饱和区域操作,若连接点P电压由-5V变化到7V时,TFT晶体管对(F-B)会逐一进入线性区域;然而VDDD电压及连接点P的压降落在TFT晶体管对A上,因此TFT晶体管对A仍操作在饱和模式,且提供一定电流。通过连接点P电压变化时皆可提供大放电电流的电流源。Referring to FIG. 6 , it is a circuit diagram of the first discharge current source 20 used in the capacitance measuring device 100 according to a preferred embodiment of the present invention. The first discharge current source 20 includes an input TFT transistor and six thin film transistor (TFT) pairs (A-F) to provide a large discharge current source when the voltage at the connection point P changes from -5V to 7V (or greater). Current source for the discharge current. When the voltage at the connection point P is -5V, the six TFT transistor pairs (A-F) operate in the saturation region. If the voltage at the connection point P changes from -5V to 7V, the TFT transistor pairs (F-B) will enter the linear region one by one; however, VDDD The voltage and the voltage of the connection point P drop on the TFT transistor pair A, so the TFT transistor pair A still operates in a saturation mode and provides a certain current. A current source that can provide a large discharge current when the voltage across the connection point P changes.
参见图7,为依据本发明一较佳具体实例的电容测量装置100所使用的差动比较器50的电路图。该差动比较器50包含7个晶体管Q1-Q7,其中正电压VDDA连接至晶体管Q1-Q3,Q5闸极提供第一输入端,Q4闸极提供第二输入端。晶体管Q6-Q7连接到参考偏压Vb及负电压VSSA以提供偏压基准。晶体管Q3及Q7的接点则提供差动比较器50的输出,藉此提供一比较输入电压Vin及修正参考电压Vref′的差动比较器。Referring to FIG. 7 , it is a circuit diagram of the
参见图8,为依据本发明一较佳具体实例的电容测量装置100所使用的第一低通滤波器40的电路图。现有的低通滤波器例如可为电阻-电容电路(RC电路),且负载端接于电容上,本发明的第一低通滤波器40包含三个串接的RC电路,且每一串接级(stage)的电阻值为原先单一RC低通滤波器的1/3,而电容值也为原先低通滤波器的1/3,这样即可降低低通截止频率,有效抑制噪声。依据发明人的分析,若串接的RC电路超过四级,则会使滤波波形变差。再者,第二低通滤波器42亦可采取与第一低通滤波器40相同的多级实现方式,以有效降低噪声。Referring to FIG. 8 , it is a circuit diagram of the first low-
参见图9,为说明本发明一较佳具体实例的电容测量装置100操作的波形图,图中所示波形为对于一电极的完整检测过程。同时参考图3及图9,首先控制器控制预充电开关SW_C将来自充电电流源Ic的充电电流对接触电容Cs及寄生电容Cp充电。随后控制器分别控制第一充电开关SW_A及第二充电开关SW_B。而将接触电容Cs及寄生电容Cp的电荷分别由较大的第一电流源20(提供电流IL)放电及较小的第二电流源22(提供电流IS)放电。在较小的第二电流源22放电阶段,控制器可控制第一时脉CLK1及第二时脉CLK2,以产生参考电压源30的修正参考电压Vref′。差动比较器50比较修正参考电压Vref′及来自接触电容Cs及寄生电容Cp的输入信号Vin,即可产生脉宽调变(PWM)输出信号(Vout)。控制器可以判断PWM输出信号的脉宽以判断电容变化。因此配合图4A及图4B所示,当多工器10通过控制信号SWXY选择X或是Y方向开关,再通过控制信号SW1-SWM来选择特定的电极输出至连接点P,且将其余未被选择的电极接地;控制器即可由PWM输出信号的脉宽以判断电容变化,进而判断接触位置。再者,控制器可在该第二放电电流放电期间,比对该修正参考电压及该输入电压,以产生多个脉宽调变信号,且由所述这些脉宽调变信号的平均值判断该接触电容。Referring to FIG. 9 , it is a waveform diagram illustrating the operation of the capacitance measuring device 100 in a preferred embodiment of the present invention. The waveform shown in the figure is a complete detection process for an electrode. Referring to FIG. 3 and FIG. 9 at the same time, firstly, the controller controls the pre-charging switch SW_C to charge the contact capacitance Cs and the parasitic capacitance Cp with the charging current from the charging current source Ic. Then the controller controls the first charging switch SW_A and the second charging switch SW_B respectively. The charges of the contact capacitance Cs and the parasitic capacitance Cp are respectively discharged by the larger first current source 20 (providing the current IL) and the smaller second current source 22 (providing the current IS). During the discharge phase of the second current source 22 , the controller can control the first clock CLK1 and the second clock CLK2 to generate the modified reference voltage Vref′ of the
参见图10,为说明使用电容式触控面板的电容测量装置进行的电容测量方法流程图,其中该电容测量方法测量该电容式触控面板的一电极的一接触电容Cs。该电容测量方法首先经由一连接点P对于该电极预充电后,对该电极以一第一放电电流放电,其中该第一放电电流可以由图6所示的第一放电电流源20提供(S100)。随后对该电极以一第二放电电流放电,其中该第一放电电流大于该第二放电电流(S102)。该电容测量方法接着提供一修正参考电压Vref′,该修正参考电压Vref′为一参考电压Vref及一直流共同电压(DCVCOM)的叠加结果,且该直流共同电压(DCVCOM)亦电连接到该触控面板(S104)。最后,在该第二放电电流放电期间,比对该修正参考电压Vref′及在该连接点P上的一输入电压Vin,以判断该接触电容的数值(S106)。Referring to FIG. 10 , it is a flowchart illustrating a capacitance measurement method using a capacitance measurement device of a capacitive touch panel, wherein the capacitance measurement method measures a contact capacitance Cs of an electrode of the capacitive touch panel. In the capacitance measuring method, firstly, after precharging the electrode via a connection point P, the electrode is discharged with a first discharge current, wherein the first discharge current can be provided by the first discharge current source 20 shown in FIG. 6 (S100 ). Then discharge the electrode with a second discharge current, wherein the first discharge current is greater than the second discharge current ( S102 ). The capacitance measurement method then provides a modified reference voltage Vref', which is the superposition result of a reference voltage Vref and a DC common voltage (DCVCOM), and the DC common voltage (DCVCOM) is also electrically connected to the contactor. control panel (S104). Finally, during the discharge period of the second discharge current, compare the revised reference voltage Vref′ with an input voltage Vin on the connection point P to determine the value of the contact capacitance ( S106 ).
再者,在上述的步骤S104时,该修正参考电压Vref′可由图5所示的参考电压源30提供。该参考电压源30包含多个第一切换开关电容C11,C12,C13、多个第二切换开关电容C21,C22及一储存电容Cx,其中所述这些第一切换开关电容C11,C12,C13及所述这些第二切换开关电容C21,C22由时间不重叠的时脉(CLK1,CLK2)轮流切换,以使该参考电压Vref与该直流共同电压(DCVCOM)叠加以产生该修正参考电压Vref′。相同地,配合图3及图8,该修正参考电压Vref′及该输入电压Vin可在比对前先做低通滤波处理,其中低通滤波处理由多个的串接电阻-电容电路进行。再者,在上述的步骤S104中,在该第二放电电流放电期间,可持续比对该修正参考电压Vref′及该输入电压,以产生多个脉宽调变信号,且由所述这些脉宽调变信号的平均值判断该接触电容。Furthermore, in the above step S104, the modified reference voltage Vref′ may be provided by the
参见图11,为依据本发明另一具体实例的影像显示系统500的方块示意图。该影像显示系统500包含一显示模块300,其中该显示模块300具有一电容式触控面板200(例如图4A所示的电容式触控面板200A),其中本发明图3、图4A及图4B所示电容测量装置100及多工器10,可设置于电容式触控面板200上或设置于电容式触控面板200外。一输入模块400耦接至显示模块300,以将包含影像信号的输入信号显示模块300,经处理后显示影像。该显示模块300可为一液晶显示模块或是一有机电激发光(OLED)显示模块。该影像显示系统500例如可为一个人数字助理(personal digital assistant,PDA)、一显示器(display)、一笔记型计算机(notebook computer)、一数字相机(digital camera)、一车用显示器(car display)、一平板计算机(panel computer)、一电视(television)、一全球定位系统(global positioning system,GPS)、一航空用显示器(avionicsdisplay)、一数字像框(digital photo frame)、一便携式DVD放影机(portable DVDplayer)或一移动电话(mobile phone)或其他便携式电子装置。Referring to FIG. 11 , it is a schematic block diagram of an
本发明的电容式触控面板及其电容测量装置与方法以参考电流源产生的修正参考电压以叠加噪声,再由差动比较以去除噪声,可增加比对精确度。再者,本发明的电容测量装置提供一个有稳定电压的第一放电电流源,可以提升比对解析度。In the capacitive touch panel and its capacitance measuring device and method of the present invention, the modified reference voltage generated by the reference current source is used to superimpose noise, and then the noise is removed by differential comparison, which can increase the comparison accuracy. Furthermore, the capacitance measuring device of the present invention provides a first discharge current source with a stable voltage, which can improve the comparison resolution.
综上所述,本发明已具有产业利用性、新颖性与进步性,又本发明的构造也未曾见于同类产品及公开使用,完全符合发明专利申请要件,故依专利法提出申请。To sum up, the present invention has industrial applicability, novelty and progress, and the structure of the present invention has never been seen in similar products and public use. It fully meets the requirements of the invention patent application, so the application is filed in accordance with the Patent Law.
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