WO2018076204A1 - 一种电容变化量检测电路及触摸屏、触摸检测方法 - Google Patents

一种电容变化量检测电路及触摸屏、触摸检测方法 Download PDF

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WO2018076204A1
WO2018076204A1 PCT/CN2016/103379 CN2016103379W WO2018076204A1 WO 2018076204 A1 WO2018076204 A1 WO 2018076204A1 CN 2016103379 W CN2016103379 W CN 2016103379W WO 2018076204 A1 WO2018076204 A1 WO 2018076204A1
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Prior art keywords
capacitor
denoising
operational amplifier
switch
power source
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PCT/CN2016/103379
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English (en)
French (fr)
Inventor
范硕
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深圳市汇顶科技股份有限公司
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Priority to KR1020187003870A priority Critical patent/KR102056018B1/ko
Priority to EP16911786.8A priority patent/EP3343335B1/en
Priority to CN201680001772.4A priority patent/CN108431749B/zh
Priority to PCT/CN2016/103379 priority patent/WO2018076204A1/zh
Priority to US15/879,760 priority patent/US10372284B2/en
Publication of WO2018076204A1 publication Critical patent/WO2018076204A1/zh

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0416—Control or interface arrangements specially adapted for digitisers
    • G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0412—Digitisers structurally integrated in a display
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/13—Sensors therefor
    • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/1365—Matching; Classification

Definitions

  • the embodiment of the invention belongs to the field of touch detection, and particularly relates to a capacitance change amount detecting circuit, a touch screen, a touch screen and a touch detecting method.
  • touch or fingerprint operations are typically detected by detecting a change in capacitance.
  • the prior art provides a circuit structure as shown in FIGS. 1 and 2.
  • S1, S3, and S5 are closed, and the capacitance Ctp to be charged is charged, and the charges stored in the capacitors C1 and C2 are discharged, and the other switches are turned off.
  • S2 and S4 are closed, the other switches are turned off, and the stored charge is re-allocated on Ctp. According to the charge conservation principle of the capacitor, the following equation is obtained:
  • Ctp contains the basic values and changes before the change, which can be divided into Cbg and Csig. After N sampling, there are the following equations:
  • Vpwr contains noise
  • the noise comes from the driver circuit that generates Vpwr, and other interferences, including in the mobile or wearable device, but not limited to screen drive signal interference, but also from charger interference, other parts of the chip itself.
  • the interference generated therefore, after N sampling integration, the noise and interference will also become larger with the integration, resulting in too high signal-to-noise ratio of the output signal, reducing the accuracy of touch detection or fingerprint recognition.
  • the embodiments of the present invention provide a capacitance change amount detecting circuit, a touch screen, and a touch detecting method, so as to solve the problem that the accuracy of touch detection or fingerprint recognition is reduced due to the presence of noise and interference in the prior art, by reducing Or eliminate the influence of the driving voltage noise and other interference signals superimposed on the driving voltage on the signal output by the integrating circuit, thereby improving the signal-to-noise ratio of the useful signal, thereby reducing the design requirements of the circuit for other modules and reducing the overall power consumption of the chip.
  • the embodiment of the present invention provides a capacitance change amount detecting circuit for detecting a capacitance change amount of a capacitor to be tested, wherein one end of the detected capacitor is connected to a reference ground, and the other end is connected to the first power source through a first switch.
  • the detecting circuit comprises:
  • An operational amplifier a denoising capacitor, an integrating capacitor, and a plurality of switches
  • the non-inverting input terminal of the operational amplifier is connected to the second power source, and the inverting input terminal of the operational amplifier is connected to the other end of the measured capacitor through the first switch;
  • One end of the denoising capacitor is connected to the other end of the measured capacitor through a second switch, and is connected to a reference ground through a third switch, and the other end of the denoising capacitor is connected to the first power source through the fourth switch, and Accessing the reference ground through the fifth switch;
  • Both ends of the integrating capacitor are connected by a sixth switch.
  • the first power source is a driving voltage source or a driving current source.
  • the denoising capacitor is a capacitor with an adjustable capacitance value.
  • a first resistor is connected between the second switch and the inverting input terminal of the operational amplifier.
  • a second resistor is connected between the second power source and the non-inverting input terminal of the operational amplifier.
  • an embodiment of the present invention provides a touch screen, where the touch screen includes the capacitance change amount detecting circuit.
  • an embodiment of the present invention provides a touch detection method, where the method includes:
  • one end of the detected capacitor and one end of the denoising capacitor are simultaneously connected to the first power source, and the other end of the detected capacitor and the other end of the denoising capacitor are connected to a ground;
  • the obtaining the output result of the operational amplifier specifically includes: repeatedly performing the first phase and the second phase according to a preset number of executions to obtain an output result.
  • the preset execution times are different for different measured capacitances.
  • the switch between the two electrode plates of the integrating capacitor is closed, and the integrating capacitor is discharged, and after the discharge is completed, the switch between the two electrode plates of the integrating capacitor is newly opened.
  • the capacitance value of the denoising capacitor is adjusted according to the capacitance value of the measured capacitance.
  • the capacitance variation detecting circuit and the touch screen and the touch detecting method provided by the embodiment of the present invention sample the noise and interference received by the detected capacitor through a denoising capacitor, and then eliminate the influence of noise and interference by redistributing the charge; specifically While charging the capacitor being sensed, by connecting the same power source to the denoising capacitor, the noise and interference loaded on the detected capacitor and the denoising capacitor are in phase, and then in the charge redistribution and integration process, The noise and interference superimposed on the denoising capacitor can cancel the noise and interference superimposed on the detected capacitor.
  • the noise and interference of the driving voltage do not adversely affect the signal-to-noise ratio of the circuit, the signal noise of the final output signal is improved. Correspondingly, this can reduce the design requirements of other modules, reduce the difficulty of software detection and the difficulty of detection algorithms, thereby reducing chip complexity and overall power consumption.
  • FIG. 1 is a schematic diagram of a state of a conventional capacitance change amount detecting circuit
  • FIG. 2 is a schematic diagram of another state of a conventional capacitance change amount detecting circuit
  • FIG. 3 is a schematic diagram of a state of a schematic diagram of a capacitance variation detecting circuit according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of another capacitance change amount detecting circuit according to an embodiment of the present invention.
  • FIG. 5 is a schematic diagram of another state of a schematic diagram of a capacitance variation detecting circuit according to an embodiment of the present invention.
  • FIG. 6 is a flowchart of a touch detection method according to an embodiment of the present invention.
  • references to "an embodiment” herein mean that a particular feature, structure, or characteristic described in connection with the embodiments can be included in at least one embodiment of the invention.
  • the appearances of the phrases in various places in the specification are not necessarily referring to the same embodiments, and are not exclusive or alternative embodiments that are mutually exclusive. Those skilled in the art will understand and implicitly understand that the embodiments described herein can be combined with other embodiments.
  • FIG. 3 is a state diagram of the capacitance variation detecting circuit provided in the embodiment, including:
  • the circuit includes a sampling module I and an integration module II.
  • the sampling module 1 includes a detected capacitance Ctp, a denoising capacitor C1, and a plurality of switches, as shown in FIG.
  • the switches SW1 to SW6 are shown
  • the integration module II includes an operational amplifier SOP1, an integrating capacitor C2, and a switch SW7; between the components of the sampling module I and the integration module II and between the modules, the following can be adopted Way to connect:
  • One end of the detected capacitor Ctp is connected to the reference ground, the other end of the detected capacitor Ctp is connected to the power source Vch through the switch SW1, and is connected to one end of the denoising capacitor C1 through the switch SW2, and is connected to the operational amplifier SOP1 through the switch SW3.
  • the other end of the denoising capacitor C1 is connected to the power source Vch through the switch SW5, and is connected to the reference ground through the switch SW6.
  • the denoising capacitor C1 is a capacitor with an adjustable capacitance value, according to the detecting capacitor Ctp. The size of the denoising capacitor C1 is adjusted to the appropriate capacitance value.
  • Both ends of the integrating capacitor C2 are connected by a switch SW7;
  • the positive phase input terminal of the operational amplifier SOP1 is connected to the power source Vcm.
  • a resistor R2 is connected between the power source Vcm and the positive phase input terminal of the operational amplifier SOP1.
  • the power source Vch is a driving voltage source or a driving current source
  • the capacitance variation detecting circuit is driven by the driving voltage source or the driving current source.
  • the capacitance variation detecting circuit provided by the embodiment of the invention has two working states, including:
  • switches SW1, SW4, SW5 are closed and switches SW2, SW3, SW6 are open.
  • the circuit operates as shown in FIG. 5, in which the switches SW1, SW4, SW5, SW7 are open and the switches SW2, SW3, SW6 are closed.
  • the capacitance variation detecting circuit provided by the embodiment of the invention can quickly detect the capacitance change caused by the touch operation or the fingerprint recognition.
  • a touch screen is further provided, and the touch screen includes the capacitance change amount detecting circuit described in the foregoing embodiment.
  • the capacitance change amount detecting circuit described in the foregoing embodiment.
  • a touch detection method is provided.
  • the method is based on the capacitance change amount detection circuit described in the foregoing embodiment, and the method includes:
  • the one end of the detected capacitor and the end of the denoising capacitor are simultaneously connected to the first power source, and the other end of the detected capacitor and the other end of the denoising capacitor are connected to the ground.
  • the switch SW1 between the detected capacitor Ctp and the power source Vch is closed, and one end of the denoising capacitor C1 is connected to the power source Vch.
  • the other end of the noise capacitor C1 is connected to the ground, that is, the switches SW1, SW4, and SW5 are closed, and the switches SW2, SW3, and SW6 are turned off.
  • the power supply Vch charges the detected Ctp, and the denoising capacitance C1 for canceling the noise is also charged by the Vch. Since the detected capacitor Ctp and the denoising capacitor C1 are simultaneously charged by the power source Vch, the noise applied by the power source Vch to the detected capacitor Ctp and the denoising capacitor C1 and the other interference signals are in phase with the same amplitude.
  • the switch between the detected capacitor Ctp and the power source Vch is disconnected, and the inverting input terminal of the operational amplifier SOP1 is connected, and The denoising capacitor C1 is switched to the ground referenced at one end of the first stage of the power supply Vch, and the other end of the denoising capacitor C1 is connected to the inverting input of the operational amplifier SOP1. That is, the switches SW1, SW4, and SW5 are turned off, and the switches SW2, SW3, and SW6 are closed.
  • the denoising capacitor C1 is equivalent to being connected to the circuit after being flipped, and the charge on the detected capacitor Ctp and the denoising capacitor C1 is redistributed, so that the output of the output of the operational amplifier SOP1 can be obtained according to the principle of conservation of charge.
  • Vout is:
  • N the noise or interference loaded on Vch.
  • Vch N
  • the same is true for the conservation of charge.
  • the output after integration is:
  • the change value of the capacitance Ctp can be obtained, thereby determining whether there is a touch operation or fingerprint recognition.
  • the obtaining the output result of the operational amplifier SOP1 specifically includes: repeatedly performing the first phase according to a preset number of executions N and The operation of the second stage is performed to obtain an output result, where the number of executions N is a positive integer, which may be selected several times or hundreds of times according to a specific circuit.
  • the preset The number of executions N is different. By multi-sampling the integral, the value of the output result Vout can be amplified, thereby facilitating detection and judgment.
  • the switch SW7 can be kept in the off state, that is, the switch is not provided in the circuit.
  • the switch SW7 between the two electrode plates of the integrating capacitor C2 is closed, and the residual charge on C2 is discharged, and after the integrating capacitor C2 is discharged, The switch SW7 between the two electrode plates of the integrating capacitor C2 is newly opened to start a new integration period, so that it is ensured that the new integration period is not affected by the residual charge in C2.
  • the capacitance value of the denoising capacitor C1 is adjustable, and the method further includes adjusting a capacitance value of the denoising capacitor C1 according to a capacitance value of the measured capacitance Ctp, and adjusting a size of the denoising capacitor C1.
  • a signal to noise ratio that meets the detection requirements can be obtained.
  • the capacitance variation detecting circuit and the touch screen and the touch detecting method provided by the embodiment of the present invention sample the noise and interference received by the detected capacitor through a denoising capacitor, and then eliminate the influence of noise and interference by redistributing the charge; specifically While charging the capacitor being sensed, by connecting the same power source to the denoising capacitor, the noise and interference loaded on the detected capacitor and the denoising capacitor are in phase, and then in the charge redistribution and integration process, The noise and interference superimposed on the denoising capacitor can cancel the noise and interference superimposed on the detected capacitor.
  • the noise and interference of the driving voltage do not adversely affect the signal-to-noise ratio of the circuit, the signal noise of the final output signal is improved. Correspondingly, this can reduce the design requirements of other modules, reduce the difficulty of software detection and the difficulty of detection algorithms, thereby reducing chip complexity and overall power consumption.

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Abstract

属于触摸检测领域一种涉及电容变化量检测电路及触摸屏、触摸检测方法，所述方法包括：将被检测电容（Ctp）的一端和去噪电容（C1）的一端同时接入所述第一电源（Vch），并将所述被检测电容（Ctp）的另一端和所述去噪电容（C1）的另一端接参考地；断开所述被检测电容（Ctp）与所述第一电源（Vch）的连接，并接入运算放大器（SOP1）的反相输入端，同时将所述去噪电容（C1）在第一阶段接第一电源（Vch）的一端切换为接参考地，同时，将所述去噪电容（C1）的另一端接入所述运算放大器（SOP1）的反相输入端；根据所述运算放大器（SOP1）的输出结果判断是否有触摸操作。通过提供的检测电路及方法，可以降低或消除驱动电压的噪声以及其他叠加在驱动电压上的干扰信号对积分电路输出的信号的影响，从而提高有用信号的信噪比。

Description

一种电容变化量检测电路及触摸屏、触摸检测方法 【技术领域】
本发明实施例属于触摸检测领域，尤其涉及一种电容变化量检测电路及触摸屏、触摸屏及触摸检测方法。
【背景技术】
在触摸屏的触摸检测或者指纹识别应用中，一般通过检测电容变化量来检测触摸或指纹操作。在电容变化量的检测电路中，现有技术提供一种电路结构如图1和图2所示。在图1所示的状态下，S1、S3、S5闭合，对待测电容Ctp充电，释放电容C1和C2存储的电荷，其他开关断开。在图2所示的状态下，S2、S4闭合，其他开关断开，Ctp上存储电荷重新分配，根据电容的电荷守恒原理，有如下等式：
Q＝CtpVpwr＝CtpVref+C1Vref+C2(Vref-Vout)
N次采样后的输出为：
Figure PCTCN2016103379-appb-000001
当Ctp的电容大小由于触摸按压或者指纹等发生改变时，通过该电路的输出可以检测出来Ctp的变化量。Ctp包含了变化前的基本值和变化量，可分为Cbg和Csig，则N次采样后有如下等式：
Figure PCTCN2016103379-appb-000002
可以看到由于加入了C1，无用的电容基本值Cbg部分带来的电荷变化被消掉，针对输出结果可以只分析变化量部分。
然而，发明人在实现本发明的过程中发现，上述过程存在一个问题：
由于Vpwr当中包含噪声，该噪声来自于产生Vpwr的驱动电路，以及其他干扰，干扰源在一个移动或者可穿戴设备中包括但不仅限于屏幕驱动信号干扰，还可能来自充电器干扰，芯片本身其他部分产生的干扰，因此，在N次采样积分后，噪声和干扰也会随着积分而变大，导致输出信号信噪比过高，降低触摸检测或指纹识别的准确度。
【发明内容】
有鉴于此，本发明实施例提供一种电容变化量检测电路及触摸屏、触摸检测方法，以解决现有技术中由于存在噪声和干扰，导致触摸检测或指纹识别的准确度降低的问题，通过降低或消除驱动电压的噪声以及其他叠加在驱动电压上的干扰信号对积分电路输出的信号的影响，从而提高有用信号的信噪比，以降低电路对其他模块的设计要求，降低芯片整体功耗。
第一方面，本发明实施例提供一种电容变化量检测电路，用于检测待测电容的电容变化量，所述被检测电容一端接入参考地，另一端通过第一开关接入第一电源，其特征在于，所述检测电路包括：
运算放大器、去噪电容、积分电容和多个开关；
所述运算放大器的正相输入端接入第二电源，所述运算放大器的反相输入端通过第一开关连接所述被测电容的另一端；
所述去噪电容的一端通过第二开关连接所述被测电容的另一端，并通过第三开关接入参考地，所述去噪电容的另一端通过第四开关接入第一电源，以及通过第五开关接入参考地；
所述积分电容的两端通过第六开关连接。
进一步的，所述第一电源为驱动电压源或驱动电流源。
进一步的，所述去噪电容为电容值可调的电容。
进一步的，所述第二开关与运算放大器反相输入端之间接有第一电阻。
进一步的，所述第二电源与运算放大器正相输入端之间接有第二电阻。
第二方面，本发明实施例提供一种触摸屏，所述触摸屏包括上述电容变化量检测电路。
第三方面，本发明实施例提供一种触摸检测方法，所述方法包括：
第一阶段，将被检测电容的一端和去噪电容的一端同时接入所述第一电源，并将所述被检测电容的另一端和所述去噪电容的另一端接参考地；
第二阶段，断开所述被检测电容与所述第一电源的连接，并接入运算放大器的反相输入端，同时将所述去噪电容在第一阶段接第一电源的一端切换为接参考地，同时，将所述去噪电容的另一端接入所述运算放大器的反相输入端；
获取所述运算放大器的输出结果，根据所述输出结果判断是否有触摸操作。
进一步的，所述获取所述运算放大器的输出结果具体包括：根据预设的执行次数重复执行所述第一阶段和所述第二阶段，以得到输出结果。
进一步的，对于不同的被测电容，所述预设的执行次数不同。
进一步的，在执行所述第一阶段前将积分电容两电极板之间的开关闭合，对所述积分电容进行放电，放电完成后重新断开所述积分电容两电极板之间的开关。
进一步的，根据所述被测电容的电容值调整所述去噪电容的电容值。
通过本发明实施例提供的电容变化量检测电路及触摸屏、触摸检测方法，通过一个去噪电容来采样被检测电容受到的噪声跟干扰，然后通过电荷的再分配消除噪声跟干扰影响；具体是在对被检测电容进行充电的同时，通过在去噪电容上接入同一电源，因此在被检测电容和去噪电容上加载的噪声和干扰是同相位的，继而在电荷重分配和积分过程中，可以将去噪电容上叠加的噪声和干扰抵消被检测电容上叠加的噪声和干扰，当驱动电压的噪声和干扰对电路的信号噪声比不会产负面影响时，从而提高最终输出信号的信噪比，相应地，这样可以降低其他模块的设计要求，降低软件的检测难度跟检测算法的难度，从而降低芯片复杂度和整体功耗。
【附图说明】
为了更清楚地说明本发明或现有技术中的方案，下面将对实施例或现有技术描述中所需要使用的附图作一个简单介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有电容变化量检测电路的一种状态示意图；
图2为现有电容变化量检测电路的另一种状态示意图；
图3为本发明实施例提供的电容变化量检测电路的示意图的一种状态示意图；
图4为本发明实施例提供的另一电容变化量检测电路的示意图；
图5为本发明实施例提供的电容变化量检测电路的示意图另一种状态示意图；
图6为本发明实施例提供的触摸检测方法的流程图。
【具体实施方式】
为了使本技术领域的人员更好地理解本发明方案，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述。显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例,附图中给出了本发明的较佳实施例。本发明可以以许多不同的形式来实现，并不限于本文所描述的实施例，相反地，提供这些实施例的目的是使对本发明的公开内容的理解更加透彻全面。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范 围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本发明的技术领域的技术人员通常理解的含义相同。本文中在本发明的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本发明。本发明的说明书和权利要求书及上述附图中的术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本发明的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本发明实施例中，图3所示为本实施例提供的电容变化量检测电路的一种状态图，包括：
该电路包括采样模块I和积分模块II，具体地，如图3中两个虚线框所示的内容，所述采样模块I包括被检测电容Ctp、去噪电容C1和多个开关，如图3中所示的开关SW1～SW6，所述积分模块II包括运算放大器SOP1、积分电容C2和开关SW7；所述采样模块I和积分模块II内部的各元器件之间以及模块之间可通过下述方式连接：
所述被检测电容Ctp一端接入参考地，所述被检测电容Ctp另一端通过开关SW1接入电源Vch，以及通过开关SW2与去噪电容C1的一端相连，并通过开关SW3接入运算放大器SOP1的反相输入端，其中所述去噪电容C1的一端通过开关SW4接入参考地；可选的，如图4所示，所述开关SW3与运算放大器SOP1反相输入端之间接有电阻R1。
所述去噪电容C1的另一端通过开关SW5接入电源Vch，以及通过开关SW6接入参考地；可选的，所述去噪电容C1为电容值可调的电容，具体根据本检测电容Ctp的大小将去噪电容C1调整至合适的电容值。
所述积分电容C2的两端通过开关SW7连接；
所述运算放大器SOP1的正相输入端接入电源Vcm；可选的，如图4所示，所述电源Vcm与运算放大器SOP1正相输入端之间接有电阻R2。
可选的，所述电源Vch为驱动电压源或驱动电流源，通过所述驱动电压源或者驱动电流源驱动电容变化量检测电路。
本发明实施例提供的电容变化量检测电路有两种工作状态，包括：
在采样阶段下，如图3所示的电路工作状态，在该工作状态下，开关SW1、SW4、SW5闭合，而开关SW2、SW3、SW6断开。
在积分阶段下，如图5所示的电路工作状态，在该工作状态下，开关SW1、SW4、SW5、SW7断开，而开关SW2、SW3、SW 6闭合。
通过本发明实施例提供的电容变化量检测电路，可以快速检测触摸操作或者指纹识别带来的电容变化。
在本实施例中，还提供一种触摸屏，所述触摸屏包括前述实施例所述的电容变化量检测电路。所述电容变化量检测电路的具体组成可参考前述实施例的相关内容，在此不再赘述。
在本发明实施例中，如图6所述提供一种触摸检测方法，所述方法基于前述实施例所述的电容变化量检测电路，所述方法包括：
S1、第一阶段，将被检测电容的一端和去噪电容的一端同时接入第一电源，并将所述被检测电容的另一端和所述去噪电容的另一端接参考地。
具体的，参考图3所示的电路工作状态图，将所述被检测电容Ctp与所述电源Vch之间的开关SW1闭合，同时将所述去噪电容C1的一端接电源Vch，所述去噪电容C1的另一端接参考地，即开关SW1、SW4、SW5闭合，而开关SW2、SW3、SW6断开。
可以看到，电源Vch对被检测的Ctp充电，同时用于抵消噪声的去噪电容C1也被Vch充电。由于被检测电容Ctp和去噪电容C1同时被电源Vch充电，故而电源Vch加载在被检测电容Ctp和去噪电容C1上的噪声和其他干扰信号同相位同幅值。
S2、第二阶段，断开所述被检测电容与所述第一电源的连接，并接入运算放大器的反相输入端，同时将所述去噪电容在第一阶段接第一电源的一端切换为接参考地，同时，将所述去噪电容的另一端接入所述运算放大器的反相输入端；
具体的，参考图5所示的电路工作状态图，将所述被检测电容Ctp与所述电源Vch之间的开关断开，并接入所述运算放大器SOP1的反相输入端，同时将所述去噪电容C1在第一阶段接电源Vch的一端切换为接参考地，同时，将所述去噪电容C1的另一端接入所述运算放大器SOP1的反相输入端。即开关SW1、SW4、SW5断开，而开关SW2、SW3、SW6闭合。
可以知道，在第二阶段，去噪电容C1相当于被翻转后接入电路，被检测电容Ctp和去噪电容C1上的电荷重新分配，从而根据电荷守恒原理可以求得运算放大器SOP1输出端的输出Vout为：
Figure PCTCN2016103379-appb-000003
用Vch,N代表加载在Vch上的噪声或者干扰，对于Vch,N而言，同样通过电荷守恒原 理，其通过积分后的输出为：
Figure PCTCN2016103379-appb-000004
可以看到由于检测电容Ctp和去噪电容C1均通过Vch充电，如果式(2)中Ctp-C1的值够小，可使得Vch,N对应的噪声或者干扰输出被减弱或者消除。
S3、获取所述运算放大器的输出结果，根据所述输出结果判断是否有触摸操作。
具体的，将变化前的输出Vout与变化后的输出Vout对比，可求得电容Ctp的变化值，从而可判断是否存在触摸操作或者进行指纹识别。
可选的，在根据所述运算放大器SOP1的输出结果判断是否有触摸操作前，所述获取所述运算放大器SOP1的输出结果具体包括：根据预设的执行次数N重复执行所述第一阶段和所述第二阶段的操作，以得到输出结果，所述执行次数N为正整数，根据具体电路可选择几次或者上百次，可选的，对于不同的被测电容，所述预设的执行次数N不同。通过多次采样积分，可以放大输出结果Vout的数值，从而便于进行检测判断。上述实施方式中，开关SW7可保持断开状态，也即相当于该电路中未设置该开关。
在另一实施方式中，可选的，在执行所述第一阶段时将积分电容C2两电极板之间的开关SW7闭合，泄放掉C2上的残留电荷，待所述积分电容C2放电后重新断开所述积分电容C2两电极板之间的开关SW7，以开始新的积分周期，这样可以保证不会因为C2中残留的电荷对新的积分周期产生影响。
可选的，所述去噪电容C1的电容值可调，所述方法还包括根据所述被测电容Ctp的电容值调整所述去噪电容C1的电容值，通过调整去噪电容C1的大小可以得到满足检测要求的信噪比。
通过本发明实施例提供的电容变化量检测电路及触摸屏、触摸检测方法，通过一个去噪电容来采样被检测电容受到的噪声跟干扰，然后通过电荷的再分配消除噪声跟干扰影响；具体是在对被检测电容进行充电的同时，通过在去噪电容上接入同一电源，因此在被检测电容和去噪电容上加载的噪声和干扰是同相位的，继而在电荷重分配和积分过程中，可以将去噪电容上叠加的噪声和干扰抵消被检测电容上叠加的噪声和干扰，当驱动电压的噪声和干扰对电路的信号噪声比不会产负面影响时，从而提高最终输出信号的信噪比，相应地，这样可以降低其他模块的设计要求，降低软件的检测难度跟检测算法的难度，从而降低芯片复杂度和整体功耗。
以上仅为本发明的实施例，但并不限制本发明的专利范围，尽管参照前述实施例对本发明进行了详细的说明，对于本领域的技术人员来而言，其依然可以对前述各具体实施方 式所记载的技术方案进行修改，或者对其中部分技术特征进行等效替换。凡是利用本发明说明书及附图内容所做的等效结构，直接或间接运用在其他相关的技术领域，均同理在本发明专利保护范围之内。

Claims (11)

  1. 一种电容变化量检测电路，用于检测待测电容的电容变化量，所述被检测电容一端接入参考地，另一端接入第一电源，其特征在于，所述检测电路包括：
    运算放大器、去噪电容、积分电容和多个开关；
    所述运算放大器的正相输入端接入第二电源，所述运算放大器的反相输入端通过第一开关连接所述被测电容的另一端；
    所述去噪电容的一端通过第二开关连接所述被测电容的另一端，并通过第三开关接入参考地，所述去噪电容的另一端通过第四开关接入第一电源，以及通过第五开关接入参考地；
    所述积分电容的两端通过第六开关连接。
  2. 根据权利要求1所述的电容变化量检测电路，其特征在于，所述第一电源为驱动电压源或驱动电流源。
  3. 根据权利要求1所述的电容变化量检测电路，其特征在于，所述去噪电容为电容值可调的电容。
  4. 根据权利要求1-3任意一项所述的电容变化量检测电路，其特征在于，所述第二开关与运算放大器反相输入端之间接有第一电阻。
  5. 根据权利要求4所述的电容变化量检测电路，其特征在于，所述第二电源与运算放大器正相输入端之间接有第二电阻。
  6. 一种触摸屏，其特征在于，包括权利要求1-5任意一项所述的电容变化量检测电路。
  7. 一种触摸检测方法，所述方法应用于权利要求6所述的触摸屏，其特征在于，所述方法包括：
    第一阶段，将被检测电容的一端和去噪电容的一端同时接入所述第一电源，并将所述被检测电容的另一端和所述去噪电容的另一端接参考地；
    第二阶段，断开所述被检测电容与所述第一电源的连接，并接入运算放大器的反相输入端，同时将所述去噪电容在第一阶段接第一电源的一端切换为接参考地，同时，将所述去噪电容的另一端接入所述运算放大器的反相输入端；
    获取所述运算放大器的输出结果，根据所述输出结果判断是否有触摸操作。
  8. 根据权利要求7所述的方法，其特征在于，所述获取所述运算放大器的输出结果具体包括：根据预设的执行次数重复执行所述第一阶段和所述第二阶段，以得到输出结果。
  9. 根据权利要求8所述的方法，其特征在于，对于不同的被测电容，所述预设的执 行次数不同。
  10. 根据权利要求7所述的方法，其特征在于，在执行所述第一阶段时将积分电容两电极板之间的开关闭合，对所述积分电容进行放电，放电完成后重新断开所述积分电容两电极板之间的开关。
  11. 根据权利要求7所述的方法，其特征在于，根据所述被测电容的电容值调整所述去噪电容的电容值。
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