WO2021128209A1 - 电容检测电路、触控芯片和电子设备 - Google Patents

电容检测电路、触控芯片和电子设备 Download PDF

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Publication number
WO2021128209A1
WO2021128209A1 PCT/CN2019/128859 CN2019128859W WO2021128209A1 WO 2021128209 A1 WO2021128209 A1 WO 2021128209A1 CN 2019128859 W CN2019128859 W CN 2019128859W WO 2021128209 A1 WO2021128209 A1 WO 2021128209A1
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WIPO (PCT)
Prior art keywords
circuit
feedback resistor
capacitance detection
capacitance
capacitor
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PCT/CN2019/128859
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English (en)
French (fr)
Inventor
袁广凯
李国炮
姚志
廖观亮
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深圳市汇顶科技股份有限公司
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Application filed by 深圳市汇顶科技股份有限公司 filed Critical 深圳市汇顶科技股份有限公司
Priority to CN201980013382.2A priority Critical patent/CN113316759B/zh
Priority to PCT/CN2019/128859 priority patent/WO2021128209A1/zh
Priority to EP19932245.4A priority patent/EP3862857B1/en
Priority to US17/121,754 priority patent/US11275428B2/en
Publication of WO2021128209A1 publication Critical patent/WO2021128209A1/zh

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/26—Power supply means, e.g. regulation thereof
    • G06F1/32—Means for saving power
    • G06F1/3203—Power management, i.e. event-based initiation of a power-saving mode
    • G06F1/3234—Power saving characterised by the action undertaken
    • G06F1/325—Power saving in peripheral device
    • G06F1/3262—Power saving in digitizer or tablet
    • 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
    • G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
    • 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
    • G06F3/04166—Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving
    • 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
    • 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
    • G06F3/0443—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a single layer of sensing electrodes
    • 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
    • G06F3/0446—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45522—Indexing scheme relating to differential amplifiers the FBC comprising one or more potentiometers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45528—Indexing scheme relating to differential amplifiers the FBC comprising one or more passive resistors and being coupled between the LC and the IC
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45534—Indexing scheme relating to differential amplifiers the FBC comprising multiple switches and being coupled between the LC and the IC

Definitions

  • the embodiments of the present application relate to the field of capacitance detection, and more specifically, to a capacitance detection circuit, a touch chip, and an electronic device.
  • Capacitive sensors are widely used in electronic products to realize touch detection.
  • a conductor such as a finger
  • the capacitance corresponding to the detection electrode will change.
  • the information of the finger approaching or touching the detection electrode can be obtained to determine the user's operation.
  • the noise generated by the screen of the electronic device will affect the above-mentioned detection result. Therefore, how to reduce the influence of display noise on capacitance detection has become an urgent problem to be solved.
  • the embodiments of the present application provide a capacitance detection circuit, a touch chip, and an electronic device, which can reduce the influence of screen noise on capacitance detection.
  • a capacitance detection circuit for detecting the capacitance of a capacitor to be tested, the capacitor to be tested is a capacitor used for touch detection in a screen of an electronic device, and the capacitance detection circuit includes:
  • An amplifier circuit connected to the capacitor under test, and used to convert the capacitance signal of the capacitor under test into a voltage signal, the voltage signal being associated with the capacitance of the capacitor under test;
  • a control circuit connected to the amplifying circuit, is used for controlling the amplification of the amplifying circuit to be the first amplifying factor in the first period, and controlling the magnification of the amplifying circuit to the second amplifying factor in the second period, wherein The noise generated by the screen in the first period is less than the noise generated by the screen in the second period, and the first magnification is greater than the second magnification.
  • the amplifying circuit includes an operational amplifier, and a first feedback resistor and a second feedback resistor connected between the input terminal and the output terminal of the operational amplifier, and the first feedback resistor is The resistance value is greater than the resistance value of the second feedback resistor, and the control circuit is specifically configured to control the connection of the first feedback resistor and the disconnection of the second feedback resistor during the first period of time, so that the The magnification of the amplifying circuit is the first magnification; and, in the second period, the second feedback resistor is controlled to be connected, and the first feedback resistor is disconnected, so that the magnification of the amplifying circuit is The second magnification.
  • the operational amplifier is a differential operational amplifier, between the first input terminal and the first output terminal of the differential operational amplifier, and the second input terminal and the second input terminal of the differential operational amplifier. Between the output terminals, the first feedback resistor and the second feedback resistor are connected.
  • the amplifying circuit further includes a switch connected in series with each feedback resistor, and the control circuit controls the connection or disconnection of each feedback resistor through the switch.
  • the first time period and the second time period are determined according to the scanning frequency of the screen.
  • the capacitance detection circuit further includes: a driving circuit connected to the capacitor to be tested and used for inputting a driving signal to the capacitor to be tested.
  • the capacitance detection circuit further includes: a filter circuit, connected to the amplifying circuit, and configured to filter the voltage signal output by the amplifying circuit.
  • the capacitance detection circuit further includes: a sampling circuit, connected to the filter circuit, and configured to convert the filtered voltage signal into a digital signal.
  • a touch control chip including: the foregoing first aspect and the capacitance detection circuit in any one of the possible implementations of the first aspect.
  • an electronic device including: a screen; and, the aforementioned second aspect and the touch chip in any one of the possible implementations of the second aspect.
  • the control circuit in the capacitance detection circuit controls the amplification factor of the amplification circuit so that the amplification factor of the amplification circuit has a larger amplification factor in the first period of low noise on the screen, so as to improve the capacitance detection signal.
  • Signal Noise Ratio Signal Noise Ratio (Signal Noise Ratio, SNR); and make the amplifying factor of the amplifying circuit have a smaller magnifying factor in the second period of high noise on the screen to avoid saturation of the amplifying circuit.
  • the capacitance detection circuit improves the signal-to-noise ratio of capacitance detection while ensuring the effective operation of the amplifying circuit, and has better detection performance.
  • Fig. 1 is a schematic block diagram of a capacitance detection circuit according to an embodiment of the present application.
  • FIG. 2 is a possible schematic structural diagram of an amplifier circuit in an embodiment of the present application.
  • FIG. 3 is a possible schematic structural diagram of an amplifying circuit of an embodiment of the present application.
  • FIG. 4 is a schematic diagram based on the operation timing of the amplifying circuit shown in FIG. 3.
  • Fig. 5 is a possible implementation based on the circuit shown in Fig. 1.
  • the display layer of the screen will generate a lot of noise when scanning. This noise will affect the touch layer and easily make the amplifying circuit in the capacitance detection circuit of the touch layer. Saturation occurs. If saturation is avoided by reducing the magnification of the amplifying circuit, the effective detection signal will also be affected, thereby reducing the performance of the capacitance detection circuit.
  • the present application provides a capacitance detection circuit, which can reduce the influence of screen noise on capacitance detection.
  • Fig. 1 is a schematic block diagram of a capacitance detection circuit according to an embodiment of the present application.
  • the capacitance detection circuit 100 is used to detect the capacitance of the capacitor Cx to be tested, and the capacitor Cx to be tested is a capacitor used for touch detection in a screen of an electronic device.
  • the capacitance detection circuit 100 includes an amplifier circuit 110 and a control circuit 120.
  • the amplifying circuit 110 is connected to the capacitor Cx to be tested, and is used to convert the capacitance signal of the capacitor Cx to be tested into a voltage signal, and the voltage signal is related to the capacitance of the capacitor Cx to be tested.
  • the control circuit 120 is connected to the amplifying circuit 110, and is used for controlling the magnification 110 of the amplifying circuit to be the first magnification in the first period T1, and control the magnification of the amplifying circuit 110 to be the second magnification in the second period T2.
  • the noise generated by the screen in the first period T1 is smaller than the noise generated by the screen in the second period T2, and the first magnification is greater than the second magnification.
  • FIG. 4 shows the vertical synchronization signal (Vsync) and the horizontal synchronization signal (Hsync) of the screen.
  • the horizontal synchronization signal changes according to a certain rule.
  • the phase difference between the screen noise and the horizontal synchronization signal is basically unchanged, and the screen noise also changes according to a certain rule.
  • the noise generated by the screen can be divided into a first period T1 and a second period T2 in time.
  • the first period T1 is a low-noise period
  • the second period T2 is a high-noise period.
  • the embodiment of the present application does not make any limitation on how to determine the first time period T1 and the second time period T2.
  • the screen noise can be detected directly, and the first time period T1 and the second time period T2 can be determined according to the detected noise changes; or, by analyzing the output signal of the capacitance detection circuit 100, according to the quality of the output signal, The first time period T1 and the second time period T2 are determined.
  • the amplifying circuit 110 may amplify and output the signal.
  • the input terminal of the amplifying circuit 110 is connected to the capacitor Cx to be measured, and the output terminal of the amplifying circuit 110 outputs a voltage signal.
  • the voltage signal is related to the capacitance of the capacitor Cx to be tested.
  • the amplifying circuit 110 can convert the capacitance signal of the capacitor Cx to be tested into a voltage signal, so as to realize the detection of the capacitor Cx to be tested.
  • the control circuit 120 is used to control the magnification of the amplifying circuit 110.
  • the amplifying circuit 110 has a larger magnification in the first period T1 to improve the SNR of capacitance detection; and the amplifying circuit 110 has a smaller magnification in the second period T2 to avoid saturation of the amplifying circuit 110 and ensure the amplifying circuit 110 effective work. Therefore, while ensuring the effective operation of the amplifying circuit 110, the capacitance detection circuit 100 improves the signal-to-noise ratio of capacitance detection and has better detection performance.
  • the capacitance detection circuit in the embodiment of the present application may be used for mutual capacitance detection or self-capacitance detection, and the capacitor Cx to be tested may be the self-capacitance of each electrode to the ground.
  • the capacitor Cx to be measured is the mutual capacitance between the driving electrode and the detecting electrode.
  • the driving electrode is used to input a driving signal, which is denoted as TX.
  • the detection electrode can also be called a sensing electrode, which is used to sense a driving signal and generate a detection signal, which is denoted as RX.
  • the magnification of the amplifying circuit 110 can be adjusted through a feedback resistor.
  • the amplifying circuit 110 includes an operational amplifier, and a first feedback resistor and a second feedback resistor connected between the input terminal and the output terminal of the operational amplifier. Wherein, the resistance of the first feedback resistor is greater than the resistance of the second feedback resistor.
  • control circuit 120 may control the first feedback resistor to be connected in the first period and the second feedback resistor to be disconnected, so that the magnification of the amplifying circuit 110 is the first magnification; and, in the second period, it controls the second The feedback resistor is connected, and the first feedback resistor is disconnected, so that the magnification of the amplifying circuit 110 is the second magnification.
  • the control circuit 120 can control the connection or disconnection of the first feedback resistor and the second feedback resistor, for example, through a switch.
  • the capacitance value of the capacitor Cx under test at the corresponding position will change.
  • the capacitance signal of the capacitor Cx under test is converted into a voltage signal by the amplifying circuit 110.
  • the voltage signal can reflect the capacitance of the capacitor Cx under test. Capacitance changes, so as to obtain the user's touch information.
  • different feedback resistors can be used at different time periods to adjust the amplification factor of the amplifying circuit 110, so as to reduce the influence of screen noise on the capacitance detection as much as possible.
  • the amplifying circuit 110 includes an operational amplifier 101, a feedback resistor R f1, and a feedback resistor R f2 .
  • the switch K1 and the feedback resistor R f1 are connected in series between an input terminal and the output terminal of the operational amplifier 101, and the switch K2 and the feedback resistor R f2 are connected in series between the input terminal and the output terminal of the operational amplifier 101, and the input terminal and One end of the capacitor Cx to be tested is connected, and the other end of the capacitor Cx to be tested is grounded.
  • the other input terminal of the operational amplifier is connected to the voltage V CM .
  • the resistance value of the feedback resistor R f1 is greater than the resistance value of the feedback resistor R f2 .
  • the control circuit 120 can control the switch K1 to be closed and K2 to be opened in the first period T1, so that the amplifying circuit 110 has a larger magnification; and in the second period T2, control the switch K2 to be closed and K1 to be opened to make the amplifying circuit 110 has a smaller magnification.
  • the operational amplifier in the amplifying circuit 110 may be a differential operational amplifier. At this time, between the first input terminal and the first output terminal of the differential operational amplifier, and between the second input terminal and the second output terminal of the differential operational amplifier, the first feedback resistor and One of the second feedback resistors.
  • the amplifying circuit 110 may further include a switch connected in series with each feedback resistor, and the control circuit 120 controls the connection or disconnection of each feedback resistor through the switch.
  • the amplifying circuit 110 includes a differential operational amplifier 102, a feedback resistor R f1 and a feedback resistor R f2 , a feedback resistor R f3 and a feedback resistor R f4 .
  • the switch K1 and the feedback resistor R f1 are connected in series between the first input terminal and the first output terminal of the differential operational amplifier 102, and the switch K2 and the feedback resistor R f2 are connected in series between the first input terminal and the first output terminal of the differential operational amplifier 102.
  • the switch K3 and the feedback resistor R f3 are connected in series between the second input terminal and the second output terminal of the differential operational amplifier 102, and the switch K4 and the feedback resistor R f4 are connected in series between the second input terminal and the second output of the differential operational amplifier 102.
  • One end of the capacitor Cx under test is connected to the first input terminal of the differential operational amplifier 102, and the other end of the capacitor Cx under test is grounded.
  • the second input terminal of the operational amplifier is connected to the voltage V CM .
  • the terminal is a negative output terminal and the second output terminal is a positive output terminal as an example for description.
  • R f1 R f2
  • R f4 R f3 .
  • the resistors R f1 and R f4 are connected.
  • the amplifying circuit 110 has a larger magnification factor, such as V OUT as shown in FIG. 4.
  • the resistors R f2 and R f3 are connected.
  • the amplifying circuit 110 has a smaller magnification factor, such as V OUT as shown in FIG. 4.
  • the differential operational amplifier 102 can convert the capacitance signal of the capacitance Cx to be measured into a voltage signal V OUT .
  • the output signal V OUT of the differential operational amplifier 102 is a differential signal.
  • the output signal V OUT of the differential operational amplifier 102 has a higher signal-to-noise ratio.
  • a feedback capacitor connected in parallel with the feedback resistor may also be provided.
  • the capacitance detection circuit 100 further includes: a driving circuit 130, which is connected to the capacitor Cx to be tested, and is used to input a driving signal to the capacitor Cx to be tested.
  • a driving circuit 130 which is connected to the capacitor Cx to be tested, and is used to input a driving signal to the capacitor Cx to be tested.
  • the capacitance detection circuit 100 further includes: a filter circuit 140 connected to the amplifying circuit 110 and configured to filter the voltage signal output by the amplifying circuit 110.
  • the capacitance detection circuit 100 further includes: a sampling circuit 150 connected to the filter circuit 140 for converting the filtered voltage signal into a digital signal.
  • Fig. 5 shows a possible implementation based on the circuit shown in Fig. 1.
  • the capacitance detection circuit in FIG. 5 includes a driving circuit 130, an amplifying circuit 110, a control circuit 120, a filter circuit 140, and a sampling circuit 150.
  • the screen mutual capacitance model 160 in Figure 5 is an equivalent diagram of the touch model in the screen, where Csg is the equivalent capacitance of the detection electrode (RX) in the screen, and Cdg is the equivalent capacitance of the drive electrode (TX) in the screen. Effective capacitance, the capacitor Cx to be tested is the equivalent capacitance between RX and TX, and 161 is the noise signal source in the screen.
  • One end of the capacitor Cx to be tested is connected to the system ground, and the other end is connected to the amplifying circuit 110.
  • the capacitance detection circuit detects the change in the capacitance of the capacitor Cx to be tested, and the user's touch information can be obtained.
  • the driving circuit 130 is used to generate a driving signal. After the driving signal is input to the driving electrode TX, the sensing electrode TX at the corresponding position senses the driving signal and generates a detection signal.
  • the detection signal may be, for example, a voltage signal, and the capacitance signal of the capacitor Cx to be measured can be converted into the voltage signal by the amplifier circuit 110.
  • the filter circuit 140 may be, for example, an analog anti-aliasing filter (Analog Antialiasing Filter, AAF) having a low-pass characteristic to avoid aliasing of high-frequency signals or noise into the sampling circuit 150.
  • AAF analog Anti-aliasing Filter
  • the sampling circuit 150 is, for example, an analog-to-digital conversion (Analog-to-Digital Converter, ADC) circuit for converting a voltage signal into a digital signal so that the digital system can process it.
  • the control circuit 120 can control the states of the switches K1 to K4 so that the amplification factor of the amplifying circuit has a larger amplification factor in the first period T1 and a smaller amplification factor in the second period T2.
  • the control circuit can also control other parts in the capacitance detection circuit, such as the cut-off frequency of the filter circuit 140 and so on.
  • control circuit 120 controls the magnification of the amplifying circuit 110 so that the magnification of the amplifying circuit 110 has a larger magnification in the first period T1 when the screen is low-noise, so as to increase the SNR of the capacitance detection; and the amplifying circuit In the second period T2 when the screen is high-noise, the amplification factor has a smaller amplification factor to avoid saturation of the amplifier in the amplifying circuit 110. Therefore, while ensuring the effective operation of the amplifying circuit 110, the signal-to-noise ratio of the capacitance detection is improved, and the capacitance detection circuit has better detection performance.
  • the embodiment of the present application also provides a touch control chip, which includes the capacitance detection circuit in the various embodiments of the present application described above.
  • the embodiments of the present application also provide an electronic device, which includes: a screen; and the touch chip in the above-mentioned various embodiments of the present application.
  • the electronic devices in the embodiments of the present application may be portable or mobile computing devices such as terminal devices, mobile phones, tablet computers, notebook computers, desktop computers, game devices, in-vehicle electronic devices or wearable smart devices, and Electronic databases, automobiles, bank automated teller machines (Automated Teller Machine, ATM) and other electronic equipment.
  • the wearable smart device includes full-featured, large-sized, complete or partial functions that can be realized without relying on smart phones, such as smart watches or smart glasses, etc., and only focus on a certain type of application function, and need to cooperate with other devices such as smart phones. Use, such as various types of smart bracelets, smart jewelry and other equipment for physical sign monitoring.

Abstract

本申请提供一种电容检测电路，能够降低屏幕噪声对电容检测的影响。所述电容检测电路用于检测待测电容器的电容，所述待测电容器为电子设备的屏幕中用于进行触摸检测的电容器，所述电容检测电路包括：放大电路，与所述待测电容器相连，用于将所述待测电容器的电容信号转换为电压信号，所述电压信号关联于所述待测电容器的电容；以及，控制电路，与所述放大电路相连，用于在第一时段控制所述放大电路的放大倍数为第一放大倍数，以及在第二时段控制所述放大电路的放大倍数为第二放大倍数，其中，所述屏幕在所述第一时段产生的噪声小于所述屏幕在所述第二时段产生的噪声，所述第一放大倍数大于所述第二放大倍数。

Description

电容检测电路、触控芯片和电子设备 技术领域
本申请实施例涉及电容检测领域，并且更具体地，涉及一种电容检测电路、触控芯片和电子设备。
背景技术
电容式传感器广泛应用于电子产品中，用来实现触摸检测。当有导体例如手指，靠近或触摸检测电极时，检测电极对应的电容会发生变化，通过检测该电容的变化量，就可以获取手指靠近或触摸检测电极的信息，从而判断用户的操作。但是，电子设备的屏幕产生的噪声，会对上述检测结果造成影响。因此，如何降低显示屏噪声对电容检测的影响，成为亟待解决的问题。
发明内容
本申请实施例提供一种电容检测电路、触控芯片和电子设备，能够降低屏幕噪声对电容检测的影响。
第一方面，提供了一种电容检测电路，用于检测待测电容器的电容，所述待测电容器为电子设备的屏幕中用于进行触摸检测的电容器，所述电容检测电路包括：
放大电路，与所述待测电容器相连，用于将所述待测电容器的电容信号转换为电压信号，所述电压信号关联于所述待测电容器的电容；以及，
控制电路，与所述放大电路相连，用于在第一时段控制所述放大电路的放大倍数为第一放大倍数，以及在第二时段控制所述放大电路的放大倍数为第二放大倍数，其中，所述屏幕在所述第一时段产生的噪声小于所述屏幕在所述第二时段产生的噪声，所述第一放大倍数大于所述第二放大倍数。
在一种可能的实现方式中，所述放大电路包括运算放大器，以及连接在所述运算放大器的输入端和输出端之间的第一反馈电阻和第二反馈电阻，所述第一反馈电阻的阻值大于所述第二反馈电阻的阻值，所述控制电路具体用于：在所述第一时段，控制所述第一反馈电阻连通，所述第二反馈电阻断开，以使所述放大电路的放大倍数为所述第一放大倍数；以及，在所述第二时段，控制所述第二反馈电阻连通，所述第一反馈电阻断开，以使所述放大电路的 放大倍数为所述第二放大倍数。
在一种可能的实现方式中，所述运算放大器为差分运算放大器，所述差分运算放大器的第一输入端和第一输出端之间、以及所述差分运算放大器的第二输入端和第二输出端之间，均连接有一个所述第一反馈电阻和一个所述第二反馈电阻。
在一种可能的实现方式中，所述放大电路还包括与每个反馈电阻串联的开关，所述控制电路通过所述开关控制所述每个反馈电阻的连通或断开。
在一种可能的实现方式中，所述第一时段和所述第二时段是根据所述屏幕的扫描频率确定的。
在一种可能的实现方式中，所述电容检测电路还包括：驱动电路，与所述待测电容器相连，用于向所述待测电容器输入驱动信号。
在一种可能的实现方式中，所述电容检测电路还包括：滤波电路，与所述放大电路相连，用于对所述放大电路输出的所述电压信号进行滤波处理。
在一种可能的实现方式中，所述电容检测电路还包括：采样电路，与所述滤波电路相连，用于将滤波后的所述电压信号转换为数字信号。
第二方面，提供了一种触控芯片，包括：前述第一方面以及第一方面的任一种可能的实现方式中的电容检测电路。
第三方面，提供了一种电子设备，包括：屏幕；以及，前述第二方面以及第二方面的任一种可能的实现方式中的触控芯片。
基于上述技术方案，电容检测电路中的控制电路通过对放大电路的放大倍数进行控制，使放大电路的放大倍数在屏幕低噪声的第一时段内具有较大的放大倍数，以提高电容检测的信噪比信噪比(Signal Noise Ratio，SNR)；并使放大电路的放大倍数在屏幕高噪声的第二时段内具有较小的放大倍数，以避免放大电路饱和。该电容检测电路在保证放大电路有效工作的同时，提高了电容检测的信噪比，具有更好的检测性能。
附图说明
图1是本申请实施例的电容检测电路的示意性框图。
图2是本申请实施例的放大电路的一种可能的示意性结构图。
图3是本申请实施例的放大电路的一种可能的示意性结构图。
图4是基于图3所示的放大电路的工作时序的示意图。
图5是基于图1所示的电路的一种可能的实现方式。
具体实施方式
下面将结合附图，对本申请中的技术方案进行描述。
对于电子设备的屏幕，尤其是Y-OCTA屏幕，屏幕的显示层在进行扫描时会产生较大的噪声，该噪声会影响触控层，极易使触控层的电容检测电路中的放大电路发生饱和。如果通过降低放大电路的放大倍数来避免饱和，则有效的检测信号也会受到影响，从而降低电容检测电路的性能。
本申请提供一种电容检测电路，能够降低屏幕噪声对电容检测的影响。
图1是本申请实施例的电容检测电路的示意性框图。该电容检测电路100用于检测待测电容器Cx的电容，待测电容器Cx为电子设备的屏幕中用于进行触摸检测的电容器。如图1所示，电容检测电路100包括放大电路110和控制电路120。
放大电路110与待测电容器Cx相连，用于将待测电容器Cx的电容信号转换为电压信号，所述电压信号关联于待测电容器Cx的电容。
控制电路120与放大电路110相连，用于在第一时段T1控制放大电路的放大倍数110为第一放大倍数，以及在第二时段T2控制放大电路110的放大倍数为第二放大倍数。
其中，所述屏幕在所述第一时段T1产生的噪声小于所述屏幕在所述第二时段T2产生的噪声，所述第一放大倍数大于所述第二放大倍数。
屏幕在进行扫描时，扫描信号与屏幕产生的噪声之间具有关联。图4示出了屏幕的场同步信号(Vsync)和行同步信号(Hsync)。其中，行同步信号按照一定规律变化，从图4可以看出，屏幕的噪声与行同步信号之间的相位差基本不变，屏幕的噪声也按照一定规律变化。基于此，可以将屏幕产生的噪声在时间上划分为第一时段T1和第二时段T2，第一时段T1为低噪声时段，第二时段T2为高噪声时段。
本申请实施例对如何确定第一时段T1和第二时段T2不做任何限定。例如，可以直接对屏幕噪声进行检测，根据检测到的噪声变化情况，确定第一时段T1和第二时段T2；或者，通过对电容检测电路100的输出信号进行分析，从而根据输出信号的质量，确定第一时段T1和第二时段T2。
放大电路110可以对信号进行放大并输出，在该实施例中，放大电路110 的输入端与待测电容器Cx相连，放大电路110的输出端输出电压信号。其中，该电压信号关联于待测电容器Cx的电容。待测电容器Cx的电容发生变化时，放大电路110输出的电压信号也会发生变化，因此，通过放大电路110输出的电压信号，就可以判断待测电容器Cx的电容的变化情况。也就是说，该放大电路110可以将待测电容器Cx的电容信号转换为电压信号，以实现对待测电容器Cx的检测。
控制电路120用于控制放大电路110的放大倍数。其中，放大电路110在第一时段T1具有较大的放大倍数，以提高电容检测的SNR；而放大电路110在第二时段T2具有较小的放大倍数，以避免放大电路110饱和，保证放大电路110的有效工作。因此，电容检测电路100在保证放大电路110有效工作的同时，提高了电容检测的信噪比，具有更好的检测性能。
本申请实施例中的电容检测电路可以用于互容检测或者自容检测，该待测电容器Cx可以是各个电极对地的自电容。或者，该待测电容器Cx是驱动电极和检测电极之间的互电容。驱动电极用于输入驱动信号，记为TX。检测电极也可以称为感应电极，用于感应驱动信号并产生检测信号，记为RX。以下仅以互容检测为例进行描述。
该实施例中，可以通过反馈电阻，对放大电路110的放大倍数进行调节。
例如，放大电路110包括：运算放大器，以及连接在所述运算放大器的输入端和输出端之间的第一反馈电阻和第二反馈电阻。其中，所述第一反馈电阻的阻值大于所述第二反馈电阻的阻值。
这时，控制电路120可以在第一时段，控制第一反馈电阻连通，第二反馈电阻断开，以使放大电路110的放大倍数为第一放大倍数；以及，在第二时段，控制第二反馈电阻连通，第一反馈电阻断开，以使放大电路110的放大倍数为第二放大倍数。
控制电路120例如可以通过开关控制第一反馈电阻和第二反馈电阻的连通或断开。
当用户在屏幕上执行触摸操作时，对应位置的待测电容器Cx的电容值会发生变化，待测电容器Cx的电容信号通过放大电路110转换为电压信号，该电压信号可以反映待测电容器Cx的电容变化情况，从而获取用户的触摸信息。在待测电容器Cx的检测过程中，可以通过在不同时段分别使用不同的反馈电阻，调节放大电路110的放大倍数，从而尽可能地降低屏幕噪声对 电容检测的影响。
例如图2所示，放大电路110中包括运算放大器101、反馈电阻R f1和反馈电阻R f2。开关K1与反馈电阻R f1串联在运算放大器101的一个输入端和输出端之间，且开关K2与反馈电阻R f2串联在运算放大器101的该输入端和输出端之间，并且该输入端与待测电容器Cx的一端相连，待测电容器Cx的另一端接地。运算放大器的另一输入端接电压V CM。反馈电阻R f1的阻值大于反馈电阻R f2的阻值。控制电路120可以在第一时段T1控制开关K1闭合且K2断开，以使放大电路110的具有较大的放大倍数；以及在第二时段T2控制开关K2闭合且K1断开，以使放大电路110具有较小的放大倍数。
本申请实施例中，放大电路110中的运算放大器可以是差分运算放大器。这时，该差分运算放大器的第一输入端和第一输出端之间、以及所述差分运算放大器的第二输入端和第二输出端之间，均连接有一个所述第一反馈电阻和一个所述第二反馈电阻。
放大电路110还可以包括与每个反馈电阻串联的开关，控制电路120通过所述开关控制所述每个反馈电阻的连通或断开。
例如图3所示，放大电路110包括差分运算放大器102、反馈电阻R f1和反馈电阻R f2、反馈电阻R f3和反馈电阻R f4。开关K1与反馈电阻R f1串联在差分运算放大器102的第一输入端和第一输出端之间，开关K2与反馈电阻R f2串联在差分运算放大器102的第一输入端和第一输出端之间，开关K3与反馈电阻R f3串联在差分运算放大器102的第二输入端和第二输出端之间，开关K4与反馈电阻R f4串联在差分运算放大器102的第二输入端和第二输出端之间。待测电容器Cx的一端连接至差分运算放大器102的第一输入端，待测电容器Cx的另一端接地。运算放大器的第二输入端接电压V CM。这里对第一输入端、第二输入端、第一输出端和第二输出端并不做任何限定，仅以第一输入端为正输入端、第二输入端为负输入端、第一输出端为负输出端、以及第二输出端为正输出端为例进行描述。
其中，R f1＞R f2，R f4＞R f3。优选地，R f1＝R f4，R f2＝R f3。
控制电路120在第一时段T1，控制开关K1和开关K4闭合，开关K2和开关K3断开，即Φ1＝1，Φ2＝0，Φ1和Φ2为控制信号。这时，电阻R f1和R f4连通。放大电路110具有较大的放大倍数，例如图4所示的V OUT。
控制电路120在第二时段T2，控制开关K2和开关K3闭合，开关K1 和开关K4断开，即Φ1＝0，Φ2＝1。这时，电阻R f2和R f3连通。放大电路110具有较小的放大倍数，例如图4所示的V OUT。
差分运算放大器102可以将待测电容Cx的电容信号转换为电压信号V OUT。在图3中，差分运算放大器102的输出信号V OUT为差分信号，相比于图2所示的放大器101，差分运算放大器102的输出信号V OUT具有更高的信噪比。
本申请实施例中，在运算放大器的输入端和输出端之间，还可以设置有与反馈电阻并联的反馈电容。
可选地，电容检测电路100还包括：驱动电路130，与待测电容器Cx相连，用于向待测电容器Cx输入驱动信号。
可选地，电容检测电路100还包括：滤波电路140，与放大电路110相连，用于对放大电路110输出的电压信号进行滤波处理。
可选地，电容检测电路100还包括：采样电路150，与滤波电路140相连，用于将滤波后的电压信号转换为数字信号。
图5示出了基于图1所示的电路的一种可能的实现方式。图5中的电容检测电路中包括驱动电路130、放大电路110、控制电路120、滤波电路140和采样电路150。图5中的屏体互容模型160是屏幕中的触控模型的等效图，其中Csg为屏幕中的检测电极(RX)的等效电容，Cdg为屏幕中的驱动电极(TX)的等效电容，待测电容器Cx为RX和TX之间的等效电容，161为屏体中的噪声信号源。待测电容器Cx的一端接系统地，另一端与放大电路110相连。当待测电容器Cx上有触摸操作时，其相对系统地的电容会变大，电容检测电路检测待测电容器Cx的电容变化，就可以获取用户的触摸信息。
驱动电路130用于产生驱动信号，驱动信号输入驱动电极TX后，对应位置的感应电极TX感应该驱动信号并产生检测信号。该检测信号例如可以是电压信号，通过放大电路110可以将待测电容器Cx的电容信号转换为该电压信号。滤波电路140例如可以是具有低通特性的模拟抗混叠滤波器(Analog Antialiasing Filter，AAF)，以避免高频信号或噪声混叠到采样电路150中。采样电路150例如为模数转换(Analog-to-Digital Converter，ADC)电路，用于将电压信号转化为数字信号，以便于数字系统对其进行处理。控制电路120可以控制开关K1至K4的状态，以使放大电路的放大倍数在第 一时段T1具有较大的放大倍数，而在第二时段T2具有较小的放大倍数。此外，控制电路还可以控制电容检测电路中的其他部分，例如滤波电路140的截止频率等。
可见，控制电路120通过对放大电路110的放大倍数进行控制，使放大电路110的放大倍数在屏幕低噪声的第一时段T1具有较大的放大倍数，以提高电容检测的SNR；并使放大电路的放大倍数在屏幕高噪声的第二时段T2具有较小的放大倍数，以避免放大电路110中的放大器饱和。从而在保证放大电路110有效工作的同时，提高了电容检测的信噪比，是电容检测电路具有更好的检测性能。
本申请实施例还提供一种触控芯片，包括上述本申请各种实施例中的电容检测电路。
本申请实施例还提供了一种电子设备，该电子设备包括：屏幕；以及，上述本申请各种实施例中的触控芯片。
作为示例而非限定，本申请实施例中的电子设备可以为终端设备、手机、平板电脑、笔记本电脑、台式机电脑、游戏设备、车载电子设备或穿戴式智能设备等便携式或移动计算设备，以及电子数据库、汽车、银行自动柜员机(Automated Teller Machine，ATM)等其他电子设备。该穿戴式智能设备包括功能全、尺寸大、可不依赖智能手机实现完整或部分的功能，例如：智能手表或智能眼镜等，以及只专注于某一类应用功能，需要和其它设备如智能手机配合使用，如各类进行体征监测的智能手环、智能首饰等设备。
需要说明的是，在不冲突的前提下，本申请描述的各个实施例和/或各个实施例中的技术特征可以任意的相互组合，组合之后得到的技术方案也应落入本申请的保护范围。
应理解，本申请实施例中的具体的例子只是为了帮助本领域技术人员更好地理解本申请实施例，而非限制本申请实施例的范围，本领域技术人员可以在上述实施例的基础上进行各种改进和变形，而这些改进或者变形均落在本申请的保护范围内。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (10)

  1. 一种电容检测电路，其特征在于，用于检测待测电容器的电容，所述待测电容器为电子设备的屏幕中用于进行触摸检测的电容器，所述电容检测电路包括：
    放大电路，与所述待测电容器相连，用于将所述待测电容器的电容信号转换为电压信号，所述电压信号关联于所述待测电容器的电容；以及，
    控制电路，与所述放大电路相连，用于在第一时段控制所述放大电路的放大倍数为第一放大倍数，以及在第二时段控制所述放大电路的放大倍数为第二放大倍数，其中，所述屏幕在所述第一时段产生的噪声小于所述屏幕在所述第二时段产生的噪声，所述第一放大倍数大于所述第二放大倍数。
  2. 根据权利要求1所述的电容检测电路，其特征在于，所述放大电路包括运算放大器，以及连接在所述运算放大器的输入端和输出端之间的第一反馈电阻和第二反馈电阻，所述第一反馈电阻的阻值大于所述第二反馈电阻的阻值，所述控制电路具体用于：
    在所述第一时段，控制所述第一反馈电阻连通，所述第二反馈电阻断开，以使所述放大电路的放大倍数为所述第一放大倍数；以及，
    在所述第二时段，控制所述第二反馈电阻连通，所述第一反馈电阻断开，以使所述放大电路的放大倍数为所述第二放大倍数。
  3. 根据权利要求2所述的电容检测电路，其特征在于，所述运算放大器为差分运算放大器，
    所述差分运算放大器的第一输入端和第一输出端之间、以及所述差分运算放大器的第二输入端和第二输出端之间，均连接有一个所述第一反馈电阻和一个所述第二反馈电阻。
  4. 根据权利要求2或3所述的电容检测电路，其特征在于，所述放大电路还包括与每个反馈电阻串联的开关，所述控制电路通过所述开关控制所述每个反馈电阻的连通或断开。
  5. 根据权利要求2至4中任一项所述的电容检测电路，其特征在于，所述第一时段和所述第二时段是根据所述屏幕的扫描频率确定的。
  6. 根据权利要求1至5中任一项所述的电容检测电路，其特征在于，所述电容检测电路还包括：
    驱动电路，与所述待测电容器相连，用于向所述待测电容器输入驱动信 号。
  7. 根据权利要求1至6中任一项所述的电容检测电路，其特征在于，所述电容检测电路还包括：
    滤波电路，与所述放大电路相连，用于对所述放大电路输出的所述电压信号进行滤波处理。
  8. 根据权利要求7所述的电容检测电路，其特征在于，所述电容检测电路还包括：
    采样电路，与所述滤波电路相连，用于将滤波后的所述电压信号转换为数字信号。
  9. 一种触控芯片，其特征在于，包括根据权利要求1至8任一项所述的电容检测电路。
  10. 一种电子设备，其特征在于，包括：
    屏幕；以及，
    根据权利要求9所述的触控芯片。
PCT/CN2019/128859 2019-12-26 2019-12-26 电容检测电路、触控芯片和电子设备 WO2021128209A1 (zh)

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