WO2021147007A1 - 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
WO2021147007A1
WO2021147007A1 PCT/CN2020/073841 CN2020073841W WO2021147007A1 WO 2021147007 A1 WO2021147007 A1 WO 2021147007A1 CN 2020073841 W CN2020073841 W CN 2020073841W WO 2021147007 A1 WO2021147007 A1 WO 2021147007A1
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channel
capacitance
signal
detection circuit
numbered
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PCT/CN2020/073841
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English (en)
French (fr)
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张冠军
蒋宏
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深圳市汇顶科技股份有限公司
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Priority to CN202080001522.7A priority Critical patent/CN111902801B/zh
Priority to PCT/CN2020/073841 priority patent/WO2021147007A1/zh
Publication of WO2021147007A1 publication Critical patent/WO2021147007A1/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
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2605—Measuring capacitance
    • 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
    • G06F3/04186—Touch location disambiguation

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 self-capacitance of the first channel in the screen, and the capacitance detection circuit includes:
  • a driving circuit for inputting a driving signal to the first channel
  • the amplifying circuit includes a differential amplifier, one input end of the differential amplifier is connected to the first channel, and the other input end of the differential amplifier is connected to the second channel on the screen where no drive signal is input.
  • the amplifier is used to output a voltage signal according to the first capacitance signal of the self-capacitance of the first channel and the second capacitance signal of the self-capacitance of the second channel, wherein the second capacitance signal is used to cancel the first capacitance signal
  • a noise signal from the screen included in a capacitance signal, and the voltage signal represents the self-capacitance of the first channel after the noise is canceled.
  • the amplifying circuit further includes a resistor connected across each input terminal and an output terminal of the differential amplifier, and a resistor connected to each input terminal of the differential amplifier.
  • the capacitance detection circuit further includes a first resistor, a second resistor, a first buffer, and a second buffer.
  • the first resistor is connected between the driving circuit and one end of the first channel, and the other end of the first channel is connected to the input end of the first buffer.
  • the second resistor is connected between the reference voltage and one end of the second channel, and the other end of the second channel is connected to the input end of the second buffer.
  • the output ends of the first buffer and the second buffer are respectively connected to the two input ends of the amplifying circuit.
  • the screen includes N channels, which are sequentially numbered from 1 to N, and N is an even number.
  • the channel numbered even is the first channel
  • the adjacent channel numbered odd is the second channel
  • the channel numbered odd is used as the second channel.
  • the screen includes M channels, which are sequentially numbered from 1 to M, where M is an odd number greater than 1, and the number of odd-numbered channels among the M channels is K.
  • the capacitance detection circuit detects each channel except for the number 2i-1 in the i-th detection cycle in the continuous K detection cycles, and 1 ⁇ i ⁇ K.
  • the channel numbered even is the first channel
  • the adjacent channel numbered odd is the second channel
  • the odd-numbered channel serves as the first channel
  • the adjacent even-numbered channel serves as the second channel.
  • 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: an analog-to-digital conversion 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 possible implementation manner of the second aspect.
  • the two input ends of the differential amplifier in the amplifying circuit are respectively connected to the first channel and the second channel, where the first channel is the channel to be detected, and the second channel is the noise reference channel.
  • the driving circuit inputs a driving signal to the first channel, and the first channel generates the first capacitance signal.
  • the second channel does not input a driving signal, so the second capacitance signal generated by the second channel can be considered to be caused by screen noise.
  • the second capacitance signal can cancel the screen noise carried in the first capacitance signal, so that the voltage signal output by the amplifying circuit represents the first capacitance signal after canceling the noise.
  • the self-capacitance of the channel thereby reducing the impact of screen noise on capacitance detection.
  • Figure 1 is a schematic diagram of screen noise generation.
  • Fig. 2 is a schematic diagram of the principle of touch detection.
  • Figure 3 is a schematic diagram of a capacitance detection circuit.
  • Figure 4 is a schematic diagram of another capacitance detection circuit.
  • Fig. 5 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of the RC divided voltage self-capacitance detection circuit based on FIG. 5.
  • the display layer of the screen will generate a lot of noise when scanning, and this noise will affect the capacitance detection circuit of the touch layer, so that the signal-to-noise ratio obtained by the capacitance detection circuit (Signal Noise Ratio, SNR) is low.
  • the screen 100 includes a substrate 101, an anode 102, an organic light-emitting layer 103, a cathode 104, a thin-film encapsulation layer 105, a touch layer 106 and a protective layer 107 in order from bottom to top.
  • a capacitor C L is formed between the touch layer 106 and the display cathode 104.
  • the screen 100 generated by the refresh noise 108 is coupled to the cathode 104, and through the capacitance C L is coupled to the touch layer 106, so that the capacitive touch detection circuit layer 106 is affected by the capacitance detection result.
  • Fig. 2 is a schematic diagram of the principle of touch detection.
  • Fig. 2 shows the horizontal and vertical channels in the touch layer.
  • a capacitive touch system using this pattern can usually use both self-capacitance and mutual-capacitance detection methods at the same time.
  • the touch chip When performing self-capacitance detection, the touch chip will scan the change of the self-capacitance of each horizontal channel and vertical channel to ground. When the finger approaches or touches, the self-capacitance of the channel near the finger becomes larger. For example, as shown in Figure 2, the finger and its nearby horizontal channel C RXN-1 will generate capacitance Cs, and the finger and its nearby vertical channel C TX1 will generate capacitance Cd. Since the human body is a conductor and connected to the ground, the self-capacitance of the channel touched or approached by the finger will change.
  • the touch chip can calculate the touch position of the finger based on the detected change of the self-capacitance.
  • the differential circuit structure can eliminate the influence of screen noise on capacitance detection.
  • channel 401 and channel 402 are respectively connected to the two input terminals of amplifier 403, and drive signal 404 is input to channel 401 and channel 402 respectively.
  • the screen noise 405 received by channel 401 and channel 402 is the same, they will pass through amplifier 403.
  • the output signal V OUT of the amplifier 403 is the difference between the self-capacitance C1 of the channel 401 and the self-capacitance C2 of the channel 402. Therefore, the detection result of the self-capacitance of each channel cannot be obtained, that is, the result of the capacitance detection is not Does not have single-ended characteristics.
  • the present application provides a capacitance detection circuit, which can reduce the influence of screen noise on capacitance detection and make the capacitance detection result have single-ended characteristics.
  • Fig. 5 is a schematic block diagram of a capacitance detection circuit according to an embodiment of the present application.
  • the capacitance detection circuit 500 is used to detect the self-capacitance C1 of the first channel 531 in the screen of the electronic device, that is, the capacitance of the first channel 531 to ground.
  • the screen may include a touch control layer and a display layer.
  • the touch control layer is used to realize the touch detection function of the screen
  • the display layer is used to realize the display function of the screen.
  • screen noise When the display layer is refreshed, a certain amount of noise is generated, which is referred to as screen noise here.
  • the screen noise will be coupled to the touch layer through the cathode of the display layer, thereby affecting the touch layer.
  • the capacitance detection circuit 500 includes a driving circuit 510 and an amplifying circuit 520.
  • the driving circuit 510 is used to input a driving signal to the first channel 531.
  • the amplifying circuit 520 may include a differential amplifier 521. Among them, one input end of the differential amplifier 521 is connected to the first channel 531, and the other input end of the differential amplifier 521 is connected to the second channel 532 where no drive signal is input on the screen.
  • the first capacitance signal of the capacitor C1 and the second capacitance signal of the self-capacitance C2 of the second channel 532 output a voltage signal V OUT .
  • the second capacitance signal is used to cancel the noise signal 540 from the screen included in the first capacitance signal, and the voltage signal V OUT represents the self-capacitance C1 of the first channel 531 after the noise has been canceled.
  • the two input ends of the differential amplifier 521 are respectively connected to the first channel 531 and the second channel 532, where the first channel 531 is the channel currently to be detected, and the second channel 532 is the noise reference channel.
  • the driving circuit 510 inputs a driving signal to the first channel 531, and the first channel 531 generates a first capacitance signal.
  • the second channel 532 does not input a driving signal, so the second capacitance signal generated by the second channel 532 can be considered to be caused by screen noise.
  • the second capacitance signal can cancel the screen noise carried in the first capacitance signal, so that the voltage signal V OUT output by the amplifier circuit 520 indicates that the noise is canceled
  • the self-capacitance C1 of the first channel 531 thereby reducing the impact of screen noise on capacitance detection.
  • the non-inverting input terminal of the differential amplifier 521 may be connected to the first channel 531, and the inverting input terminal may be connected to the second channel 532; or the non-inverting input terminal of the differential amplifier 521 may be connected to the second channel 532, and the inverting input terminal may be connected First channel 531.
  • the first capacitance signal can be considered as the electrical signal generated by the self-capacitance C1 of the first channel 531
  • the second capacitance signal can be considered as the electrical signal generated by the self-capacitance C2 of the second channel 532.
  • These two electrical signals are respectively Input to the two input terminals of the differential amplifier 521, the amplifying circuit 520 can differentially amplify the two input signals and output a voltage signal V OUT .
  • the self-capacitance C1 of the first channel 531 changes, the voltage signal V OUT output by the amplifying circuit 520 will also change. Therefore, the self-capacitance of the first channel 531 can be determined by the voltage signal V OUT output by the amplifying circuit 520.
  • the amplifying circuit 520 converts the capacitance signal of the self-capacitance C1 of the first channel 531 into a voltage signal V OUT to realize the detection of the self-capacitance C1 of the first channel 531.
  • the first channel 531 and the second channel 532 may both be transverse channels, or both longitudinal channels, or one of them is a transverse channel and the other is a longitudinal channel, which is not limited in the embodiment of the present application. However, considering that the closer the two channels are, the closer the noise coupled to the channel will be, and the better the effect of noise cancellation. Therefore, when detecting the self-capacitance C1 of the first channel 531, the distance should be closer, such as adjacent
  • the second channel 532 is used as a noise reference channel, and the noise reference channel is used to generate a noise cancellation signal to cancel the noise signal in the first channel 531.
  • the first channel 531 and the second channel 532 may also be referred to as sensor channels.
  • the capacitance detection circuit 500 shown in FIG. 5 is only to illustrate the principle of capacitance detection in the embodiment of the present application, that is, noise charge cancellation (NCC).
  • NCC noise charge cancellation
  • various types of circuit structures can be used to implement NCC-based capacitance detection.
  • a resistance-capacitance (RC) voltage divider circuit can be used to realize capacitance detection. The following describes the process of capacitance detection using the RC divided voltage self-capacitance detection circuit in conjunction with Figure 6.
  • the amplifying circuit 520 further includes a resistor connected between each input terminal and the output terminal of the differential amplifier 521, and a resistor connected with each input terminal of the differential amplifier 521.
  • a resistor R2 is connected across the first input terminal and the output terminal of the differential amplifier 521
  • a resistor R2 is connected across the second input terminal and the output terminal of the differential amplifier 521.
  • the first input terminal and the second input terminal of the differential amplifier 521 are both connected to the resistor R1.
  • the size of R1 and R2 can determine the amplification factor of the differential amplifier 521.
  • a first resistor R A connected between one end of the driving circuit 510 and the first passage 531, an input terminal connected to the other end of the first passage 531 to the first buffer 541.
  • a second resistor R B is connected between one end of the reference voltage V CMI and a second channel 532 connected to the input terminal of the other end of the second passageway 532 and the second buffer 542.
  • the output terminals of the first buffer 541 and the second buffer 542 are connected to the two input terminals of the amplifying circuit 520, respectively.
  • the voltage signal V OUT output by the differential amplifier 521 is:
  • V OUT R2 / R1 * [ Vtx * (SC1 / Z1) + Vnoise1 * R A / Z1-Vnoise2 * R B / Z2].
  • Vnoise1 * R A / Z1 and Vnoise2 * R B / Z2 represent the influence of noise on the screen from the capacitor C1 of the first channel 531 and second channel 532 of the impact from the capacitor C2, Vnoise1 * R /Z1-Vnoise2*R/Z2 realizes the cancellation of screen noise.
  • Vtx*(SC1/Z1) represents the impact on the self-capacitance C1 of the first channel 531 when the finger approaches or touches. Therefore, by detecting the component of the useful signal Vtx, the self-capacitance C1 of the first channel can be detected. Among them, the closer the second channel 532 and the first channel 531 are, the closer Vnoise1 and Vnoise2 are, the cleaner the noise cancellation, and the better the noise cancellation effect.
  • the voltage signal V OUT output by the amplifier 521 is used to represent the self-capacitance C1 of the first channel 531 after canceling the screen noise, so the capacitance detection circuit can directly detect the self-capacitance of each channel ,
  • the circuit signal presents single-ended characteristics, which will not affect the calculation of the subsequent finger touch position.
  • the screen includes N channels, numbered from 1 to N in sequence, with N being an even number.
  • the N channels may be longitudinal channels, or transverse channels, or include longitudinal channels and transverse channels.
  • the even-numbered channel serves as the first channel 531, and the adjacent odd-numbered channel serves as the second channel 532; at the second moment, the number is The odd-numbered channel serves as the first channel 531, and the adjacent even-numbered channel serves as the second channel 532.
  • the even-numbered channels are RX 2 , RX 4 , ..., RX N-2 , RX N
  • the odd-numbered channels are RX 1 , RX 3 , ..., RX N-3 and RX N-1 are used as noise reference channels to generate noise cancellation signals
  • the odd-numbered channels are RX 1 , RX 3 , ..., RX N-3 , RX N-1
  • the even-numbered channels namely RX 2 , RX 4 , ..., RX N-2 , RX N, are used as noise reference channels to generate noise cancellation signals. In this way, all the horizontal channels RX 1 to RX N can be detected.
  • the M channels may be longitudinal channels, or transverse channels, or include longitudinal channels and transverse channels.
  • the capacitance detection circuit 500 detects each channel except the number 2i-1 in the i-th detection period in the continuous K detection periods, and 1 ⁇ i ⁇ K.
  • Fig. 2 take the longitudinal channel TX 1 to the channel TX M as an example, assuming that M is an odd number.
  • the M TX channels include K odd-numbered TX channels, and K-1 even-numbered TX channels.
  • the channels detected in the i-th detection cycle are all channels except the number 2i-1. That is, in the K cycles, the channel TX 1 is not detected in the first cycle, the channel TX 3 is not detected in the second cycle, the channel TX 5 is not detected in the third cycle,..., the channel TX M is not detected in the K cycle .
  • each of the K channels is detected K-1 times, and there is only one undetected, so the detection frequency is (K-1)/K.
  • the detection frequency is (K-1)/K.
  • M-1 channels can be detected with reference to the detection timing shown in Case 1.
  • the even-numbered channel serves as the first channel 531
  • the adjacent odd-numbered channel serves as the second channel 532
  • the odd-numbered channel serves as the first channel 531, adjacent
  • the even-numbered channel is used as the second channel 532.
  • the i-th detection cycle detect M-1 channels other than the channel TX 2i-1 , where, at the first moment, detect the even-numbered channels of the M-1 channels, and the number is The odd-numbered channel is used as the noise reference channel to generate the noise cancellation signal; at the second moment, the odd-numbered channel among the M-1 channels is detected, and the even-numbered channel is used as the noise reference channel to generate the noise cancellation signal.
  • the detection frequencies of different channels may not be equal. For example, in one detection cycle, only channel TX 1 to channel TX M-1 are detected, and in the next detection cycle, channel TX 2 to channel TX M are detected. In this way, the detection frequency of the channels TX 1 and TX M is half of the detection frequency of the channel TX 2 to the channel TX M-1.
  • the second channel 532 is used as the noise reference channel of the first channel 531, and the capacitance signals generated by the first channel 531 and the second channel 532 are differentiated through the amplifier circuit 520, and the voltage signal is output, thereby The voltage signal is used to determine the change of the self-capacitance of the first channel 531 to determine the touch position of the finger.
  • the horizontal channel is detected first and then the vertical channel, or the vertical channel is detected first and then the horizontal channel is detected, or the horizontal channel and the vertical channel can be detected at the same time.
  • the channel to be tested and the noise reference channel may both be horizontal channels or both vertical channels, or one of them may be a horizontal channel and the other may be a vertical channel.
  • the capacitance detection circuit 500 may further include a filter circuit, which is connected to the amplifying circuit 520 and configured to perform filter processing on the voltage signal output by the amplifying circuit 520.
  • the capacitance detection circuit 500 may further include an analog-to-digital conversion circuit, the analog-to-digital conversion circuit is connected to the filter circuit, and is configured to convert the filtered voltage signal into a digital signal.
  • 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.
  • An embodiment of the present application further provides an electronic device, which includes: a screen; and the touch chip in the various embodiments of the present application described above.
  • 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 devices include full-featured, large-sized devices that can achieve complete or partial functions 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.

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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屏幕中的第一通道的自电容，所述电容检测电路包括：驱动电路，用于向所述第一通道输入驱动信号；以及，放大电路，包括差分放大器，所述差分放大器的一个输入端与所述第一通道相连，所述差分放大器的另一个输入端与所述屏幕中未输入驱动信号的第二通道相连，所述差分放大器用于根据所述第一通道的自电容的第一电容信号和所述第二通道的自电容的第二电容信号，输出电压信号，其中，所述第二电容信号用于抵消所述第一电容信号中包括的来自所述屏幕的噪声信号，所述电压信号表示抵消噪声后的所述第一通道的自电容。

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，用于检测屏幕中的第一通道的自电容，所述电容检测电路包括：
驱动电路，用于向所述第一通道输入驱动信号；以及，
放大电路，包括差分放大器，所述差分放大器的一个输入端与所述第一通道相连，所述差分放大器的另一个输入端与所述屏幕中未输入驱动信号的第二通道相连，所述差分放大器用于根据所述第一通道的自电容的第一电容信号和所述第二通道的自电容的第二电容信号，输出电压信号，其中，所述第二电容信号用于抵消所述第一电容信号中包括的来自所述屏幕的噪声信号，所述电压信号表示抵消噪声后的所述第一通道的自电容。
在一种可能的实现方式中，所述放大电路还包括跨接在所述差分放大器的每个输入端与输出端之间的电阻，以及连接在所述差分放大器的每个输入端的电阻。
在一种可能的实现方式中，所述电容检测电路还包括第一电阻、第二电阻、第一缓冲器以及第二缓冲器。所述第一电阻连接在所述驱动电路和所述第一通道的一端之间，所述第一通道的另一端与所述第一缓冲器的输入端相 连。所述第二电阻连接在参考电压和所述第二通道的一端之间，所述第二通道的另一端与所述第二缓冲器的输入端相连。所述第一缓冲器和所述第二缓冲器的输出端分别连接在所述放大电路的两个输入端。
在一种可能的实现方式中，所述屏幕包括N个通道，依次编号为1至N，N为偶数。其中，在一个检测周期中，在第一时刻，编号为偶数的通道作为所述第一通道，相邻的编号为奇数的通道作为所述第二通道；在第二时刻，编号为奇数的通道作为所述第一通道，相邻的编号为偶数的通道作为所述第二通道。
在一种可能的实现方式中，所述屏幕包括M个通道，依次编号为1至M，M为大于1的奇数，所述M个通道中编号为奇数的通道的数量为K。其中，所述电容检测电路在连续K个检测周期中的第i个检测周期，检测除编号2i-1之外的各个通道，1≤i≤K。
在一种可能的实现方式中，在第i个检测周期中，在第一时刻，编号为偶数的通道作为所述第一通道，相邻的编号为奇数的通道作为所述第二通道；在第二时刻，编号为奇数的通道作为所述第一通道，相邻的编号为偶数的通道作为所述第二通道。
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：模数转换电路，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，放大电路中的差分放大器的两个输入端分别连接第一通道和第二通道，其中第一通道为待检测的通道，第二通道为噪声参考通道。在检测第一通道的自电容时，驱动电路向第一通道输入驱动信号，第一通道产生第一电容信号。而第二通道未输入驱动信号，因此第二通道产生的第二电容信号可以认为是由屏幕噪声引起的。这样，第一电容信号和第二电容信号在差分放大器中进行差分后，第二电容信号就可以抵消第一电容信号中携带的屏幕噪声，使放大电路输出的电压信号表示抵消噪声后的第一通道 的自电容，从而降低屏幕噪声对电容检测的影响。
附图说明
图1是屏幕噪声产生的示意图。
图2是触摸检测的原理的示意图。
图3是一种电容检测电路的示意图。
图4是另一种电容检测电路的示意图。
图5是本申请实施例的电容检测电路的示意图。
图6是基于图5的RC分压自电容检测电路的示意图。
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的电容检测电路，从而使电容检测电路获得的信噪比(Signal Noise Ratio，SNR)较低。例如图1所示，屏幕100由下至上依次包括基板101、阳极102、有机发光层103、阴极104、薄膜封装层105、触控层106和保护层107。其中，触控层106和显示阴极104之间形成电容C L。在屏幕100点亮时，屏幕100刷新所产生的噪声108被耦合至阴极104，并通过电容C L耦合至触控层106，从而使触控层106的电容检测电路的电容检测结果受到影响。
图2是触摸检测的原理的示意图。图2中示出了触控层中的横向和纵向的两层通道，采用这种图案的电容触控系统通常可以同时采用自电容和互电容这两种电容检测方式。在进行自电容检测时，触控芯片会扫描每一个横向通道和纵向通道对地的自电容的变化情况。当手指靠近或接触时，手指附近的通道的自电容会变大。例如图2所示，手指和其附近的横向通道C RXN-1会产生电容Cs，手指和其附近的纵向通道C TX1会产生电容Cd。由于人体是导体并且和地相连，手指触摸或接近的通道的自电容会发生变化，触控芯片根据检测到的自电容的变化，就可以计算出手指的触摸位置。
在进行电容检测时，例如图3所示，以通道301的检测为例，驱动信号302输入通道301时，通道301与地之间形成自电容C1，但是该自电容C1受到屏幕噪声303的影响，因此放大器304的输出信号V OUT无法准确地反 映通道301的自电容C1变化情况，从而影响电容检测的结果。
采用差分式的电路结构可以消除屏幕噪声对电容检测的影响。例如图4所示，通道401和通道402分别连接在放大器403的两个输入端，驱动信号404分别输入通道401和通道402，假设通道401和通道402受到的屏幕噪声405相同，则通过放大器403的差分运算后，通道401和通道402中的屏幕噪声405因相减而抵消。但是，放大器403的输出信号V OUT为通道401的自电容C1和通道402的自电容C2的差值，因此无法获得每个通道各自的自电容的检测结果，也就是说，电容检测的结果并不具有单端特性。
为此，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，并且使电容检测结果具有单端特性。
图5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500用于检测电子设备的屏幕中的第一通道531的自电容C1，也即第一通道531对地的电容。
应理解，该屏幕可以包括触控层和显示层，触控层用于实现屏幕的触摸检测功能，显示层用于实现屏幕的显示功能。显示层在进行刷新时，会产生一定的噪声，这里称为屏幕噪声。该屏幕噪声会通过显示层的阴极耦合至触控层，从而对触控层造成影响。
如图5所示，电容检测电路500包括驱动电路510和放大电路520。
驱动电路510用于向第一通道531输入驱动信号。
放大电路520可以包括差分放大器521。其中，差分放大器521的一个输入端与第一通道531相连，差分放大器521的另一个输入端与屏幕中未输入驱动信号的第二通道532相连，差分放大器521用于根据第一通道531的自电容C1的第一电容信号和第二通道532的自电容C2的第二电容信号，输出电压信号V OUT。
其中，所述第二电容信号用于抵消所述第一电容信号中包括的来自所述屏幕的噪声信号540，电压信号V OUT表示抵消噪声后的第一通道531的自电容C1。
该实施例中，差分放大器521的两个输入端分别连接第一通道531和第二通道532，其中第一通道531为当前需要检测的通道，第二通道532为噪声参考通道。在检测第一通道531的自电容C1时，驱动电路510向第一通道531输入驱动信号，第一通道531产生第一电容信号。而第二通道532未 输入驱动信号，因此第二通道532产生的第二电容信号可以认为是由屏幕噪声引起的。这样，第一电容信号和第二电容信号在差分放大器521进行差分后，第二电容信号就可以抵消第一电容信号中携带的屏幕噪声，使放大电路520输出的电压信号V OUT表示抵消噪声后的第一通道531的自电容C1，从而降低屏幕噪声对电容检测的影响。
其中，可以是差分放大器521的正相输入端连接第一通道531，反相输入端连接第二通道532；也可以是差分放大器521的正相输入端连接第二通道532，反相输入端连接第一通道531。
应理解，第一电容信号可以认为是第一通道531的自电容C1产生的电信号，第二电容信号可以认为是第二通道532的自电容C2产生的电信号，这两个电信号分别被输入至差分放大器521的两个输入端，放大电路520可以对两个输入信号进行差分放大，并输出电压信号V OUT。当第一通道531的自电容C1发生变化时，放大电路520输出的电压信号V OUT也会发生变化，因此，通过放大电路520输出的电压信号V OUT，就可以判断第一通道531的自电容C1的变化情况。也就是说，该放大电路520通过将第一通道531的自电容C1的电容信号转换为电压信号V OUT，以实现对第一通道531的自电容C1的检测。
第一通道531和第二通道532可以都是横向通道、或者都是纵向通道、或者其中一个为横向通道另一个为纵向通道，本申请实施例对此不做限定。但是，考虑到两个通道越接近时，被耦合至通道的噪声大小也越相近，噪声抵消的效果越好，因此在检测第一通道531的自电容C1时，应选择距离较近例如相邻的第二通道532作为噪声参考通道，该噪声参考通道用于产生噪声抵消信号，以抵消第一通道531中的噪声信号。
本申请实施例中，在进行自电容检测时，也可以将第一通道531和第二通道532称为感应通道(sensor channel)。
图5所示的电容检测电路500仅仅为了示意本申请实施例的电容检测原理，即噪声电荷抵消(Noise Charge Cannel，NCC)。在具体实现时，可以采用各种类型的电路结构实现基于NCC的电容检测。例如可以采用电阻-电容(Resistance-Capacitance，RC)分压电路实现电容检测。下面结合图6，描述采用RC分压自电容检测电路进行电容检测的过程。
本申请实施例中，放大电路520还包括跨接在差分放大器521的每个输 入端与输出端之间的电阻，以及连接在差分放大器521的每个输入端的电阻。例如图6所示，差分放大器521的第一输入端与输出端之间跨接电阻R2，差分放大器521的第二输入端与输出端之间跨接电阻R2。并且，差分放大器521的第一输入端和第二输入端处均连接电阻R1。R1和R2的大小可以确定差分放大器521的放大倍数。
在采用RC分压电路实现电容检测时，电容检测电路500还包括第一电阻R A、第二电阻R B、第一缓冲器541以及第二缓冲器542，R A＝R B。其中，例如图6所示，第一电阻R A连接在驱动电路510和第一通道531的一端之间，第一通道531的另一端与第一缓冲器541的输入端相连。第二电阻R B连接在参考电压V CMI和第二通道532的一端之间，第二通道532的另一端与第二缓冲器542的输入端相连。第一缓冲器541和第二缓冲器542的输出端分别连接在放大电路520的两个输入端。
如图6所示，差分放大器521输出的电压信号V OUT为：
V OUT＝R2/R1*[Vtx*(SC1/Z1)+Vnoise1*R A/Z1-Vnoise2*R B/Z2]。
其中，R A＝R B＝R，Z1为R A和C1串联的等效阻抗，Z2为R B和C2串联的等效阻抗，C1和C2分别为第一通道531的自电容和第二通道532的自电容。在上述表达式中，Vnoise1*R A/Z1和Vnoise2*R B/Z2分别表示屏幕噪声对第一通道531的自电容C1的影响以及对第二通道532的自电容C2的影响，Vnoise1*R/Z1-Vnoise2*R/Z2实现了对屏幕噪声的抵消。Vtx*(SC1/Z1)表示手指接近或触摸时对第一通道531的自电容C1造成的影响。因此，通过检测有用信号Vtx的分量，即可检测第一通道的自电容C1。其中，第二通道532与第一通道531越接近，Vnoise1与Vnoise2越相近，噪声抵消的越干净，噪声消除效果越好。
可见，采用图6所示的电容检测电路，放大器521输出的电压信号V OUT用于表示抵消屏幕噪声后的第一通道531自电容C1，因此电容检测电路可以直接检测到每个通道的自电容，电路信号呈现单端特性，不会对后续手指触摸位置的计算产生影响。
为了获取手指在屏幕上的触摸位置，需要检测屏幕中的全部通道的自电容。例如图1所示，需要检测横向的通道TX 1至通道TX M，以及纵向的通道RX 1至通道RX N。各个通道的检测时序可以基于以下两种情况分别进行设计。
情况1
屏幕包括N个通道，依次编号为1至N，N为偶数。
其中，所述N个通道可以是纵向通道，或者是横向通道，或者包括纵向通道和横向通道。
这时，可选地，在一个检测周期中，在第一时刻，编号为偶数的通道作为第一通道531，相邻的编号为奇数的通道作为第二通道532；在第二时刻，编号为奇数的通道作为第一通道531，相邻的编号为偶数的通道作为第二通道532。
例如，结合图2，以横向通道RX 1至通道RX N为例，假设N为偶数。在一个检测周期中，在第一时刻，检测编号为偶数的通道即RX 2、RX 4、……、RX N-2、RX N，编号为奇数的通道即RX 1、RX 3、……、RX N-3、RX N-1作为噪声参考通道用来产生噪声抵消信号；在第二时刻，检测编号为奇数的通道即RX 1、RX 3、……、RX N-3、RX N-1，编号为偶数的通道即RX 2、RX 4、……、RX N-2、RX N作为噪声参考通道用来产生噪声抵消信号。这样，就可以将横向通道RX 1至通道RX N全部检测完。
当然，也可以在第一时刻检测编号为奇数的通道，在第二时刻检测编号为偶数的通道，这里对奇数通道和偶数通道的检测顺序不做限定。
情况2
屏幕包括M个通道，依次编号为1至M，M为大于1的奇数，所述M个通道中编号为奇数的通道的数量为K。K＝(M+1)/2。
其中，所述M个通道可以是纵向通道，或者是横向通道，或者包括纵向通道和横向通道。
这时，可选地，电容检测电路500在连续K个检测周期中的第i个检测周期，检测除编号2i-1之外的各个通道，1≤i≤K。
仍以图2为例，以纵向通道TX 1至通道TX M为例，假设M为奇数。其中，M个TX通道中包括K个编号为奇数的TX通道，以及K-1个编号为偶数的TX通道。在连续K个检测周期中，第i个检测周期中检测的通道为除编号2i-1之外的各个通道。即，在K个周期中，第1个周期不检测通道TX 1，第2个周期不检测通道TX 3，第3个周期不检测通道TX 5，……，第K个周期不检测通道TX M。这样，在K个检测周期中，K个通道中的每个通道被检测K-1次，仅有一次未检测，因此检测频率为(K-1)/K。当通道数量较多时，该检测频率不会对电容检测的结果造成较大的影响。
进一步地，在每个检测周期内，可以参考情况1中所示的检测时序对M-1个通道进行检测。其中，在第一时刻，编号为偶数的通道作为第一通道531，相邻的编号为奇数的通道作为第二通道532；在第二时刻，编号为奇数的通道作为第一通道531，相邻的编号为偶数的通道作为第二通道532。
即，在第i个检测周期内，检测除通道TX 2i-1之外的M-1个通道，其中，在第一时刻，检测这M-1个通道中编号为偶数的通道，而编号为奇数的通道作为噪声参考通道用来产生噪声抵消信号；在第二时刻，检测这M-1个通道中编号为奇数的通道，而编号为偶数的通道作为噪声参考通道用来产生噪声抵消信号。
以上仅为示例，在实际应用中，不同通道的检测频率也可以不相等。例如，在一个检测周期中，只检测通道TX 1至通道TX M-1，在下一个检测周期中，检测通道TX 2至通道TX M。这样，通道TX 1和TX M的检测频率就为通道TX 2至通道TX M-1的检测频率的一半。
可见，本申请实施例中，将第二通道532作为第一通道531的噪声参考通道，通过放大电路520对第一通道531和第二通道532产生的电容信号进行差分，并输出电压信号，从而通过该电压信号判断第一通道531的自电容的变化情况，以确定手指的触摸位置。
本申请实施例中，可以按照情况1和情况2示例的方式，先检测横向通道再检测纵向通道，或者先检测纵向通道再检测横向通道，也可以同时对横向通道和纵向通道进行检测。
另外，在进行自电容检测时，待测通道与噪声参考通道可以均是横向通道或者均是纵向通道，也可以其中一个是横向通道而另一个是纵向通道。
上述对各个通道的检测时序的设计仅为示例，本申请实施例对各个通道的检测时序不做任何限定。
此外，电容检测电路500还可以包括滤波电路，所述滤波电路与所述放大电路520相连，用于对放大电路520输出的所述电压信号进行滤波处理。
进一步地，电容检测电路500还可以包括模数转换电路，所述模数转换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。
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功能的设备，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的设备，例如各类进行体征监测的智能手环、智能首饰等。
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，用于检测屏幕中的第一通道的自电容，所述电容检测电路包括：
    驱动电路，用于向所述第一通道输入驱动信号；以及，
    放大电路，包括差分放大器，所述差分放大器的一个输入端与所述第一通道相连，所述差分放大器的另一个输入端与所述屏幕中未输入驱动信号的第二通道相连，所述差分放大器用于根据所述第一通道的自电容的第一电容信号和所述第二通道的自电容的第二电容信号，输出电压信号，其中，所述第二电容信号用于抵消所述第一电容信号中包括的来自所述屏幕的噪声信号，所述电压信号表示抵消噪声后的所述第一通道的自电容。
  2. 根据权利要求1所述的电容检测电路，其特征在于，所述放大电路还包括跨接在所述差分放大器的每个输入端与输出端之间的电阻，以及连接在所述差分放大器的每个输入端的电阻。
  3. 根据权利要求1或2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第一电阻、第二电阻、第一缓冲器以及第二缓冲器，
    所述第一电阻连接在所述驱动电路和所述第一通道的一端之间，所述第一通道的另一端与所述第一缓冲器的输入端相连，
    所述第二电阻连接在参考电压和所述第二通道的一端之间，所述第二通道的另一端与所述第二缓冲器的输入端相连，
    所述第一缓冲器和所述第二缓冲器的输出端分别连接在所述放大电路的两个输入端。
  4. 根据权利要求1至3中任一项所述的电容检测电路，其特征在于，所述屏幕包括N个通道，依次编号为1至N，N为偶数，
    其中，在一个检测周期中，在第一时刻，编号为偶数的通道作为所述第一通道，相邻的编号为奇数的通道作为所述第二通道，
    在第二时刻，编号为奇数的通道作为所述第一通道，相邻的编号为偶数的通道作为所述第二通道。
  5. 根据权利要求1至3中任一项所述的电容检测电路，其特征在于，所述屏幕包括M个通道，依次编号为1至M，M为大于1的奇数，所述M个通道中编号为奇数的通道的数量为K，
    其中，所述电容检测电路在连续K个检测周期中的第i个检测周期，检 测除编号2i-1之外的各个通道，1≤i≤K。
  6. 根据权利要求5所述的电容检测电路，其特征在于，
    在第i个检测周期中，在第一时刻，编号为偶数的通道作为所述第一通道，相邻的编号为奇数的通道作为所述第二通道，
    在第二时刻，编号为奇数的通道作为所述第一通道，相邻的编号为偶数的通道作为所述第二通道。
  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，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，还包括：
    模数转换电路，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中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/CN2020/073841 2020-01-22 2020-01-22 电容检测电路、触控芯片和电子设备 WO2021147007A1 (zh)

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