WO2022016359A1 - 电容检测电路和触控芯片 - Google Patents

电容检测电路和触控芯片 Download PDF

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Publication number
WO2022016359A1
WO2022016359A1 PCT/CN2020/103215 CN2020103215W WO2022016359A1 WO 2022016359 A1 WO2022016359 A1 WO 2022016359A1 CN 2020103215 W CN2020103215 W CN 2020103215W WO 2022016359 A1 WO2022016359 A1 WO 2022016359A1
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Prior art keywords
channel
switch
capacitance
stage
capacitor
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PCT/CN2020/103215
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English (en)
French (fr)
Inventor
袁广凯
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深圳市汇顶科技股份有限公司
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Priority to PCT/CN2020/103215 priority Critical patent/WO2022016359A1/zh
Publication of WO2022016359A1 publication Critical patent/WO2022016359A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches

Definitions

  • the embodiments of the present application relate to the field of capacitance detection, and more particularly, to a capacitance detection circuit and a touch control chip.
  • Capacitive sensors are widely used in electronic products for touch detection.
  • a conductor such as a finger approaches or touches the detection electrode
  • the capacitance corresponding to the detection electrode will change.
  • the information of the finger approaching or touching the detection electrode can be obtained to judge the user's operation.
  • the noise generated by the screen of the electronic device will affect the above detection result. Therefore, how to reduce the influence of the noise of the screen on the capacitance detection has become an urgent problem to be solved.
  • Embodiments of the present application provide a capacitance detection circuit and a touch control chip, which can reduce the influence of screen noise on capacitance detection.
  • a capacitance detection circuit for detecting the self-capacitance of a first channel in the screen, and the capacitance detection circuit includes:
  • a drive circuit connected to the first channel and the second channel in the screen, for charging and discharging the first channel and the second channel;
  • a cancellation circuit including a cancellation capacitor, the cancellation capacitor is connected to the first channel, and the cancellation capacitor is used to cancel the basic capacitance of the first channel;
  • a release circuit is connected to the second channel, and the release circuit is used to release the charge on the second channel to cancel the self-capacitance of the second channel, so that the capacitance signal of the second channel only includes the noise signal of the screen;
  • an amplifying circuit respectively connected to the first channel and the second channel
  • the amplifying circuit is used for receiving the capacitance signal of the first channel and the capacitance signal of the second channel, and according to the first channel
  • the capacitance signal of the second channel and the capacitance signal of the second channel output a voltage signal, wherein the voltage signal is used to determine the capacitance change of the self-capacitance of the first channel relative to the base capacitance after canceling the noise signal .
  • the capacitance detection circuit further includes a compensation circuit
  • the step circuit includes a compensation capacitance equal to the cancellation capacitance, and the compensation capacitance is connected to the second channel; wherein the The release circuit is also connected to the compensation capacitor, and is used for charging and discharging the compensation capacitor.
  • a detection cycle of the capacitance detection circuit includes a first stage, a second stage and a third stage, wherein:
  • the drive circuit charges or discharges the first channel and the second channel
  • the cancellation circuit charges or discharges the cancellation capacitor
  • the release circuit charges the compensation capacitor to the preset voltage
  • charge transfer is performed between the first channel and the cancellation capacitor to cancel the base capacitance of the first channel through the cancellation capacitor, and the release circuit reduces the voltage of the second channel pulled to the preset voltage;
  • the first channel and the second channel input capacitance signals to the amplifying circuit, and the amplifying circuit outputs the capacitance signal according to the capacitance signal of the first channel and the capacitance signal of the second channel voltage signal.
  • the preset voltage is a common-mode voltage of the input terminal of the amplifying circuit, and/or the preset voltage is equal to half of the power supply voltage.
  • the driving circuit includes a first switch and a second switch, one end of the first channel is connected to a power supply voltage through the first switch, and is connected to the amplifier through a third switch
  • One input end of the circuit, the other end of the first channel is connected to the ground
  • one end of the second channel is connected to the power supply voltage through the second switch, and is connected to the other end of the amplifier circuit through the fourth switch
  • the input end, the other end of the second channel is connected to the ground.
  • the release circuit includes a fifth switch and a sixth switch, one end of the compensation capacitor is connected to a preset voltage through the fifth switch, and is connected to the The second channel is connected, and the other end of the compensation capacitor is grounded.
  • the cancellation circuit includes a seventh switch and an eighth switch, one end of the cancellation capacitor is connected to ground through the seventh switch, and the eighth switch is connected to the first switch through the eighth switch.
  • the channels are connected, and the other end of the cancellation capacitor is grounded.
  • the first switch, the second switch, the fifth switch, and the seventh switch are closed, wherein the first channel and the The second channel is charged to the power supply voltage, the offset capacitor is discharged to 0, and the compensation capacitor is charged to a preset voltage; in the second stage, the fifth switch, the sixth switch and the first Eight switches are closed, wherein the first channel discharges to the cancellation capacitor, and the voltage of the second channel is pulled to the preset voltage; in the third stage, the third switch, the first The fourth switch, the sixth switch and the eighth switch are closed, wherein the first channel and the second channel discharge to the amplifier circuit.
  • the driving circuit further includes a ninth switch and a tenth switch, one end of the first channel is connected to the ground through the ninth switch, and one end of the second channel is connected to the ground through the ninth switch
  • the tenth switch is connected to the ground
  • the cancellation circuit further includes an eleventh switch, and one end of the cancellation capacitor is connected to the power supply voltage through the eleventh switch.
  • the detection cycle further includes a fourth stage, a fifth stage and a sixth stage, wherein:
  • the fifth switch, the ninth switch, the tenth switch and the eleventh switch are closed, wherein the first channel and the second channel discharge to 0, the offset capacitor is charged to the power supply voltage, and the compensation capacitor is charged to the preset voltage;
  • the fifth switch, the sixth switch and the eighth switch are closed, wherein the cancellation capacitor is discharged to the first channel and the voltage of the second channel is pulled to the preset voltage;
  • the third switch, the fourth switch, the sixth switch and the eighth switch are closed, wherein the amplifying circuit supplies the first channel and the second channel discharge;
  • the capacitance change of the self-capacitance of the first channel relative to the base capacitance is determined according to the voltage signals output by the amplifier circuit in the third stage and the sixth stage.
  • the cancellation capacitance is equal to the base capacitance of the first channel.
  • the cancellation circuit includes a seventh switch, an eighth switch, a twelfth switch, and a thirteenth switch, and one end of the cancellation capacitor is connected to the ground through the seventh switch, and is connected to the ground through the seventh switch.
  • the eighth switch is connected to the first channel, and the other end of the cancellation capacitor is connected to the power supply voltage and the ground through the twelfth switch and the thirteenth switch, respectively.
  • the first switch, the second switch, the fifth switch, the seventh switch and the twelfth switch are closed, wherein, The first channel and the second channel are charged to the power supply voltage, the voltage of the upper plate of the offset capacitor is 0 and the voltage of the lower plate is the power supply voltage, and the compensation capacitor is charged to a preset voltage;
  • the fifth switch, the sixth switch, the eighth switch and the thirteenth switch are closed, wherein the voltage of the upper plate of the cancellation capacitor is a negative power supply voltage and the lower The voltage of the plate is 0, the first channel discharges to the cancellation capacitor, and the voltage of the second channel is pulled to the preset voltage; in the third stage, the third switch, the The fourth switch, the sixth switch, the eighth switch and the thirteenth switch are closed, wherein the first channel and the second channel discharge to the amplifying circuit.
  • the driving circuit further includes a ninth switch and a tenth switch, one end of the first channel is connected to the ground through the ninth switch, and one end of the second channel is connected to the ground through the ninth switch
  • the tenth switch is connected to the ground
  • the cancellation circuit further includes an eleventh switch, and one end of the cancellation capacitor is connected to the power supply voltage through the eleventh switch.
  • the detection cycle further includes a fourth stage, a fifth stage and a sixth stage, wherein:
  • the fifth switch, the ninth switch, the tenth switch, the eleventh switch and the thirteenth switch are closed, wherein the first channel and the The second channel is discharged to 0, the offset capacitor is charged to the power supply voltage, and the compensation capacitor is charged to the preset voltage;
  • the fifth switch, the sixth switch, the eighth switch and the twelfth switch are closed, wherein the cancellation capacitor discharges into the first channel, the second channel charging to the preset voltage;
  • the third switch, the fourth switch, the sixth switch, the eighth switch and the twelfth switch are closed, wherein the amplification circuit supplies the first switch to the first switch. channel and the second channel discharge.
  • the cancellation capacitance is equal to one third of the base capacitance of the first channel.
  • the screen includes a plurality of horizontal channels and a plurality of vertical channels, wherein the self-capacitance of the first channel of the plurality of horizontal channels is detected in parallel in each detection period, and The self-capacitance of the first channel of the plurality of longitudinal channels.
  • a touch control chip including: the first aspect and the capacitance detection circuit in any possible implementation manner of the first aspect.
  • the two input ends of the amplifier circuit are respectively connected to the first channel and the second channel, wherein the first channel is the channel to be detected, and the second channel is the noise reference channel.
  • the basic capacitance of the first channel can be canceled by the canceling circuit, so that the voltage signal output by the amplifying circuit is only associated with the variation of the self-capacitance of the first channel relative to the basic capacitance.
  • the drive circuit inputs the drive signal to the first channel and the second channel, but the charge on the second channel will be released through the release circuit, so the second channel inputs the capacitance signal of the amplifier circuit includes only the noise signal from the screen.
  • the same noise signal carried in the first channel can be cancelled, so that the voltage signal output by the amplifier circuit can represent the noise-cancelled signal.
  • the variation of the self-capacitance of the first channel thereby reducing the influence of screen noise on capacitance detection.
  • FIG. 1 is a schematic diagram of the principle of touch detection.
  • FIG. 2 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application.
  • FIG. 3 is a schematic diagram of a capacitance detection circuit according to another embodiment of the present application.
  • FIG. 4 is a detection timing chart based on the circuit shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a possible implementation based on the circuits shown in FIGS. 2 and 3 .
  • FIG. 6 is a detection timing chart based on the circuit shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a possible implementation based on the circuits shown in FIGS. 2 and 3 .
  • FIG. 8 is a detection timing chart based on the circuit shown in FIG. 7 .
  • the display layer of the screen will generate large noise when scanning, and the 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 lower.
  • FIG. 1 is a schematic diagram of the principle of touch detection.
  • Figure 1 shows the horizontal and vertical channels in the touch layer.
  • Capacitive touch systems using this pattern can usually use two capacitance detection methods, self-capacitance and mutual capacitance, at the same time.
  • the touch chip When performing self-capacitance detection, the touch chip will scan the change of the self-capacitance to ground of each horizontal channel and vertical channel.
  • the self-capacitance of the channel near the finger becomes larger. For example, as shown in FIG. 1, the finger and its nearby lateral 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 is connected to the ground, the self-capacitance of the channel touched or approached by the finger will change, and the touch chip can obtain the touch information of the finger according to the detected change of the self-capacitance.
  • the present application provides a capacitance detection circuit, which can reduce the influence of screen noise on capacitance detection.
  • FIG. 2 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application.
  • the capacitance detection circuit 200 is used to detect the self-capacitance of the first channel in the screen, which is also referred to as capacitance hereinafter.
  • the capacitance detection circuit 200 includes a driving circuit 210 , a canceling circuit 220 , a releasing circuit 230 and an amplifying circuit 240 .
  • the signal source 300 is used here to represent the noise caused by the screen.
  • the driving circuit 210 is connected to the first channel and the second channel in the screen, and is used for charging and discharging the first channel and the second channel.
  • the canceling circuit 220 includes a canceling capacitor C C , the canceling capacitor C C is connected to the first channel, and the canceling capacitor C C is used to cancel the basic capacitance C X1 of the first channel.
  • the release circuit 230 is connected to the second channel, and the release circuit 230 is used to release the charge on the second channel to cancel the self-capacitance of the second channel, so that the capacitance signal of the second channel only includes the noise signal from the screen;
  • the amplifying circuit 240 is respectively connected with the first channel and the second channel.
  • the amplifying circuit 240 is used to receive the capacitance signal of the first channel and the capacitance signal of the second channel, and output the capacitance signal of the first channel and the capacitance signal of the second channel according to the capacitance signal of the first channel and the capacitance signal of the second channel. voltage signal.
  • the current self-capacitance of the first channel includes two parts : the base capacitance C X1 and the capacitance change amount ⁇ C X1.
  • the basic capacitance C X1 always exists.
  • the self-capacitance of the first channel is equal to the basic capacitance C X1
  • the self-capacitance of the first channel is generates capacitance variation ⁇ C X1 on the basis on the basis of the capacitance C X1. Therefore, it can be determined whether there is a finger touch according to whether the first channel produces a capacitance change ⁇ C X1 .
  • the two input ends of the amplifying circuit 240 are respectively connected to the first channel and the second channel, wherein the first channel is the channel to be detected, and the second channel is the noise reference channel.
  • the basic capacitance C X1 of the first channel can be canceled by the canceling circuit 220 , so that the voltage signal output by the amplifying circuit 240 is only associated with the capacitance change ⁇ C X1 of the first channel.
  • the driving circuit 210 inputs the driving signal to the first channel and the second channel, but the charge on the second channel will be released by the release circuit 230 afterward, so the second channel is input to the amplifier circuit 240 Only the noise signal from the screen is included in the capacitive signal.
  • the same noise signal carried in the first channel can be canceled, so that the voltage signal output by the amplifying circuit 240 can represent The variation ⁇ C X1 of the self-capacitance of the first channel after the noise is canceled, thereby reducing the influence of screen noise on the capacitance detection.
  • first channel and the second channel may be any two channels in the screen.
  • the first channel and the second channel may be two adjacent channels, such as TX 1 and TX 2 shown in FIG. 1 , or RX N-1 and RX N ; the first channel and the second channel may also be out of phase. two adjacent channels.
  • the capacitance detection circuit 200 of this embodiment can implement all-channel detection (All Driving).
  • the capacitance of the first channel of the plurality of horizontal channels and the capacitance of the first channel of the plurality of vertical channels can be detected in parallel in each detection period.
  • TX 1 to TX M and RX 1 to RX N in FIG. 1 are detected, assuming that M and N are even numbers.
  • the first round of the self-capacitance detection may be TX 1, TX 3, TX 5 , ising, TX M-1 as a first channel, TX 2, TX 4, TX 6 , ising, TX M , respectively, as a TX 1, TX 3, TX 5 , ising, a second channel corresponding to TX M-1, to detect TX 1, TX 3, TX 5 , ...., TX M-1 of change in capacitance.
  • TX 2 , TX 4 , TX 6 , ..., TX M can be used as the first channel
  • TX 1 , TX 3 , TX 5 , ..., TX M-1 can be used as TX 2, TX 4, TX 6 , whil, a second channel corresponding to TX M, thereby detecting the TX 2, TX 4, TX 6 , whil, amount of capacitance variation of the TX M.
  • the self-capacitance detection can be carried out in the above manner, that is, the channel with an odd number is used as the first channel and the channel with an even number is used as the first channel.
  • channel as the second channel then take the even-numbered channel as the first channel and the odd-numbered channel as the second channel; or, first take the even-numbered channel as the first channel and set the channel number as the first channel.
  • the odd-numbered channel is used as the second channel, the odd-numbered channel is used as the first channel, and the even-numbered channel is used as the second channel.
  • TX 1 to TX M in FIG. 1 M is an odd number
  • TX 1 to TX M-1 can be detected first
  • TX 2 to TX M can be detected.
  • TX 1 and TX M are detected. detecting the frequency of TX 2 TX M to 1/2 TX M-1 detected frequency.
  • TX 1 to TX M in FIG. 1 is an odd number
  • TX 2 to TX M can be detected first, that is, TX 1 is not detected
  • TX 1 , TX 2 , TX 4 to TX M can be detected , that is, TX 3 is not detected
  • TX 1 to TX 4 and TX 6 to TX M are detected, that is, TX 5 is not detected
  • TX 1 to TX M-1 are finally detected, that is, TX M is not detected.
  • the detection frequency of each channel in TX 1 , TX 3 , ..., TX M-2 , TX M is (K-1)/K, where K is TX 1 , TX 3 , ..., TX M-2 , the number of TX M. It can be seen that when the number of channels is large, the detection frequency of each channel is not much different, and it will not have a great impact on the results of capacitance detection.
  • the capacitance detection circuit 200 further includes a compensation circuit 250 .
  • the compensation circuit 250 includes a compensation capacitance Cp equal to the cancellation capacitance C C , and the compensation capacitance C C is connected to the second channel.
  • the release circuit 230 is also connected to the compensation capacitor 250 and used to charge and discharge the compensation capacitor Cp.
  • a detection cycle of the capacitance detection circuit 200 includes a first stage, a second stage and a third stage, wherein:
  • the drive circuit 210 charges or discharges the first channel and the second channel
  • the offset circuit 220 charges or discharges the offset capacitor C C
  • the release circuit 230 charges the offset capacitor Cp to a preset voltage
  • charge transfer is performed between the first channel and the canceling capacitor C C to cancel the base capacitance C X1 of the first channel through the canceling capacitor C C , and the release circuit 230 charges the second channel or discharges the second channel to a predetermined level. set voltage;
  • the first channel and the second channel input capacitance signals to the amplifying circuit 240, and the amplifying circuit 240 outputs a voltage signal according to the capacitance signal of the first channel and the capacitance signal of the second channel.
  • the driver circuit 210 charges the first channel and the second channel, eg, to a supply voltage.
  • the capacitance of the first channel comprises base capacitance C with respect to the X1 and the capacitance variations of the X1 base capacitance C ⁇ C X1
  • capacitance of the second channel comprises base capacitance C relative to the base X2 and the capacitance C of the capacitance X2 variation ⁇ C X2 .
  • switches K8, K6 and K5 are closed and the remaining switches are opened.
  • the canceling circuit 220 is connected to the first channel, and the charges on the first channel are transferred to the canceling capacitor C C in the canceling circuit 220 , thereby canceling the basic capacitance C X1 of the first channel through the canceling capacitor C C .
  • the remaining capacity of the first channel relative to the amount of capacitance change of base capacitance C X1 ⁇ C X1.
  • the release circuit 230 is connected to the second channel and the compensation circuit 250.
  • the release circuit 230 directly pulls the second channel to the preset voltage, and charges the compensation capacitor Cp in the compensation circuit 250 to the preset voltage , such as V CMI , thereby releasing any charge on the second channel and compensation capacitor Cp.
  • switches K3 and K4 are closed, and the remaining switches are opened. Therefore, the first channel and the second channel input capacitance signals to the amplifying circuit 240 , that is, the remaining charges on the first channel and the second channel are transferred to the amplifying circuit 240 .
  • the capacitance signal input by the first channel to the amplifying circuit 240 is the capacitance signal corresponding to the capacitance change ⁇ C X1 of the first channel, and due to the influence of screen noise, there is still a noise signal on the first channel, while on the second channel Since the charge has been released, only the noise signal remains.
  • the second amplifying circuit 240 through the first capacitor and the second channel signal difference can be eliminated the noise signal of the first channel, and the output voltage signal V OUT, V OUT of the voltage signal may reflect the noise cancellation signal
  • the capacitance variation ⁇ C X1 of a channel can be known from the capacitance variation ⁇ C X1 of the first channel according to the voltage signal V OUT output by the amplifying circuit 240 .
  • the switches K1 and K2 are closed, and the remaining switches are opened.
  • the first channel and the second channel discharge to the driver circuit 210, eg, to zero.
  • the capacitance of the first channel comprises base capacitance C with respect to the X1 and the capacitance variations of the X1 base capacitance C ⁇ C X1
  • capacitance of the second channel comprises base capacitance C relative to the base X2 and the capacitance C of the capacitance X2 variation ⁇ C X2 .
  • switches K8, K6 and K5 are closed and the remaining switches are opened.
  • the canceling circuit 220 is connected to the first channel, and the canceling capacitor C C in the canceling circuit 220 transfers charges to the first channel, thereby canceling the basic capacitance C X1 of the first channel through the canceling capacitor C C .
  • the remaining capacity of the first channel relative to the amount of capacitance change of base capacitance C X1 ⁇ C X1.
  • the release circuit 230 is connected to the second channel and the compensation circuit 250.
  • the release circuit 230 directly pulls the second channel to the preset voltage, and charges the compensation capacitor Cp in the compensation circuit 250 to the preset voltage , such as V CMI , thereby releasing any charge on the second channel and compensation capacitor Cp.
  • switches K3 and K4 are closed, and the remaining switches are opened. Therefore, the first channel and the second channel input capacitance signals to the amplifying circuit 240 .
  • the capacitance signal input by the first channel to the amplifying circuit 240 is the capacitance signal corresponding to the capacitance change ⁇ C X1 of the first channel, and due to the influence of screen noise, there is still a noise signal on the first channel, while on the second channel Since the charge has been released, only the noise signal remains.
  • the second amplifying circuit 240 through the first capacitor and the second channel signal difference can be eliminated the noise signal of the first channel, and the output voltage signal V OUT, V OUT of the voltage signal may reflect the noise cancellation signal
  • the capacitance variation ⁇ C X1 of a channel can be known from the capacitance variation ⁇ C X1 of the first channel according to the voltage signal V OUT output by the amplifying circuit 240 .
  • the cancellation circuit 220 can realize the cancellation of the basic capacitance C X1 of the first channel
  • the release circuit 230 can realize the cancellation of the basic capacitance C X2 and the capacitance change ⁇ C X2 of the second channel, so that the amplifying circuit 240 after the first capacitance signal and second channels is a differential input, a first capacitance may be obtained after passage of cancellation noise signal capacitance variations with respect to the basis of the capacitance C X1 ⁇ C X1, improve the sensitivity and accuracy of the capacitance detection sex.
  • the above-mentioned preset voltage is not limited in the embodiments of the present application.
  • the preset voltage is the common-mode voltage of the input terminal of the amplifier circuit, or the preset voltage is the neutral point voltage, which is denoted as V CMI .
  • the specific circuit structure of the capacitance detection circuit 200 is not limited in this embodiment of the present application.
  • two possible implementation manners of the circuit structure are provided in conjunction with FIG. 5 to FIG. 8 , that is, manner 1 and manner 2, so as to realize the self-capacitance detection of the first channel.
  • the driving circuit 210 includes a first switch K1 and a second switch K2, one end of the first channel is connected to the power supply voltage V CC through the first switch K1, and is connected to the power supply voltage V CC through the third switch K3.
  • One input terminal of the amplifying circuit 240 and the other terminal of the first channel are connected to the ground.
  • One end of the second channel is connected to the power supply voltage through the second switch K2, and is connected to the other input end of the amplifying circuit 240 through the fourth switch K4, and the other end of the second channel is connected to the ground.
  • the release circuit 230 includes a fifth switch K5 and a sixth switch K6, one end of the compensation capacitor Cp is connected to the preset voltage through the fifth switch K5, and is connected to the second through the sixth switch K6.
  • the channels are connected, and the other end of the compensation capacitor Cp is grounded.
  • the cancellation capacitance C C is equal to the base capacitance C X1 of the first channel.
  • the cancellation circuit 220 includes a seventh switch K7 and an eighth switch K8, one end of the cancellation capacitor 220 is connected to the ground through the seventh switch K7, and the eighth switch K8 communicates with the first switch K8 through the seventh switch K7. One channel is connected, and the other end of the cancellation capacitor C is grounded.
  • the first switch K1, the second switch K2, the seventh switch K7 and the fifth switch K5 are closed, wherein the first channel and the second channel are charged to the supply voltage V CC , the offset capacitor C C is discharged to 0, and the compensation capacitor Cp is charged to a preset voltage, such as V CMI ; in the second stage T2, the eighth switch K8, the fifth switch K5 and the sixth switch K6 are closed, wherein the first switch K8, the fifth switch K5 and the sixth switch K6 are closed.
  • the channel discharges to the cancellation capacitor C C , and the second channel discharges to a preset voltage, such as V CMI ; in the third stage T3, the eighth switch K8, the sixth switch K6, the third switch K3 and the fourth switch K4 are closed, wherein, The first channel and the second channel discharge to the amplifying circuit 240 .
  • the capacitance signal of the first channel includes the capacitance change amount ⁇ C X1 and the capacitance change caused by screen noise. Since the second channel is connected to the voltage V CMI , all the charge on the second channel is released, so only the noise signal from the screen remains on the second channel.
  • the signal amplifying circuit 240 of the first capacitor and second channels is a differential input, the first channel can be obtained after the cancellation noise signal with respect to the capacitance of the capacitance variation amount of the base capacitance C X1 ⁇ C X1 , thereby improving the sensitivity and accuracy of capacitance detection.
  • the capacitance detection circuit of the embodiment of the present application can be applied in various scenarios. For example, when the capacitance detection circuit is applied in the touch field, the touch of a finger on the screen will cause the corresponding channel to generate a capacitance change relative to the basic capacitance. The above circuit can obtain the capacitance change of the channel, thereby obtaining the touch information of the finger.
  • the voltage signal V OUT output by the amplifier circuit 240 is a constant value such as 0; when there is a finger touch, the parallel offset capacitance C C , the base capacitance C X1 and the capacitance change ⁇ C X1 after the charge transfer When the corresponding voltage is greater than V CMI , the voltage signal V OUT output by the amplifier circuit 240 changes.
  • the offset capacitor C C can be an adjustable capacitor.
  • the canceling capacitance C C can cancel the basic capacitance C X1 . Within an acceptable error range, it can also be adjusted to C C ⁇ C X1 , so that the offset capacitor C C C can offset enough basic capacitor C X1 .
  • the self-capacitance of the first channel may be detected by means of correlated double sampling.
  • the driving circuit 210 further includes a ninth switch K9 and a tenth switch K10, one end of the first channel is connected to the ground through the ninth switch K9, and one end of the second channel is connected to the ground through the tenth switch K10. connected to ground, cancellation circuit 220 further includes an eleventh switch K11, offset end of the capacitor C C is connected to the power supply voltage V CC through eleventh switch K11.
  • the detection cycle further includes a fourth stage T4, a fifth stage T5 and a sixth stage T6. 5 and 6, in the fourth stage T4, the ninth switch K9, the tenth switch K10, the eleventh switch K11 and the fifth switch K5 are closed, wherein the first channel and the second channel are discharged to 0, the offset capacitor C C is charged to the power supply voltage V CC , and the compensation capacitor Cp is charged to a preset voltage, such as V CMI ; in the fifth stage T5, the eighth switch K8, the fifth switch K5 and the sixth switch K6 are closed, wherein, The cancellation capacitor C C is discharged to the first channel, and the voltage of the second channel is pulled to a preset voltage, such as V CMI ; in the sixth stage T6, the eighth switch K8, the sixth switch K6, the third switch K3 and the fourth switch K4 is closed, wherein the amplifier circuit 240 discharges into the first and second channels.
  • the capacitance of the first passage with respect to the amount of capacitance change of base capacitance C X1 ⁇ C X1 is determined based on the voltage signal output from the amplifying circuit 240 in the third stage and the sixth stage T3 T6.
  • the voltage signals output by the amplifying circuit 240 are equal but opposite. Therefore, the cancellation can be determined by the voltage signals output by the third stage T3 and the sixth stage T6. Capacitance change ⁇ C X1 of the first channel after screen noise.
  • the cancellation capacitor C C is smaller than the basic capacitance C X1 of the first channel, thereby reducing the area of the cancellation capacitor and reducing the cost of the capacitance detection circuit.
  • the cancellation circuit 220 includes a seventh switch K7, an eighth switch K8, a twelfth switch K12 and a thirteenth switch K13, and one end of the cancellation capacitor C C passes through the seventh switch K7 connected to ground, and connected to a supply voltage V CC through the K8 eighth switch, the other end of the capacitor C C is connected offset to the power supply voltage V CC and the ground through the twelfth and thirteenth switch switches K12 K13, respectively.
  • the first switch K1, the second switch K2, the seventh switch K7, the fifth switch K5 and the twelfth switch K12 are closed, wherein the first channel and the two-channel charging to the supply voltage V CC, the offset voltage of the capacitor C C is the voltage on the plate and the lower plate 0 power supply voltage V CC, the compensation capacitor is charged to a predetermined voltage, for example V CMI; T2 in the second stage , the eighth switch K8, the fifth switch K5, the sixth switch K6 and the thirteenth switch 13 are closed, wherein the second channel is discharged to a preset voltage, such as V CMI , the voltage of the upper plate of the offset capacitor C C is negative voltage of the supply voltage -V CC 0 and the lower plate, so that the first discharge passage to the cancel capacitor C C; in the third stage T3, the K8 eighth switch, the sixth switch K6, a third switch K3, the fourth switch K4 and the thirteenth switch K13 are closed, wherein the first channel and the
  • the cancellation capacitor C C needs to cancel the basic capacitance C X1 of the first channel.
  • the voltages of the upper plate and the lower plate of the cancellation capacitor C C are -V CC and 0 respectively, and then charge transfer is performed between the cancellation capacitor C C and the first channel.
  • the capacitance signal of the first channel includes the capacitance change amount ⁇ C X1 and the capacitance change caused by screen noise. Since the second channel is connected to the voltage V CMI , all the charge on the second channel is released, so only the noise signal from the screen remains on the second channel.
  • the signal amplifying circuit 240 of the first capacitor and second channels is a differential input, the first channel can be obtained after the cancellation noise signal with respect to the capacitance of the capacitance variation amount of the base capacitance C X1 ⁇ C X1 , thereby improving the sensitivity and accuracy of capacitance detection.
  • the capacitance detection circuit When the capacitance detection circuit is applied in the touch field, the touch of the finger on the screen will cause the corresponding channel to generate capacitance change relative to the basic capacitance. Using the above circuit, the capacitance change of the channel can be obtained, thereby obtaining the touch information of the finger. .
  • the voltage signal V OUT output by the amplifier circuit 240 is a constant value such as 0; when there is a finger touch, the parallel offset capacitance C C , the base capacitance C X1 and the capacitance change ⁇ C X1 after the charge transfer When the corresponding voltage is greater than V CMI , the voltage signal V OUT output by the amplifier circuit 240 changes.
  • the offset capacitor C C can be an adjustable capacitor.
  • the canceling capacitance C C can cancel the basic capacitance C X1 . Within an acceptable error range, it can also be adjusted to C C ⁇ C X1 /3, so that the offset capacitor C C can offset enough basic capacitor C X1 .
  • the self-capacitance of the first channel may be detected by means of correlated double sampling.
  • the driving circuit 210 further includes a ninth switch K9 and a tenth switch K10, one end of the first channel is connected to the ground through the ninth switch K9, and one end of the second channel is connected to the ground through the tenth switch K10. connected to ground, cancellation circuit 220 further includes an eleventh switch K11, offset end of the capacitor C C is connected to the power supply voltage V CC through eleventh switch K11.
  • the detection cycle further includes a fourth stage T4, a fifth stage T5 and a sixth stage T6.
  • the ninth switch K9, the tenth switch K10, the eleventh switch K11, the fifth switch K5 and the thirteenth switch K13 are closed, wherein the first channel And the second channel is discharged to 0, the offset capacitor C C is charged to the power supply voltage V CC , and the compensation capacitor Cp is charged to a preset voltage, such as V CMI ;
  • the eighth switch K8 the fifth switch K5, the first The six switches K6 and the twelfth switch K12 are closed, wherein the offset capacitor C C is discharged to the first channel, and the voltage of the second channel is pulled to a preset voltage, such as V CMI ;
  • the sixth stage T6, the eighth switch K8, The sixth switch K6, the third switch K3, the fourth switch K4 and the twelve switches K12 are closed, where
  • the capacitance of the first passage with respect to the amount of capacitance change of base capacitance C X1 ⁇ C X1 is determined based on the voltage signal output from the amplifying circuit 240 in the third stage and the sixth stage T3 T6. As shown in FIG. 8 , in the third stage T3 and the sixth stage T6, the voltage signals output by the amplifying circuit 240 are equal but opposite. Therefore, the cancellation can be determined by the voltage signals output by the third stage T3 and the sixth stage T6. Capacitance change ⁇ C X1 of the first channel after screen noise.
  • the fourth stage T4 to the sixth stage T6 may also be executed first, and then the first stage T1 to the third stage T3 may be executed; The first stage T1 to the third stage T3 are performed; or, only the fourth stage T4 to the sixth stage T6 is performed. This application does not limit this.
  • the amplifying circuit 240 is, for example, a programmable gain amplifier (Programmable Gain Amplifier, PGA) circuit, which includes a differential operational amplifier, and uses the differential operational amplifier to collect capacitance signals to implement capacitance detection.
  • PGA programmable Gain Amplifier
  • a feedback resistor may be connected across the input terminal and the output terminal of the differential operational amplifier, so as to collect signals through the feedback resistor.
  • the capacitance detection circuit 200 may further include a filter circuit, and the filter circuit is connected to the amplifying circuit 520 for filtering the voltage signal output by the amplifying circuit 520 .
  • the capacitance detection circuit 500 may further include an analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected to the filter circuit for converting the filtered voltage signal into a digital signal.
  • the analog-to-digital converter Analog to Digital Converter, ADC
  • ADC Analog to Digital Converter
  • An embodiment of the present application further provides a touch control chip, including the capacitance detection circuit 200 in the above-mentioned various embodiments of the present application.
  • the embodiment of the present application further provides an electronic device, the electronic device includes: a screen; and the touch chip in the above-mentioned various embodiments of the present application.
  • the electronic device in the embodiments of the present application may be a portable or mobile computing device such as a terminal device, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a game device, a vehicle-mounted electronic device, or a wearable smart device, and Electronic databases, automobiles, bank ATMs (Automated Teller Machine, ATM) and other electronic devices.
  • the wearable smart device includes full-featured, large-sized devices that can achieve complete or partial functions without relying on smart phones, such as smart watches or smart glasses; Devices used in conjunction with mobile phones, such as various types of smart bracelets and smart jewelry that monitor physical signs.

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Abstract

一种电容检测电路（200），能够降低屏幕噪声对电容检测的影响。该电容检测电路（200）包括：驱动电路（210），与第一通道和屏幕中的第二通道相连，用于使第一通道和第二通道进行充放电；抵消电路（220），包括与第一通道相连的抵消电容（Cc），用于抵消第一通道的基础电容（Cx1）；释放电路（230），与第二通道相连，用于释放第二通道上的电荷以抵消第二通道的自电容，使得第二通道的电容信号中仅包括来自屏幕的噪声信号；放大电路（240），分别与第一通道和第二通道相连，用于接收第一通道的电容信号和第二通道的电容信号，并根据第一通道的电容信号和第二通道的电容信号输出电压信号，其中，电压信号用于确定抵消噪声信号后的第一通道的自电容相对于基础电容的电容变化量。

Description

电容检测电路和触控芯片 技术领域
本申请实施例涉及电容检测领域，并且更具体地，涉及电容检测电路和触控芯片。
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，如何降低屏幕的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和触控芯片，能够降低屏幕的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，用于检测所述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，与所述第一通道和所述屏幕中的第二通道相连，用于使所述第一通道和所述第二通道进行充放电；
抵消电路，包括抵消电容，所述抵消电容与所述第一通道相连，所述抵消电容用于抵消所述第一通道的基础电容；
释放电路，与所述第二通道相连，所述释放电路用于释放所述第二通道上的电荷以抵消所述第二通道的自电容，使得所述第二通道的电容信号中仅包括来自所述屏幕的噪声信号；
放大电路，分别与所述第一通道和所述第二通道相连，所述放大电路用于接收所述第一通道的电容信号和所述第二通道的电容信号，并根据所述第一通道的电容信号和所述第二通道的电容信号输出电压信号，其中，所述电压信号用于确定抵消所述噪声信号后的所述第一通道的自电容相对于所述基础电容的电容变化量。
在一种可能的实现方式中，所述电容检测电路还包括补偿电路，所述步 长电路包括与所述抵消电容相等的补偿电容，所述补偿电容与所述第二通道相连；其中，所述释放电路还与所述补偿电容相连，并用于使所述补偿电容进行充放电。
在一种可能的实现方式中，所述电容检测电路的一个检测周期包括第一阶段、第二阶段和第三阶段，其中：
在所述第一阶段，所述驱动电路使所述第一通道和所述第二通道充电或者放电，所述抵消电路使所述抵消电容充电或者放电，所述释放电路将所述补偿电容充电至预设电压；
在所述第二阶段，所述第一通道和所述抵消电容之间进行电荷转移以通过所述抵消电容抵消所述第一通道的基础电容，所述释放电路将所述第二通道的电压拉至所述预设电压；
在所述第三阶段，所述第一通道和所述第二通道向所述放大电路输入电容信号，所述放大电路根据所述第一通道的电容信号和所述第二通道的电容信号输出电压信号。
在一种可能的实现方式中，所述预设电压为所述放大电路的输入端的共模电压，和/或，所述预设电压等于所述电源电压的二分之一。
在一种可能的实现方式中，所述驱动电路包括第一开关和第二开关，所述第一通道的一端通过所述第一开关连接至电源电压，且通过第三开关连接至所述放大电路的一个输入端，所述第一通道的另一端连接至地，所述第二通道的一端通过所述第二开关连接至电源电压，且通过第四开关连接至所述放大电路的另一输入端，所述第二通道的另一端连接至地。
在一种可能的实现方式中，所述释放电路包括第五开关和第六开关，所述补偿电容的一端通过所述第五开关连接至预设电压，且通过所述第六开关与所述第二通道相连，所述补偿电容的另一端接地。
在一种可能的实现方式中，所述抵消电路包括第七开关和第八开关，所述抵消电容的一端通过所述第七开关连接至地，以及通过所述第八开关与所述第一通道相连，所述抵消电容的另一端接地。
在一种可能的实现方式中，在所述第一阶段，所述第一开关、所述第二开关、所述第五开关、和所述第七开关闭合，其中，所述第一通道和所述第二通道充电至电源电压，所述抵消电容放电至0，所述补偿电容充电至预设电压；在所述第二阶段，所述第五开关、所述第六开关和所述第八开关闭合， 其中，所述第一通道向所述抵消电容放电，所述第二通道的电压被拉至所述预设电压；在所述第三阶段，所述第三开关、所述第四开关、所述第六开关和所述第八开关闭合，其中，所述第一通道和所述第二通道向所述放大电路放电。
在一种可能的实现方式中，所述驱动电路还包括第九开关和第十开关，所述第一通道的一端通过所述第九开关连接至地，所述第二通道的一端通过所述第十开关连接至地，所述抵消电路还包括第十一开关，所述抵消电容的一端通过所述第十一开关连接至电源电压。
在一种可能的实现方式中，所述检测周期还包括第四阶段、第五阶段和第六阶段，其中：
在所述第四阶段，所述第五开关、所述第九开关、所述第十开关和所述第十一开关闭合，其中，所述第一通道和所述第二通道放电至0，所述抵消电容充电至电源电压，所述补偿电容充电至预设电压；
在所述第五阶段，所述第五开关、所述第六开关和所述第八开关闭合，其中，所述抵消电容向所述第一通道放电，所述第二通道的电压被拉至所述预设电压；
在所述第六阶段，所述第三开关、所述第四开关、所述第六开关和所述第八开关闭合，其中，所述放大电路向所述第一通道和所述第二通道放电；
其中，所述第一通道的自电容相对于所述基础电容的电容变化量是根据所述放大电路在所述第三阶段和所述第六阶段输出的电压信号确定的。
在一种可能的实现方式中，所述抵消电容等于所述第一通道的基础电容。
在一种可能的实现方式中，所述抵消电路包括第七开关、第八开关、第十二开关和第十三开关，所述抵消电容的一端通过所述第七开关连接至地，以及通过所述第八开关与所述第一通道相连，所述抵消电容的另一端通过所述第十二开关和所述第十三开关分别连接至电源电压和地。
在一种可能的实现方式中，在所述第一阶段，所述第一开关、所述第二开关、所述第五开关、所述第七开关和所述第十二开关闭合，其中，所述第一通道和所述第二通道充电至电源电压，所述抵消电容的上极板的电压为0且下极板的电压为电源电压，所述补偿电容充电至预设电压；在所述第二阶段，所述第五开关、所述第六开关、所述第八开关和所述第十三开关闭合，其中，所述抵消电容的上极板的电压为负的电源电压且下极板的电压为0， 所述第一通道向所述抵消电容放电，所述第二通道的电压被拉至所述预设电压；在所述第三阶段，所述第三开关、所述第四开关、所述第六开关、所述第八开关和所述第十三开关闭合，其中，所述第一通道和所述第二通道向所述放大电路放电。
在一种可能的实现方式中，所述驱动电路还包括第九开关和第十开关，所述第一通道的一端通过所述第九开关连接至地，所述第二通道的一端通过所述第十开关连接至地，所述抵消电路还包括第十一开关，所述抵消电容的一端通过所述第十一开关连接至电源电压。
在一种可能的实现方式中，所述检测周期还包括第四阶段、第五阶段和第六阶段，其中：
在所述第四阶段，所述第五开关、所述第九开关、所述第十开关、所述第十一开关和所述第十三开关闭合，其中，所述第一通道和所述第二通道放电至0，所述抵消电容充电至电源电压，所述补偿电容充电至预设电压；
在第五阶段，所述第五开关、所述第六开关、所述第八开关和所述第十二开关闭合，其中，所述抵消电容向所述第一通道放电，所述第二通道充电至所述预设电压；
在所述第六阶段，所述第三开关、所述第四开关、所述第六开关、所述第八开关和所述第十二开关闭合，其中，所述放大电路向所述第一通道和所述第二通道放电。
在一种可能的实现方式中，所述抵消电容等于所述第一通道的基础电容的三分之一。
在一种可能的实现方式中，所述屏幕包括多个横向通道和多个纵向通道，其中，每个检测周期中并行检测所述多个横向通道中的所述第一通道的自电容，以及所述多个纵向通道中的所述第一通道的自电容。
在一种可能的实现方式中，在对奇数个横向通道或者纵向通道进行检测时，先对除第一个通道之外的剩余偶数个通道进行检测，再对除最后一个通道之外的剩余偶数个通道进行检测。
在一种可能的实现方式中，在对偶数个横向通道或者纵向通道进行检测时，先将编号为奇数的通道作为所述第一通道并将编号为偶数的通道作为所述第二通道，再将编号为偶数的通道作为所述第一通道并将编号为奇数的通道作为所述第二通道。
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。
基于上述技术方案，放大电路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。通过抵消电路可以抵消第一通道的基础电容，从而使放大电路输出的电压信号仅与第一通道的自电容相对于该基础电容的变化量相关联。在检测第一通道的自电容时，驱动电路向第一通道和第二通道输入驱动信号，但是第二通道上的电荷之后会通过释放电路被释放掉，因此第二通道输入放大电路的电容信号中仅包括来自屏幕的噪声信号。这样，第一通道和第二通道输入放大电路的电容信号在放大电路中进行差分后，就可以抵消第一通道中携带的相同的噪声信号，从而使放大电路输出的电压信号可以表示抵消噪声后的第一通道的自电容的变化量，从而降低屏幕噪声对电容检测的影响。
附图说明
图1是触摸检测的原理的示意图。
图2是本申请实施例的电容检测电路的示意图。
图3是本申请另一实施例的电容检测电路的示意图。
图4是基于图3所示的电路的检测时序图。
图5是基于图2和图3所示的电路的一种可能的实现方式的示意图。
图6是基于图5所示的电路的检测时序图。
图7是基于图2和图3所示的电路的一种可能的实现方式的示意图。
图8是基于图7所示的电路的检测时序图。
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。
图1是触摸检测的原理的示意图。图1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***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1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，就可以获得手指的触摸信息。
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。
图2是本申请实施例的电容检测电路的示意图。该电容检测电路200用于检测屏幕中的第一通道的自电容，以下也简称电容。如图2所示，电容检测电路200包括驱动电路210，抵消电路220，释放电路230和放大电路240。其中，信号源300在这里用来表示屏幕引起的噪声。
驱动电路210与第一通道和屏幕中的第二通道相连，用于使第一通道和第二通道进行充放电。
抵消电路220包括抵消电容C C，抵消电容C C与第一通道相连，抵消电容C C用于抵消第一通道的基础电容C X1。
释放电路230与第二通道相连，释放电路230用于释放第二通道上的电荷以抵消第二通道的自电容，使得第二通道的电容信号中仅包括来自该屏幕的噪声信号；
放大电路240分别与第一通道和第二通道相连，放大电路240用于接收第一通道的电容信号和第二通道的电容信号，并根据第一通道的电容信号和第二通道的电容信号输出电压信号。
其中，该电压信号用于确定抵消该噪声信号后的所述第一通道的自电容相对于基础电容C X1的电容变化量△C X1。
应理解，第一通道当前的自电容包括基础电容C X1和电容变化量△C X1两部分。基础电容C X1一直存在，当第一通道对应的位置没有手指触摸时，第一通道的自电容就等于基础电容C X1，而当第一通道对应的位置有手指触摸，第一通道的自电容会在基础电容C X1的基础上产生电容变化量△C X1。因此可以根据第一通道是否产生了电容变化量△C X1，来确定是否有手指触摸。
该实施例中，放大电路240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。通过抵消电路220 可以抵消第一通道的基础电容C X1，从而使放大电路240输出的电压信号仅与第一通道的电容变化量△C X1相关联。在检测第一通道的自电容时，驱动电路210向第一通道和第二通道输入驱动信号，但是第二通道上的电荷之后会通过释放电路230被释放掉，因此第二通道输入放大电路240的电容信号中仅包括来自屏幕的噪声信号。这样，第一通道和第二通道输入放大电路240的电容信号在放大电路240中进行差分后，就可以抵消第一通道中携带的相同的噪声信号，从而使放大电路240输出的电压信号可以表示抵消噪声后的第一通道的自电容的变化量△C X1，从而降低屏幕噪声对电容检测的影响。
应理解，第一通道和第二通道可以是屏幕中的任意两个通道。第一通道和第二通道可以是相邻的两个通道，例如图1中所示的TX 1和TX 2，或者RX N-1和RX N；第一通道和第二通道也可以是不相邻的两个通道。
该实施例的电容检测电路200可以实现全通道检测(All Driving)。当屏幕包括多个横向通道和多个纵向通道时，每个检测周期中可以并行检测多个横向通道中的该第一通道的电容，以及多个纵向通道中的该第一通道的电容。
例如，对图1中的TX 1至TX M和RX 1至RX N进行检测，假设M和N为偶数。在第一轮自容检测时，可以将TX 1、TX 3、TX 5、……、TX M-1作为第一通道，将TX 2、TX 4、TX 6、……、TX M分别作为与TX 1、TX 3、TX 5、……、TX M-1对应的第二通道，从而检测TX 1、TX 3、TX 5、……、TX M-1的电容变化量。其中，在检测TX 1、TX 3、TX 5、……、TX M-1的同时，将RX 1、RX 3、RX 5、……、RX N-1作为第一通道，将RX 2、RX 4、RX 6、……、TX N分别作为与RX 1、RX 3、RX 5、……、RX N-1对应的第二通道，从而检测RX 1、RX 3、RX 5、……、RX N-1的电容变化量。在第二轮自容检测时，可以将TX 2、TX 4、TX 6、……、TX M作为第一通道，将TX 1、TX 3、TX 5、……、TX M-1分别作为与TX 2、TX 4、TX 6、……、TX M对应的第二通道，从而检测TX 2、TX 4、TX 6、……、TX M的电容变化量。其中，在检测TX 2、TX 4、TX 6、……、TX M的同时，将RX 2、RX 4、RX 6、……、RX N作为第一通道，将RX 1、RX 3、RX 5、……、RX N-1分别作为与RX 2、RX 4、RX 6、……、RX N对应的第二通道，从而检测RX 2、RX 4、RX 6、……、RX N的电容变化量。这样，经过这两轮检测，就可以检测完屏幕中的所有通道的电容变化量。
当M或者N为偶数时，在对偶数个横向通道或者纵向通道进行检测时，可以通过上述方式进行自容检测，即：先将编号为奇数的通道作为该第一通 道并将编号为偶数的通道作为该第二通道，再将编号为偶数的通道作为该第一通道并将编号为奇数的通道作为该第二通道；或者，先将编号为偶数的通道作为该第一通道并将编号为奇数的通道作为该第二通道，再将编号为奇数的通道作为该第一通道并将编号为偶数的通道作为该第二通道。
而当M或者N为奇数时，在对奇数个横向通道或者纵向通道进行检测时，可以先对除第一个通道之外的剩余偶数个通道进行检测，再对除最后一个通道之外的剩余偶数个通道进行检测。其中，剩余偶数个通道可以采用前述方式进行检测。例如，以图1中的TX 1至TX M为例，M为奇数，那么，可以先对TX 1至TX M-1进行检测，再对TX 2至TX M进行检测，这时，TX 1和TX M的检测频率为TX 2至TX M-1的检测频率的1/2。
上述的检测方式仅仅为示例，也可以采用其他检测方式对多个通道进行自容检测。例如，仍以图1中的TX 1至TX M为例，M为奇数，那么，可以先检测TX 2至TX M，即不检测TX 1；接着检测TX 1、TX 2、TX 4至TX M，即不检测TX 3；接着检测TX 1至TX 4以及TX 6至TX M，即不检测TX 5；……；最后检测TX 1至TX M-1，即不检测TX M。这样，TX 1、TX 3、……、TX M-2、TX M中的每个通道的检测频率为(K-1)/K，K为TX 1、TX 3、……、TX M-2、TX M的数量。可见，当通道数量较多时，每个通道的检测频率相差不大，不会对电容检测的结果造成较大影响。
可选地，在一种实现方式中，如图3所示，电容检测电路200还包括补偿电路250。补偿电路250包括与抵消电容C C相等的补偿电容Cp，补偿电容C C与第二通道相连。其中，释放电路230还与补偿电容250相连，并用于对补偿电容Cp进行充放电。
应理解，该补偿电容Cp与抵消电容C C相等，即Cp＝C C，能够使电容检测过程中的第一通道和第二通道对称，即待检测通道和噪声参考通道对称，因此待检测通道和噪声参考通道对电容检测过程具有等量的影响，从而有助于噪声的抵消。
下面结合图3和图4描述电容检测电路200的检测原理。
可选地，在一种实现方式中，电容检测电路200的一个检测周期包括第一阶段、第二阶段和第三阶段，其中：
在第一阶段，驱动电路210使第一通道和第二通道充电或者放电，抵消电路220使抵消电容C C充电或者放电，释放电路230将补偿电容Cp充电至 预设电压；
在第二阶段，第一通道和抵消电容C C之间进行电荷转移以通过抵消电容C C抵消第一通道的基础电容C X1，释放电路230将第二通道充电或者使第二通道放电至预设电压；
在第三阶段，第一通道和第二通道向放大电路240输入电容信号，放大电路240根据第一通道的电容信号和第二通道的电容信号输出电压信号。
举例来说，在一种实现方式中，如图3和图4所示，在第一阶段T1，将开关K1、K2和K6闭合，其余开关断开。驱动电路210向第一通道和第二通道充电，例如充电至电源电压。其中，第一通道的电容包括基础电容C X1和相对于基础电容C X1的电容变化量△C X1，第二通道的电容包括基础电容C X2和相对于基础电容C X2的电容变化量△C X2。
在第二阶段T2，将开关K8、K6和K5闭合，其余开关断开。当开关K8闭合时，抵消电路220与第一通道相连，第一通道上的电荷向抵消电路220中的抵消电容C C转移，从而通过抵消电容C C抵消第一通道的基础电容C X1。在理想情况下，抵消之后，第一通道的电容仅剩下相对于基础电容C X1的电容变化量△C X1。当开关K6和K5闭合时，释放电路230与第二通道和补偿电路250相连，释放电路230将第二通道直接拉至预设电压，并将补偿电路250中的补偿电容Cp充电至预设电压，例如V CMI，从而释放第二通道和补偿电容Cp上的所有电荷。
在第三阶段T3，将开关K3和K4闭合，其余开关断开。从而第一通道和第二通道向放大电路240输入电容信号，即第一通道和第二通道上剩余的电荷向放大电路240转移。
其中，第一通道向放大电路240输入的电容信号为第一通道的电容变化量△C X1对应的电容信号，并且由于屏幕噪声的影响，第一通道上还存在噪声信号，而第二通道上的电荷由于已经被释放，因此只剩该噪声信号。通过放大电路240对第一通道和第二通道的电容信号进行差分，就可以消除第一通道中的噪声信号，并输出电压信号V OUT，该电压信号V OUT可以反映抵消噪声信号后的该第一通道的电容变化量△C X1，根据放大电路240输出的电压信号V OUT就可以知道第一通道的电容变化量△C X1。
又例如，在另一种实现方式中，在第一阶段T1，将开关K1和K2闭合，其余开关断开。第一通道和第二通道向驱动电路210放电，例如放电至0。 其中，第一通道的电容包括基础电容C X1和相对于基础电容C X1的电容变化量△C X1，第二通道的电容包括基础电容C X2和相对于基础电容C X2的电容变化量△C X2。
在第二阶段T2，将开关K8、K6和K5闭合，其余开关断开。当开关K8闭合时，抵消电路220与第一通道相连，抵消电路220中的抵消电容C C向第一通道进行电荷转移，从而通过抵消电容C C抵消第一通道的基础电容C X1。在理想情况下，抵消之后，第一通道的电容仅剩下相对于基础电容C X1的电容变化量△C X1。当开关K6和K5闭合时，释放电路230与第二通道和补偿电路250相连，释放电路230将第二通道直接拉至预设电压，并将补偿电路250中的补偿电容Cp充电至预设电压，例如V CMI，从而释放第二通道和补偿电容Cp上的所有电荷。
在第三阶段T3，将开关K3和K4闭合，其余开关断开。从而第一通道和第二通道向放大电路240输入电容信号。
其中，第一通道向放大电路240输入的电容信号为第一通道的电容变化量△C X1对应的电容信号，并且由于屏幕噪声的影响，第一通道上还存在噪声信号，而第二通道上的电荷由于已经被释放，因此只剩该噪声信号。通过放大电路240对第一通道和第二通道的电容信号进行差分，就可以消除第一通道中的噪声信号，并输出电压信号V OUT，该电压信号V OUT可以反映抵消噪声信号后的该第一通道的电容变化量△C X1，根据放大电路240输出的电压信号V OUT就可以知道第一通道的电容变化量△C X1。
可见，通过抵消电路220可以实现对第一通道的基础电容C X1的抵消，通过释放电路230可以实现对第二通道的基础电容C X2和电容变化量△C X2的抵消，从而使放大电路240对第一通道和第二通道输入的电容信号进行差分后，可以得到抵消噪声信号后的第一通道的电容相对于基础电容C X1的电容变化量△C X1，提高了电容检测的灵敏度和准确性。
应理解，本申请实施例对上述的预设电压不做限定，优选地，该预设电压为放大电路的输入端的共模电压，或者说该预设电压为中性点电压，记为V CMI。V CMI例如等于电源电压V CC的二分之一，即V CMI＝V CC/2。
本申请实施例对电容检测电路200的具体电路结构不做限定。以下，结合图5至图8提供电路结构的两种可能的实现方式，即方式1和方式2，以实现对第一通道的自电容检测。
可选地，在一种实现方式中，驱动电路210包括第一开关K1和第二开关K2，第一通道的一端通过第一开关K1连接至电源电压V CC，且通过第三开关K3连接至放大电路240的一个输入端，第一通道的另一端连接至地。第二通道的一端通过第二开关K2连接至电源电压，且通过第四开关K4连接至放大电路240的另一输入端，第二通道的另一端连接至地。
可选地，在一种实现方式中，释放电路230包括第五开关K5和第六开关K6，补偿电容Cp的一端通过第五开关K5连接至预设电压，且通过第六开关K6与第二通道相连，补偿电容Cp的另一端接地。
在方式1中，抵消电容C C等于第一通道的基础电容C X1。
这时，可选地，在一种实现方式中，抵消电路220包括第七开关K7和第八开关K8，抵消电容220的一端通过第七开关K7连接至地，以及通过第八开关K8与第一通道相连，抵消电容C C的另一端接地。
参见图5和图6，在检测周期的第一阶段T1，第一开关K1、第二开关K2、第七开关K7和第五开关K5闭合，其中，第一通道和第二通道充电至电源电压V CC，抵消电容C C放电至0，补偿电容Cp充电至预设电压，例如V CMI；在第二阶段T2，第八开关K8、第五开关K5和第六开关K6闭合，其中，第一通道向抵消电容C C放电，第二通道放电至预设电压，例如V CMI；在第三阶段T3，第八开关K8、第六开关K6、第三开关K3和第四开关K4闭合，其中，第一通道和第二通道向放大电路240放电。
可以看出，在第二阶段T2，抵消电容C C需要抵消第一通道的基础电容C X1，那么抵消电容C C应当与第一通道的基础电容C X1相等，即C C＝C X1。在抵消之后，第一通道的电容信号中包括电容变化量△C X1以及屏幕噪声引起的电容变化。由于第二通道连接至电压V CMI，第二通道上的电荷都被释放掉了，因此第二通道上仅剩来自屏幕的噪声信号。在第三阶段T3，放大电路240对第一通道和第二通道输入的电容信号进行差分后，可以得到抵消噪声信号后的第一通道的电容相对于基础电容C X1的电容变化量△C X1，从而提高了电容检测的灵敏度和准确性。
本申请实施例的电容检测电路可以应用在各种场景中，例如，当该电容检测电路应用在触控领域时，手指在屏幕上的触摸会引起相应通道相对于基础电容产生电容变化量，采用上述电路即可以获得该通道的电容变化量，从而获得手指的触摸信息。
当没有手指触摸到第一通道对应的位置时，由于第二阶段T2的抵消电容C C、基础电容C X1、补偿电容Cp、以及C X2和△C X2对应的电压均为V CMI，无电荷向放大电路240转移，放大电路240输出的电压信号V OUT为一恒定值例如0；当有手指触摸时，并联的抵消电容C C、基础电容C X1和电容变化量△C X1在电荷转移后对应的电压大于V CMI，放大电路240输出的电压信号V OUT就有变化。
该抵消电容C C可以为可调电容，当没有手指触摸到第一通道对应的位置时，通过调节C C的值，使得放大电路240输出的电压信号V OUT为一恒定值例如0，此时认为已经调节到C C＝C X1。在之后进行电容检测时，如果有手指触摸，则该抵消电容C C可以抵消基础电容C X1。在可接受的误差范围内，也可以调节至C C≈C X1，使抵消电容C C抵消足够的基础电容C X1即可。
为了抑制低频干扰信号对电容检测电路的影响，进一步地，可以采用相关双采样的方式检测第一通道的自电容。
可选地，在一种实现方式中，驱动电路210还包括第九开关K9和第十开关K10，第一通道的一端通过第九开关K9连接至地，第二通道的一端通过第十开关K10连接至地，抵消电路220还包括第十一开关K11，抵消电容C C的一端通过第十一开关K11连接至电源电压V CC。
这时，可选地，在一种实现方式中，该检测周期还包括第四阶段T4、第五阶段T5和第六阶段T6。其中，例如图5和图6所示，在第四阶段T4，第九开关K9、第十开关K10、第十一开关K11和第五开关K5闭合，其中，第一通道和第二通道放电至0，抵消电容C C充电至电源电压V CC，补偿电容Cp充电至预设电压，例如V CMI；在第五阶段T5，第八开关K8、第五开关K5和第六开关K6闭合，其中，抵消电容C C向第一通道放电，第二通道的电压被拉至预设电压，例如V CMI；在第六阶段T6，第八开关K8、第六开关K6、第三开关K3和第四开关K4闭合，其中，放大电路240向第一通道和第二通道放电。
这时，第一通道的自电容相对于基础电容C X1的电容变化量△C X1是根据放大电路240在第三阶段T3和第六阶段T6输出的电压信号确定的。如图6所示，在第三阶段T3和第六阶段T6，放大电路240输出的电压信号是相等但相反的，因此，可以通过第三阶段T3和第六阶段T6输出的电压信号，确定抵消屏幕噪声后的第一通道的电容变化量△C X1。例如，假设放大电路 240在第三阶段T3输出的电压信号为V OUT+V’，在第六阶段T6输出的电压信号为-V OUT+V’，其中V’为低频干扰电压，那么根据[(V OUT+V’)-(-V OUT+V’)]/2就可以抵消低频干扰噪声V’，并得到电压信号V OUT，从而确定第一通道的电容变化量△C X1。
方式2
在方式2中，抵消电容C C小于第一通道的基础电容C X1，从而减小了抵消电容的面积，也降低了电容检测电路的成本。
这时，可选地，在一种实现方式中，抵消电路220包括第七开关K7、第八开关K8、第十二开关K12和第十三开关K13，抵消电容C C的一端通过第七开关K7连接至地，以及通过第八开关K8连接至电源电压V CC，抵消电容C C的另一端通过第十二开关K12和第十三开关K13分别连接至电源电压V CC和地。
参见图7和图8，在检测周期的第一阶段T1，第一开关K1、第二开关K2、第七开关K7、第五开关K5和第十二开关K12闭合，其中，第一通道和第二通道充电至电源电压V CC，抵消电容C C的上极板的电压为0且下极板的电压为电源电压V CC，补偿电容充电至预设电压，例如V CMI；在第二阶段T2，第八开关K8、第五开关K5、第六开关K6和第十三开关13闭合，其中，第二通道放电至预设电压，例如V CMI，抵消电容C C的上极板的电压为负的电源电压-V CC且下极板的电压为0，从而第一通道向抵消电容C C放电；在第三阶段T3，第八开关K8、第六开关K6、第三开关K3、第四开关K4和第十三开关K13闭合，其中，第一通道和第二通道向放大电路240放电。
可以看出，在第二阶段T2，抵消电容C C需要抵消第一通道的基础电容C X1，以预设电压为V CC/2为例，那么抵消电容C C应当等于第一通道的基础电容C X1的1/3，即C C＝C X1/3。具体地，在第二阶段T2，抵消电容C C的上极板和下极板的电压分别为-V CC和0，接着抵消电容C C和第一通道之间进行电荷转移，当抵消电容C C对第一通道的基础电容C X1进行抵消后，抵消电容C C和基础电容C X1的电压均变成V CMI即V CC/2。因此，抵消电容C C的电压从-V CC变化至V CC/2，变化了1.5V CC；而基础电容C X1对应的电压从V CC变化至V CC/2，变化了0.5V CC。根据公式Q＝U*C可以得到，0.5*C X1＝1.5*C C，因此C C＝C X1/3。在抵消之后，第一通道的电容信号中包括电容变化量△C X1 以及屏幕噪声引起的电容变化。由于第二通道连接至电压V CMI，第二通道上的电荷都被释放掉了，因此第二通道上仅剩来自屏幕的噪声信号。在第三阶段T3，放大电路240对第一通道和第二通道输入的电容信号进行差分后，可以得到抵消噪声信号后的第一通道的电容相对于基础电容C X1的电容变化量△C X1，从而提高了电容检测的灵敏度和准确性。
当该电容检测电路应用在触控领域时，手指在屏幕上的触摸会引起相应通道相对于基础电容产生电容变化量，采用上述电路即可以获得该通道的电容变化量，从而获得手指的触摸信息。
当没有手指触摸到第一通道对应的位置时，由于第二阶段T2的抵消电容C C、基础电容C X1、补偿电容Cp、以及C X2和△C X2对应的电压均为V CMI，无电荷向放大电路240转移，放大电路240输出的电压信号V OUT为一恒定值例如0；当有手指触摸时，并联的抵消电容C C、基础电容C X1和电容变化量△C X1在电荷转移后对应的电压大于V CMI，放大电路240输出的电压信号V OUT就有变化。
该抵消电容C C可以为可调电容，当没有手指触摸到第一通道对应的位置时，通过调节C C的值，使得放大电路240输出的电压信号V OUT为一恒定值例如0，此时认为已经调节到C C＝C X1/3。在之后进行电容检测时，如果有手指触摸，则该抵消电容C C可以抵消基础电容C X1。在可接受的误差范围内，也可以调节至C C≈C X1/3，使抵消电容C C抵消足够的基础电容C X1即可。
为了抑制低频干扰信号对电容检测电路的影响，进一步地，可以采用相关双采样的方式检测第一通道的自电容。
可选地，在一种实现方式中，驱动电路210还包括第九开关K9和第十开关K10，第一通道的一端通过第九开关K9连接至地，第二通道的一端通过第十开关K10连接至地，抵消电路220还包括第十一开关K11，抵消电容C C的一端通过第十一开关K11连接至电源电压V CC。
这时，可选地，在一种实现方式中，该检测周期还包括第四阶段T4、第五阶段T5和第六阶段T6。其中，例如图7和图8所示，在第四阶段T4，第九开关K9、第十开关K10、第十一开关K11、第五开关K5和第十三开关K13闭合，其中，第一通道和第二通道放电至0，抵消电容C C充电至电源电压V CC，补偿电容充Cp充电至预设电压，例如V CMI；在第五阶段T5，第八开关K8、第五开关K5、第六开关K6和第十二开关K12闭合，其中，抵消 电容C C向第一通道放电，第二通道的电压被拉至预设电压，例如V CMI；在第六阶段T6，第八开关K8、第六开关K6、第三开关K3、第四开关K4和十二开关K12闭合，其中，放大电路240向第一通道和第二通道放电。
这时，第一通道的自电容相对于基础电容C X1的电容变化量△C X1是根据放大电路240在第三阶段T3和第六阶段T6输出的电压信号确定的。如图8所示，在第三阶段T3和第六阶段T6，放大电路240输出的电压信号是相等但相反的，因此，可以通过第三阶段T3和第六阶段T6输出的电压信号，确定抵消屏幕噪声后的第一通道的电容变化量△C X1。例如，假设放大电路240在第三阶段T3输出的电压信号为V OUT+V’，在第六阶段T6输出的电压信号为-V OUT+V’，其中V’为低频干扰电压，那么根据[(V OUT+V’)-(-V OUT+V’)]/2就可以抵消低频干扰噪声V’，并得到电压信号V OUT，从而确定第一通道的电容变化量△C X1。
应理解，在方式1和方式2中，在对第一通道的一次检测中，也可以先执行第四阶段T4至第六阶段T6，再执行第一阶段T1至第三阶段T3；或者，仅执行第一阶段T1至第三阶段T3；或者，仅执行第四阶段T4至第六阶段T6。本申请对此不做限定。
本申请实施例中，放大电路240例如是可编程增益放大器(Programmable Gain Amplifier，PGA)电路，其包括差分运算放大器，以利用差分运算放大器对电容信号进行采集以实现电容检测。差分运算放大器的输入端和输出端之间例如可以跨接反馈电阻，从而通过反馈电阻采集信号。
此外，电容检测电路200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。例如图3中所示的抗混叠滤波器(Anti-Alias Filter，AAF)260。
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。例如图3中所示的模数转换器(Analog to Digital Converter，ADC)270。
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200。
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，且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 (20)

  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，与所述第一通道和所述屏幕中的第二通道相连，用于使所述第一通道和所述第二通道进行充放电；
    抵消电路，包括抵消电容，所述抵消电容与所述第一通道相连，所述抵消电容用于抵消所述第一通道的基础电容；
    释放电路，与所述第二通道相连，所述释放电路用于释放所述第二通道上的电荷以抵消所述第二通道的自电容，使得所述第二通道的电容信号中仅包括来自所述屏幕的噪声信号；
    放大电路，分别与所述第一通道和所述第二通道相连，所述放大电路用于接收所述第一通道的电容信号和所述第二通道的电容信号，并根据所述第一通道的电容信号和所述第二通道的电容信号输出电压信号，其中，所述电压信号用于确定抵消所述噪声信号后的所述第一通道的自电容相对于所述基础电容的电容变化量。
  2. 根据权利要求1所述的电容检测电路，其特征在于，还包括：
    补偿电路，包括与所述抵消电容相等的补偿电容，所述补偿电容与所述第二通道相连；
    其中，所述释放电路还与所述补偿电容相连，并用于使所述补偿电容进行充放电。
  3. 根据权利要求2所述的电容检测电路，其特征在于，所述电容检测电路的一个检测周期包括第一阶段、第二阶段和第三阶段，其中：
    在所述第一阶段，所述驱动电路使所述第一通道和所述第二通道充电或者放电，所述抵消电路使所述抵消电容充电或者放电，所述释放电路将所述补偿电容充电至预设电压；
    在所述第二阶段，所述第一通道和所述抵消电容之间进行电荷转移以通过所述抵消电容抵消所述第一通道的基础电容，所述释放电路将所述第二通道的电压拉至所述预设电压；
    在所述第三阶段，所述第一通道和所述第二通道向所述放大电路输入电容信号，所述放大电路根据所述第一通道的电容信号和所述第二通道的电容信号输出电压信号。
  4. 根据权利要求3所述的电容检测电路，其特征在于，所述预设电压为所述放大电路的输入端的共模电压，和/或，所述预设电压等于电源电压的二分之一。
  5. 根据权利要求3或4所述的电容检测电路，其特征在于，所述驱动电路包括第一开关和第二开关，
    所述第一通道的一端通过所述第一开关连接至电源电压，且通过第三开关连接至所述放大电路的一个输入端，所述第一通道的另一端连接至地，
    所述第二通道的一端通过所述第二开关连接至电源电压，且通过第四开关连接至所述放大电路的另一输入端，所述第二通道的另一端连接至地。
  6. 根据权利要求5所述的电容检测电路，其特征在于，所述释放电路包括第五开关和第六开关，所述补偿电容的一端通过所述第五开关连接至预设电压，且通过所述第六开关与所述第二通道相连，所述补偿电容的另一端接地。
  7. 根据权利要6所述的电容检测电路，其特征在于，所述抵消电路包括第七开关和第八开关，所述抵消电容的一端通过所述第七开关连接至地，以及通过所述第八开关与所述第一通道相连，所述抵消电容的另一端接地。
  8. 根据权利要求7所述的电容检测电路，其特征在于，
    在所述第一阶段，所述第一开关、所述第二开关、所述第五开关、和所述第七开关闭合，其中，所述第一通道和所述第二通道充电至电源电压，所述抵消电容放电至0，所述补偿电容充电至预设电压；
    在所述第二阶段，所述第五开关、所述第六开关和所述第八开关闭合，其中，所述第一通道向所述抵消电容放电，所述第二通道的电压被拉至所述预设电压；
    在所述第三阶段，所述第三开关、所述第四开关、所述第六开关和所述第八开关闭合，其中，所述第一通道和所述第二通道向所述放大电路放电。
  9. 根据权利要8所述的电容检测电路，其特征在于，所述驱动电路还包括第九开关和第十开关，
    所述第一通道的一端通过所述第九开关连接至地，所述第二通道的一端通过所述第十开关连接至地，
    所述抵消电路还包括第十一开关，所述抵消电容的一端通过所述第十一开关连接至电源电压。
  10. 根据权利要求9所述的电容检测电路，其特征在于，所述检测周期还包括第四阶段、第五阶段和第六阶段，其中：
    在所述第四阶段，所述第五开关、所述第九开关、所述第十开关和所述第十一开关闭合，其中，所述第一通道和所述第二通道放电至0，所述抵消电容充电至电源电压，所述补偿电容充电至预设电压；
    在所述第五阶段，所述第五开关、所述第六开关和所述第八开关闭合，其中，所述抵消电容向所述第一通道放电，所述第二通道的电压被拉至所述预设电压；
    在所述第六阶段，所述第三开关、所述第四开关、所述第六开关和所述第八开关闭合，其中，所述放大电路向所述第一通道和所述第二通道放电；
    其中，所述第一通道的自电容相对于所述基础电容的电容变化量是根据所述放大电路在所述第三阶段和所述第六阶段输出的电压信号确定的。
  11. 根据权利要求7至10中任一项所述电容检测电路，其特征在于，所述抵消电容等于所述第一通道的基础电容。
  12. 根据权利要求6所述的电容检测电路，其特征在于，所述抵消电路包括第七开关、第八开关、第十二开关和第十三开关，所述抵消电容的一端通过所述第七开关连接至地，以及通过所述第八开关与所述第一通道相连，所述抵消电容的另一端通过所述第十二开关和所述第十三开关分别连接至电源电压和地。
  13. 根据权利要求12所述的电容检测电路，其特征在于，
    在所述第一阶段，所述第一开关、所述第二开关、所述第五开关、所述第七开关和所述第十二开关闭合，其中，所述第一通道和所述第二通道充电至电源电压，所述抵消电容的上极板的电压为0且下极板的电压为电源电压，所述补偿电容充电至预设电压；
    在所述第二阶段，所述第五开关、所述第六开关、所述第八开关和所述第十三开关闭合，其中，所述抵消电容的上极板的电压为负的电源电压且下极板的电压为0，所述第一通道向所述抵消电容放电，所述第二通道的电压被拉至所述预设电压；
    在所述第三阶段，所述第三开关、所述第四开关、所述第六开关、所述第八开关和所述第十三开关闭合，其中，所述第一通道和所述第二通道向所述放大电路放电。
  14. 根据权利要求13所述的电容检测电路，其特征在于，
    所述驱动电路还包括第九开关和第十开关，所述第一通道的一端通过所述第九开关连接至地，所述第二通道的一端通过所述第十开关连接至地，
    所述抵消电路还包括第十一开关，所述抵消电容的一端通过所述第十一开关连接至电源电压。
  15. 根据权利要求14所述的电容检测电路，其特征在于，所述检测周期还包括第四阶段、第五阶段和第六阶段，其中：
    在所述第四阶段，所述第五开关、所述第九开关、所述第十开关、所述第十一开关和所述第十三开关闭合，其中，所述第一通道和所述第二通道放电至0，所述抵消电容充电至电源电压，所述补偿电容充电至预设电压；
    在第五阶段，所述第五开关、所述第六开关、所述第八开关和所述第十二开关闭合，其中，所述抵消电容向所述第一通道放电，所述第二通道充电至所述预设电压；
    在所述第六阶段，所述第三开关、所述第四开关、所述第六开关、所述第八开关和所述第十二开关闭合，其中，所述放大电路向所述第一通道和所述第二通道放电。
  16. 根据权利要求12至15中任一项所述电容检测电路，其特征在于，所述抵消电容等于所述第一通道的基础电容的三分之一。
  17. 根据权利要求1至4中任一项所述的电容检测电路，其特征在于，所述屏幕包括多个横向通道和多个纵向通道，其中，每个检测周期中并行检测所述多个横向通道中的所述第一通道的自电容，以及所述多个纵向通道中的所述第一通道的自电容。
  18. 根据权利要求17所述的电容检测电路，其特征在于，在对奇数个横向通道或者纵向通道进行检测时，先对除第一个通道之外的剩余偶数个通道进行检测，再对除最后一个通道之外的剩余偶数个通道进行检测。
  19. 根据权利要求17所述的电容检测电路，其特征在于，在对偶数个横向通道或者纵向通道进行检测时，先将编号为奇数的通道作为所述第一通道并将编号为偶数的通道作为所述第二通道，再将编号为偶数的通道作为所述第一通道并将编号为奇数的通道作为所述第二通道。
  20. 一种触控芯片，其特征在于，包括根据权利要求1至19中任一项所述的电容检测电路。
PCT/CN2020/103215 2020-07-21 2020-07-21 电容检测电路和触控芯片 WO2022016359A1 (zh)

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