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WO2022016359A1 - Circuit de détection de capacité et puce tactile - Google Patents

Circuit de détection de capacité et puce tactile 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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WIPO (PCT)
Prior art keywords
channel
switch
capacitance
stage
capacitor
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PCT/CN2020/103215
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English (en)
Chinese (zh)
Inventor
袁广凯
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Shenzhen Goodix Technology Co Ltd
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Shenzhen Goodix Technology Co Ltd
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Priority to PCT/CN2020/103215 priority Critical patent/WO2022016359A1/fr
Publication of WO2022016359A1 publication Critical patent/WO2022016359A1/fr
Anticipated expiration legal-status Critical
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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

Circuit de détection de capacité (200), pouvant réduire l'influence du bruit d'écran sur la détection de capacité. Le circuit de détection de capacité (200) comprend : un circuit d'attaque (210) connecté à un premier canal et à un second canal dans un écran, et utilisé pour charger ou décharger le premier canal et le second canal ; un circuit d'annulation (220) comprenant un condensateur d'annulation (Cc) connecté au premier canal et utilisé pour annuler un condensateur de base (Cx1) du premier canal ; un circuit de libération (230) connecté au second canal, et utilisé pour libérer des charges sur le second canal de façon à annuler l'auto-capacité du second canal, de telle sorte que seul un signal de bruit provenant de l'écran est compris dans un signal de capacité du second canal ; et un circuit d'amplification (240) connecté séparément au premier canal et au second canal, et utilisé pour recevoir un signal de capacité du premier canal et le signal de capacité du second canal, et pour délivrer un signal de tension en fonction du signal de capacité du premier canal et du signal de capacité du second canal, le signal de tension étant utilisé pour déterminer une quantité de variation de capacité d'auto-capacité du premier canal par rapport au condensateur de base après que le signal de bruit a été annulé.
PCT/CN2020/103215 2020-07-21 2020-07-21 Circuit de détection de capacité et puce tactile Ceased WO2022016359A1 (fr)

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CN119315989A (zh) * 2024-09-30 2025-01-14 上海维珈科技有限公司 差分模数转换器、转换方法及电子设备

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