Touch detection circuit, method, chip, and device

Abstract

This application provides a touch detection circuit, method, chip, and device. The touch detection circuit includes: a switching circuit for setting the voltage of the target electrode to a first preset voltage and connecting the non-target electrode to ground in a first stage of the scanning cycle, and for disconnecting the electrical connection between the non-target electrode and ground and connecting the electrical connection between the target electrode and the non-target electrode in a second stage of the scanning cycle; and an amplifier circuit for outputting an indicator voltage. Therefore, the touch detection circuit, method, chip, and touch device provided by this application can use the non-target electrode as a canceling capacitor to carry the charge output by the target electrode during scanning, reducing the manufacturing cost of the touch chip and touch device.

Description

[Technical Field]

[0001] This application relates to the field of touch control, and more specifically, to a touch detection circuit, method, chip, and device. [Previous Technology]

[0002] In touch devices, a self-capacitance detection scheme is used to detect user touch operations. In the self-capacitance detection scheme, when a conductor approaches or touches the touch electrode in the touch device, the parasitic capacitance between the touch electrode and ground will change. By detecting the amount of change in parasitic capacitance between the touch electrode and ground, the user's touch position can be obtained. Since the parasitic capacitance between the touch electrode and ground is often relatively large, while the amount of capacitance change caused by a conductor approaching or touching the detection electrode is relatively small, a canceling capacitor with a capacitance similar to the parasitic capacitance is needed to cancel the original parasitic capacitance between the touch electrode and ground when the conductor approaches or touches the detection electrode, thereby improving the detection accuracy of user touch.

[0003] However, since the parasitic capacitance between the touch electrode and ground is often relatively large, the capacitance, volume, and layout area of ​​the offset capacitor also need to be larger, which increases the manufacturing cost of the touch circuit. [Summary of the Invention]

[0004] In view of the above problems, this application provides a touch detection circuit, method, chip and device.

[0005] In its first aspect, this application provides a touch detection circuit, comprising: N receiving ports, each connected to a corresponding N touch electrodes, wherein each touch electrode generates a corresponding parasitic capacitance with ground; a switching circuit, used to set the voltage of the target electrode to a first preset voltage in a first stage of a scanning cycle, thereby connecting the non-target electrode to ground, and used to disconnect the electrical connection between the non-target electrode and ground in a second stage of the scanning cycle, thereby connecting the target electrode and the non-target electrode; wherein the target electrode is one of the N touch electrodes, and the non-target electrodes are the other N-1 of the N touch electrodes; and an amplification circuit, electrically connected to the N receiving ports via the switching circuit, receiving a second preset voltage, and outputting an indication voltage based on the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage, and the second preset voltage, wherein the change in the indication voltage indicates the touch information of the target electrode. The first stage and the second stage are executed alternately to constitute multiple scanning cycles.

[0006] In conjunction with the first state, in some possible implementations, the switching circuit includes N pull-up switches, N pull-down switches, and N interconnect switches, each corresponding to one of the N touch electrodes. One end of each of the N pull-up switches receives a first preset voltage, and the other end of each of the N pull-up switches is electrically connected to the corresponding N touch electrodes. One end of each of the N pull-down switches is grounded, and the other end of each of the N pull-down switches is electrically connected to the corresponding N touch electrodes. One end of each of the N interconnect switches is electrically connected to the corresponding N touch electrodes, and the other end of each of the N interconnect switches is electrically connected to an amplifier circuit.

[0007] In conjunction with the first state, in some possible implementations, during the first stage of the scan cycle, the pull-up switch corresponding to the target electrode is turned on, and the corresponding pull-down switch is turned off; the pull-up switch corresponding to the non-target electrode is turned off, and the corresponding pull-down switch is turned on; all N interconnecting switches are turned off. During the second stage of the scan cycle, the pull-up switches and corresponding pull-down switches corresponding to both the target electrode and the non-target electrode are turned off, and all N interconnecting switches are turned on.

[0008] In conjunction with the first state, in some possible implementations, the amplifier circuit includes an operational amplifier and a feedback capacitor, and the switching circuit further includes a feedback pull-up switch, a feedback parallel switch, and a feedback output switch. The inverting input terminal of the operational amplifier is electrically connected to the other end of N interconnecting switches, one end of the feedback capacitor, and one end of the feedback parallel switch. The non-inverting input terminal of the operational amplifier receives a second preset voltage. The other end of the feedback capacitor is electrically connected to one end of the feedback pull-up switch and one end of the feedback output switch. The other end of the feedback pull-up switch receives a first preset voltage, and the other end of the feedback output switch is electrically connected to the output terminal of the operational amplifier.

[0009] In conjunction with the first state, in some possible implementations, during the first stage of the scan cycle, the feedback pull-up switch and the feedback parallel switch are turned on, and the feedback output switch is turned off. During the second stage of the scan cycle, the feedback pull-up switch and the feedback parallel switch are turned off, and the feedback output switch is turned on.

[0010] In combination with the first state, in some possible implementations, the first preset voltage is N times the second preset voltage.

[0011] In a second embodiment, this application provides a touch detection method using a touch detection circuit provided in any possible implementation as described in the first embodiment. The method includes: in a first stage within a scanning cycle, setting the voltage of the target electrode to a first preset voltage and connecting the electrical connection between the non-target electrode and ground; in a second stage within the scanning cycle, disconnecting the electrical connection between the non-target electrode and ground and connecting the electrical connection between the target electrode and the non-target electrode; wherein the first stage and the second stage are executed alternately to constitute a plurality of scanning cycles; and outputting an indicator voltage based on the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage, and the second preset voltage.

[0012] In conjunction with the second state, in some possible implementations, the method further includes: adjusting the second preset voltage from a threshold voltage to a target voltage, such that when the target electrode is not touched, the indicated voltage is the first preset voltage. The amount of change in the indicated voltage is adjusted from a real-time change to a calibration change, the ratio of the calibration change to the real-time change being equal to the ratio of the target voltage to the threshold voltage.

[0013] In the third embodiment, this application provides a touch chip, including an analog-to-digital converter circuit, an arithmetic circuit, and a touch detection circuit provided in any possible implementation as in the first embodiment. The analog-to-digital converter circuit is used to convert the change in an indicator voltage into a digital signal. The arithmetic circuit is used to output an indicator signal based on the digital signal, and the indicator signal is used to indicate the touch information of N touch electrodes.

[0014] In the fourth state, this application provides a touch device, including a touch panel and a touch chip provided in any possible implementation as in the third state. The touch panel includes N touch electrodes, and the touch chip is used to detect touch information from the N touch electrodes.

[0015] The touch detection circuit, method, chip and touch device provided in this application can use non-target electrodes as canceling capacitors to carry the charge output when the target electrode is scanned, thereby reducing the manufacturing cost of touch chips and touch devices.

Implementation Method

[0017] The technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings.

[0018] It is understood that the connection relationship described in this application refers to a direct or indirect connection. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thereby achieving a connection between A and B through C. It is also understood that the "A connects to B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0019] In the description of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "AND / OR" in this document is merely a description of the relationship between related objects, indicating that there are three kinds of relationships. For example, A AND / OR B can mean: existing only in A, existing in both A and B, or existing only in B.

[0020] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, and the words "first," "second," etc., are not necessarily different. In addition, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0021] Please refer to Figure 1, which is a schematic diagram of a touch device 10 provided in an embodiment of this application.

[0022] The touch device 10 includes a touch panel 11 and a touch chip 12. The touch panel 11 includes n touch electrodes S1-Sn. Parasitic capacitances Crx1-Crxn are generated between each touch electrode S1-Sn and ground. The touch electrodes S1-Sn are all electrically connected to the touch chip 12.

[0023] When the touch panel 11 receives a touch operation, the parasitic capacitances Crx1-Crxn corresponding to the touched touch electrodes S1-Sn will change. The touch chip 12 can obtain the touch information of the touch electrodes S1-Sn based on the change in the parasitic capacitances Crx1-Crxn corresponding to the touch electrodes S1-Sn. For example, whether the touch electrodes S1-Sn are touched, and the specific location of the touched touch electrodes S1-Sn, etc.

[0024] As shown in Figure 2, n touch electrodes S1-Sn are electrically connected to the touch chip 12 via touch electrode switches SW1-SWn. The touch chip 12 includes a complex switch, a cancellation capacitor CB, an operational amplifier CA, a feedback capacitor CF, an analog-to-digital converter circuit, and an operational circuit (not shown in the figure).

[0025] n touch electrodes S1-Sn are electrically connected to the input bus 121 via touch electrode switches SW1-SWn, respectively. One end of the input bus 121 is electrically connected to one end of switch P11 and one end of switch P21. The other end of switch P11 receives the reference voltage VREF. The other end of switch P21 is electrically connected to the inverting input terminal of operational amplifier CA, one end of switch P14, and one end of feedback capacitor CF. The other end of switch P14 is electrically connected to the other end of feedback capacitor CF and the output terminal of operational amplifier CA. One end of switch P22 is electrically connected to the input bus 121, and the other end of switch P22 is electrically connected to one end of switch P12 and one end of cancellation capacitor CB. The other end of cancellation capacitor CB receives the reference voltage VREF via switch P13 and is grounded via switch P23. The other end of switch P12 is grounded.

[0026] When it is necessary to detect touch information from n touch electrodes S1-Sn, each touch electrode S1-Sn is sequentially connected to the input bus 121 via its corresponding touch electrode switch SW1-SWn. For example, when touch switch SW1 is on, touch switches SW2-SWn are off. At this time, touch electrode S1 is electrically connected to the input bus 121, while touch electrodes S2-Sn are disconnected from the input bus 121. Furthermore, when touch switch SW1 is on, the scanning wheel of touch electrode S1 is activated. During the scanning wheel of touch electrode S1, the touch chip 12 can obtain touch information from touch electrode S1. Similarly, after the scanning wheel of touch electrode S1 finishes, touch switch SW2 is turned on, and touch switches SW1, SW3-SWn are turned off. At this time, touch electrode S2 is electrically connected to input bus 121, while touch electrodes S1, S3-Sn are disconnected from input bus 121 and enter the scanning wheel of touch electrode S2. Touch chip 12 can obtain touch information from touch electrode S2. Therefore, when the scanning wheels of all touch electrodes S1-Sn have finished, touch chip 12 can obtain touch information from n touch electrodes S1-Sn on the entire touch panel 11.

[0027] Each scanning wheel includes multiple scanning cycles, and each scanning cycle includes a first stage and a second stage. The first stage is a reset stage. During this stage, switches P11, P13, P12, and P14 are turned on, while switches P21, P23, and P22 are turned off. The second stage is a charge transfer stage. During this stage, switches P21, P23, and P22 are turned on, while switches P11, P13, P12, and P14 are turned off. The reset stage and the charge transfer stage are executed alternately to constitute multiple scanning cycles.

[0028] Taking one scan cycle of the touch electrode S1 as an example, during the reset phase, because switches P11, P13, P12, and P14 are turned on and switches P21, P23, and P22 are turned off, the voltage of the parasitic capacitor Crx1 of the touch electrode S1 is pulled up to the reference voltage VREF. During the charge transfer phase, because switches P21, P23, and P22 are turned on and switches P11, P13, P12, and P14 are turned off, the charge accumulated on the parasitic capacitor Crx1 corresponding to the touch electrode S1 neutralizes the charge accumulated on the cancelling capacitor CB, and the voltage of the parasitic capacitor Crx1, the voltage of the cancelling capacitor CB, and the voltage of the feedback capacitor CF of the touch electrode S1 gradually stabilize. According to the circuit structure of the touch chip 12, the output voltage CAOUT of the operational amplifier CA satisfies the following formula (1).

[0029]

[0030] Where Crx1 is the capacitance value of the parasitic capacitance generated by the touch electrode S1, CB is the capacitance value of the canceling capacitor, CF is the capacitance value of the feedback capacitor, and VREF is the reference voltage value.

[0031] The analog-to-digital conversion circuit receives the output voltage CAOUT of the operational amplifier CA and generates a corresponding digital signal based on the change in the output voltage CAOUT of the operational amplifier CA. The operational circuit outputs an indication signal based on this digital signal, thereby indicating the touch information of the N touch electrodes S1-Sn. Specifically, the analog-to-digital conversion circuit generates a corresponding digital signal based on the change in the output voltage CAOUT of the operational amplifier CA. Compared to generating a corresponding digital signal based solely on the output voltage CAOUT of the operational amplifier CA, this avoids measuring the absolute value of the output voltage CAOUT of the operational amplifier CA, simplifying the circuit design, reducing complexity, and lowering circuit power consumption. Simultaneously, it eliminates the need for calibration or adjustment circuits to eliminate the initial bias voltage of the operational amplifier CA, improving the reliability of detection. Furthermore, when the touch device 10 is interfered with, the change in the output voltage CAOUT of the operational amplifier CA can still accurately reflect the actual touch information of the touch electrodes S1-Sn, enhancing the robustness of touch detection.

[0032] Based on this, according to formula (1), the change ΔCAOUT of the output voltage CAOUT of the operational amplifier CA satisfies the following formula (2).

[0033]

[0034] Where ΔCrx represents the change in capacitance of the touch electrode. When the touch electrode is touched, its capacitance increases. The analog-to-digital converter (ADC) converts the change in output voltage CAOUT of operational amplifier CA, ΔCAOUT, into a corresponding digital signal for subsequent digital processing by the arithmetic circuit. After processing the digital signal, the arithmetic circuit obtains the touch information of N touch electrodes S1-Sn.

[0035] However, since the capacitance value of each touch electrode is generally not exactly the same, the capacitance value of the cancellation capacitor CB needs to be adjusted before the scanning wheel of each touch electrode starts, so that the capacitance value of the cancellation capacitor CB is approximately equal to or of the same order of magnitude as the parasitic capacitance value of the touch electrode currently being scanned and detected, thereby preventing the indicator voltage CAOUT output by the operational amplifier CA from saturating, affecting the touch detection result or even causing the touch detection to fail.

[0036] Therefore, this application provides a touch detection circuit 100, which uses non-target electrodes, i.e. touch electrodes S1-Sn that are not currently being scanned or touched for detection, as a cancellation capacitor CB to carry the charge output when the target electrode is scanned. This eliminates the need to set up the cancellation capacitor CB, thereby reducing the manufacturing cost of the touch chip.

[0037] Specifically, please refer to Figure 3, which is a schematic diagram of a touch detection circuit 100 provided in an embodiment of this application. The touch detection circuit 100 includes N receiving ports, a switching circuit, and an amplifier circuit. The operational amplifier CA, the feedback capacitor CF, the voltage divider resistor RH, and the voltage divider resistor RL constitute the amplifier circuit.

[0038] Each receiving port is electrically connected to a touch electrode. For example, receiving port 1 is electrically connected to touch electrode S1, and receiving port N is electrically connected to touch electrode Sn. Each touch electrode forms a parasitic capacitance with ground; for example, touch electrode S1 forms a parasitic capacitance Crx1 with ground.

[0039] The switching circuit includes N pull-up switches, N pull-down switches, N interconnecting switches P2, a feedback pull-up switch PHf, a feedback parallel switch P1, and a feedback output switch Po, each corresponding to one of the N touch electrodes. One end of each of the N pull-up switches receives a first preset voltage VH, and the other end of each of the N pull-up switches is electrically connected to the corresponding N touch electrodes S1-Sn. One end of each of the N pull-down switches is grounded, and the other end of each of the N pull-down switches is electrically connected to the corresponding N touch electrodes S1-Sn. One end of each of the N interconnecting switches P2 is electrically connected to the corresponding N touch electrodes S1-Sn, and the other end of each of the N interconnecting switches P2 is electrically connected to the inverting input of operational amplifier CA, one end of the feedback capacitor CF, and one end of the feedback parallel switch P1. The non-inverting input of operational amplifier CA receives a second preset voltage VL. The other end of the feedback capacitor CF is electrically connected to one end of the feedback pull-up switch PHf and one end of the feedback output switch Po. The other end of the feedback pull-up switch PHf receives the first preset voltage VH, and the other end of the feedback output switch Po is electrically connected to the output terminal of the operational amplifier CA.

[0040] Specifically, one end of each of the pull-up switches PH1, ..., PHk, ..., PHn receives a first preset voltage VH, and the other end of each of the pull-up switches PH1, ..., PHk, ..., PHn is electrically connected to a receiving port, that is, the other end of each of the pull-up switches PH1, ..., PHk, ..., PHn is electrically connected to touch electrodes S1-Sn. One end of each of the pull-down switches PL1, ..., PLk, ..., PLn is grounded, and the other end of each of the pull-down switches PL1, ..., PLk, ..., PLn is electrically connected to a receiving port, that is, the other end of each of the pull-down switches PL1, ..., PLk, ..., PLn is electrically connected to touch electrodes S1-Sn. In addition, each touch electrode S1-Sn is electrically connected to one end of a corresponding interconnect switch P2 through a corresponding receiving port. The other end of each interconnect switch P2 is electrically connected to the inverting input of operational amplifier CA. The non-inverting input of the operational amplifier CA is electrically connected to one end of the voltage divider resistors RH and RL. The other end of the voltage divider resistor RH receives the first preset voltage VH, and the other end of the voltage divider resistor RL is grounded.

[0041] In some embodiments, the voltage divider resistor RL can be an adjustable resistor. In this way, the voltage division relationship between the voltage divider resistors RH and RL can be adjusted by adjusting the resistance value of the voltage divider resistor RL, thereby adjusting the voltage value of the second preset voltage VL received by the operational amplifier CA.

[0042] Based on the circuit structure of the touch detection circuit 100, the scanning wheel of the touch electrode Sk will be explained below using the touch electrode Sk as an example.

[0043] Please refer to Figure 4, which is a schematic diagram of the scanning wheel of the touch electrode Sk provided in an embodiment of this application. One frame of touch detection in the touch panel 11 includes a plurality of touch electrode scanning wheels, with each touch electrode scanning wheel performed sequentially. That is, one frame of touch detection in the touch panel 11 begins with the touch electrode S1 scanning wheel and ends with the touch electrode Sn scanning wheel. During each touch electrode scanning wheel phase, the touch chip 12 can obtain the touch information of the corresponding touch electrode. Therefore, when the touch electrode Sn scanning wheel ends, one frame of touch detection in the touch panel 11 ends, and the touch chip 12 can obtain the touch information of all touch electrodes, thereby determining whether the touch panel 11 has received a touch operation and the specific touch electrode that was touched, thus enabling precise positioning of the touch location.

[0044] Taking the Sk scanning wheel as an example, the Sk scanning wheel includes multiple Sk scanning cycles. Within each Sk scanning cycle, the operational amplifier CA can output a corresponding indicator voltage based on the parasitic capacitance Crxk of the touch electrode Sk. When the touch electrode Sk receives a touch operation, the parasitic capacitance Crxk of the touch electrode Sk will change, and the indicator voltage output by the operational amplifier CA will also change. Therefore, the analog-to-digital converter circuit can convert the change in the output voltage CAOUT of the operational amplifier CA, ΔCAOUT, into a corresponding digital signal for subsequent digital processing by the arithmetic circuit. After the arithmetic circuit performs digital processing on the digital signal, it can obtain the touch information of the touch electrode Sk.

[0045] Specifically, a Sk scan cycle includes a reset phase and a charge transfer phase. During the reset phase, the touch electrode currently in the scanning and touch detection state, i.e., the target electrode, is the touch electrode Sk. Its corresponding pull-up switch PHk is turned on, and the pull-down switch PLk is turned off. The touch electrodes not currently in the scanning and touch detection state, i.e., the non-target electrodes, i.e., all electrodes other than the touch electrode Sk, have their corresponding pull-up switches turned off and their pull-down switches turned on. That is, the pull-up switches PH1-PH(k-1) and PH(k+1)-PHn are turned off, and the pull-down switches PL1-PL(k-1) and PL(k+1)-PLn are turned on. In addition, all N interconnect switches P2 are turned off, the feedback pull-up switch PHf and the feedback parallel switch P1 are turned on, and the feedback output switch Po is turned off.

[0046] Therefore, during the reset phase, the target electrode receives the first preset voltage VH via the corresponding pull-up switch, that is, the switching circuit sets the voltage of the target electrode to the first preset voltage VH during the reset phase of the scan cycle. At this time, the parasitic capacitance of the target electrode, Crxk, is charged, and the voltage of the touch electrode Sk rises. When the parasitic capacitance Crxk is fully charged, the voltage of the touch electrode Sk rises to the first preset voltage VH. According to the virtual short principle of the operational amplifier CA, the voltage at the inverting input terminal of the operational amplifier CA and the indicated voltage CAOUT at the output terminal are both equal to the second preset voltage VL received at the non-inverting input terminal. The voltage VCF at the right node of the feedback capacitor CF is pulled up to the first preset voltage VH by the feedback pull-up switch PHf. In addition, during the reset phase, the non-target electrode is grounded via the corresponding pull-down switch, that is, the switching circuit conducts the electrical connection between the non-target electrode and ground during the reset phase of the scan cycle. At this time, the non-target electrodes, namely the touch electrodes S1-S(k-1) and S(k+1)-Sn, are grounded, and the voltage of the touch electrodes S1-S(k-1) and S(k+1)-Sn remains at the ground level.

[0047] During the charge transfer phase, the pull-up switch corresponding to the target electrode is open, the pull-down switch is open, and the pull-down switch corresponding to the non-target electrode is open. In addition, all N interconnecting switches P2 are turned on, the feedback pull-up switch PHf and the feedback parallel switch P1 are turned off, the feedback output switch Po is turned on, and the right node of the feedback capacitor CF is electrically connected to the output terminal of the operational amplifier CA, so that the voltage VCF at the right node of the feedback capacitor CF is the indicator voltage CAOUT.

[0048] Therefore, during the charge transfer stage, the target electrode is electrically connected to all non-target electrodes via the corresponding interconnect switch P2, so that the charge accumulated by the parasitic capacitance of the target electrode after charging is transferred to the parasitic capacitances corresponding to all non-target electrodes. That is, the parasitic capacitances corresponding to the non-target electrodes carry the charge accumulated by the parasitic capacitance of the target electrode after charging, thereby ensuring that the indicator voltage CAOUT output by the operational amplifier CA will not be oversaturated. At this time, the voltage of the touch electrode Sk decreases as the charge of the parasitic capacitance Crxk decreases, and the voltage of the non-target electrode increases as its corresponding parasitic capacitance receives the charge of the touch electrode Sk. When the charge on the parasitic capacitance of the target electrode is transferred to the parasitic capacitance of the non-target electrode, the voltages of the target electrode and the non-target electrode will tend to stabilize. At this time, the indicator voltage CAOUT output by the operational amplifier CA satisfies the following formula (3).

[0049]

[0050] Where Crxk is the capacitance value corresponding to the target electrode. Crxo is the sum of the capacitance values ​​corresponding to the non-target electrodes. VH is the voltage value of the first preset voltage, VL is the voltage value of the second preset voltage, Cf is the capacitance value of the feedback capacitor, and the current indication voltage CAOUT is equal to the right node voltage VCF of the feedback capacitor CF.

[0051] Since the indicator voltage CAOUT output by the operational amplifier CA is related to the second preset voltage VL, the indicator voltage CAOUT output by the operational amplifier CA can be adjusted to be within a reasonable voltage range. In some embodiments, when the indicator voltage CAOUT output by the operational amplifier CA is configured to the first preset voltage VH when the touch panel 11 does not receive a touch operation, the indicator voltage CAOUT output by the operational amplifier CA satisfies formula (3). In some embodiments, the parasitic capacitances Crx1-Crxn corresponding to all touch electrodes S1-Sn are relatively close, so the parasitic capacitance of the target electrode is approximately equal to the average value of all target capacitances. According to formula (3), the first preset voltage VH is n times the second preset voltage VL. Thus, by configuring the second preset voltage VL to be one-nth of the first preset voltage VH, the indicator voltage CAOUT output by the operational amplifier CA can be within a reasonable voltage range, improving the accuracy of touch detection.

[0052] When the target electrode and / or the adjacent touch electrode receive a touch operation, the parasitic capacitance corresponding to the target electrode and / or the adjacent touch electrode will change. At this time, the change ΔCAOUT of the indicator voltage CAOUT output by the operational amplifier CA satisfies the following formula (4).

[0053]

[0054] When the number of touch electrodes is large, for example, when the number of touch electrodes N≥10, the following can be derived from formula (4).

[0055]

[0056] Therefore, ΔCAOUT is proportional to ΔCrxk, so the touch information of the target electrode can be detected by ΔCAOUT.

[0057] Please refer to Figure 5. Figure 5(a) shows the capacitance of the parasitic capacitance of the touch electrode before touch and the capacitance change after touch according to an embodiment of this application. Figure 5(b) is a schematic diagram of the capacitance change of the touch electrode and the change of the indicator voltage output by the operational amplifier CA. Here, N=20, the capacitance value of each parasitic capacitor is 300pF±20%, the first preset voltage VH=3.3V, the second preset voltage VL=0.165V, and the capacitance value of the feedback capacitor Cf is 10pF. The touch electrode S8 and the adjacent touch electrodes S5-S13 undergo capacitance changes due to touch operation. Among them, the change of the parasitic capacitance Crx8 corresponding to the touch electrode S8 is 0.2pF. The change of the parasitic capacitance corresponding to the other adjacent touch electrodes gradually decreases as the distance from the touch electrode S8 increases. The touch circuit provided in this embodiment has high precision.

[0058] As shown in Figure 5, when the touch electrode S8 receives a touch operation, the change in the indicator voltage ΔCAOUT of the operational amplifier CA output decreases significantly. Thus, the analog-to-digital conversion circuit and the operational circuit can accurately determine that the touch electrodes S5-S13 are affected by the touch operation, and the specific location where the touch operation occurs is the touch electrode S8.

[0059] Please refer to Figure 6, which is a schematic diagram of a touch detection method provided in an embodiment of this application. The touch detection method can be applied to the touch detection circuit 100 provided in this application. Specifically, the touch detection circuit 100 may further include a control circuit. The touch detection method may include the following steps.

[0060] Step S1, in the first stage of the scanning cycle, the voltage of the target electrode is set to a first preset voltage VH, and the electrical connection between the non-target electrode and ground is turned on.

[0061] Specifically, step S1 can be executed by the control circuit. The first stage within the scan cycle is the reset stage. During this stage, the control circuit can output a first control signal to control the on or off of the multiple switches. For example, the control circuit can output the first control signal to the switch circuit, causing the pull-up switch corresponding to the target electrode to be turned on and the pull-down switch to be turned off, while the pull-up switch corresponding to the non-target electrode is turned off and the pull-down switch to be turned on. In addition, the first control signal can also cause all N interconnecting switches P2 to be turned off, the feedback pull-up switch PHf and the feedback parallel switch P1 to be turned on, and the feedback output switch Po to be turned off. This achieves setting the voltage of the target electrode to the first preset voltage VH and connecting the electrical connection between the non-target electrode and ground.

[0062] Step S2, in the second stage of the scanning cycle, disconnect the electrical connection between the non-target electrode and ground, and connect the electrical connection between the target electrode and the non-target electrode.

[0063] Specifically, step S2 can be executed by the control circuit. The second stage within the scanning cycle is the charge transfer stage. During this stage, the control circuit can output a second control signal to control the on or off of the multiple switches. For example, the control circuit can output a second control signal to the switch circuit, causing the pull-up switch corresponding to the target electrode to be off, and the pull-down switch corresponding to the non-target electrode to be off. All pull-down switches of the touch electrodes remain off. In addition, the second control signal can also cause all N interconnecting switches P2 to be on, the feedback pull-up switch PHf and the feedback parallel switch P1 to be off, and the feedback output switch Po to be on. This achieves the disconnection of the electrical connection between the non-target electrode and ground, and the connection between the target electrode and the non-target electrode.

[0064] Step S3: Output an indicator voltage based on the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage, and the second preset voltage.

[0065] Step S3 can be executed by operational amplifier CA. The relationship between the indicated voltage and the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage VH and the second preset voltage VL can be referred to the explanation of formula (3), and will not be repeated here.

[0066] In some embodiments, during touch detection, the indicator voltage output by the operational amplifier CA may be oversaturated. Therefore, before scanning each target electrode, a second preset voltage VL can be adaptively adjusted so that the indicator voltage CAOUT output by the operational amplifier CA is configured to the first preset voltage VH when the touch panel 11 does not receive a touch operation. This solves the problem of potential oversaturation of the indicator voltage output by the operational amplifier CA caused by the large difference in parasitic capacitances between the multiple touch electrodes S1-Sn.

[0067] Specifically, as shown in Figure 7, the touch detection method may also include the following steps.

[0068] Step S4: Adjust the second preset voltage VL from the threshold voltage to the target voltage so that when the target electrode is not touched, the indicated voltage is the first preset voltage VH.

[0069] Step S4 can be executed by the control circuit before step S1. The threshold voltage is the second preset voltage VL before calibration. The target voltage is the voltage value of the second preset voltage VL, which is such that when the target electrode is not touched, the indicator voltage output by the operational amplifier CA is the first preset voltage VH. In this way, by calibrating the second preset voltage VL, it can be ensured that the indicator voltage output by the operational amplifier CA is within a reasonable voltage range, thereby achieving accurate touch detection.

[0070] Step S5: Adjust the change in the indicated voltage from the real-time change to the calibration change. The ratio of the calibration change to the real-time change is equal to the ratio of the target voltage to the threshold voltage.

[0071] Step S5 can be executed by the control circuit after step S3. The real-time change is the change in the indicator voltage output by the operational amplifier CA during step S3. By adjusting the real-time change to a calibration change, the change in the indicator voltage can be calibrated based on the ratio of the calibrated second preset voltage VL to the uncalibrated second preset voltage VL, thereby obtaining a more accurate result for touch detection.

[0072] Thus, the touch detection circuit 100, method, touch chip 12 and touch device 10 provided in this application can use non-target electrodes as offset capacitors CB to carry the charge output when the target electrode is scanned, thereby reducing the manufacturing cost of touch chip 12 and further contributing to the cost reduction of touch device 10.

[0073] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the spirit and scope of this application shall fall within the scope of protection claimed by this application. [Simplified Explanation of the Diagram]

[0016] Figure 1 is a schematic diagram of a touch device provided in an embodiment of this application. Figure 2 is a schematic diagram of a touch chip provided in an embodiment of this application. Figure 3 is a schematic diagram of a touch detection circuit provided in an embodiment of this application. Figure 4 is a schematic diagram of a scanning wheel of a touch electrode provided in an embodiment of this application. Figure 5 is a schematic diagram of the change in capacitance of the parasitic capacitance of the touch electrode and the change in the indicator voltage output by the amplifier circuit provided in an embodiment of this application. Figure 6 is a schematic diagram of a touch detection method provided in an embodiment of this application. Figure 7 is another schematic diagram of a touch detection method provided in an embodiment of this application.

Claims

1. A touch detection circuit, improved in that it includes: N receiving ports are connected to the corresponding N touch electrodes, and each touch electrode generates a corresponding parasitic capacitance with ground. A switching circuit is used to set the voltage of the target electrode to a first preset voltage in the first stage of the scan cycle, and to connect the electrical connection between the non-target electrode and ground. In the second stage of the scan cycle, it disconnects the electrical connection between the non-target electrode and ground and connects the electrical connection between the target electrode and the non-target electrode. The target electrode is one of the N touch electrodes, and the non-target electrodes are the other N-1 of the N touch electrodes. An amplifier circuit is electrically connected to the N receiving ports via the switching circuit and receives the second preset voltage. It outputs an indicator voltage based on the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage, and the second preset voltage. The change in the indicator voltage indicates the touch message of the target electrode. The first stage and the second stage are executed alternately to constitute a plurality of scan cycles.

2. The touch detection circuit as described in claim 1, wherein, The switching circuit includes N pull-up switches, N pull-down switches, and N interconnect switches, each corresponding to one of the N touch electrodes. One end of each of the N pull-up switches receives the first preset voltage, and the other end of each of the N pull-up switches is electrically connected to the corresponding N touch electrodes. One end of each of the N pull-down switches is grounded, and the other end of each of the N pull-down switches is electrically connected to the corresponding N touch electrodes. One end of each of the N interconnect switches is electrically connected to the corresponding N touch electrodes, and the other end of each of the N interconnect switches is electrically connected to the amplification circuit.

3. The touch detection circuit as described in claim 2, wherein, During the first phase of the scan cycle, the pull-up switch corresponding to the target electrode is turned on, and the corresponding pull-down switch is turned off; the pull-up switch corresponding to the non-target electrode is turned off, and the corresponding pull-down switch is turned on; all N interconnecting switches are turned off. During the second phase of the scan cycle, the pull-up switches and pull-down switches corresponding to the target electrode and the non-target electrode are both turned off, and all N interconnecting switches are turned on.

4. The touch detection circuit as described in claim 2, wherein, The amplification circuit includes an operational amplifier and a feedback capacitor. The switching circuit further includes a feedback pull-up switch, a feedback parallel switch, and a feedback output switch. The inverting input terminal of the operational amplifier is electrically connected to the other end of the N interconnecting switches, one end of the feedback capacitor, and one end of the feedback parallel switch. The non-inverting input terminal of the operational amplifier receives the second preset voltage. The other end of the feedback capacitor is electrically connected to one end of the feedback pull-up switch and one end of the feedback output switch. The other end of the feedback pull-up switch receives the first preset voltage. The other end of the feedback output switch is electrically connected to the output terminal of the operational amplifier.

5. The touch detection circuit as described in claim 4, wherein, During the first phase of the scan cycle, the feedback pull-up switch and the feedback parallel switch are turned on, and the feedback output switch is turned off; during the second phase of the scan cycle, the feedback pull-up switch and the feedback parallel switch are turned off, and the feedback output switch is turned on.

6. The touch detection circuit as described in claim 4, wherein, The first preset voltage is N times the second preset voltage.

7. A touch detection method, applied to a touch detection circuit as described in any one of claims 1 to 6, wherein the improvement is that the method comprises: During the first phase of the scanning cycle, the voltage of the target electrode is set to a first preset voltage, thereby connecting the non-target electrode to ground. During the second phase of the scan cycle, the electrical connection between the non-target electrode and ground is disconnected, and the electrical connection between the target electrode and the non-target electrode is connected. The first phase and the second phase are executed alternately to form a plurality of the scan cycles. The indicator voltage is output based on the parasitic capacitance of the target electrode, the parasitic capacitance of the non-target electrode, the first preset voltage, and the second preset voltage.

8. The touch detection method as described in claim 7, wherein, The method further includes: adjusting the second preset voltage from a threshold voltage to a target voltage, such that when the target electrode is not touched, the indicated voltage is the first preset voltage; adjusting the change in the indicated voltage from a real-time change to a calibration change, wherein the ratio of the calibration change to the real-time change is equal to the ratio of the target voltage to the threshold voltage.

9. A touch chip, improved in that it includes an analog-to-digital conversion circuit, an arithmetic circuit, and a touch detection circuit as described in any one of claims 1 to 6; the analog-to-digital conversion circuit is used to convert the change in the indication voltage into a digital signal; the arithmetic circuit is used to output an indication signal according to the digital signal, the indication signal being used to indicate touch messages of the N touch electrodes.

10. A touch device, improved in that it includes a touch panel and a touch chip as described in claim 9, the touch panel including N touch electrodes, and the touch chip for detecting touch information of the N touch electrodes.

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