Touch detection circuit, method, chip and equipment
By using the capacitor neutralization circuit and the amplification circuit to neutralize the charge of the parasitic capacitors multiple times during the scanning cycle of the touch electrode, the problem of high manufacturing costs in the touch circuit is solved, and cost reduction and detection efficiency improvement is achieved.
Patent Information
- Application Number
- CN202510450229.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-29
AI Technical Summary
The parasitic capacitance between the touch electrode and the ground is large, resulting in an increase in the capacitance, volume and layout area of the neutralizing capacitor, which increases the manufacturing cost of the touch circuit.
Capacitor neutralization circuit and amplifier circuit are used to neutralize the charge of the parasitic capacitor multiple times during the scanning cycle by at least two neutralization capacitors, and to buffer the charge changes with the feedback capacitor, reducing the capacitance and volume of the neutralization capacitor.
It reduces the manufacturing cost of touch chips and equipment, improves detection efficiency and robustness, simplifies circuit design, and reduces power consumption.
Smart Images
Figure CN120389740A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of touch control, and more particularly, to a touch detection circuit, method, chip, and device. Background Art
[0002] In a touch device, a self-capacitance detection scheme can be used to detect a user's touch operation. In the self-capacitance detection scheme, when a conductor approaches or touches a touch electrode in the touch device, the parasitic capacitance between the touch electrode and the ground will change. By detecting the change amount of the parasitic capacitance between the touch electrode and the ground, the touch position of the user can be obtained. Since the parasitic capacitance between the touch electrode and the ground is often relatively large, and the capacitance change amount caused by the conductor approaching or touching the detection electrode is small, it is necessary to set a neutralization capacitance similar to the capacitance of the parasitic capacitance to neutralize the original parasitic capacitance between the touch electrode and the ground when there is no touch, thereby improving the detection accuracy of the user's touch.
[0003] However, since the parasitic capacitance between the touch electrode and the ground is often relatively large, the capacitance, volume, layout area, etc. of the neutralization capacitance also need to be set relatively large, 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 a first aspect, this application provides a touch detection circuit electrically connected to a touch electrode, and a parasitic capacitance is formed between the touch electrode and the ground. The touch detection circuit includes: a capacitance neutralization circuit including a switching circuit and an electrode conduction switch, and the switching circuit includes at least two neutralization capacitances; an amplification circuit including an operational amplifier, a feedback capacitance, and a feedback switch, the non-inverting input terminal of the operational amplifier receives a reference voltage, and the inverting input terminal of the operational amplifier is electrically connected to the output terminal of the operational amplifier through the feedback capacitance; a reference voltage generation circuit for outputting a reference voltage. In a first stage within the scanning period of the touch electrode, the switching circuit, the electrode conduction switch, and the feedback switch cooperate to set the voltage of the touch electrode to the reference voltage, and in a second stage within the scanning period, the neutralization capacitance neutralizes the charge of the parasitic capacitance multiple times, and conducts the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier. In a third stage within the scanning period, the operational amplifier obtains charge change amount information based on the charge after the parasitic capacitance is neutralized and the reference voltage, and the change amount of the charge change amount information is used to indicate the touch information of the touch electrode.
[0006] In combination with the first aspect, in a possible implementation, at least two neutralization capacitors include a first capacitor and a second capacitor, the switching circuit includes a first switching circuit and a second switching circuit, and the second stage within the scanning period includes a plurality of alternately performed charging stages and discharging stages. During the charging stage, the first switching circuit is configured to charge the first capacitor, and the second switching circuit is configured to discharge the second capacitor to the touch electrode so that the second capacitor neutralizes the charge of the parasitic capacitance. During the discharging stage, the first switching circuit is configured to discharge the first capacitor to the touch electrode so that the first capacitor neutralizes the charge of the parasitic capacitance, and the second switching circuit is configured to charge the second capacitor.
[0007] In combination with the first aspect, in a possible implementation, during the charging stage, the first switching circuit is configured to make the first capacitor receive a preset charging voltage so as to charge the first capacitor. During the discharging stage, the second switching circuit is configured to make the second capacitor receive the charging voltage so as to charge the second capacitor.
[0008] In combination with the first aspect, in a possible implementation, during the charging stage, the second switching circuit is configured to make both ends of the second capacitor receive a reference voltage so as to discharge the second capacitor to the touch electrode. During the discharging stage, the first switching circuit is configured to make both ends of the first capacitor receive the reference voltage so as to discharge the first capacitor to the touch electrode.
[0009] In combination with the first aspect, in a possible implementation, both the first switching circuit and the second switching circuit include a charging pull-up switch, a charging pull-down switch, and a discharging conduction switch. The first ends of the first capacitor and the second capacitor respectively receive a charging high voltage through the charging pull-up switches of the first switching circuit and the second switching circuit, and are respectively electrically connected to the touch electrode through the discharging conduction switches of the first switching circuit and the second switching circuit. The second ends of the first capacitor and the second capacitor respectively receive a charging low voltage through the charging pull-down switches of the first switching circuit and the second switching circuit, and the voltage difference between the charging high voltage and the charging low voltage is a preset charging voltage. During the charging stage, the charging pull-up switch and the charging pull-down switch of the first switching circuit are turned on so as to charge the first capacitor, and the discharging conduction switch of the second switching circuit is turned on so as to discharge the second capacitor to the touch electrode. During the discharging stage, the discharging conduction switch of the first switching circuit is turned on so as to discharge the first capacitor to the touch electrode, and the charging pull-up switch and the charging pull-down switch of the second switching circuit are turned on so as to charge the second capacitor.
[0010] In combination with the first aspect, in a possible implementation, the electrode conduction switch is electrically connected between the touch electrode and the inverting input terminal of the operational amplifier, and the feedback switch is electrically connected between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier. In the first stage, the electrode conduction switch and the feedback switch are turned on to set the voltage of the touch electrode to the reference voltage. In the second stage, the electrode conduction switch is turned on and the feedback switch is turned off to make the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier conductive.
[0011] In combination with the first aspect, in a possible implementation, the first switch circuit and the second switch circuit both further include a reference voltage switch. The second ends of the first capacitor and the second capacitor respectively receive the reference voltage through the reference voltage switches of the first switch circuit and the second switch circuit. During the charging stage, the reference voltage switch of the second switch circuit is turned on so that the voltages at both ends of the second capacitor are the reference voltage, and the second capacitor is discharged to the touch electrode. During the discharging stage, the reference voltage switch of the first switch circuit is turned on so that the voltages at both ends of the first capacitor are the reference voltage, and the first capacitor is discharged to the touch electrode.
[0012] In a second aspect, the present application provides a touch detection method, which is applied to the touch detection circuit provided by any possible implementation of the first aspect. The method includes: in the first stage within the scanning period of the touch electrode, setting the voltage of the touch electrode to the reference voltage. In the second stage within the scanning period, making the neutralization capacitor neutralize the charge of the parasitic capacitor multiple times and turning on the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier. In the third stage within the scanning period, obtaining the charge change amount information according to the charge after the parasitic capacitor is neutralized and the reference voltage, and the change amount of the charge change amount information is used to indicate the touch information of the touch electrode.
[0013] In a third aspect, the present application provides a touch chip, including an arithmetic circuit and the touch detection circuit provided by any possible implementation of the first aspect. The arithmetic circuit is used to convert the change amount of the charge change amount information into a digital signal and output an indication signal according to the digital signal, and the indication signal is used to indicate the touch information of the touch electrode.
[0014] In a fourth aspect, the present application provides a touch device, including a touch panel and the touch chip provided by any possible implementation of the third aspect. The touch panel includes touch electrodes, and the touch chip is used to detect the touch information of the touch electrodes.
[0015] Therefore, the touch detection circuit, method, chip and touch device provided by the present application can continuously cycle charge and discharge through at least two neutralization capacitors within the scanning period of the touch electrode, and neutralize the charge of the parasitic capacitor of the touch electrode through the feedback capacitor, which can reduce the manufacturing cost of the touch chip and the touch device. Description of the Drawings
[0016] Figure 1 Schematic diagram of a touch device provided by an embodiment of the present application.
[0017] Figure 2 Schematic diagram of a touch chip provided by an embodiment of the present application.
[0018] Figure 3 Schematic diagram of a touch detection circuit provided by an embodiment of the present application.
[0019] Figure 4 Schematic diagram of a scanning wheel of a touch electrode provided by an embodiment of the present application.
[0020] Figure 5 Schematic diagram of a touch detection method provided by an embodiment of the present application. Detailed implementation manners
[0021] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the accompanying drawings in the embodiments of the present application.
[0022] It can be understood that the connection relationships described in the present application refer to direct or indirect connections. For example, when A is connected to B, it can be either that A is directly connected to B, or that A and B are indirectly connected through one or more other electrical components. For example, it can be that A is directly connected to C, and C is directly connected to B, so that A and B are connected through C. It can also be understood that the "A is connected to B" described in the present application can be that A is directly connected to B, or that A and B are indirectly connected through one or more other electrical components.
[0023] In the description of the present application, unless otherwise specified, " / " means "or". For example, A / B can represent A or B. The "and / or" herein is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone.
[0024] In the description of the present application, words such as "first" and "second" are only used to distinguish different objects, and do not limit the quantity and execution order, and the words "first" and "second" do not necessarily mean different. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion.
[0025] Please refer to Figure 1 , Figure 1 which is a schematic diagram of a touch device 10 provided by an embodiment of the present application.
[0026] 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 capacitors Crx1 - Crxn respectively correspond to between the touch electrodes S1 - Sn and the ground. The touch electrodes S1 - Sn are all electrically connected to the touch chip 12.
[0027] When the touch panel 11 receives a touch operation, the parasitic capacitors 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 according to the change amount of the parasitic capacitors Crx1 - Crxn corresponding to the touch electrodes S1 - Sn. For example, whether the touch electrodes S1 - Sn are touched, the specific positions of the touched touch electrodes S1 - Sn, etc.
[0028] As Figure 2 shown, the touch chip 12 includes a touch detection circuit and an arithmetic circuit 123. The touch detection circuit includes a capacitance neutralization circuit 1211 and an amplification circuit 1212. The touch electrode S1 is electrically connected to the capacitance neutralization circuit 1211.
[0029] The capacitance neutralization circuit 1211 and the amplification circuit 1212 cooperate to neutralize the charge amount of the corresponding parasitic capacitor Crx1 multiple times within the scan period of the touch electrode S1.
[0030] The amplification circuit 1212 is further configured to obtain charge change amount information according to the neutralized charge amount output by the touch electrode S1 and a preset reference voltage VREF.
[0031] The arithmetic circuit 123 is configured to convert the charge change amount information into a corresponding digital signal. In this way, compared with generating a corresponding digital signal according to the charge information, it is possible to avoid measuring the absolute value of the charge information, simplify the circuit design, reduce the complexity, and lower the circuit power consumption. At the same time, it is not necessary to calibrate or adjust the circuit to eliminate the initial bias voltage of the operational amplifier CA in the touch detection circuit 121, improving the reliability of detection. In addition, when the touch device 10 is interfered, the charge change amount information can still accurately reflect the true touch information of the touch electrode S1, enhancing the robustness of touch detection.
[0032] The arithmetic circuit 123 is also used to perform digital processing on digital signals to obtain the touch information of the touch electrode S1. Specifically, when the touch electrode S1 is not touched, since the parasitic capacitance Crx1 corresponding to the touch electrode S1 does not change, the change in the amount of charge output by the touch electrode S1 is zero, and the change in the charge change information also does not occur, so the corresponding digital signal does not change. The arithmetic circuit 123 can determine that the touch electrode S1 is not touched based on the unchanged digital signal. When the touch electrode S1 is touched, the parasitic capacitance Crx1 corresponding to the touch electrode S1 is superimposed with the equivalent capacitance of the touch conductor, so that the change in the amount of charge output by the touch electrode S1 is not zero, and the change in the charge change information will occur, so the corresponding digital signal will also change. The arithmetic circuit 123 can determine that the touch electrode S1 is not touched based on the changed digital signal.
[0033] Please refer to Figure 3 , Figure 3 The figure shows the circuit diagram of the touch detection circuit 121 provided by the present application. The touch detection circuit 121 includes a capacitance neutralization circuit 1211, an amplification circuit 1212, and a reference voltage generation circuit 1213. The capacitance neutralization circuit 1211 includes a switching circuit and an electrode conduction switch P2. The amplification circuit 1212 includes an operational amplifier CA, a feedback capacitor CF, and a feedback switch P1. The switching circuit includes a first switching circuit and a second switching circuit.
[0034] The capacitance neutralization circuit 1211 is electrically connected to the touch electrode S1 through the switching circuit. The touch electrode S1 is electrically connected to the amplification circuit 1212 through the electrode conduction switch P2. The reference voltage generation circuit 1213 is electrically connected to the amplification circuit 1212. The reference voltage generation circuit 1213 is also electrically connected to the capacitance neutralization circuit 1211 through the switching circuit.
[0035] In the first stage of the scanning period of the touch electrode S1, the switching circuit, the electrode conduction switch P2, and the feedback switch P1 cooperate with each other to set the voltage of the touch electrode S1 to the reference voltage VREF.
[0036] In the second stage of the scanning period, the switching circuit, the electrode conduction switch P2, and the feedback switch P1 cooperate with each other to neutralize the charge of the parasitic capacitance Crx1 by the neutralization capacitor multiple times, and are used to conduct the electrical connection between the touch electrode S1 and the amplification circuit 1212.
[0037] In the third stage of the scanning period, the amplification circuit 1212 is used to obtain the charge change information according to the charge after the parasitic capacitance Crx1 is neutralized and the reference voltage VREF provided by the reference voltage generation circuit 1213. Among them, the charge change information is used to indicate the touch information of the touch electrode S1.
[0038] Specifically, the switch circuit includes two neutralizing capacitors, namely the first capacitor CB1 and the second capacitor CB2. The switch circuit further includes a first switch circuit and a second switch circuit. The first switch circuit includes a charging pull-up switch P3A, P3B, a charging pull-down switch P5A, P5B, a discharge conduction switch P4A, P4B, and a reference voltage switch P6A, P6B. The second switch circuit includes a charging pull-up switch P3A, P3B, a charging pull-down switch P5A, P5B, a discharge conduction switch P4A, P4B, and a reference voltage switch P6A, P6B.
[0039] The first ends of the first capacitor CB1 and the second capacitor CB2 respectively receive a charging high voltage through the charging pull-up switch P3A and the charging pull-up switch P3B, and are respectively electrically connected to the touch electrode S1 through the discharge conduction switch P4A and the discharge conduction switch P4B.
[0040] The second ends of the first capacitor CB1 and the second capacitor CB2 respectively receive a charging low voltage through the charging pull-down switch P5A and the charging pull-down switch P5B, and are respectively electrically connected to the reference voltage generation circuit 1213 through the reference voltage switch P6A and the reference voltage switch P6B to receive the generated reference voltage VREF. Wherein, the voltage difference between the charging high voltage and the charging low voltage is a preset charging voltage.
[0041] The electrode conduction switch P2 is electrically connected between the touch electrode S1 and the inverting input terminal of the operational amplifier CA, and the feedback switch P1 is electrically connected between the inverting input terminal of the operational amplifier CA and the output terminal of the operational amplifier CA. The non-inverting input terminal of the operational amplifier CA is electrically connected to the reference voltage generation circuit 1213 to receive the generated reference voltage VREF.
[0042] In some embodiments, the capacitance values of the first capacitor CB1 and the second capacitor CB2 may be the same or different. Hereinafter, the capacitance values of the first capacitor CB1 and the second capacitor CB2 are both CB as an example for illustration, but the present application does not make any limitation on the capacitance values of the first capacitor CB1 and the second capacitor CB2.
[0043] During the scanning cycle of the touch electrode S1, the touch electrode 12 can obtain the touch information of the touch electrode S1. The scanning cycle of the touch electrode S1 includes a plurality of scanning periods, and each scanning period includes a first stage, a second stage, and a third stage.
[0044] The first stage is the reset stage. In this stage, the operational amplifier CA is reset, and the switch circuit, the electrode conduction switch P2, and the feedback switch P1 cooperate with each other to set the voltage of the touch electrode S1 to the reference voltage VREF.
[0045] The second stage is the neutralization stage. In this stage, the switch circuit, the electrode conduction switch P2, and the feedback switch P1 cooperate with each other so that the neutralization capacitor neutralizes the charge of the parasitic capacitor Crx1 multiple times. Thus, by setting the neutralization stage within the scanning period of the touch electrode S1, the switch circuit can cause the neutralization capacitor to charge and discharge in multiple cycles during the neutralization stage, so that the neutralization capacitor transfers the charge to the parasitic capacitor Crx1 of the touch electrode S1 multiple times, and thus the capacitance, volume, and layout area of the neutralization capacitor can be significantly reduced, and the manufacturing cost of the touch circuit can be lowered.
[0046] In addition, in the second stage, the electrode conduction switch P2 is turned on, thereby realizing the electrical connection between the touch electrode S1 and the inverting input terminal of the operational amplifier CA. Thus, the feedback capacitor CF can also buffer the charge output by the parasitic capacitor Crx1 in the second stage, improve the speed at which the neutralization capacitor transfers more charge to the parasitic capacitor Crx1 of the touch electrode S1, and thus improve the touch detection efficiency of the touch electrode S1.
[0047] The third stage is the stabilization stage. In this stage, after the neutralization capacitor neutralizes the charge of the parasitic capacitor Crx1 multiple times, the voltages of the touch electrode S1, the first capacitor CB1, the second capacitor CB2, and the feedback capacitor CF gradually stabilize. The operational amplifier CA obtains the charge change amount information based on the charge after the neutralization of the parasitic capacitor Crx1 and the reference voltage VREF. The arithmetic circuit 123 then obtains the touch information of the touch electrode S1 based on the change amount of the charge change amount information.
[0048] Based on the circuit structure of the touch detection circuit 121, the scanning cycle of the touch electrode S1 will be specifically described below.
[0049] Please refer to Figure 4 , Figure 4 which is a schematic diagram of the scanning cycle of the touch electrode S1 provided by an embodiment of the present application. Among them, one frame of touch detection period of the touch panel 11 includes multiple scanning cycles of the touch electrodes S1 - Sn, and the scanning cycles of each touch electrode S1 - Sn are carried out in sequence. That is, one frame of touch detection period of the touch panel 11 starts from the scanning cycle of the touch electrode S1 and ends with the scanning cycle of the touch electrode Sn. In the scanning cycle stage of each touch electrode S1 - Sn, the touch electrode 12 can obtain the touch information of the corresponding touch electrode S1 - Sn. Therefore, when the scanning cycle of the touch electrode Sn ends, one frame of touch detection period of the touch panel 11 ends, and the touch electrode 12 can obtain the touch information of all touch electrodes S1 - Sn, so as to obtain whether the touch panel 11 receives a touch operation and the specific touch electrodes S1 - Sn that receive the touch operation, and thus can accurately locate the touch position.
[0050] Taking the S1 scanning wheel as an example, the S1 scanning wheel includes multiple S1 scanning cycles. The operational amplifier CA can output corresponding charge change amount information according to the parasitic capacitance Crx1 of the touch electrode S1 in each S1 scanning cycle. When the touch electrode S1 receives a touch operation, the parasitic capacitance Crx1 of the touch electrode S1 will change, and the charge change amount information output by the operational amplifier CA will also change. Thus, the operation circuit 123 can convert the change amount ΔCAOUT of the charge change amount information output by the operational amplifier CA into a corresponding digital signal and perform subsequent digital processing. After the operation circuit 123 performs digital processing on the digital signal, the touch information of the touch electrode S1 can be obtained.
[0051] Specifically, an S1 scanning cycle includes a reset stage, a neutralization stage, and a stabilization stage, which are the first stage, the second stage, and the third stage of the scanning cycle, respectively.
[0052] In the reset stage, the feedback switch P1 and the electrode conduction switch P2 are both turned on. At this time, the operational amplifier CA operates in a negative feedback mode, thus satisfying the virtual short condition. Therefore, the voltage of the inverting input terminal of the operational amplifier CA is the same as the voltage of the non-inverting output terminal, both of which are the reference voltage VREF. Since the touch electrode S1 is electrically connected to the inverting input terminal of the operational amplifier CA, the voltage of the touch electrode S1 can be set to the reference voltage VREF by turning on both the feedback switch P1 and the electrode conduction switch P2.
[0053] In this embodiment, the reference voltage VREF output by the reference voltage generation circuit 1213 is the first preset voltage VREF1 in the reset stage, gradually increases in the neutralization stage, and reaches and maintains the second preset voltage VREF2 in the stabilization stage. The second preset voltage VREF2 is greater than the first preset voltage VREF1. Therefore, in the reset stage, the parasitic capacitance Crx1 is charged, and the voltage of the touch electrode S1 is set to the first preset voltage VREF1.
[0054] The neutralization stage includes multiple alternately performed charging stages and discharging stages corresponding to each neutralization capacitor, and each adjacent charging stage and discharging stage form a charge-discharge cycle. As Figure 4 shown, the neutralization stage includes 6 charge-discharge cycles of the first capacitor CB1 and 5 charge-discharge cycles of the second capacitor CB2. Taking the charge-discharge cycle of the first capacitor CB1 as an example for description. The charge-discharge cycle of the second capacitor CB2 is similar to that of the first capacitor CB1 and will not be elaborated here.
[0055] During the charging phase of the first capacitor CB1, the feedback switch P1 is turned off, and the electrode conduction switch P2 is turned on. The charging pull-up switch P3A and the charging pull-down switch P5A are turned on, and the discharge conduction switch P4A and the reference voltage switch P6A are turned off. As a result, the first terminal of the first capacitor CB1 receives a charging high voltage through the charging pull-up switch P3A, and the second terminal of the first capacitor CB1 receives a charging low voltage through the charging pull-down switch P5A, thereby charging the first capacitor CB1. Among them, the voltage difference between the charging high voltage and the charging low voltage is the preset charging voltage.
[0056] When the charging of the first capacitor CB1 is completed, the charge quantity Q1 on the first capacitor CB1 = CB1×(VRH - VRL), where CB1 is the capacitance value of the first capacitor CB1, VRH is the charging high voltage value, and VRL is the charging low voltage value.
[0057] At the same time, the charging phase of the first capacitor CB1 can also be the discharging phase of the second capacitor CB2. That is, during the charging phase of the first capacitor CB1, the charging pull-up switch P3B and the charging pull-down switch P5B are turned off, and the discharge conduction switch P4B and the reference voltage switch P6B are turned on, so that the first terminal of the second capacitor CB2 is electrically connected to the inverting input terminal of the operational amplifier CA, and the second terminal of the second capacitor CB2 receives the reference voltage VREF. Due to the virtual short principle of the operational amplifier CA, the voltage at the inverting input terminal of the operational amplifier CA is also the reference voltage VREF. At this time, the voltages at both ends of the second capacitor CB2 are the reference voltage VREF. After the charging of the second capacitor CB2 in the previous cycle is completed, the charge on the second capacitor CB2 is transferred to the parasitic capacitor Crx1 during the discharging phase of the second capacitor CB2. In addition, since the electrode conduction switch P2 is turned on, the feedback capacitor CF can also absorb part of the charge of the parasitic capacitor Crx1 as a buffer, thereby accelerating the speed of neutralizing the charges of the first capacitor CB1, the second capacitor CB2, and the parasitic capacitor Crx1, and improving the touch detection speed of the touch electrode S1. Since the reference voltage VREF is changing, the conduction of the electrode conduction switch P2 can also effectively prevent the voltage at the second terminal of the first capacitor CB1 and the second capacitor CB2 from changing too fast, resulting in overshoot of the voltage at the first terminal of the first capacitor CB1 and the second capacitor CB2 and causing leakage.
[0058] Similarly, during the discharge phase of the first capacitor CB1, the feedback switch P1 is turned off, and the electrode conduction switch P2 is turned on. The charging pull-up switch P3A and the charging pull-down switch P5A are turned off, and the discharge conduction switch P4A and the reference voltage switch P6A are turned on, so that the first end of the first capacitor CB1 is electrically connected to the inverting input terminal of the operational amplifier CA, and the second end of the first capacitor CB1 receives the reference voltage VREF. At this time, the voltages at both ends of the first capacitor CB1 are the reference voltage VREF. The charge on the first capacitor CB1 is transferred to the parasitic capacitor Crx1 during its discharge phase. During each charge-discharge cycle of the first capacitor CB1, the amount of charge transferred from the first capacitor CB1 to the parasitic capacitor Crx1 is Q1 = CB1×(VRH - VRL).
[0059] During the neutralization phase, the voltage of the touch electrode S1 changes with the change of the reference voltage VREF, that is, the change trend of the voltage of the touch electrode S1 is the same as that of the reference voltage VREF.
[0060] In this way, the charging phase of the first capacitor CB1 coincides with the discharge phase of the second capacitor CB2 in time, and the discharge phase of the first capacitor CB1 coincides with the charging phase of the second capacitor CB2 in time. That is, when the first capacitor CB1 is charging, the second capacitor CB2 discharges to the touch electrode S1, so that the second capacitor CB2 neutralizes the charge on the parasitic capacitor Crx1. When the first capacitor CB1 discharges to the touch electrode S1, so that the first capacitor CB1 neutralizes the charge on the parasitic capacitor Crx1, the second capacitor CB2 is charged. In this way, the first capacitor CB1 and the second capacitor CB2 alternately neutralize the charge on the parasitic capacitor Crx1 multiple times. There is no need to set an additional waiting time during the scanning period of the touch electrode S1 to wait for the first capacitor CB1 or the second capacitor CB2 to complete charging, which can save the scanning time of the touch electrode S1 and improve the touch detection efficiency of the touch electrode S1.
[0061] During the stable phase, the first capacitor CB1 and the second capacitor CB2 complete the neutralization of the charge on the parasitic capacitor Crx1, and the charging pull-up switches P3A, P3B, the charging pull-down switches P5A, P5B are all turned off. At this time, the reference voltage VREF is stabilized at the second preset voltage VREF2. And the voltage of the touch electrode S1 is also stabilized at the second preset voltage VREF2. During the stable phase, since the first capacitor CB1 and the second capacitor CB2 have neutralized the charge on the parasitic capacitor Crx1 multiple times during the neutralization phase, the charge change amount information CAOUT output by the operational amplifier CA will not be oversaturated.
[0062] The charge change amount information CAOUT output by the operational amplifier CA satisfies the following formula (1). The change amount ΔCAOUT of the charge change amount information satisfies the following formula (2).
[0063] 。
[0064] Therefore, ΔCAOUT is proportional to the capacitance change ΔCrxk1 of the touch electrode S1, so that the touch information of the touch electrode S1 can be detected through ΔCAOUT.
[0065] Please refer to Figure 5 ، Figure 5 which is a schematic diagram of the touch detection method provided by an embodiment of the present application. The touch detection method can be applied to the touch detection circuit 121 provided by the present application. Specifically, the touch detection circuit 121 may further include a control circuit. Among them, the touch detection method may include the following steps.
[0066] Step S51: In the first stage within the scanning period of the touch electrode S1, set the voltage of the touch electrode S1 to the reference voltage VREF.
[0067] Step S52: In the second stage within the scanning period, make the neutralization capacitor neutralize the charge of the parasitic capacitor Crx1 multiple times, and conduct the electrical connection between the touch electrode S1 and the inverting input terminal of the operational amplifier CA.
[0068] Step S53: In the third stage within the scanning period, obtain the charge change information according to the charge after the parasitic capacitor Crx1 is neutralized and the reference voltage VREF, and the change amount of the charge change information is used to indicate the touch information of the touch electrode S1.
[0069] Among them, the detailed description of each step can be seen in the function description of each part of the touch detection circuit 121 above, and will not be repeated here.
[0070] Thus, the touch detection circuit, method, touch chip and touch device provided by the present application can continuously charge and discharge through at least one neutralization capacitor within the scanning period of the touch electrodes S1-Sn, and neutralize the charge of the parasitic capacitors Crx1 of the touch electrodes S1-Sn through the feedback capacitor CF, which can reduce the manufacturing cost of the touch chip 12 and the touch device 10, and is beneficial to the miniaturization and integration development of the touch device 10.
[0071] Those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present application, rather than to limit the present application. As long as within the scope of the essential spirit of the present application, appropriate changes and variations made to the above embodiments fall within the scope of protection required by the present application.
Claims
1. A touch detection circuit is electrically connected to a touch electrode, and a parasitic capacitance is formed between the touch electrode and the ground. It is characterized in that The touch detection circuit includes: A capacitance neutralization circuit, including a switching circuit and an electrode conduction switch, where the switching circuit includes at least two neutralization capacitors; An amplification circuit, including an operational amplifier, a feedback capacitor, and a feedback switch, where the non-inverting input terminal of the operational amplifier receives a reference voltage, and the inverting input terminal of the operational amplifier is electrically connected to the output terminal of the operational amplifier through the feedback capacitor; A reference voltage generation circuit for outputting the reference voltage; In a first stage within the scanning period of the touch electrode, the switching circuit, the electrode conduction switch, and the feedback switch cooperate to set the voltage of the touch electrode to the reference voltage, and in a second stage within the scanning period, the neutralization capacitors repeatedly neutralize the charges of the parasitic capacitance and conduct the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier; In a third stage within the scanning period, the operational amplifier obtains charge change amount information based on the charges after the parasitic capacitance is neutralized and the reference voltage, and the change amount of the charge change amount information is used to indicate the touch information of the touch electrode.
2. The touch detection circuit according to claim 1, wherein The at least two neutralization capacitors include a first capacitor and a second capacitor, the switching circuit includes a first switching circuit and a second switching circuit, and the second stage within the scanning period includes a plurality of alternately performed charging stages and discharging stages; During the charging stage, the first switching circuit is used to charge the first capacitor, and the second switching circuit is used to discharge the second capacitor to the touch electrode so that the second capacitor neutralizes the charges of the parasitic capacitance; During the discharging stage, the first switching circuit is used to discharge the first capacitor to the touch electrode so that the first capacitor neutralizes the charges of the parasitic capacitance, and the second switching circuit is used to charge the second capacitor.
3. The touch detection circuit according to claim 2, wherein: During the charging stage, the first switching circuit is used to make the first capacitor receive a preset charging voltage to charge the first capacitor; During the discharging stage, the second switching circuit is used to make the second capacitor receive the charging voltage to charge the second capacitor.
4. The touch detection circuit according to claim 2, wherein: During the charging stage, the second switching circuit is used to make both ends of the second capacitor receive the reference voltage to discharge the second capacitor to the touch electrode; During the discharging stage, the first switching circuit is used to make both ends of the first capacitor receive the reference voltage to discharge the first capacitor to the touch electrode.
5. The touch detection circuit according to claim 2, wherein Both the first switching circuit and the second switching circuit include a charging pull-up switch, a charging pull-down switch, and a discharging conduction switch; The first ends of the first capacitor and the second capacitor respectively receive a charging high voltage through the charging pull-up switches of the first switching circuit and the second switching circuit, and are respectively electrically connected to the touch electrode through the discharging conduction switches of the first switching circuit and the second switching circuit; The second ends of the first capacitor and the second capacitor respectively receive a charging low voltage through the charging pull-down switches of the first switching circuit and the second switching circuit, and the voltage difference between the charging high voltage and the charging low voltage is a preset charging voltage; During the charging stage, the charging pull-up switch and the charging pull-down switch of the first switching circuit are turned on to charge the first capacitor, and the discharge conduction switch of the second switching circuit is turned on to discharge the second capacitor to the touch electrode; During the discharging stage, the discharge conduction switch of the first switching circuit is turned on to discharge the first capacitor to the touch electrode, and the charging pull-up switch and the charging pull-down switch of the second switching circuit are turned on to charge the second capacitor.
6. The touch detection circuit according to claim 5, characterized in that The electrode conduction switch is electrically connected between the touch electrode and the inverting input terminal of the operational amplifier, and the feedback switch is electrically connected between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier; In the first stage, the electrode conduction switch and the feedback switch are turned on to set the voltage of the touch electrode to the reference voltage; In the second stage, the electrode conduction switch is turned on and the feedback switch is turned off to make the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier conductive.
7. The touch detection circuit according to claim 6, characterized in that, The first switching circuit and the second switching circuit also each include a reference voltage switch; The second ends of the first capacitor and the second capacitor respectively receive the reference voltage through the reference voltage switches of the first switching circuit and the second switching circuit; During the charging stage, the reference voltage switch of the second switching circuit is turned on to make the voltages at both ends of the second capacitor the reference voltage, so that the second capacitor discharges to the touch electrode; During the discharging stage, the reference voltage switch of the first switching circuit is turned on to make the voltages at both ends of the first capacitor the reference voltage, so that the first capacitor discharges to the touch electrode.
8. A touch detection method, applied to the touch detection circuit according to any one of claims 1 to 7, characterized in that, The method includes: In a first stage within the scanning period of the touch electrode, setting the voltage of the touch electrode to the reference voltage; In a second stage within the scanning period, enabling the neutralization capacitor to neutralize the charges of the parasitic capacitor multiple times and making the electrical connection between the touch electrode and the inverting input terminal of the operational amplifier conductive; In a third stage within the scanning period, obtaining charge change amount information according to the charges after the parasitic capacitor is neutralized and the reference voltage, and the change amount of the charge change amount information is used to indicate the touch information of the touch electrode.
9. A touch chip, characterized in that, Comprising an arithmetic circuit and the touch detection circuit according to any one of claims 1 to 7; The arithmetic circuit is configured to convert the change amount of the charge change amount information into a digital signal and output an indication signal according to the digital signal, and the indication signal is used to indicate the touch information of the touch electrode.
10. A touch device, characterized in that, It includes a touch panel and a touch chip as described in claim 9. The touch panel includes touch electrodes, and the touch chip is used to detect touch information of the touch electrodes.