Touch signal-to-noise ratio amplifier circuit, chip, and electronic device

Abstract

Embodiments of the present application provide a touch signal-to-noise ratio amplifier circuit, a chip, and an electronic device. The touch signal-to-noise ratio amplifier circuit is provided with a first bias resistor and a first-stage operational amplifier module after an output end of a touch sensor, a first end of the first bias resistor is connected to a preset voltage, and a second end of the first bias resistor is connected to the output end of the touch sensor and is connected to an in-phase input end of a first-stage operational amplifier. In this way, it is possible to achieve voltage-based in-phase amplification of electrical signals outputted by a touch sensor electrical signal receiving module, thus discarding traditional current-based amplification methods, and hence the noise gain will not increase along with an increase in load capacitance, thus reducing the attenuation of signals outputted by the touch sensor due to a change in a cathode panel, reducing the influence of the increased size of a capacitive screen on the signal-to-noise ratio (SNR), amplifying the SNR of the capacitive screen, and improving the precision of signals of the touch sensor of the capacitive screen.

Description

Touch signal-to-noise ratio increasing circuit, chip and electronic device Technical Field

[0001] This application belongs to the technical field of display screens, and in particular to a touch signal-to-noise ratio increasing circuit, chip, and electronic device. Background Art

[0002] Capacitive screens use touch sensors to detect the induced current generated by a human touch to determine the user's touch location. With the development of capacitive screen technology, capacitive screens have become increasingly widely used in various display scenarios, and their sizes have also increased.

[0003] However, increasing the size of a capacitive screen also increases the size of the cathode plate inside the capacitive screen. This also brings the cathode plate closer to the touch sensor, increasing the capacitance between the plates and causing more charge to flow away from the cathode plate. This, in turn, can reduce the SNR (Signal-to-Noise Ratio) of the capacitive screen, affecting the signal accuracy of the capacitive touch sensor.

[0004] In this application, the capacitance between the plates is collectively referred to as the load capacitance of the touch sensor. How to improve the SNR of a capacitive screen with a large size and large load capacitance has become a technical problem that needs to be solved urgently in this field.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a touch signal-to-noise ratio increasing circuit, chip and electronic device to improve the SNR of a capacitive screen with large size and large load capacitance.

[0007] In a first aspect, the present application provides a touch signal-to-noise ratio increasing circuit, the touch signal-to-noise ratio increasing circuit comprising:

[0008] A first bias resistor, a first-stage inverting input resistor, and a first-stage operational amplifier module; wherein the first-stage operational amplifier module is a non-inverting amplifier module;

[0009] The first end of the first bias resistor is connected to a preset voltage, the second end of the first bias resistor is connected to the output end of the touch sensor, and the second end of the first bias resistor is connected to the non-inverting input end of the first-stage operational amplifier module;

[0010] If the touch signal-to-noise ratio increasing circuit is powered by a single power supply, the first end of the first-stage inverting input resistor is connected to the inverting input end of the first-stage operational amplifier module, and the second end of the first-stage inverting input resistor is grounded; or, if the touch signal-to-noise ratio increasing circuit is powered by a dual power supply, the first end of the first-stage inverting input resistor is connected to the inverting input end of the first-stage operational amplifier module, and the second end of the first-stage inverting input resistor is connected to the preset voltage.

[0011] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes: a first bias capacitor, wherein:

[0012] A first end of the first bias capacitor is connected to the preset voltage, and a second end of the first bias capacitor is connected to the non-inverting input end of the first-stage operational amplifier module.

[0013] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes a filter, wherein:

[0014] The filter is connected to the output end of the first-stage operational amplification module and is used to output a target filtering result based on the output result of the first-stage operational amplification module.

[0015] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes an analog-to-digital conversion module, wherein:

[0016] The analog-to-digital conversion module is connected to the output end of the filter and is used to convert the target filtering result into a target digital signal.

[0017] In some possible implementations, the first-stage operational amplifier module is a buffer, and the touch signal-to-noise ratio increasing circuit further includes:

[0018] A second-stage operational amplifier module, a second-stage non-inverting input resistor, and a second-stage inverting input resistor, wherein the output end of the buffer is connected to the first end of the second-stage non-inverting input resistor, and the second end of the second-stage non-inverting input resistor is connected to the non-inverting input end of the second-stage operational amplifier module;

[0019] A first end of the second-stage inverting input resistor is connected to the inverting input end of the second-stage operational amplifier module, and a second end of the second-stage inverting input resistor is grounded.

[0020] In some possible implementations, the first-stage operational amplifier module is a buffer, and the touch signal-to-noise ratio increasing circuit further includes:

[0021] The second-stage operational amplifier module, the second-stage non-inverting input resistor, and the second-stage inverting input resistor, among which:

[0022] The non-inverting output terminal of the buffer is connected to the first terminal of the second-stage non-inverting input resistor, and the second terminal of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module;

[0023] The inverting output terminal of the buffer is connected to the first terminal of the second-stage inverting input resistor, and the second terminal of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module.

[0024] In some possible embodiments, the common-mode amplifier module includes: a common-mode amplifier and a first-stage amplification feedback resistor, wherein the first end of the first-stage amplification feedback resistor is connected to the output end of the common-mode amplifier, and the second end of the first-stage amplification feedback resistor is connected to the inverting input end of the common-mode amplifier.

[0025] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes:

[0026] The second stage operational amplifier module, the second stage non-inverting input resistor, the second stage inverting input resistor, and the filter, among which:

[0027] The first end of the second-stage non-inverting input resistor is connected to the output end of the non-inverting amplifier module, and the second end of the second-stage non-inverting input resistor is connected to the non-inverting input end of the second-stage operational amplifier module;

[0028] A first end of the second-stage inverting input resistor is connected to the inverting input end of the second-stage operational amplifier module, and a second end of the second-stage inverting input resistor is grounded;

[0029] The output end of the second-stage operational amplifier module is connected to the filter.

[0030] In some possible implementations, a gain of the in-phase amplification module is less than a preset gain threshold.

[0031] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes: a second-stage non-inverting input resistor, a second-stage inverting input resistor, and a second-stage operational amplifier module, wherein:

[0032] The non-inverting output terminal of the first-stage operational amplifier module is connected to the first terminal of the second-stage non-inverting input resistor, and the second terminal of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module;

[0033] The inverting output terminal of the first-stage operational amplifier module is connected to the first terminal of the second-stage inverting input resistor, and the second terminal of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module.

[0034] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes:

[0035] A first control switch, a second control switch, a first differential connection resistor, and a second differential connection resistor, wherein:

[0036] A first end of the first control switch is connected to a second end of a second-stage non-inverting input resistor of the i-th RX channel, a second end of the first control switch is connected to a first end of the first differential connection resistor, and a second end of the first differential connection resistor is connected to a second end of a second-stage inverting input resistor of the (i+1)-th RX channel;

[0037] a first end of the second control switch connected to the second end of the second-stage inverting input resistor of the i-th RX channel, a second end of the second control switch connected to the first end of the second differential connection resistor, and a second end of the second differential connection resistor connected to the second end of the second-stage non-inverting input resistor of the (i+1)-th RX channel;

[0038] The i-th RX channel and the (i+1)-th RX channel are two adjacent channels in the multiple Rx channels; and the RX channel is a touch signal-to-noise ratio increasing circuit corresponding to the RX electrode.

[0039] In some possible implementations, when the first control switch is closed, the non-inverting output end of the i-th RX channel and the inverting output end of the i+1-th RX channel are adjacently differenced; when the second control switch is closed, the inverting output end of the i-th RX channel and the non-inverting output end of the i+1-th RX channel are adjacently differenced to obtain a target differential result.

[0040] In some possible implementations, the touch sensor further includes a reference channel; the reference channel includes: a first bias resistor, a first-stage inverting input resistor, and a first-stage operational amplifier module; wherein the first-stage operational amplifier module is a non-inverting amplifier module,

[0041] The first end of the first bias resistor is connected to a preset voltage, the second end of the first bias resistor is connected to the touch sensor, and the second end of the first bias resistor is connected to the non-inverting input end of the first-stage operational amplifier module;

[0042] The first end of the first-stage inverting input resistor is connected to the inverting input end of the first-stage operational amplifier module, and the second end of the first-stage inverting input resistor is connected to the preset voltage.

[0043] In some possible implementations, the second-stage non-inverting input resistor includes: a first second-stage non-inverting input resistor and a second second-stage non-inverting input resistor; the second-stage inverting input resistor includes: a first second-stage inverting input resistor and a second second-stage inverting input resistor, wherein:

[0044] The first end of the first-second-stage non-inverting input resistor in the i-th RX channel is connected to the non-inverting output terminal of the first-stage operational amplifier module, and the second end of the first-second-stage non-inverting input resistor is connected to the second end of the second-second-stage non-inverting input resistor in the i-th RX channel and the non-inverting input terminal of the second-stage operational amplifier module in the i-th RX channel;

[0045] The first end of the second second-stage non-inverting input resistor in the i-th RX channel is connected to the first end of the second second-stage non-inverting input resistor in each of the RX channels and the inverting output end of the reference channel;

[0046] The first end of the first-second-stage inverting input resistor in the i-th RX channel is connected to the inverting output end of the first-stage operational amplifier module, and the second end of the first-second-stage inverting input resistor is connected to the second end of the second-second-stage inverting input resistor in the i-th RX channel and the inverting input end of the second-stage operational amplifier in the i-th RX channel;

[0047] The first end of the second second-stage inverting input resistor in the i-th RX channel is connected to the first end of the second second-stage inverting input resistor in each of the RX channels and the non-inverting output end of the reference channel;

[0048] The in-phase output end of the i-th RX channel is subtracted from the in-phase output end of the reference channel, and the in-phase output end of the i-th RX channel is subtracted from the in-phase output end of the reference channel to obtain a target differential result; the RX channel is a touch signal-to-noise ratio enhancement circuit corresponding to the RX electrode, and the reference channel is a touch signal-to-noise ratio enhancement circuit corresponding to the reference electrode.

[0049] In some possible implementations, the touch signal-to-noise ratio increasing circuit further includes a mean value generating channel;

[0050] The mean value generation channel includes: a mean non-inverting input resistor, a mean inverting input resistor, a second-stage operational amplifier module, a filter, and a sample-and-hold device. The mean value generation channel is used to collect the average value of the output results of each of the RX channels.

[0051] In some possible implementations, the second-stage non-inverting input resistor includes: a first second-stage non-inverting input resistor and a second second-stage non-inverting input resistor, and the second-stage inverting input resistor includes: a first second-stage inverting input resistor and a second second-stage inverting input resistor;

[0052] The second end of the average non-inverting input resistor is connected to the non-inverting input end of the second-stage operational amplifier module, the second end of the average inverting input resistor is connected to the inverting input end of the second-stage operational amplifier module, the output end of the second-stage operational amplifier module is connected to the input end of the filter, and the output end of the filter is connected to the input end of the sample and hold;

[0053] Each of the RX channels and the mean value generation channel includes: a first input resistor, a second input resistor, a first input capacitor, and a second input capacitor, wherein:

[0054] The first end of the first-second stage non-inverting input resistor in the i-th RX channel is connected to the non-inverting output terminal of the first-stage operational amplifier module of the i-th channel and the first end of the first input resistor, and the second end of the first-second stage non-inverting input resistor of the i-th RX channel is connected to the second end of the second-second stage non-inverting input resistor of the i-th RX channel and the non-inverting input terminal of the second-stage operational amplifier module of the i-th RX channel;

[0055] The first end of the second second-stage non-inverting input resistor of the i-th RX channel is connected to the first end of the second second-stage non-inverting input resistor of each of the RX channels and the inverting output end of the second-stage operational amplifier module of the mean value generation channel;

[0056] The first end of the first and second stage inverting input resistors of the i-th RX channel is connected to the inverting output end of the first stage operational amplifier module of the i-th channel and the first end of the second input resistor; the second end of the first and second stage inverting input resistors of the i-th RX channel is connected to the second end of the second second stage inverting input resistor of the i-th RX channel and the inverting input end of the second stage operational amplifier of the i-th RX channel;

[0057] The first end of the second second-stage inverting input resistor of the i-th RX channel is connected to the first end of the second second-stage inverting input resistor of each of the RX channels and the non-inverting output end of the second-stage operational amplifier module of the mean value generation channel;

[0058] The second end of the first input resistor is connected to the first end of the average in-phase input resistor and the first end of the first input capacitor; the second end of the first input capacitor is grounded;

[0059] The second end of the second input resistor is connected to the first end of the average inverting input resistor and the first end of the second input capacitor; the second end of the second input capacitor is grounded;

[0060] The in-phase output end of the i-th RX channel is subtracted from the inverting output end of the mean generation channel, and the inverting output end of the i-th RX channel is subtracted from the in-phase output end of the mean generation channel to obtain a target differential result.

[0061] In a second aspect, the present application provides a capacitive screen, wherein the capacitive screen includes any touch signal-to-noise ratio increasing circuit described in the first aspect.

[0062] In a third aspect, the present application provides a chip, wherein the chip includes the touch signal-to-noise ratio increasing circuit described in any one of the first aspects.

[0063] In a fourth aspect, the present application provides an electronic device, wherein the electronic device includes the chip described in the third aspect.

[0064] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0065] Embodiments of the present application provide a touch signal-to-noise ratio (SNR) enhancement circuit, chip, and electronic device. The touch signal-to-noise ratio enhancement circuit comprises a first bias resistor and a first-stage operational amplifier module disposed after the output terminal of a touch sensor. The first end of the first bias resistor is connected to a preset voltage, and the second end of the first bias resistor is connected to the output terminal of the touch sensor and the non-inverting input terminal of the first-stage operational amplifier. In this manner, the electrical signal output by the touch sensor electrical signal receiving module can be amplified in phase based on voltage, eliminating the traditional current-based amplification method. The noise gain does not increase with increasing load capacitance, thereby reducing attenuation of the touch sensor output signal due to changes in the cathode plate. This reduces the impact of increased capacitive screen size on the SNR signal-to-noise ratio, increases the SNR of the capacitive screen, and improves the signal accuracy of the capacitive screen touch sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0067] FIG1 shows a circuit diagram of a touch sensor electrical signal amplifying circuit commonly used in the prior art;

[0068] FIG2 shows a circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0069] FIG3 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0070] FIG4 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0071] FIG5 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0072] FIG6 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0073] FIG7 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0074] FIG8 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0075] FIG9 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0076] FIG10 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0077] FIG11 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0078] FIG12 shows another circuit diagram of a touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application;

[0079] FIG13 is a schematic diagram showing a technical effect of the measured SNR of the touch signal-to-noise ratio enhancement circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0080] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described below with reference to the accompanying drawings and examples. It should be understood that the described examples are only some examples of the present invention, not all examples. All other examples derived by persons of ordinary skill in the art based on the examples of the present invention fall within the scope of protection of the present invention.

[0081] In the field of capacitive screens, mutual capacitance detection of capacitive screens regards the capacitive screen as a sensing matrix constructed by multiple RX electrodes and TX electrodes. The touch sensor determines the area where the finger touches by identifying the specific RX electrodes and TX electrodes where the touch occurs to achieve touch recognition.

[0082] Specifically, in a capacitive touch screen, the TX electrode can be called the driving electrode, and the RX electrode can be called the sensing electrode. A coupling capacitor is formed between the TX and RX electrodes. When the capacitive touch screen is touched, such as when a finger touches it, the finger's touch causes the coupling capacitor to change. The touch sensor identifies the changed capacitance value and determines the area where the touch occurred.

[0083] Therefore, the circuit set inside the capacitive screen can be composed of the following circuits:

[0084] Part 1: A touch sensor that captures user touch operations. The touch sensor is equivalent to a circuit combination, as shown in Figure 1, consisting of a cross-coupling capacitor Cm, self-capacitance Cr1 between the TX electrode and the cathode plate, self-capacitance Cr2 between the RX electrode and the cathode plate, and trace impedance Rr. One end of the touch sensor is connected to the TX electrode, and the other end is connected to the RX electrode. When performing mutual capacitance detection on the TX and RX electrodes, an excitation signal is input to the TX electrode. The cross-coupling capacitor and self-capacitance within the touch sensor interact to output a response signal from the RX electrode.

[0085] Part 2: An amplifier circuit amplifies the response signal output by the touch sensor. A commonly used amplifier circuit in the prior art is shown in FIG1 , where a first-stage current amplification module, a trans-impedance amplifier (TIA), amplifies the current to produce an amplified response signal.

[0086] Part 3: A signal processing circuit that filters and performs analog-to-digital conversion on the amplified response signal to obtain the final target digital signal.

[0087] In the circuit of the second part, the transimpedance amplifier commonly used in the prior art functions to convert the input current into a proportional output voltage, i.e., the transimpedance amplifier is essentially an inverting amplifier. Furthermore, as described in the background art, as the size of the capacitive screen gradually increases, the size of the cathode plate also gradually increases, and the load capacitance of the touch sensor also gradually increases. This causes more and more charge signals to flow away from the cathode plate, which in turn causes the amount of charge entering the transimpedance amplifier to gradually decrease. This can easily lead to a decrease in the output voltage signal converted by the transimpedance amplifier, which in turn causes the SNR of the capacitive screen circuit to gradually decrease, reducing the signal accuracy of the touch sensor.

[0088] In view of this, the present application provides a touch signal-to-noise ratio increasing circuit, chip and electronic device for increasing the SNR signal-to-noise ratio of a capacitive screen circuit and improving the accuracy of the touch sensor.

[0089] In some embodiments, the touch signal-to-noise ratio enhancement circuit provided by the embodiments of the present application can be a comprehensive circuit of the above three circuit parts, or can be the amplifier circuit of the second part, or any combination circuit of the amplifier circuit and the other two circuit parts.

[0090] In some embodiments, the capacitive screen signal-to-noise ratio enhancement circuit provided by the present application may be shown in FIG2 , and specifically includes the following parts:

[0091] A first bias resistor Rb1, a first-stage inverting input resistor R12, and a first-stage operational amplifier module, wherein the first-stage operational amplifier module is a non-inverting amplifier module.

[0092] Specifically, in some embodiments, the first-stage operational amplifier module may include a first-stage operational amplifier, a first feedback resistor Rf1, and a first feedback capacitor Cf1, as shown in FIG2. The connection relationship between the first feedback resistor Rf1 and the first feedback capacitor Cf1 is shown in FIG2, and the first feedback resistor Rf1 and the first feedback capacitor Cf1 are connected in parallel between the inverting input terminal (-) and the non-inverting output terminal (+) of the first-stage operational amplifier.

[0093] As shown in FIG2 , the connection relationship between the components of the touch signal-to-noise ratio enhancement circuit provided in the embodiment of the present application can be:

[0094] A first end of the first bias resistor Rb1 is connected to a preset voltage, a second end of the first bias resistor Rb1 is connected to the output end of the touch sensor, and a second end of the first bias resistor Rb1 is connected to the non-inverting input end (+) of the first-stage operational amplifier module;

[0095] If the touch signal-to-noise ratio enhancement circuit is powered by a single power supply, the first end of the first-stage inverting input resistor R12 is connected to the inverting input terminal (-) of the first-stage operational amplifier module, and the second end of the first-stage inverting input resistor R12 is grounded.

[0096] In some embodiments, during the mutual capacitance detection process, the touch sensor is equivalent to a capacitor. Since capacitors only pass AC signals but not DC signals, the DC signal generated during the mutual capacitance detection process cannot pass through the touch sensor to enter the amplifier circuit, which requires positive and negative power supplies. Based on this, in an embodiment of the present application, a preset voltage is added after the touch sensor. This preset voltage is essentially a DC bias power supply, which is used to provide a single power supply for the circuit. A DC bias is added to the response signal without DC bias transmitted from the touch sensor, so that the response signal output by the touch sensor can smoothly enter the amplifier circuit for amplification.

[0097] As an implementation manner, the preset voltage is VCMI (Voltage Control Mode Input), and the voltage value of VCMI may be 1 / 2 of the power supply voltage of the first-stage operational amplifier. Preferably, the preset voltage VCMI is within the range of 1-2V.

[0098] Since the preset voltage is connected after the touch sensor, there is no impedance between the preset voltage VCMI and the first-stage operational amplifier module. At this time, the response signal output by the touch sensor can easily short-circuit from the preset voltage VCMI and flow out without entering the first-stage operational amplifier module. Based on this, in an embodiment of the present application, a first bias resistor Rb1 is added between the preset voltage VCMI and the output end of the touch sensor. The first bias resistor should be a high-impedance resistor that prevents the response signal output by the touch sensor from flowing out from the preset voltage VCMI. As an embodiment, the resistance range of the first bias resistor Rb1 is 2KΩ to 50KΩ. Preferably, the resistance value of the first bias resistor Rb1 is 10KΩ.

[0099] It can be seen that compared with the common solution of FIG1 in which the response signal output by the touch sensor is input into the inverting amplifier for current amplification, the touch signal-to-noise ratio increasing circuit provided in the embodiment of the present application inputs the response signal output by the touch sensor into the non-inverting input terminal (+) of the first-stage operational amplifier module. When the capacitive screen is single-ended, the DC bias is increased by means of a preset voltage, thereby reducing the attenuation of the charge or the amount of charge flowing away from the cathode plate due to the increase in the size of the cathode plate when the load capacitance of the touch sensor increases. This reduces the impact of the increase in the size of the capacitive screen on the signal-to-noise ratio (SNR), increases the SNR of the capacitive screen, and improves the signal accuracy of the touch sensor of the capacitive screen.

[0100] In some embodiments, the touch signal-to-noise ratio enhancement circuit provided in the embodiments of the present application may also be as shown in FIG3 , where a first bias resistor Rb1 and a first bias capacitor Cb1 are connected between the preset voltage VCMI and the first-stage operational amplifier. The first end of the first bias capacitor Cb1 is connected to the preset voltage, and the second end of the first bias capacitor Cb1 is connected to the non-inverting input (+) of the first-stage operational amplifier module. That is, the first bias resistor Rb1 and the first bias capacitor Cb1 are connected in parallel between the touch sensor output and the preset voltage output, and the first bias resistor Rb1 and the first bias capacitor Cb1 are connected in parallel between the non-inverting input (+) and the preset voltage output of the first-stage operational amplifier module.

[0101] Since the capacitive screen detects whether a touch has occurred by monitoring the capacitance change between the TX / RX electrodes, and then detects the specific coordinate changes where the touch has occurred. Also, since the distance between the touch sensor and the display layer is very close, when there is a touch on the display layer, the display layer is likely to interfere with the capacitance change between the TX / RX electrodes, resulting in errors in the touch sensor detection. In this application, the interference caused by the display layer on the capacitance change between the TX / RX electrodes is determined to be display interference. Usually, the signal amplitude of the display interference far exceeds the amplitude of the touch signal detected by the touch sensor.

[0102] Based on this, an embodiment of the present application is selected, and a first bias capacitor Cb1 is connected in parallel to the first bias resistor Rb1. The first bias capacitor Cb1 and the first bias resistor Rb1 are combined to form a low-pass filter, which allows the high-amplitude display interference signal to flow out of the first bias capacitor Cb1 without entering the first-stage operational amplifier. In this way, the display interference signal and the common-mode interference signal can be effectively reduced from entering the first-stage operational amplifier module, further improving the conversion accuracy of the first-stage operational amplifier module. As an embodiment, the capacitance value of the first bias capacitor Cb1 ranges from 0.5pf to 20pf. Preferably, the capacitance value of the first bias capacitor Cb1 is 10pf.

[0103] In some embodiments, if the circuit of the capacitive screen is powered by dual power supplies, the touch signal-to-noise ratio enhancement circuit provided in the present application is adaptively adjusted based on the dual power supply situation. The specific adjustment circuit structure diagram is shown in Figure 4. The second end of the first-stage inverting input resistor R12 is adjusted from the original ground connection to the second end of the first-stage inverting input resistor R12 connected to the preset voltage VCMI, and no other adjustments are made.

[0104] In the embodiment of the present application, when the capacitive touch screen is powered by dual power supplies, one power supply is connected to a preset voltage VCMI via the first bias resistor Rb1, and the other power supply is connected to a preset voltage VCMI via the first-stage inverting input resistor R12. In this way, the touch signal-to-noise ratio enhancement circuit provided by the present application is applicable not only to capacitive touch screens powered by a single power supply, but also to capacitive touch screens powered by dual power supplies.

[0105] In some embodiments, the capacitive touch screen has two power supplies: an analog power supply and a digital power supply. The analog power supply has a voltage range of 2.6V to 3.6V, and the digital power supply has a voltage range of 1.8V to 3.3V. The specific power supply used depends on the capacitive touch screen motherboard. If either the analog power supply or the digital power supply is used for power supply, it is called a single power supply. If both the analog power supply and the digital power supply are used for power supply, it is called a dual power supply.

[0106] In some embodiments, as shown in FIG5 , the touch signal-to-noise ratio enhancement circuit provided in the present application may further include a filter, wherein the filter is connected to the output terminal of the first-stage operational amplifier module and is configured to output a target filtering result based on the output result of the first-stage operational amplifier module.

[0107] The internal circuit structure and connection relationship of the internal components of the filter in Figure 5 can be referred to the circuit structure diagram shown in Figure 6. Specifically, the internal components of the filter include: a filter amplifier, a first filter input resistor, a second filter input resistor, a filter input capacitor, a filter feedback resistor, and a filter feedback capacitor. The connection relationship between the components is:

[0108] The first end of the filter input capacitor is connected to the first end of the first filter input resistor and the inverting output end (-) of the first-stage operational amplifier module, and the second end of the filter input capacitor is connected to the first end of the second filter input resistor and the non-inverting output end (+) of the first-stage operational amplifier module.

[0109] The second end of the first filter input resistor is connected to the non-inverting input terminal (+) of the filter amplifier. The second end of the second filter input resistor is connected to the inverting input terminal (-) of the filter amplifier.

[0110] Among them, one end of a filter feedback resistor is connected to the first end of the first filter input resistor, and the other end is connected to the first filter output end (-) of the filter amplifier; one end of a filter feedback capacitor is connected to the second end of the first filter input resistor, and the other end is connected to the first filter output end (-) of the filter amplifier; one end of another filter feedback resistor is connected to the first end of the second filter input resistor, and the other end is connected to the second filter output end (+) of the filter amplifier; one end of a filter feedback capacitor is connected to the second end of the second filter input resistor, and the other end is connected to the second filter output end (+) of the filter amplifier. For the specific electrical signal conversion process, please refer to the introduction of the working principles of other filters.

[0111] In some embodiments, the touch signal-to-noise ratio enhancement circuit may further include an analog-to-digital conversion (ADC) module in addition to the filter, wherein the ADC module is connected to the output end of the filter and is configured to convert a target filtering result into a target digital signal.

[0112] In the present application, the first-stage operational amplifier module in the touch signal-to-noise ratio enhancement circuit provided in the embodiments of the present application is essentially a non-inverting amplifier module, that is, a voltage amplifier circuit that increases input impedance through negative feedback. It can be a buffer with non-inverting amplification function or a non-inverting amplifier with non-inverting amplification function. The non-inverting amplifier type can be a conventional single-supply non-inverting amplifier or a dual-supply non-inverting amplifier, and can be a fixed-gain non-inverting amplifier or a PGA (Programmable Gain Amplifier) ​​with adjustable gain.

[0113] In some embodiments, when the first-stage operational amplifier module is a buffer with a non-inverting amplification function, and the buffer outputs a single-ended signal, the circuit structure of the touch signal-to-noise ratio enhancement circuit provided in the embodiment of the present application may be as shown in FIG7 , and further includes:

[0114] The second-stage operational amplifier module, the second-stage non-inverting input resistor R21, and the second-stage inverting input resistor R22. The connection relationship between the various circuit components is shown in Figure 7:

[0115] The output end of the buffer is connected to the first end of the first and second stage non-inverting input resistor R21, and the second end of the first and second stage non-inverting input resistor R21 is connected to the non-inverting input end (+) of the second stage operational amplifier module;

[0116] The first end of the first and second stage inverting input resistor R22 is connected to the inverting input terminal (-) of the second stage operational amplifier module, and the second end of the first and second stage inverting input resistor R22 is grounded.

[0117] In some embodiments, the first-stage operational amplifier module is a buffer with a non-inverting amplification function, and the buffer outputs a fully differential signal. The circuit structure of the touch signal-to-noise ratio enhancement circuit provided in the embodiment of the present application may be as shown in FIG8 , and further includes:

[0118] The second stage operational amplifier module, the first and second stage non-inverting input resistors R21, and the first and second stage inverting input resistors R22. The connection relationship between the various circuit components is shown in Figure 8:

[0119] The non-inverting output terminal of the buffer is connected to the first end of the first and second stage non-inverting input resistors R21, and the second ends of the first and second stage non-inverting input resistors R21 are connected to the non-inverting input terminal (+) of the second stage operational amplifier module;

[0120] The inverting output terminal of the buffer is connected to the first end of the first and second stage inverting input resistors R22, and the second ends of the first and second stage inverting input resistors R22 are connected to the inverting input terminal (-) of the second stage operational amplifier module.

[0121] The second-stage operational amplifier module in FIG7 and FIG8 is shown in the figure, and is composed of a second-stage operational amplifier, two sets of second feedback resistors Rf2 and second feedback capacitors Cf2. The connection relationship between the internal components of the second-stage operational amplifier module is as follows:

[0122] One set of second feedback resistors Rf2 and second feedback capacitors Cf2 are connected in parallel between the inverting input terminal (-) and the non-inverting output terminal (+) of the second-stage operational amplifier. Another set of second feedback resistors Rf2 and second feedback capacitors Cf2 are connected in parallel between the non-inverting input terminal (+) and the inverting output terminal (-) of the second-stage operational amplifier. The values ​​of the two sets of second feedback resistors Rf2 and second feedback capacitors Cf2 can be the same or different, and can be flexibly adjusted according to actual needs. This application does not impose strict restrictions.

[0123] Because the gain of the buffer may be fixed, there is a possibility that the amplification gain of the buffer is insufficient to amplify the response signal output by the touch sensor to meet the filter input voltage requirement. In the embodiment of the present application, a second-stage operational amplifier module is connected to the output of the buffer. The second-stage operational amplifier module performs a second amplification on the response signal amplified by the first-stage operational amplifier module, so that the response signal output by the touch sensor is amplified to meet the filter input voltage requirement.

[0124] In some embodiments, the touch signal-to-noise ratio enhancement circuit provided by the embodiment of the present application may also be shown in FIG9 , wherein the first-stage operational amplifier module (the circuit portion in the dashed box on the left side of the figure) is composed of a simple non-inverting amplifier AMP and a first feedback resistor Rf1. As shown in FIG9 , the touch signal-to-noise ratio enhancement circuit provided by the embodiment of the present application may also include:

[0125] The second-stage operational amplifier module, the first and second-stage non-inverting input resistors R21, and the first and second-stage inverting input resistors R22, wherein the connection relationship between the components can be shown in FIG9:

[0126] A first end of the first feedback resistor Rf1 is connected to the output end of the non-inverting amplifier AMP, and a second end of the first feedback resistor Rf1 is connected to the inverting input end (-) of the non-inverting amplifier AMP.

[0127] The first end of the first and second stage non-inverting input resistor R21 is connected to the output end of the non-inverting amplifier AMP, and the second end of the first and second stage non-inverting input resistor R21 is connected to the non-inverting input end (+) of the second stage operational amplifier module.

[0128] The first end of the first and second stage inverting input resistor R22 is connected to the inverting input terminal (-) of the second stage operational amplifier module, and the second end of the first and second stage inverting input resistor R22 is grounded.

[0129] The output end of the second-stage operational amplifier module is connected to the filter.

[0130] In some embodiments, when the gain of the buffer or the gain of the non-inverting amplifier AMP is sufficient to amplify the response signal output by the touch sensor to the input voltage requirement of the filter, the second-stage operational amplifier module and the corresponding second-stage non-inverting input resistor and the second-stage inverting input resistor may be omitted, and the first-stage operational amplifier module is directly connected to the filter, and the amplified response signal is directly input into the filter for filtering processing to obtain the target filtered signal.

[0131] If the gain of the buffer or the gain of the non-inverting amplifier AMP is less than the preset gain threshold, a second-stage operational amplifier module is added between the first-stage operational amplifier module and the filter. The second-stage operational amplifier module performs a second amplification on the amplified response signal, and then inputs the second-amplified signal into the filter for filtering to obtain the target filtered signal.

[0132] Among them, in some embodiments, the second-stage operational amplifier module can also be a programmable gain amplifier, and the amplification gain of the second-stage operational amplifier module can be adjusted by software, thereby ensuring that the amplification gain of the amplifier circuit obtained by combining the first-stage operational amplifier module and the second-stage operational amplifier module meets the requirements.

[0133] Since the mutual capacitance detection of the capacitive screen regards the capacitive screen as a sensing matrix constructed by multiple RX electrodes and TX electrodes, the touch sensor determines the specific touch coordinates of the touch point triggered by the user based on the difference in the response signals output by the TX electrode and the RX electrode under the action of the excitation signal. Based on this, in order to improve the SNR of the entire capacitive screen, the touch signal-to-noise ratio enhancement circuit provided in the embodiment of the present application can be connected after each RX electrode. As another embodiment, the touch signal-to-noise ratio enhancement circuit provided in the embodiment of the present application can be selectively connected after some RX electrodes, and the specific number of connections can be flexibly selected based on actual operation.

[0134] The touch signal-to-noise ratio amplification circuit in this application can increase the signal-to-noise ratio of touch detection to enhance touch detection sensitivity. Based on this, in some embodiments, each signal-to-noise ratio amplification circuit is of the same type. Each RX channel can also flexibly select a different signal-to-noise ratio amplification circuit based on the differences in each output signal.

[0135] When a touch occurs on a capacitive screen, the coupling capacitance between the TX electrode and the RX electrode changes. During the capacitive screen touch detection process, the specific location of the touch is determined by determining the change in the coupling capacitance. In this application, a reference capacitance is set as a comparison benchmark to determine the difference between the coupling capacitance and the reference capacitance, and to determine whether the coupling capacitance has changed and the magnitude of the change. This method of capacitive screen touch detection based on the difference between the coupling capacitance and the reference capacitance is called a differential detection method.

[0136] In an application scenario based on the differential detection method, that is, a scenario in which the touch sensor is used for differential detection, the touch signal-to-noise ratio enhancement circuit provided in the present application may be shown in Figures 10 to 12 . The touch signal-to-noise ratio enhancement circuit corresponding to each RX electrode specifically includes a preset voltage VCMI, a first bias resistor Rb1, a first-stage operational amplifier module, first and second-stage non-inverting input resistors R21, first and second-stage inverting input resistors R22, a second-stage operational amplifier module, a filter, and a sample-and-hold device.

[0137] Among them, in the connection relationship of the various components of the touch signal-to-noise ratio enhancement circuit corresponding to each RX electrode, the connection relationship between the preset voltage VCMI, the first bias resistor Rb1 and the cross-coupling capacitor Cm is the same as the connection relationship between the preset voltage VCMI, the first bias resistor Rb1 and the touch sensor mentioned above, wherein the cross-coupling capacitor Cm is the coupling capacitor formed between each RX electrode and each TX electrode.

[0138] The first-stage operational amplifier module can be the first-stage operational amplifier module shown in any of Figures 2 to 9, wherein the first-stage operational amplifier module circuit shown in the dotted box on the left in Figures 10 to 12 takes the first-stage operational amplifier module in Figure 2 as an example, and is a non-inverting amplifier module composed of a first-stage operational amplifier AMP, a first feedback resistor Rf1, and a first feedback capacitor Cf1, wherein the first feedback resistor Rf1 and the first feedback capacitor Cf1 are connected in parallel to the negative feedback circuit of the first-stage operational amplifier.

[0139] The connection relationship between the components in the touch signal-to-noise ratio enhancement circuit can be shown in Figures 10 to 12:

[0140] The non-inverting output terminal of the first stage operational amplifier module is connected to the first end of the first and second stage non-inverting input resistors R21, and the second ends of the first and second stage non-inverting input resistors R21 are connected to the non-inverting input terminal (+) of the second stage operational amplifier module.

[0141] The inverting output terminal of the first stage operational amplifier module is connected to the first end of the first and second stage inverting input resistors R22, and the second ends of the first and second stage inverting input resistors R22 are connected to the inverting input terminal (-) of the second stage operational amplifier module.

[0142] The inverting output terminal (-) of the second-stage operational amplifier module is connected to the non-inverting input terminal (+) of the filter, the non-inverting output terminal (+) of the second-stage operational amplifier module is connected to the inverting input terminal (-) of the filter, the first filter output terminal (-) of the filter is connected to the first input terminal (Vin1) of the sample and holder, and the second filter output terminal (+) of the filter is connected to the second input terminal (Vin2) of the sample and holder.

[0143] Among them, the first sampling output end of the sample and holder in the touch signal-to-noise ratio enhancement circuit corresponding to each RX electrode is connected to the non-inverting input end (+) of the analog-to-digital conversion buffer, and the second sampling output end of the sample and holder in the touch signal-to-noise ratio enhancement circuit corresponding to each RX electrode is connected to the inverting input end (-) of the analog-to-digital conversion buffer.

[0144] The sample-and-hold circuit, as shown in Figures 10 to 12, consists of a sample-and-hold capacitor C1, a sample-and-hold capacitor C2, and switches S1 to S4. The first end of switch S1 is connected to the first filter output terminal of the filter, the second end of switch S1 is connected to the first end of sample-and-hold capacitor C1 and the first end of switch S3, the second end of sample-and-hold capacitor C1 is grounded, and the second end of switch S3 is connected to the second end of the switch S3 of the sample-and-hold circuit in the other RX channel and the non-inverting input terminal (+) of the analog-to-digital converter buffer.

[0145] A first end of the switch S2 is connected to the second filter output end of the filter, a second end of the switch S2 is connected to the first end of the sampling and holding capacitor C2 and the first end of the switch S4, a second end of the sampling and holding capacitor C2 is grounded, and a second end of the switch S4 is connected to the second end of the switch S4 of the sample and hold of the other RX channel and the inverting input end (-) of the analog-to-digital conversion buffer.

[0146] Switches S1 to S4 are closed or opened based on the high or low level of the sampling clock. Specifically, as an embodiment, when the sampling clock is at a high level, the switches are closed, and when the sampling clock is at a low level, the switches are opened. The specific control method can be flexibly set according to actual needs and is not strictly limited in this application.

[0147] When switches S1 and S3 are closed, the filter's in-phase output signal enters the sample-and-hold device for sampling. When switches S1 and S3 are open, the sample-and-hold device maintains and outputs the in-phase output signal. Similarly, when switches S2 and S4 are closed, the filter's inverted output signal enters the sample-and-hold device for sampling. When switches S2 and S4 are open, the sample-and-hold device maintains and outputs the inverted output signal. The specific signal retention and output principles of the sample-and-hold device can be found in the technical documentation of the relevant sample-and-hold device and are not detailed here.

[0148] In this application, the naming of the in-phase output terminal and the inverting output terminal of each component can be replaced with other naming forms, but it is necessary to ensure that the signal polarity of the touch signal-to-noise ratio increase circuit corresponding to each RX electrode output to the in-phase input terminal (+) of the analog-to-digital conversion buffer remains consistent, and to ensure that the signal polarity of each RX channel output to the inverting input terminal (-) of the analog-to-digital conversion buffer remains consistent.

[0149] The inverting output (-) of the analog-to-digital buffer is connected to the first input (Vin1) of the analog-to-digital converter (ADC), and the non-inverting output (+) of the analog-to-digital converter (ADC) is connected to the second input (Vin2) of the ADC. The ADC buffer is essentially a non-inverting amplified follower circuit, used to indirectly provide a transient current to the ADC, preventing the ADC from drawing current from the sample-and-hold circuit, which could lead to inaccurate ADC results.

[0150] In an embodiment of the present application, the second-stage operational amplifier module may also be a PGA amplifier, which is used when the gain of the first-stage operational amplifier module is less than a preset gain threshold. The PGA amplifier may not be used when the gain of the first-stage operational amplifier module meets a preset gain threshold condition. The preset gain threshold condition may be that the voltage amplitude of the amplified output signal of the first-stage operational amplifier module meets the filtered input voltage amplitude of the filter. The specific threshold can be set based on actual experience or experimental test results, and is not strictly limited in this application.

[0151] Since the types of differential detection are divided into many types, such as adjacent differential detection, reference channel differential detection, average value differential detection, etc. Among them, adjacent differential detection determines the touch area by the difference in changes between the coupling capacitances of adjacent RX electrodes. Based on this, for the case of adjacent differential detection, the touch signal-to-noise ratio increase circuit corresponding to each RX electrode includes a preset voltage VCMI, a first bias resistor Rb1, a first-stage inverting input resistor R12, a first-stage operational amplifier module, a second-stage non-inverting input resistor R21, a first- and second-stage inverting input resistors R22, a second-stage operational amplifier module, a filter, a sample and hold, and the touch signal-to-noise ratio increase circuit corresponding to each RX electrode. On the basis of the shared analog-to-digital conversion buffer and analog-to-digital conversion module ADC, the touch signal-to-noise ratio increase circuit under adjacent differential detection provided by the present application can be shown in Figure 10. The touch signal-to-noise ratio increase circuit provided in the embodiment of the present application also includes:

[0152] A first control switch K1, a second control switch K2, a first differential connection resistor R1, and a second differential connection resistor R2.

[0153] For the convenience of description, the touch signal-to-noise ratio enhancement circuit corresponding to the RX electrode is collectively referred to as the "RX channel" in the following text of this application.

[0154] The connection relationship between the components of adjacent RX channels is shown in Figure 10:

[0155] A first end of the first control switch K1 is connected to the second end of the first and second stage non-inverting input resistors R21 of the i-th RX channel, a second end of the first control switch K1 is connected to the first end of the first differential connection resistor R1, and a second end of the first differential connection resistor R1 is connected to the second end of the first and second stage inverting input resistors R22 of the (i+1)-th RX channel;

[0156] A first end of the second control switch K2 is connected to the second end of the first-stage second-stage inverting input resistor R22 of the i-th RX channel, a second end of the second control switch K2 is connected to the first end of the second differential connection resistor R2, and a second end of the second differential connection resistor R2 is connected to the second end of the first-stage second-stage non-inverting input resistor R21 of the (i+1)-th RX channel;

[0157] The principle of differential detection is to detect whether the coupling capacitance Cm of the RX channel has changed compared to the reference channel. If it has changed, it indicates that the capacitive touch screen has been touched. In other words, if the capacitive touch screen is not touched, the difference in the coupling capacitance Cm between adjacent channels should remain stable. If the difference in the coupling capacitance Cm between adjacent channels changes, it indicates that one of the adjacent RX electrodes has been touched.

[0158] Based on this, in an embodiment of the present application, when the first control switch K1 is closed, the in-phase output result of the first-stage operational amplifier module of the i-th RX channel is input to the inverting input terminal of the second-stage operational amplifier module of the i+1-th RX channel. Since the in-phase output result of the i-th RX channel and the inverting output result of the i+1-th RX channel are in opposite phase, the addition operation between the two is equivalent to taking the difference between the two, and the result of the difference is obtained, that is, whether there is a difference between adjacent RX channels. If there is a difference, it indicates that a touch has occurred in one of the RX electrodes. Based on the result obtained by the difference, it can be further determined which specific channel of the adjacent channels has been touched.

[0159] Similarly, when the second control switch K2 is closed, the inverting output result of the first-stage operational amplifier module of the i-th RX channel is subtracted from the non-inverting output result of the first-stage operational amplifier module of the i+1-th RX channel, and the result of the subtraction is further used to determine which channel of the adjacent RX electrodes is touched.

[0160] Among them, as an implementation method, the first control switch K1 and the second control switch K2 can be controlled to close simultaneously based on the control signal clock, which can help to simultaneously determine the coupling capacitance difference between adjacent RX electrodes, and further more accurately determine which RX electrode is touched.

[0161] The difference between each RX channel and other adjacent channels enters the second-stage operational amplifier module PGA, which performs secondary amplification on the adjacent difference results. Then, through the sample-and-hold device and analog-to-digital conversion buffer, it enters the analog-to-digital conversion module ADC to output the digital signal matrix of the difference results of each RX channel. Based on the value of each element in the digital signal matrix, the coordinates of the corresponding touch location can be determined.

[0162] The use of the embodiments of the present application enables multi-channel adjacent differential detection. Specifically, during adjacent differential detection, the adjacent differential detection result can be obtained by subtracting the conversion results between adjacent channels. Furthermore, since switches K1 and K2 are closed simultaneously, the two signal lines form a differential signal line. When display interference noise is present, the display interference noise will be simultaneously coupled to these two differential signal lines. When adjacent differentials are performed between adjacent RX channels, this display interference noise is common-mode noise and will be completely offset, thereby reducing the interference of display interference on the target differential result and further improving the output result accuracy of the touch signal-to-noise ratio enhancement circuit.

[0163] In this embodiment of the present application, when both the first control switch K1 and the second control switch K2 between each RX channel are open, the capacitive touch detection between each RX channel is single-channel touch detection, rather than differential detection. This embodiment of the present application allows for flexible selection of touch detection methods by controlling whether the first control switch K1 and the second control switch K2 between each RX channel are closed simultaneously.

[0164] Based on the principle of adjacent channel differential detection, the output results of each channel need to be continuously calculated RX(i+1)-RX(i). This requires a large amount of calculation and the algorithm processing is relatively complicated. In order to save the complexity of the algorithm processing, in some embodiments, the algorithm processing complexity is reduced by reducing the circuit of the reference channel differential detection. As shown in Figure 11, the reference channel includes: a first bias resistor Rb1, a first-stage inverting input resistor R12, and a first-stage operational amplifier module; wherein the first-stage operational amplifier module is a non-inverting amplifier module,

[0165] A first end of the first bias resistor Rb1 is connected to a preset voltage VCMI, a second end of the first bias resistor Rb1 is connected to the touch sensor, and a second end of the first bias resistor Rb1 is connected to the non-inverting input terminal (+) of the first-stage operational amplifier module;

[0166] A first end of the first-stage inverting input resistor R12 is connected to the inverting input terminal (-) of the first-stage operational amplifier module, and a second end of the first-stage inverting input resistor R12 is connected to a preset voltage VCMI.

[0167] On this basis, as an implementation method, the touch signal-to-noise ratio enhancement circuit for the case of differential detection with subtracted reference channels in the embodiment of the present application can be shown in FIG11 :

[0168] In addition to the preset voltage, first bias resistor Rb1, first-stage operational module, filter, sample-and-hold, and possible second-stage operational amplifier module included in each RX channel, the second-stage non-inverting input resistors in the touch signal-to-noise ratio enhancement circuit corresponding to each RX electrode of the differential detection of the subtracted reference channel include two second-stage non-inverting input resistors (R21, R23) and two second-stage inverting input resistors (R22, R24).

[0169] The first-stage operational amplifier module is a non-inverting amplifier module composed of the first-stage operational amplifier, the first feedback resistor Rf1, and the first feedback capacitor Cf1 as shown in the dotted box in Figure 11. Similarly, the first feedback resistor Rf1 and the first feedback capacitor Cf1 are connected in parallel to the negative feedback circuit of the first-stage operational amplifier.

[0170] The second-stage operational amplifier module is also selected according to the gain of the first-stage operational amplifier module. If the second-stage operational amplifier module is not required, the second-stage non-inverting input resistor and the second-stage inverting input resistor are directly connected to the filter.

[0171] As a connection method, the connection relationship of each component in the capacitive touch screen signal-to-noise ratio circuit in the case of subtracted reference channel differential detection is shown in Figure 11:

[0172] The first end of the first-second-stage non-inverting input resistor R21 in the i-th RX channel is connected to the non-inverting output terminal of the first-stage operational amplifier module, and the second end of the first-second-stage non-inverting input resistor R21 is connected to the second end of the second-second-stage non-inverting input resistor R23 of the i-th RX channel and the non-inverting input terminal (+) of the second-stage operational amplifier module of the i-th channel.

[0173] The first end of the second second-stage non-inverting input resistor R23 of the i-th RX channel and the first ends of the second second-stage non-inverting input resistors R23 of other RX channels are connected to the inverting output end of the reference channel.

[0174] The first end of the first-second-stage inverting input resistor R22 of the i-th RX channel is connected to the inverting output end of the first-stage operational amplifier module, and the second end of the first-second-stage inverting input resistor R22 is connected to the second end of the second-second-stage inverting input resistor R24 ​​of the i-th RX channel and the inverting input end (-) of the second-stage operational amplifier of the i-th channel.

[0175] The first end of the second second-stage inverting input resistor R24 ​​of the i-th RX channel is connected to the first end of the second second-stage inverting input resistor R24 ​​of each RX channel and the non-inverting output end of the reference channel.

[0176] The non-inverting output terminal of the i-th RX channel is subtracted from the inverting output terminal of the reference channel, and the inverting output terminal of the i-th RX channel is subtracted from the non-inverting output terminal of the reference channel to obtain the target differential result.

[0177] Specifically, the reference channel is a touch signal-to-noise ratio enhancement circuit corresponding to a reference electrode, wherein the reference electrode may be an Rx electrode, which may be a target channel selected from RX0 to RXn, or an external electrode, such as a preset test point around a capacitive screen, or a cathode plate.

[0178] If adjacent differential detection determines whether a touch exists based on the difference between the coupling capacitances of adjacent channels, then fixed channel-minus or reference channel-minus differential detection determines whether a touch exists in each RX channel based on detecting the difference between the coupling capacitance of each RX channel and the coupling capacitance of the fixed channel. Based on this, in an embodiment of the present application, each RX channel subtracts the in-phase output of the first-stage operational amplifier module from the inverted output of the reference channel, and then subtracts the inverted output of the first-stage operational amplifier module from the in-phase output of the reference channel to determine whether the coupling capacitance of each RX channel has changed compared to the coupling capacitance of the reference channel. The subtraction results are then passed through a second-stage operational amplifier module, a filter, a sample-and-hold, an analog conversion buffer, and an analog-to-digital conversion module to output a digital signal matrix for each RX channel. Based on the values ​​of each element in the digital signal matrix, the area where the touch occurs can be determined.

[0179] In an embodiment of the present application, adjacent channels are not subtracted from each other. Instead, a reference channel RXm is introduced. The output result of each channel itself can be obtained by subtracting the signal of RXm from the signal of each channel. That is, RX0-RXm, RX1-RXm... are used to achieve the effect of differential detection. In this way, each channel only needs to be subtracted from the reference channel to obtain its own result. The calculation process is simpler and the implementation difficulty is lower.

[0180] In some embodiments, whether a touch has occurred on each RX channel of the capacitive screen can be detected by means of mean-subtracted differential detection. Specifically, as an implementation method, the touch signal-to-noise ratio enhancement circuit under mean-subtracted differential detection provided in the embodiment of the present application can be as shown in FIG12. On the basis of each RX channel, it also includes a mean generation channel. The mean generation channel includes: a mean non-inverting input resistor RS1, a mean inverting input resistor RS2, a second-stage operational amplifier module PGA, a filter, and a sample and hold. The mean generation channel is used to collect the output results of each RX channel and calculate the average value of the output results.

[0181] Among them, for each RX channel, the second-stage non-inverting input resistor also includes the first second-stage non-inverting input resistor R21 and the second second-stage non-inverting input resistor R23, and the second-stage inverting input resistor also includes the first second-stage inverting input resistor R22 and the second second-stage inverting input resistor R24.

[0182] As shown in FIG12 , the circuit between each RX channel and the mean value generation channel includes: a first input resistor RA1 , a second input resistor RA2 , a first input capacitor CA1 , and a second input capacitor CA2 .

[0183] As shown in FIG12 , the connection relationship between the components in the touch signal-to-noise ratio enhancement circuit under mean-subtracted differential detection is as follows:

[0184] The second end of the mean non-inverting input resistor RS1 is connected to the non-inverting input terminal (+) of the second-stage operational amplifier module, the second end of the mean inverting input resistor RS2 is connected to the inverting input terminal (-) of the second-stage operational amplifier module, the output terminal of the second-stage operational amplifier module is connected to the input terminal of the filter, and the output terminal of the filter is connected to the input terminal of the sample and hold.

[0185] The first end of the first-second-stage non-inverting input resistor R21 in the i-th RX channel is connected to the non-inverting output end of the first-stage operational amplifier module of the i-th channel and the first end of the input first input resistor RA1, and the second end of the first-second-stage non-inverting input resistor R21 of the i-th RX channel is connected to the second end of the second-second-stage non-inverting input resistor R23 of the i-th RX channel and the non-inverting input end (+) of the second-stage operational amplifier module of the i-th RX channel.

[0186] The first end of the second second-stage non-inverting input resistor R23 of the i-th RX channel is connected to the first end of the second second-stage non-inverting input resistor R23 of each RX channel and the inverting output end (-) of the second-stage operational amplifier module of the mean generation channel.

[0187] The first end of the first and second stage inverting input resistors R22 of the i-th RX channel are connected to the inverting output end of the first stage operational amplifier module of the i-th channel and the first end of the second input resistor RA2; the second end of the first and second stage inverting input resistors R22 of the i-th RX channel are connected to the second end of the second stage inverting input resistor R24 ​​of the i-th RX channel and the inverting input end (-) of the second stage operational amplifier of the i-th RX channel.

[0188] The first end of the second second-stage inverting input resistor R24 ​​of the i-th RX channel is connected to the first end of the second second-stage inverting input resistor R24 ​​of each RX channel and the non-inverting output end (+) of the second-stage operational amplifier module of the mean generation channel.

[0189] A second end of the first input resistor RA1 is connected to a first end of the average non-inverting input resistor RS1 and a first end of the first input capacitor CA1 ; a second end of the first input capacitor CA1 is grounded.

[0190] The second end of the second input resistor RA2 is connected to the first end of the average inverting input resistor RS2 and the first end of the second input capacitor CA2; the second end of the second input capacitor CA2 is grounded.

[0191] The non-inverting output of the i-th RX channel is subtracted from the inverting output of the mean generation channel, and the inverting output of the i-th RX channel is subtracted from the non-inverting output of the mean generation channel to obtain the target differential result.

[0192] The mean generation channel acts as an adder circuit, summing the output values ​​of all channels and then dividing the sum by the number of channels using input resistor RA to set the gain to produce a mean output value. The first and second input capacitors CA1 and CA2 added to the mean generation channel circuit are used to filter out high-frequency interference from the average signal.

[0193] Similar to adjacent differential detection and reference channel differential detection, in an embodiment of the present application, after the in-phase output and inverting output of each RX channel are input to the second-stage operational amplifier module of the mean generation channel, average calculation is performed to output the in-phase output result average and inverting output result average of each RX channel. Then, the in-phase output result average and inverting output result average are subtracted from the in-phase output result and inverting output result of each RX channel. Specifically, the in-phase output result of each RX channel is subtracted from the inverting output result average of the mean generation channel, and the inverting output result of each RX channel is subtracted from the in-phase output result average of the mean generation channel to obtain the difference between the coupling capacitance of each RX channel and the coupling capacitance change average of each RX channel, and determine which specific RX channel has been touched.

[0194] In the embodiment of the present application, the output results of all RX channels are collected by the mean generation channel and the average value is obtained. Then, when outputting, the output result of each RX channel is subtracted from the average value. This eliminates the need for differential restoration and effectively reduces the problem of noise accumulation caused by the introduction of white noise during the differential restoration process.

[0195] In addition, compared with the touch signal-to-noise ratio enhancement circuit of adjacent differential detection, the touch signal-to-noise ratio enhancement circuit of mean-subtracted channel differential detection has a module output method similar to the output method of single-ended signals in circuit engineering implementation. The wiring on the circuit board does not need to strictly follow a fixed line sequence, saving design and processing costs.

[0196] In a second aspect, the present application further proposes a capacitive screen, which includes the above-mentioned touch signal-to-noise ratio increasing circuit.

[0197] Thirdly, this application also proposes a chip that includes the aforementioned touch signal-to-noise ratio enhancement circuit. This chip (also known as an integrated circuit, IC) can be, but is not limited to, a SOC (System on Chip) chip or a SIP (System in Package) chip. This chip, through its internal touch signal-to-noise ratio enhancement circuit, effectively addresses the issue of reduced signal-to-noise ratio associated with increasing capacitive touch screen size.

[0198] Specifically, the touch signal-to-noise ratio enhancement circuit is connected to each RX channel of the capacitive touch screen through the pins of the chip. For the case of single-ended RX output, the touch signal-to-noise ratio enhancement circuit after each RX channel can be the same or different. For the case of differential RX output, a flexible selection can be made based on the three embodiments of differential detection, which is not strictly limited in this application.

[0199] Among them, the touch signal-to-noise ratio enhancement circuit of the voltage amplification type with high impedance input, as shown in the measured SNR curve results in Figure 13, shows that when the capacitive screen size increases, the touch signal-to-noise ratio enhancement circuit provided by this application is a new solution, and the measured SNR obtained is better than the measured SNR of the original current amplification solution. Specifically, it can be clearly seen from the following formula that the capacitive screen signal-to-noise ratio provided by this application is better than the traditional solution:

[0200] Combined with the circuit diagram shown in Figure 1, it can be deduced through circuit theory that the signal gain of the original solution satisfies the following formula 1): Signal Gain≈sC M R f ···Formula 1)

[0201] Where s is the signal, C in the formula M is the capacitance of the input capacitor, R f is the resistance of the feedback resistor.

[0202] The noise gain of the original solution satisfies the following formula 2): Noise Gain≈1+sC r R f ···Formula 2)

[0203] Among them, C in the formula r is the capacitance of the input capacitor, R f is the resistance of the feedback resistor.

[0204] According to Formula 1) and Formula 2), the noise gain and signal gain are positively correlated with the resistance of the feedback resistor and the capacitance of the input capacitor. The greater the change in the capacitance of the input capacitor, the greater the noise gain, and the lower the signal-to-noise ratio.

[0205] According to the touch signal-to-noise ratio increasing circuit shown in FIG2 provided by the present application, the signal gain of the new solution can be calculated through circuit theory to satisfy the following formula 3): Signal Gain≈(1+R f / RG1)(s C M R b / 1+s C r R b ) ···Formula 3)

[0206] Where s is the signal, C M is the capacitance of the input capacitor, R f is the resistance of the feedback resistor, R b is the resistance of the first bias resistor, and RG1 is the resistance of the first ground resistor.

[0207] The noise gain of the new solution satisfies the following formula 4): Noise Gain≈1+R f / RG1 ···Formula 4)

[0208] Equations 3) and 4) show that the noise gain of the new solution is independent of the input capacitance. Therefore, changes in input capacitance do not affect the noise gain, thereby preventing noise introduction and reducing noise interference. Furthermore, the noise gain is positively correlated only with the ratio of the feedback resistor to the ground resistor. By selecting appropriate ground and feedback resistor values, the noise gain can be controlled.

[0209] By selecting the embodiment of the present application, the built-in signal-to-noise ratio enhancement circuit of the capacitive screen can be flexibly selected according to actual needs, thereby reducing display interference and common-mode interference, and improving the signal response effect and display effect of the capacitive screen.

[0210] Fourthly, this application also proposes an electronic device including a touch signal-to-noise ratio (SNR) enhancement circuit. Specifically, the electronic device includes a device body and a chip as described above, located within the device body. The electronic device may be, but is not limited to, any electronic device including a display screen, such as a smart TV, monitor, mobile phone, or smart tablet. By implementing the touch SNR enhancement circuit within the electronic device, the electronic device can effectively address the issue of reduced SNR associated with increasing capacitive screen size.

[0211] The above is only a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application has been disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present application. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A touch signal-to-noise ratio increasing circuit, characterized in that, the touch signal-to-noise ratio increasing circuit includes: a first bias resistor, a first-stage inverting input resistor, and a first-stage operational amplifier module; wherein, the first-stage operational amplifier module is a non-inverting amplifier module; a first end of the first bias resistor is connected to a preset voltage, a second end of the first bias resistor is connected to a touch sensor, and the second end of the first bias resistor is connected to the non-inverting input terminal of the first-stage operational amplifier module; if the touch signal-to-noise ratio increasing circuit is powered by a single power supply, a first end of the first-stage inverting input resistor is connected to the inverting input terminal of the first-stage operational amplifier module, and a second end of the first-stage inverting input resistor is grounded; or, if the touch signal-to-noise ratio increasing circuit is powered by a dual power supply, a first end of the first-stage inverting input resistor is connected to the inverting input terminal of the first-stage operational amplifier module, and a second end of the first-stage inverting input resistor is connected to the preset voltage.

2. The touch signal-to-noise ratio increasing circuit according to claim 1, characterized in that, the touch signal-to-noise ratio increasing circuit further includes: a first bias capacitor, wherein: a first end of the first bias capacitor is connected to the preset voltage, and a second end of the first bias capacitor is connected to the non-inverting input terminal of the first-stage operational amplifier module.

3. The touch signal-to-noise ratio increasing circuit according to claim 1, characterized in that, the touch signal-to-noise ratio increasing circuit further includes: a filter, wherein: the filter is connected to the output terminal of the first-stage operational amplifier module and is configured to output a target filtering result based on the output result of the first-stage operational amplifier module.

4. The touch signal-to-noise ratio increasing circuit according to claim 3, characterized in that, the touch signal-to-noise ratio increasing circuit further includes: an analog-to-digital conversion module, wherein: the analog-to-digital conversion module is connected to the output terminal of the filter and is configured to convert the target filtering result into a target digital signal.

5. The touch signal-to-noise ratio increasing circuit according to claim 1, characterized in that, the first-stage operational amplifier module is a buffer, and the touch signal-to-noise ratio increasing circuit further includes: a second-stage operational amplifier module, a second-stage non-inverting input resistor, and a second-stage inverting input resistor, wherein, an output terminal of the buffer is connected to a first end of the second-stage non-inverting input resistor, and a second end of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module; a first end of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module, and a second end of the second-stage inverting input resistor is grounded.

6. The touch signal-to-noise ratio increasing circuit according to claim 1, characterized in that, the first-stage operational amplifier module is a buffer, and the touch signal-to-noise ratio increasing circuit further includes: a second-stage operational amplifier module, a second-stage non-inverting input resistor, and a second-stage inverting input resistor, wherein: a non-inverting output terminal of the buffer is connected to a first end of the second-stage non-inverting input resistor, and a second end of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module; The inverting output terminal of the buffer is connected to the first end of the second-stage inverting input resistor, and the second end of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module.

7. The touch signal-to-noise ratio increasing circuit according to claim 1, wherein, the non-inverting amplification module includes: a non-inverting amplifier and a first-stage amplification feedback resistor, the first end of the first-stage amplification feedback resistor is connected to the output terminal of the non-inverting amplifier, and the second end of the first-stage amplification feedback resistor is connected to the non-inverting input terminal of the non-inverting amplifier.

8. The touch signal-to-noise ratio increasing circuit according to claim 7, wherein, the touch signal-to-noise ratio increasing circuit further includes: a second-stage operational amplifier module, a second-stage non-inverting input resistor, a second-stage inverting input resistor, and a filter, wherein: the first end of the second-stage non-inverting input resistor is connected to the output terminal of the non-inverting amplification module, and the second end of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module; the first end of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module, and the second end of the second-stage inverting input resistor is grounded; the output terminal of the second-stage operational amplifier module is connected to the filter.

9. The touch signal-to-noise ratio increasing circuit according to claim 8, wherein, the gain of the non-inverting amplification module is less than a preset gain threshold.

10. The touch signal-to-noise ratio increasing circuit according to claim 1, wherein, the touch signal-to-noise ratio increasing circuit further includes: a second-stage non-inverting input resistor, a second-stage inverting input resistor, and a second-stage operational amplifier module, wherein: the non-inverting output terminal of the first-stage operational amplifier module is connected to the first end of the second-stage non-inverting input resistor, and the second end of the second-stage non-inverting input resistor is connected to the non-inverting input terminal of the second-stage operational amplifier module; the inverting output terminal of the first-stage operational amplifier module is connected to the first end of the second-stage inverting input resistor, and the second end of the second-stage inverting input resistor is connected to the inverting input terminal of the second-stage operational amplifier module.

11. The touch signal-to-noise ratio increasing circuit according to claim 10, wherein, the touch signal-to-noise ratio increasing circuit further includes: a first control switch, a second control switch, a first differential connection resistor, and a second differential connection resistor, wherein: the first end of the first control switch is connected to the second end of the second-stage non-inverting input resistor of the i-th RX channel, the second end of the first control switch is connected to the first end of the first differential connection resistor, and the second end of the first differential connection resistor is connected to the second end of the second-stage inverting input resistor of the (i + 1)-th RX channel; the first end of the second control switch is connected to the second end of the second-stage inverting input resistor of the i-th RX channel, the second end of the second control switch is connected to the first end of the second differential connection resistor, and the second end of the second differential connection resistor is connected to the second end of the second-stage non-inverting input resistor of the (i + 1)-th RX channel; Wherein, the i-th RX channel and the (i + 1)-th RX channel are two adjacent channels among the multiple RX channels; the RX channel is a touch signal-to-noise ratio increasing circuit corresponding to the RX electrode.

12. The touch signal-to-noise ratio increasing circuit according to claim 11, characterized in that when the first control switch is closed, the in-phase output terminal in the i-th RX channel and the anti-phase output terminal in the (i + 1)-th RX channel are adjacent and subtracted; when the second control switch is closed, the anti-phase output terminal in the i-th RX channel and the in-phase output terminal in the (i + 1)-th RX channel are adjacent and subtracted to obtain a target differential result.

13. The touch signal-to-noise ratio increasing circuit according to claim 10, characterized in that the touch sensor further includes a reference channel; the reference channel includes: a first bias resistor, a first-stage inverting input resistor, and a first-stage operational amplifier module; wherein, the first-stage operational amplifier module is a non-inverting amplifier module, the first end of the first bias resistor is connected to a preset voltage, the second end of the first bias resistor is connected to the touch sensor, and the second end of the first bias resistor is connected to the non-inverting input terminal of the first-stage operational amplifier module; the first end of the first-stage inverting input resistor is connected to the inverting input terminal of the first-stage operational amplifier module, and the second end of the first-stage inverting input resistor is connected to the preset voltage.

14. The touch signal-to-noise ratio increasing circuit according to claim 13, characterized in that the second-stage non-inverting input resistors include: a first second-stage non-inverting input resistor and a second second-stage non-inverting input resistor, and the second-stage inverting input resistors include: a first second-stage inverting input resistor and a second second-stage inverting input resistor, where: the first end of the first second-stage non-inverting input resistor in the i-th RX channel is connected to the non-inverting output terminal of the first-stage operational amplifier module, and the second end of the first second-stage non-inverting input resistor is connected to the second end of the second second-stage non-inverting input resistor in the i-th RX channel and the non-inverting input terminal of the second-stage operational amplifier module in the i-th RX channel; the first end of the second second-stage non-inverting input resistor in the i-th RX channel is connected to the first ends of the second second-stage non-inverting input resistors in each RX channel and the inverting output terminal of the reference channel; the first end of the first second-stage inverting input resistor in the i-th RX channel is connected to the inverting output terminal of the first-stage operational amplifier module, and the second end of the first second-stage inverting input resistor is connected to the second end of the second second-stage inverting input resistor in the i-th RX channel and the inverting input terminal of the second-stage operational amplifier in the i-th RX channel; the first end of the second second-stage inverting input resistor in the i-th RX channel is connected to the first ends of the second second-stage inverting input resistors in each RX channel and the non-inverting output terminal in the reference channel; The in-phase output terminal of the i-th RX channel is subtracted from the anti-phase output terminal of the reference channel, and the anti-phase output terminal of the i-th RX channel is subtracted from the in-phase output terminal of the reference channel to obtain a target differential result; the RX channel is a touch signal-to-noise ratio increasing circuit corresponding to an RX electrode, and the reference channel is a touch signal-to-noise ratio increasing circuit corresponding to a reference electrode.

15. The touch signal-to-noise ratio increasing circuit according to claim 10, wherein, the touch signal-to-noise ratio increasing circuit further includes a mean value generating channel; the mean value generating channel includes: a mean value in-phase input resistor, a mean value anti-phase input resistor, a second-stage operational amplifier module, a filter, and a sample and hold circuit, and the mean value generating channel is used to collect the average value of the output results of each RX channel.

16. The touch signal-to-noise ratio increasing circuit according to claim 15, wherein, the second-stage in-phase input resistor includes: a first second-stage in-phase input resistor and a second second-stage in-phase input resistor, and the second-stage anti-phase input resistor includes: a first second-stage anti-phase input resistor and a second second-stage anti-phase input resistor; the second end of the mean value in-phase input resistor is connected to the in-phase input terminal of the second-stage operational amplifier module, the second end of the mean value anti-phase input resistor is connected to the anti-phase input terminal of the second-stage operational amplifier module, the output terminal of the second-stage operational amplifier module is connected to the input terminal of the filter, and the output terminal of the filter is connected to the input terminal of the sample and hold circuit; between each RX channel and the mean value generating channel, there are included: a first input resistor, a second input resistor, a first input capacitor, and a second input capacitor, where: the first end of the first second-stage in-phase input resistor in the i-th RX channel is connected to the in-phase output terminal of the first-stage operational amplifier module in the i-th path and the first end of the input first input resistor, and the second end of the first second-stage in-phase input resistor in the i-th RX channel is connected to the second end of the second second-stage in-phase input resistor in the i-th RX channel and the in-phase input terminal of the second-stage operational amplifier module in the i-th RX channel; the first end of the second second-stage in-phase input resistor in the i-th RX channel is connected to the first ends of the second second-stage in-phase input resistors of each RX channel and the anti-phase output terminal of the second-stage operational amplifier module of the mean value generating channel; the first end of the first second-stage anti-phase input resistor in the i-th RX channel is connected to the anti-phase output terminal of the first-stage operational amplifier module in the i-th path and the first end of the second input resistor; the second end of the first second-stage anti-phase input resistor in the i-th RX channel is connected to the second end of the second second-stage anti-phase input resistor in the i-th RX channel and the anti-phase input terminal of the second-stage operational amplifier in the i-th RX channel; the first end of the second second-stage anti-phase input resistor in the i-th RX channel is connected to the first ends of the second second-stage anti-phase input resistors of each RX channel and the in-phase output terminal of the second-stage operational amplifier module of the mean value generating channel; The second terminal of the first input resistor is connected to the first terminal of the mean in-phase input resistor and the first terminal of the first input capacitor; the second terminal of the first input capacitor is grounded; The second terminal of the second input resistor is connected to the first terminal of the mean anti-phase input resistor and the first terminal of the second input capacitor; the second terminal of the second input capacitor is grounded; The in-phase output terminal of the i-th RX channel is subtracted from the anti-phase output terminal of the mean generation channel, and the anti-phase output terminal of the i-th RX channel is subtracted from the in-phase output terminal of the mean generation channel to obtain a target differential result.

17. A capacitive touch screen, Characterized in that, The capacitive touch screen includes the touch signal-to-noise ratio increasing circuit according to any one of claims 1 to 16.

18. A chip, Characterized in that, The chip includes the touch signal-to-noise ratio increasing circuit according to any one of claims 1 to 16.

19. An electronic device, Characterized in that, The electronic device includes the chip according to claim 16.

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