Common-mode interference suppression circuit and touch sensing system

Abstract

The invention relates to the technical field of touch sensing, and discloses a common-mode interference suppression circuit and a touch sensing system.The common-mode interference suppression circuit comprises a Gm module, a feedback module and an integrating capacitor; the first input end of the Gm module is used for receiving a sensing signal superposed with an interference signal, the sensing signal represents the state of the system to be detected, the second input end is connected with a reference voltage, and the first output end is used for generating a first current according to the voltage difference between the first input end and the second input end; the second output end outputs a second current in proportion to the first current; the feedback module is connected with the first output end and used for generating feedback voltage according to the first current and feeding back the feedback voltage to the second input end, so that the first output end adjusts the first current according to the feedback voltage to suppress interference signals; the integrating capacitor is connected with the second output end. According to the invention, common-mode interference can be directly suppressed at the analog front end, circuit saturation is avoided, and the accuracy and stability of touch detection are improved.

Description

Technical Field

[0001] This invention relates to the field of touch sensing technology, and in particular to a common-mode interference suppression circuit and a touch sensing system. Background Technology

[0002] With the rapid development of smart terminal devices, capacitive touch sensing technology has been widely used in various electronic devices such as smartphones, tablets, and automotive displays. Capacitive touch sensing detects touch by detecting changes in capacitance caused by a human finger approaching or touching the device. Among these technologies, mutual capacitance detection has become the mainstream solution due to its excellent anti-interference performance and multi-touch capability.

[0003] In practical applications, touch sensing systems face complex electromagnetic environment challenges. Electromagnetic radiation from interference sources such as LCD screens, switching power supplies, and chargers couples into the touch sensing circuit through parasitic capacitance, forming common-mode interference. This common-mode interference is characterized by large amplitude, wide spectrum, and strong time-varying characteristics; its amplitude is often much greater than the effective signal caused by touch, seriously affecting the accuracy and stability of touch detection. Especially in highly integrated modern electronic devices, the physical distance between the touch sensing circuit and the display driving circuit is getting closer and closer, making the common-mode interference problem increasingly serious.

[0004] Existing anti-interference technologies mainly employ methods such as shielding design, filter design, and digital filtering. Shielding design reduces parasitic capacitive coupling by placing a shielding layer around the sensing electrodes, but this increases system complexity and cost, and complete shielding is difficult to achieve in portable devices. While filter design can suppress interference in specific frequency bands, its effectiveness is limited when facing wide-spectrum, time-varying display noise, and it reduces the system's response speed. Digital filtering methods remove interference signals in back-end processing, but when the common-mode interference amplitude is too large, the front-end analog circuitry is prone to saturation, leading to the loss of effective signals, and the back-end digital filtering cannot recover the submerged signals.

[0005] Therefore, there is an urgent need to propose a common-mode interference suppression circuit and a touch sensing system to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to propose a common-mode interference suppression circuit and a touch sensing system that can directly suppress common-mode interference at the analog front end, avoid circuit saturation, and improve the accuracy and stability of touch detection.

[0007] To solve the above-mentioned technical problems, the present invention provides a common-mode interference suppression circuit, including a Gm module, a feedback module and an integrating capacitor; The first input terminal of the Gm module is used to receive a sensing signal superimposed with an interference signal, the sensing signal representing the state of the system under test. The second input terminal is connected to a reference voltage. The first output terminal is used to generate a first current based on the voltage difference between the first input terminal and the second input terminal. The second output terminal outputs a second current proportional to the first current. The feedback module is connected to the first output terminal and is used to generate a feedback voltage based on the first current and feed the feedback voltage back to the second input terminal, so that the first output terminal adjusts the first current based on the feedback voltage to suppress the interference signal. The integrating capacitor is connected to the second output terminal and is used to integrate the second current to generate a sensing output signal.

[0008] Furthermore, there are multiple Gm modules and integrating capacitors, with each Gm module and an integrating capacitor forming a sensing channel. The first output terminals of the plurality of Gm modules are connected to the feedback module; the feedback module is used to generate the feedback voltage based on the first current of the plurality of first output terminals and feed the feedback voltage back to the second input terminals of the plurality of Gm modules.

[0009] Furthermore, when an interference signal is coupled to the first input terminal of the plurality of Gm modules, the first current output from the first output terminal of the plurality of Gm modules is collected and flows through the feedback module to generate the feedback voltage; the feedback voltage is simultaneously fed back to the second input terminal of the plurality of Gm modules; through negative feedback, each Gm module adjusts the first current according to the feedback voltage, so that the feedback voltage follows the change of the interference voltage at the first input terminal, and suppresses the output of the interference signal at the second output terminal through the anti-phase cancellation effect.

[0010] Furthermore, the feedback module includes a feedback resistor and an amplifier; One end of the feedback resistor is connected to the first output terminal of the Gm module, and the other end is connected to the output terminal of the amplifier; the inverting input terminal of the amplifier is connected to the output terminal of the amplifier.

[0011] Furthermore, the Gm module includes an operational transconductance amplifier, a first current mirror unit, and a second current mirror unit; The operational transconductance amplifier is used to convert the voltage difference between the first input terminal and the second input terminal into a reference current. The first current mirror unit is used to mirror the reference current and generate a first current, and the second current mirror unit is used to mirror the reference current and generate a second current. The reference current, the first current and the second current are positively correlated.

[0012] Furthermore, the operational transconductance amplifier includes an operational amplifier, a DC bias unit, a first PMOS transistor, and a first NMOS transistor; the non-inverting input terminal of the operational amplifier serves as the first input terminal, and the inverting input terminal serves as the second input terminal; the DC bias unit is connected to the output terminal of the operational amplifier and is used to generate a first bias voltage and a second bias voltage; the DC bias unit is connected to the gate of the first PMOS transistor and the gate of the first NMOS transistor, the gate of the first PMOS transistor receives the first bias voltage, and the gate of the first NMOS transistor receives the second bias voltage; the source of the first PMOS transistor is connected to the power supply voltage, and the drain of the first PMOS transistor is connected to the drain of the first NMOS transistor, serving as the current output terminal of the operational transconductance amplifier and connected to the non-inverting input terminal of the operational amplifier; the source of the first NMOS transistor is grounded.

[0013] Furthermore, the first current mirror unit includes a second PMOS transistor and a second NMOS transistor; the second current mirror unit includes a third PMOS transistor and a third NMOS transistor; the gates of the second PMOS transistor, the second NMOS transistor, the third PMOS transistor, and the third NMOS transistor are all connected to the DC bias unit, respectively receiving the first bias voltage or the second bias voltage; the sources of the second PMOS transistor and the third PMOS transistor are both connected to the power supply voltage, the drain of the second PMOS transistor is connected to the drain of the second NMOS transistor, forming the output terminal of the first current mirror unit; the drain of the third PMOS transistor is connected to the drain of the third NMOS transistor, forming the output terminal of the second current mirror unit; the sources of the second NMOS transistor and the third NMOS transistor are both grounded.

[0014] Furthermore, the present invention also proposes a touch sensing system, including the common-mode interference suppression circuit as described above, and a sensing electrode; the sensing electrode is connected to the first input terminal of the Gm module in the common-mode interference suppression circuit, and is used to transmit a sensing signal to the first input terminal, the sensing signal representing the state of the system under test; external interference signals are coupled to the first input terminal through the sensing electrode.

[0015] Furthermore, it also includes a quantization module and a data processing module; the quantization module is used to convert the sensed output signal into a digital signal; the data processing module is used to process the digital signal.

[0016] Furthermore, the number of sensing electrodes corresponds to the number of sensing channels in the common-mode interference suppression circuit.

[0017] Through the above technical solution, the present invention has the following beneficial effects: By setting a feedback module at the first output of the Gm module, the first current is converted into a feedback voltage and fed back to the second input, forming a negative feedback loop. This directly suppresses common-mode interference signals at the analog front end, preventing interference signals from entering subsequent integration and quantization circuits and causing circuit saturation. Simultaneously, by outputting a second current proportional to the first current at the second output and integrating it with the integrating capacitor, effective sensing signals can be retained while suppressing interference. This improves the accuracy and stability of touch detection and reduces the amount of data signal processing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of a common-mode interference suppression circuit in one embodiment of the present invention; Figure 2 This is a schematic diagram of the Gm module in a common-mode interference suppression circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the overall structure of the touch sensing system in one embodiment of the present invention when it is a single sensing channel. Detailed Implementation

[0019] Based on the teachings of this specification, those skilled in the art can form new technical solutions through cross-combination of different implementation methods without creating technical contradictions. Such variations should all be considered to fall within the protection scope of this invention.

[0020] The common-mode interference suppression circuit and touch sensing system of the present invention will now be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0021] The invention is described more specifically by way of example in the following paragraphs with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0022] like Figures 1-3 As shown in the figure, an embodiment of the present invention proposes a common-mode interference suppression circuit, including a Gm module, a feedback module, and an integrating capacitor C.

[0023] Specifically, the first input terminal InA of the Gm module is used to receive a sensing signal Vrx superimposed with an interference signal. The sensing signal Vrx represents the state of the system under test. The second input terminal InB is connected to a reference voltage. The first output terminal OutA is used to generate a first current Iouta based on the voltage difference between the first input terminal InA and the second input terminal InB. The second output terminal OutB outputs a second current Ioutb that is proportional to the first current Iouta. The feedback module is connected to the first output terminal OutA and is used to generate a feedback voltage Vref based on the first current Iouta. The feedback voltage Vref is fed back to the second input terminal InB, so that the first output terminal OutA adjusts the first current Iouta according to the feedback voltage Vref to suppress the interference signal. The integrating capacitor C is connected to the second output terminal OutB and is used to integrate the second current Ioutb to generate a sensing output signal.

[0024] In this embodiment, for example in a touch sensing application, the sensing signal Vrx characterizes the change in touch capacitance. The second input terminal InB is connected to a reference voltage, which can be a fixed DC voltage or a voltage dynamically adjusted according to the system's operating state. Those skilled in the art will know that the reference voltage can be set according to actual needs, and the reference voltage also includes other voltage values ​​besides those in this embodiment. Furthermore, the ratio of the first current Iouta to the second current Ioutb can be 1:1, or it can be set to other ratios according to circuit design requirements, such as 1:2 or 1:0.5, thereby amplifying or reducing the current to adapt to different application scenarios. This embodiment, by dividing the output of the Gm module into two paths, enables negative feedback control for interference suppression at the first output terminal OutA, while simultaneously outputting the interference-suppressed sensing current at the second output terminal OutB, improving the circuit's anti-interference capability.

[0025] In one specific embodiment, when an interference signal is superimposed on the sensing signal Vrx and input to the first input terminal InA, the voltage at the first input terminal InA increases, leading to a greater voltage difference between the first input terminal InA and the second input terminal InB, thereby increasing the first current Iouta. The increased first current Iouta flows through the feedback module, generating a higher feedback voltage Vref. After the feedback voltage Vref is fed back to the second input terminal InB, the voltage difference between the first input terminal InA and the second input terminal InB decreases, thus suppressing the increase of the first current Iouta. This negative feedback mechanism can dynamically track and cancel the influence of interference signals, effectively improving the circuit's anti-interference performance.

[0026] In one embodiment, the capacitance value of the integrating capacitor C can be set according to the frequency characteristics of the sensing signal Vrx and the integration time. Those skilled in the art will understand that the capacitance value of the integrating capacitor C can be set according to actual needs. This embodiment, by integrating the second current Ioutb, can convert the current signal into a voltage signal, facilitating subsequent analog-to-digital conversion and digital signal processing. Simultaneously, the integration process can further filter out high-frequency noise and improve signal quality.

[0027] In this embodiment, there are multiple Gm modules and integrating capacitors C, with each Gm module and an integrating capacitor C forming a sensing channel.

[0028] Specifically, the first output terminals OutA of the multiple Gm modules are connected to the feedback module; the feedback module is used to generate the feedback voltage Vref based on the first current Iouta of the multiple first output terminals OutA, and feed the feedback voltage Vref back to the second input terminal InB of the multiple Gm modules.

[0029] In touch sensing systems, multiple sensing channels are typically required to simultaneously detect different locations on the touchscreen. This embodiment employs a structure where multiple Gm modules share a single feedback module. By pooling the first current Iouta from multiple channels, common-mode interference signal characteristics can be effectively extracted, achieving effective suppression of common-mode interference. Since all channels share the same feedback voltage Vref, when common-mode interference signals are simultaneously coupled to multiple channels, the interference suppression effect of each channel remains consistent, improving the overall system performance stability. Those skilled in the art will understand that the number of Gm modules and integrating capacitor C can be set according to actual needs, for example, it can be set to 8, 16, 32 or more, and other configurations besides those in this embodiment are also included.

[0030] Preferably, when an interference signal is coupled to the first input terminal InA of the multiple Gm modules, the first current Iouta output from the first output terminal OutA of the multiple Gm modules is collected and flows through the feedback module to generate the feedback voltage Vref. The feedback voltage Vref is simultaneously fed back to the second input terminal InB of the multiple Gm modules. Through negative feedback, each Gm module adjusts the first current Iouta according to the feedback voltage Vref, so that the feedback voltage Vref follows the change of the interference voltage at the first input terminal InA, and suppresses the output of the interference signal at the second output terminal OutB through anti-phase cancellation. In a specific example, assuming that N sensing channels are simultaneously subjected to common-mode interference, and the increment of the first current Iouta generated by the interference in each channel is ΔI, then the total current increment flowing through the feedback module after the N channels are collected is N×ΔI, and the increment of the generated feedback voltage Vref is also increased by N times accordingly, thereby achieving a stronger interference suppression effect. This multi-channel shared feedback structure can utilize the common-mode nature of the interference signal to superimpose the interference signals of each channel and suppress them uniformly, improving the suppression efficiency and effect. Meanwhile, since the feedback voltage Vref acts on all channels simultaneously, the suppression characteristics of each channel remain consistent, avoiding performance differences caused by different suppression capabilities between channels.

[0031] In one embodiment, the feedback module includes a feedback resistor Res and an amplifier Amp. Specifically, one end of the feedback resistor Res is connected to the first output terminal OutA of the Gm module, and the other end is connected to the output terminal of the amplifier Amp; the inverting input terminal of the amplifier Amp is connected to the output terminal of the amplifier Amp.

[0032] In one embodiment, such as Figure 2 As shown, the Gm module includes an operational transconductance amplifier, a first current Iouta mirror unit, and a second current Ioutb mirror unit. Specifically, the operational transconductance amplifier is used to convert the voltage difference between the first input terminal InA and the second input terminal InB into a reference current. The first current Iouta mirror unit is used to mirror the reference current and generate a first current Iouta, and the second current Ioutb mirror unit is used to mirror the reference current and generate a second current Ioutb; wherein, the reference current, the first current Iouta, and the second current Ioutb are positively correlated.

[0033] In one embodiment, the operational transconductance amplifier includes an operational amplifier Cmp, a DC bias unit (DCshift), a first PMOS transistor MP0, and a first NMOS transistor MN0. Specifically, the non-inverting input terminal of the operational amplifier Cmp serves as the first input terminal InA, and the inverting input terminal serves as the second input terminal InB; the DC bias unit is connected to the output terminal of the operational amplifier Cmp and is used to generate a first bias voltage Vbp and a second bias voltage Vbn; the DC bias unit is connected to the gate of the first PMOS transistor MP0 and the gate of the first NMOS transistor MN0, the gate of the first PMOS transistor MP0 receives the first bias voltage Vbp, and the gate of the first NMOS transistor MN0 receives the second bias voltage Vbn; the source of the first PMOS transistor MP0 is connected to the power supply voltage, and the drain of the first PMOS transistor MP0 is connected to the drain of the first NMOS transistor MN0, serving as the current output terminal of the operational transconductance amplifier and connected to the non-inverting input terminal of the operational amplifier Cmp; the source of the first NMOS transistor MN0 is grounded.

[0034] In one embodiment, the first current Iouta mirror unit includes a second PMOS transistor MPA and a second NMOS transistor MNA; the second current Ioutb mirror unit includes a third PMOS transistor MPB and a third NMOS transistor MNB. Specifically, the gates of the second PMOS transistor MPA, the second NMOS transistor MNA, the third PMOS transistor MPB, and the third NMOS transistor MNB are all connected to the DC bias unit, receiving the first bias voltage Vbp or the second bias voltage Vbn respectively; the sources of the second PMOS transistor MPA and the third PMOS transistor MPB are both connected to the power supply voltage; the drain of the second PMOS transistor MPA is connected to the drain of the second NMOS transistor MNA, forming the output terminal of the first current Iouta mirror unit; the drain of the third PMOS transistor MPB is connected to the drain of the third NMOS transistor MNB, forming the output terminal of the second current Ioutb mirror unit; the sources of the second NMOS transistor MNA and the third NMOS transistor MNB are both grounded.

[0035] In this embodiment, the DC bias unit is used to appropriately shift the output voltage of the operational amplifier to provide bias voltage Vbp for MP0, MPA, and MPB, and bias voltage Vbn for MN0, MNA, and MNB. The drains of MP0 and MN0 are coupled together and coupled to the first input terminal InA of the operational amplifier.

[0036] Secondly, the operational amplifier Cmp, the DC bias unit, the first PMOS transistor MP0, and the first NMOS transistor MN0 together constitute the operational transconductance amplifier OTA, which converts the voltage difference between the input terminals InA and InB into a current Iout0. MPA and MNA mirror Iout0 to generate a current Iouta from the first output terminal OutA, and MPB and MNB mirror Iout0 to generate a current Ioutb from the second output terminal OutB. The currents Iout0, Iouta, and Ioutb have a mirror relationship and are positively correlated. The Ioutb output from the second output terminal OutB of the Gm module passes through the integrating capacitor C to form a Gm-C integrator, which converts the current into a voltage Vout.

[0037] In one embodiment, the output terminals OutA1, OutA2, ... OutAn of the n sensing channels CH1, CH2, ... CHn respectively output currents Iouta1, Iouta2, ... Ioutan, all coupled together and coupled to the first port of the feedback resistor Res. The second port of the feedback resistor Res is coupled to the output of the amplifier Amp, and the inverting input of the amplifier Amp is coupled to the output of the amplifier Amp. The first port of the feedback resistor Res is coupled to the second input terminal InB of all sensing channels CH1, CH2, ... CHn.

[0038] Preferably, the output terminals OutB1, OutB2, ... OutBn of the n sensing channels CH1, CH2, ... CHn output currents Ioutb1, Ioutb2, ... Ioutbn respectively, and are coupled to one end of the integrating capacitors C1, C2, ... Cn. The Gm module and the integrating capacitors C1, C2, ... Cn constitute a Gm-C integrating unit, which converts the currents Ioutb1, Ioutb2, ... Ioutbn into voltages Voutb1, Voutb2, ... Voutbn for subsequent quantization and signal processing.

[0039] In addition, this embodiment also proposes a touch sensing system, including the common-mode interference suppression circuit as described above, and a sensing electrode RX.

[0040] Specifically, the sensing electrode RX is connected to the first input terminal InA of the Gm module in the common-mode interference suppression circuit, and is used to transmit a sensing signal Vrx to the first input terminal InA. The sensing signal Vrx represents the state of the system under test. External interference signals are coupled to the first input terminal InA through the sensing electrode RX.

[0041] In this embodiment, the sensing electrode RX is used to receive the sensing signal Vrx. In touchscreen applications, an excitation signal is applied to the transmitting electrode TX, and a sensing current is generated through the mutual capacitance Cm coupling between the sensing electrode RX and the transmitting electrode TX. When a touch event occurs, the capacitive coupling relationship at the touch position changes, causing a corresponding change in the sensing current, thereby achieving touch detection. Simultaneously, external interference sources (such as chargers, displays, etc.) are coupled to the sensing electrode RX through parasitic capacitance Cp, generating a common-mode interference current. This common-mode interference current is superimposed on the sensing current and input together to the first input terminal InA of the Gm module. The common-mode interference suppression circuit in this embodiment can effectively suppress this common-mode interference, improving the accuracy and reliability of touch detection.

[0042] In a specific example, the capacitance value of the mutual capacitance Cm is typically a few picofarads to tens of picofarads, while the capacitance value of the parasitic capacitance Cp may reach hundreds of picofarads to several nanofarads. Therefore, the amplitude of the interference signal coupled by the parasitic capacitance Cp is often much greater than the effective touch signal. As those skilled in the art will know, the capacitance values ​​of the mutual capacitance Cm and the parasitic capacitance Cp can be set according to the actual touch screen structure and application scenario, and also include other capacitance values ​​besides those in this embodiment.

[0043] Furthermore, this embodiment also includes a quantization module and a data processing module. The quantization module is used to convert the sensed output signal into a digital signal, and the data processing module is used to process the digital signal.

[0044] The touch sensing system in this embodiment can fully realize the entire process from touch detection to digital signal output. After the sensing electrode RX detects the touch signal, it undergoes interference suppression and integration processing by the common-mode interference suppression circuit to output a high-quality sensing output signal. This signal is then converted into a digital signal by the quantization module, and finally processed by the data processing module through filtering, calibration, coordinate calculation, etc., to output the touch position information. By introducing a common-mode interference suppression circuit at the analog front end, this embodiment can improve the system's anti-interference capability, reduce the burden of subsequent digital processing, and improve the overall system performance.

[0045] Preferably, the number of sensing electrodes RX corresponds to the number of sensing channels in the common-mode interference suppression circuit. In touchscreen applications, multiple sensing electrodes RX are typically required to achieve precise positioning of the touch location, with each sensing electrode RX corresponding to one sensing channel. This embodiment, by configuring a corresponding number of sensing electrodes RX and sensing channels, can achieve full-area coverage detection of the touchscreen. For example, in an 8×16 touchscreen, 16 sensing electrodes RX and 16 sensing channels can be configured, with each sensing channel responsible for detecting a column of touch signals. Those skilled in the art will understand that the number of sensing electrodes RX and sensing channels can be set according to the actual touchscreen size and resolution requirements, and includes other configurations besides this embodiment. This embodiment, through a multi-channel parallel detection and shared feedback interference suppression structure, can effectively suppress common-mode interference while maintaining high detection speed, improving the accuracy and stability of touch detection.

[0046] In this embodiment, the effect on common-mode noise suppression is as follows: When there is no common-mode noise suppression, the noise Vnoise is coupled to the first input terminal of the Gm module through the parasitic capacitance Cp. The corresponding noise current will be generated through negative feedback, and the noise voltage Vnoise×Cp / C will be generated in the Gm module after being copied and output to the integrating capacitor C. When common-mode noise suppression is added, the generated noise current flows through the feedback resistor Res and is fed back to the second input terminal of the Gm module. At this time, the noise voltage generated on the integrating capacitor C is 1 / (gm×n×Res)×Vnoise×Cp / C, where gm is the transconductance coefficient of the Gm module, n is the number of channels connected to the feedback resistor Res, and Res represents the resistance value. By comparison, it can be seen that the noise is suppressed to 1 / (gm×n×Res) of the original. Under the same size touch signal, the SNR will be improved by nearly gm×n×Res. The total amount of signal entering the circuit (mainly common-mode signal and noise) will also be reduced to 1 / (gm×n×Res) of the original, which greatly reduces the amount and burden of data processing.

[0047] for Figure 3 A schematic diagram of a single-channel touch detection circuit, where Vref is... Figure 1 The reference voltage generated by each channel Iouta through the feedback resistor Res is sent to the subsequent ADC circuit for quantization and further digital information processing to determine whether a target object is approaching or being touched. By combining multiple channels, the movement trajectory, shape, gesture, etc. of the target object can be determined.

[0048] Therefore, this embodiment aims to solve the technical problems of low detection accuracy and poor stability of existing touch sensing systems under strong interference environments. The circuit in this embodiment achieves real-time detection and compensation suppression of common-mode interference at the input end, suppressing interference at its source and preventing large interference signals from entering subsequent integration and quantization processing circuits, thereby reducing the data processing burden and improving system processing efficiency. This embodiment can improve the signal-to-noise ratio of touch sensing systems under strong interference, improve the user touch experience, and provide an efficient and practical anti-interference solution for touch sensing technology in highly integrated, high-speed electronic devices, improving overall system performance and processing efficiency.

[0049] In summary, the common-mode interference suppression circuit and touch sensing system proposed in this invention have the following advantages: Effective suppression of common-mode interference: Through innovative active interference suppression technology, common-mode interference caused by display noise can be detected and compensated in real time, thereby improving anti-interference capabilities. Enhanced detection accuracy and stability: High-precision touch detection is maintained even in environments with strong interference, improving system stability.

[0050] Significantly improved signal-to-noise ratio: By suppressing common-mode interference at the input, the signal-to-noise ratio of the touch sensing system is effectively improved. Reduced data processing burden: Interference compensation is performed at the input, preventing large interference signals from entering the integration and quantization circuits, thus reducing the amount of data signal processing.

[0051] Improved system processing efficiency: Eliminating the need to process large data signals reduces the processing burden on subsequent circuits, thereby improving overall system efficiency; Enhanced user touch experience: By improving detection accuracy and stability, it provides users with a smoother and more accurate touch operation experience; Adaptable to highly integrated applications: It provides an effective solution for touch sensing technology in highly integrated, high-speed electronic devices, meeting the technical requirements of modern electronic devices; Reduced system complexity: Through front-end interference suppression, it simplifies the complexity of subsequent signal processing, which is beneficial for system integration and cost control.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A common-mode interference suppression circuit, characterized in that, Includes the Gm module, feedback module, and integrating capacitor; The first input terminal of the Gm module is used to receive a sensing signal superimposed with an interference signal, the sensing signal representing the state of the system under test. The second input terminal is connected to a reference voltage. The first output terminal is used to generate a first current based on the voltage difference between the first input terminal and the second input terminal. The second output terminal outputs a second current proportional to the first current. The feedback module is connected to the first output terminal and is used to generate a feedback voltage based on the first current and feed the feedback voltage back to the second input terminal, so that the first output terminal adjusts the first current based on the feedback voltage to suppress the interference signal. The integrating capacitor is connected to the second output terminal and is used to integrate the second current to generate a sensing output signal.

2. The common-mode interference suppression circuit as described in claim 1, characterized in that, There are multiple Gm modules and integrating capacitors, with each Gm module and an integrating capacitor forming a sensing channel. The first output terminals of multiple Gm modules are connected to the feedback module. The feedback module is used to generate the feedback voltage based on the first current of the plurality of first output terminals, and to feed the feedback voltage back to the second input terminals of the plurality of Gm modules.

3. The common-mode interference suppression circuit as described in claim 2, characterized in that, When an interference signal is coupled to the first input terminal of the plurality of Gm modules, the first current output from the first output terminal of the plurality of Gm modules is collected and flows through the feedback module to generate the feedback voltage; the feedback voltage is simultaneously fed back to the second input terminal of the plurality of Gm modules; through negative feedback, each Gm module adjusts the first current according to the feedback voltage, so that the feedback voltage follows the change of the interference voltage at the first input terminal, and suppresses the output of the interference signal at the second output terminal through the anti-phase cancellation effect.

4. The common-mode interference suppression circuit as described in claim 1, characterized in that, The feedback module includes a feedback resistor and an amplifier; One end of the feedback resistor is connected to the first output terminal of the Gm module, and the other end is connected to the output terminal of the amplifier; the inverting input terminal of the amplifier is connected to the output terminal of the amplifier.

5. The common-mode interference suppression circuit as described in claim 1, characterized in that, The Gm module includes an operational transconductance amplifier, a first current mirror unit, and a second current mirror unit. The operational transconductance amplifier is used to convert the voltage difference between the first input terminal and the second input terminal into a reference current. The first current mirror unit is used to mirror the reference current and generate a first current, and the second current mirror unit is used to mirror the reference current and generate a second current. The reference current, the first current and the second current are positively correlated.

6. The common-mode interference suppression circuit as described in claim 5, characterized in that, The operational transconductance amplifier includes an operational amplifier, a DC bias unit, a first PMOS transistor, and a first NMOS transistor. The non-inverting input of the operational amplifier serves as the first input, and the inverting input serves as the second input. The DC bias unit is connected to the output of the operational amplifier and is used to generate a first bias voltage and a second bias voltage. The DC bias unit is connected to the gate of the first PMOS transistor and the gate of the first NMOS transistor. The gate of the first PMOS transistor receives the first bias voltage, and the gate of the first NMOS transistor receives the second bias voltage. The source of the first PMOS transistor is connected to a power supply voltage, and the drain of the first PMOS transistor is connected to the drain of the first NMOS transistor, serving as the current output of the operational transconductance amplifier and connected to the non-inverting input of the operational amplifier. The source of the first NMOS transistor is grounded.

7. The common-mode interference suppression circuit as described in claim 6, characterized in that, The first current mirror unit includes a second PMOS transistor and a second NMOS transistor; the second current mirror unit includes a third PMOS transistor and a third NMOS transistor; the gates of the second PMOS transistor, the second NMOS transistor, the third PMOS transistor, and the third NMOS transistor are all connected to the DC bias unit, respectively receiving the first bias voltage or the second bias voltage; the sources of the second PMOS transistor and the third PMOS transistor are both connected to the power supply voltage, the drain of the second PMOS transistor is connected to the drain of the second NMOS transistor, forming the output terminal of the first current mirror unit; the drain of the third PMOS transistor is connected to the drain of the third NMOS transistor, forming the output terminal of the second current mirror unit; the sources of the second NMOS transistor and the third NMOS transistor are both grounded.

8. A touch sensing system, comprising a common-mode interference suppression circuit as described in any one of claims 1-7, characterized in that, It also includes a sensing electrode; the sensing electrode is connected to the first input terminal of the Gm module in the common-mode interference suppression circuit, and is used to transmit a sensing signal to the first input terminal, the sensing signal representing the state of the system under test; external interference signals are coupled to the first input terminal through the sensing electrode.

9. The touch sensing system as described in claim 8, characterized in that, It also includes a quantization module and a data processing module; the quantization module is used to convert the sensed output signal into a digital signal; the data processing module is used to process the digital signal.

10. The touch sensing system as claimed in claim 8, characterized in that, The number of sensing electrodes corresponds to the number of sensing channels in the common-mode interference suppression circuit.

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