Capacitive touch detection circuit and method

Abstract

This invention relates to the field of sensor technology, and discloses a capacitive touch detection circuit and method. The capacitive touch detection circuit includes a charge compensation module, a voltage-to-current conversion module, an integrating capacitor, a quantization circuit module, and a counter. The charge compensation module is used to compensate for the charging and discharging of an external touch capacitor, adjusting the charge on the touch capacitor to a predetermined charge range corresponding to a reference voltage. The voltage-to-current conversion module is used to convert the remaining charge on the touch capacitor after compensation by the charge compensation module into current and output it. The integrating capacitor is used to integrate the current to obtain an integrated voltage. The quantization circuit module is used to quantize the integrated voltage and control the integrated voltage to be stable within a preset voltage range of the reference voltage. The counter is used to count the output of the quantization circuit module to obtain a digital code representing the touch capacitance value. This invention can achieve touch detection performance with high linearity, low power consumption, small area, and high noise immunity.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a capacitive touch detection circuit and method. Background Technology

[0002] Technological advancements continuously drive innovation in human-computer interaction, with touch sensors becoming a key interaction method due to their ease of operation, intuitive feedback, and ergonomic design. Among various touch technologies, capacitive sensing technology, with its superior durability, support for multi-touch, and adaptability to device miniaturization, has established a dominant position in electronic products such as smartphones, tablets, wearable devices, personal computers, and public display devices, gradually replacing resistive, infrared, and ultrasonic touch solutions. Therefore, in cutting-edge fields such as bio-tactile sensing, capacitive sensing technology has also become the preferred solution for performing precision sensing tasks.

[0003] Touch sensing performance is a core factor affecting the touch experience, directly determining the system's sensitivity, positioning accuracy, and anti-interference capability. However, current mainstream capacitive sensing technologies still face several technical bottlenecks, among which improving the signal-to-noise ratio (SNR) is particularly crucial—that is, maximizing the effective signal under limited conditions while suppressing various noise interferences. Research shows that capacitive touch systems mainly face challenges such as LCD driver noise, charger coupling noise, power grid noise, fluorescent lamp flicker noise, and radio frequency (RF) interference; these interference sources all have specific spectral distributions and amplitude characteristics. Existing noise reduction solutions typically employ two strategies: one is to introduce filters to suppress or attenuate noise; the other is to actively avoid the frequency bands of major noise sources by rationally planning the system's operating frequency. To achieve better noise immunity, these strategies are often combined in practical applications, with simultaneous optimization of signal strength to maintain a high-stability and reliable SNR level. However, the amplitude of environmental noise in real-world application scenarios often significantly exceeds the effective signal. To accurately measure and effectively filter out such strong noise, signal pre-scaling techniques or a measurement system with a very large dynamic range are often required, which inevitably increases the overall cost of the solution.

[0004] Therefore, there is an urgent need to propose a capacitive touch detection circuit and method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to propose a capacitive touch detection circuit and method that can achieve touch detection performance with high linearity, low power consumption, small area and high noise immunity.

[0006] To solve the above-mentioned technical problems, the present invention provides a capacitive touch detection circuit, including a charge compensation module, a voltage-to-current conversion module, an integrating capacitor, a quantization circuit module, and a counter;

[0007] The charge compensation module is used to compensate for the charging and discharging of the external touch capacitor, adjusting the amount of charge on the touch capacitor to a predetermined charge range corresponding to the reference voltage.

[0008] The voltage-to-current conversion module is used to convert the remaining charge on the touch capacitor after compensation by the charge compensation module into current and output it.

[0009] The integrating capacitor is used to integrate the current to obtain the integrated voltage.

[0010] The quantization circuit module is used to quantize the integrated voltage and control the integrated voltage to be stable within a preset voltage range of the reference voltage.

[0011] The counter is used to count the output of the quantization circuit module to obtain a digital code representing the touch capacitance value.

[0012] Furthermore, it also includes a receiving electrode. The charge compensation module includes a first compensation current source, a second compensation current source, a first compensation switch, and a second compensation switch. One end of the first compensation current source is connected to the power supply voltage, and the other end is connected to one end of the first compensation switch. The other end of the first compensation switch and one end of the second compensation current source are both connected to the receiving electrode. The other end of the second compensation current source is connected to one end of the second compensation switch, and the other end of the second compensation switch is grounded.

[0013] Furthermore, it also includes a pre-charge switch circuit; the pre-charge switch circuit is used to pre-charge the self-capacitance in the self-capacitance scanning mode, or to disable it in the mutual capacitance scanning mode.

[0014] Furthermore, it also includes a receiving electrode; the charge compensation module is connected to the receiving electrode; in the self-capacitance scanning mode, the pre-charge switch circuit is disposed between the charge compensation module and the voltage-current conversion module, specifically including a first pre-charge switch and a second pre-charge switch;

[0015] One end of the first precharge switch is connected to the power supply voltage, and the other end is connected to one end of the second precharge switch and connected to the receiving electrode; the first precharge switch is used to precharge the voltage of the self-capacitor to VDDCS; the other end of the second precharge switch is grounded, and the second precharge switch is used to precharge the voltage of the self-capacitor to VSSA.

[0016] Furthermore, it also includes a receiving electrode; the charge compensation module is connected to the receiving electrode; the voltage-to-current conversion module includes a first switching switch, a transconductance operational amplifier, and a second switching switch;

[0017] One end of the first switching switch and one end of the second switching switch are both connected to the receiving electrode; the other end of the first switching switch is connected to the inverting input terminal of the transconductance operational amplifier; the non-inverting input terminal of the transconductance operational amplifier and the other end of the second switching switch are both connected to the reference voltage; the first output terminal of the transconductance operational amplifier is connected to the inverting input terminal, and the second output terminal is connected to the integrating capacitor, for outputting the current to the integrating capacitor.

[0018] Furthermore, the quantization circuit module includes a first quantization current source, a first quantization switch, a second quantization switch, a second quantization current source, a third quantization switch, a fourth quantization switch, a comparator, a first NOT gate, and a second NOT gate;

[0019] One end of the first quantization current source is connected to the power supply voltage, and the other end is connected to one end of the first quantization switch and one end of the third quantization switch; the other end of the first quantization switch is connected to the integrating capacitor, one end of the second quantization switch, and the non-inverting input of the comparator; the other end of the second quantization switch is connected to one end of the second quantization current source and one end of the fourth quantization switch; the other end of the second quantization current source is grounded; the third quantization switch is connected to the output of the first NOT gate, and the other end of the third quantization switch is connected to the other end of the fourth quantization switch; the fourth quantization switch is connected to the output of the second NOT gate; the inputs of both the first and second NOT gates are connected to the output of the comparator; the inverting input of the comparator is connected to the reference voltage, and the output of the comparator is connected to the counter.

[0020] Furthermore, the counter includes an upward counting module and a downward counting module; both the upward counting module and the downward counting module are connected to the quantization circuit module. When the integrated voltage is higher than the reference voltage, the upward counting module counts; when the integrated voltage is lower than the reference voltage, the downward counting module counts.

[0021] Furthermore, this invention also proposes a capacitive touch detection method, using the capacitive touch detection circuit described above, specifically including the following:

[0022] The touch capacitor is charged and discharged to compensate, and the amount of charge on the touch capacitor is adjusted to a predetermined amount of charge corresponding to the reference voltage.

[0023] The remaining charge on the touch capacitor after charge-discharge compensation is converted into current.

[0024] Integrating the current yields the integrated voltage;

[0025] The integrated voltage is compared with the reference voltage;

[0026] Based on the comparison results, the integrating capacitor is charged and discharged, and the count is performed to obtain a digital code representing the value of the touch capacitance.

[0027] Furthermore, it also includes: in self-capacitance scanning mode, before performing charge and discharge compensation on the touch capacitor, pre-charging the self-capacitance voltage to VDDCS or VSSA; configuring the charge and discharge compensation time and current according to the size of the self-capacitance; or, in mutual capacitance scanning mode, not performing the pre-charging operation, and directly performing charge and discharge compensation on the mutual capacitance.

[0028] Furthermore, the charging and discharging compensation of the touch capacitor specifically includes: charging and discharging compensation of the self-capacitance / mutual capacitance, wherein the amount of charge to be compensated is Q = ICOM × tclk; where Q is the amount of charge to be compensated, ICOM is the magnitude of the constant current, and tclk is the charging and discharging time.

[0029] Furthermore, the step of converting the residual charge on the touch capacitor after charge-discharge compensation into current specifically includes:

[0030] In self-capacitance scanning mode, the voltage-to-current conversion module absorbs the remaining charge on the compensated self-capacitance; or, in mutual capacitance scanning mode, the voltage-to-current conversion module absorbs the remaining charge after mutual capacitance coupling and compensation.

[0031] The absorbed charge is converted into current according to a configurable ratio and input to the integrating capacitor through the switching of the voltage-to-current conversion module, so that the current output in each scan is positive for the integrating capacitor.

[0032] Furthermore, comparing the integrated voltage with the reference voltage specifically includes: when the integrated voltage is higher than the reference voltage, the comparator outputs a high-level signal; when the integrated voltage is lower than the reference voltage, the comparator outputs a low-level signal.

[0033] Furthermore, the charging and discharging of the integrating capacitor based on the comparison result and the counting process specifically includes: when the comparator outputs a high-level signal, discharging the integrating capacitor through the second quantization current source and causing the counter to count upwards;

[0034] When the comparator outputs a low-level signal, the integrating capacitor is charged through the first quantization current source, causing the counter to count down.

[0035] Through the above technical solution, the present invention has the following beneficial effects:

[0036] A complete closed-loop detection chain is formed by a charge compensation module, a voltage-to-current conversion module, an integrating capacitor, a quantization circuit module, and a counter, enabling high-precision detection of touch capacitance. This architecture ensures that the transconductance operational amplifier always operates within a small swing range near the reference voltage, avoiding nonlinear distortion caused by large swing operation and maintaining high linearity of the output current, thereby improving detection accuracy and system stability. The integrating capacitor only needs to perform unidirectional integration to obtain a digital code that is monotonically related to the touch capacitance value, eliminating the need for complex bidirectional integration or multi-stage conversion circuits. This significantly simplifies the control logic and timing design, reduces chip area, and lowers power consumption. The charge compensation module uses a configurable constant current source and adjustable charge / discharge time, allowing flexible adjustment of the compensation amount according to different sizes of touch capacitance. This not only expands the dynamic range of the system but also effectively suppresses residual charge errors and improves the signal-to-noise ratio.

[0037] Furthermore, the switching switch in the voltage-to-current conversion module ensures that the current direction of the output remains consistent in each scan, realizing the unidirectional integration characteristic of the integrating capacitor and improving integration consistency and measurement repeatability. The quantization circuit module uses a single comparator with simple logic circuitry, requiring only one IMS current to achieve accurate quantization, occupying a very small layout area and consuming low power. Moreover, the closed-loop feedback structure formed with the counter enables the integrated voltage to converge quickly to near the reference voltage, shortening the detection cycle and meeting the high refresh rate requirements of multi-touch systems. The precharge switch circuit can quickly precharge the self-capacitor voltage to VDDCS or VSSA in self-capacitor scanning mode. At the same time, this circuit is automatically disabled in mutual capacitance scanning mode, thereby avoiding unnecessary power consumption and achieving a balance between high integration, low power consumption, and high noise immunity. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the circuit structure of the self-capacitance mode in the capacitive touch detection circuit of one embodiment of the present invention;

[0039] Figure 2 This is a timing diagram of the self-capacitance mode in a capacitive touch detection method according to an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the mutual capacitance mode circuit structure in a capacitive touch detection circuit according to an embodiment of the present invention.

[0041] Figure 4 This is a timing diagram of the mutual capacitance mode in a capacitive touch detection method according to an embodiment of the present invention. Detailed Implementation

[0042] Based on the teachings of this specification, those skilled in the art can form new technical solutions by combining different implementation methods without creating technical contradictions. Such variations should be considered to fall within the protection scope of this application.

[0043] The capacitive touch detection circuit and method 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.

[0044] 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.

[0045] like Figure 1 and Figure 3 As shown, this embodiment of the invention proposes a capacitive touch detection circuit, which specifically includes a charge compensation module, a voltage-to-current conversion module (Conveyor), an integrating capacitor Cint, a quantization circuit module, and a counter (CNT).

[0046] More specifically, the charge compensation module is used to compensate the charging and discharging of the external touch capacitor, adjusting the charge on the touch capacitor to a predetermined charge range corresponding to the reference voltage VCM; the voltage-to-current conversion module is used to convert the remaining charge on the touch capacitor after compensation by the charge compensation module into current and output it through the output terminal; the integrating capacitor Cint is connected to the output terminal of the voltage-to-current conversion module and is used to integrate the current to obtain the integrated voltage Vcap; the quantization circuit module is connected to the integrating capacitor Cint and is used to quantize the integrated voltage Vcap and control the integrated voltage Vcap to be stable within a preset voltage range of the reference voltage VCM (i.e., within a preset voltage range of the reference voltage VCM plus or minus a certain voltage, such as the reference voltage VCM ± 10mV, the specific range can also be set according to the actual situation to keep the integrated voltage Vcap stable); the counter is connected to the quantization circuit module and is used to count the output of the quantization circuit module to obtain a digital code representing the value of the touch capacitor.

[0047] In this embodiment, a receiving electrode (RX) is also included; the receiving electrode is used to receive a sensing signal characterizing the external touch capacitance; the charge compensation module is connected to the receiving electrode. The first input terminal of the voltage-to-current conversion module is connected to the receiving electrode, and the second input terminal of the voltage-to-current conversion module is connected to the reference voltage VCM.

[0048] In one specific embodiment, in self-capacitance scanning mode, the receiving electrode is connected to the self-capacitance Cs; in mutual capacitance scanning mode, the receiving electrode is coupled to the transmitting electrode through mutual capacitance Cm.

[0049] In a preferred embodiment, this embodiment further includes a precharge switch circuit (PRE_CHARGE); the precharge switch circuit is used to precharge the self-capacitance in the self-capacitance scanning mode, or to disable it in the mutual capacitance scanning mode.

[0050] In this embodiment, the capacitive touch detection circuit can flexibly switch between self-capacitance scanning mode and mutual capacitance scanning mode, making it suitable for various touch screen and touch sensor application scenarios.

[0051] In this embodiment, the charge compensation module includes a first compensation current source ICOM_SCR, a second compensation current source ICOM_SNK, a first compensation switch sw1, and a second compensation switch sw2. One end of the first compensation current source ICOM_SCR is connected to the power supply voltage, and the other end is connected to one end of the first compensation switch sw1. The other end of the first compensation switch sw1 and one end of the second compensation current source ICOM_SNK are both connected to the receiving electrode. The other end of the second compensation current source ICOM_SNK is connected to one end of the second compensation switch sw2, and the other end of the second compensation switch sw2 is grounded.

[0052] In a specific example, both the first compensation current source ICOM_SCR and the second compensation current source ICOM_SNK employ configurable constant current sources IMS to accommodate touch capacitors of different sizes. The first compensation switch sw1 corresponds to the charging control signal ICOM_SWUP, and the second compensation switch sw2 corresponds to the discharging control signal ICOM_SWDN. When charging the touch capacitor is required, the first compensation switch sw1 is turned on and the second compensation switch sw2 is turned off; when discharging the touch capacitor is required, the first compensation switch sw1 is turned off and the second compensation switch sw2 is turned on. The amount of charge compensated is ICOM × tclk, where ICOM is the constant current magnitude and tclk is the charging / discharging time. Those skilled in the art will understand that the magnitude of the compensation current and the charging / discharging time can be set according to actual needs. This configurable compensation mechanism improves the system's adaptability to touch capacitors of different sizes and enhances the flexibility and accuracy of detection.

[0053] In one embodiment, in the self-capacitance scanning mode, the pre-charge switch circuit is disposed between the charge compensation module and the voltage-current conversion module, specifically including a second pre-charge switch sw3 and a second pre-charge switch sw4.

[0054] Specifically, one end of the second precharge switch sw3 is connected to the power supply voltage, and the other end is connected to one end of the second precharge switch sw4 and connected to the receiving electrode; the second precharge switch sw3 is used to precharge the voltage of the self-capacitor to VDDCS; the other end of the second precharge switch sw4 is grounded, and the second precharge switch sw4 is used to precharge the voltage of the self-capacitor to VSSA.

[0055] In a specific example, the second precharge switch sw3 corresponds to the TXUP control signal, and the second precharge switch sw4 corresponds to the TXDN control signal. In self-capacitance scanning mode, the voltage on the self-capacitance Cs is first rapidly precharged to VDDCS or VSSA via the precharge switches. It is worth noting that VDDCS is typically close to or equal to the system's power supply voltage, while VSSA is typically close to or equal to the system's ground level. Through the precharge mechanism, the self-capacitance RX swing has only four stages: 0 -> reference voltage VCM -> VDDCS -> reference voltage VCM -> 0, making the matching requirements of the self-capacitance's waterproof terminal simple and effective, thus improving the system's stability and reliability. In mutual capacitance scanning mode, since mutual capacitance scanning does not require a precharge stage, the precharge switch circuit is disabled in mutual capacitance scanning mode.

[0056] In this embodiment, the voltage-to-current conversion module includes a first switching switch sw_int1, a transconductance operational amplifier CMP1, and a second switching switch sw_int2.

[0057] Specifically, one end of the first switching switch sw_int1 and one end of the second switching switch sw_int2 are both connected to the receiving electrode; the other end of the first switching switch sw_int1 is connected to the inverting input terminal of the transconductance operational amplifier CMP1; the non-inverting input terminal of the transconductance operational amplifier CMP1 and the other end of the second switching switch sw_int2 are both connected to the reference voltage VCM; the first output terminal of the transconductance operational amplifier CMP1 is connected to the inverting input terminal, and the second output terminal is connected to the integrating capacitor Cint, for outputting the current to the integrating capacitor Cint.

[0058] In one embodiment, when the first switching switch sw_int1 is turned on, the receiving electrode is connected to the inverting input of the transconductance operational amplifier CMP1. Since the non-inverting input of the transconductance operational amplifier CMP1 is connected to the reference voltage VCM, the inverting input is controlled to the same level as the reference voltage VCM, forming a virtual ground point. Thus, the remaining charge after charge compensation is absorbed by the transconductance operational amplifier CMP1 and converted into current, which is output from the second output terminal. The transconductance operational amplifier CMP1 is a device that converts voltage difference into current, and can proportionally amplify or reduce the current as needed, improving the system's flexibility and adaptability. Because the operational amplifier only operates within a small swing range near the reference voltage VCM, its operating point is relatively stable, significantly improving the system's linearity.

[0059] In this embodiment, the transconductance operational amplifier CMP1 features high gain and appropriate bandwidth, enabling precise voltage-to-current conversion within a finite time while balancing noise. The first switch sw_int1 and the second switch sw_int2 control the operating state of the transconductance operational amplifier CMP1. When capacitance detection is required, the first switch sw_int1 is turned on and the second switch sw_int2 is turned off, putting the transconductance operational amplifier CMP1 in conversion mode. When capacitance detection is not required, the first switch sw_int1 is turned off and the second switch sw_int2 is turned on, connecting the receiving electrode to the reference voltage VCM to prevent unnecessary interference from port floating. By rationally designing the current gain coefficient of the transconductance operational amplifier CMP1, the signal amplification factor can be adjusted according to the needs of different application scenarios, enhancing the system's versatility and scalability.

[0060] In this embodiment, the integrating capacitor Cint is connected to the output terminal of the voltage-to-current conversion module and is used to integrate the current to obtain the integrated voltage Vcap. During the integration process, the current output by the transconductance operational amplifier CMP1 charges the integrating capacitor Cint, generating the integrated voltage Vcap. By adjusting the value of the integrating capacitor Cint, the rate of change of the integrated voltage Vcap can be controlled, thereby affecting the sensitivity and dynamic range of the system. A high-precision capacitor can be used for the integrating capacitor Cint to reduce the impact of temperature changes on the measurement results and improve the stability of the system under different environmental conditions.

[0061] In this embodiment, the quantization circuit module includes a first quantization current source IMS1, a first quantization switch S1, a second quantization switch S2, a second quantization current source IMS2, a third quantization switch S3, a fourth quantization switch S4, a comparator CMP2, a first NOT gate INV1, and a second NOT gate INV2.

[0062] Specifically, one end of the first quantization current source IMS1 is connected to the power supply voltage, and the other end is connected to one end of the first quantization switch S1 and one end of the third quantization switch S3; the other end of the first quantization switch S1 is connected to the integrating capacitor Cint, one end of the second quantization switch S2, and the non-inverting input of the comparator CMP2; the other end of the second quantization switch S2 is connected to one end of the second quantization current source IMS2 and one end of the fourth quantization switch S4; the other end of the second quantization current source IMS2 is grounded; the third quantization switch S3 is connected to the output of the first NOT gate INV1, and the other end of the third quantization switch S3 is connected to the other end of the fourth quantization switch S4; the fourth quantization switch S4 is connected to the output of the second NOT gate INV2; the inputs of both the first NOT gate INV1 and the second NOT gate INV2 are connected to the output of the comparator CMP2; the inverting input of the comparator CMP2 is connected to the reference voltage VCM, and the output of the comparator CMP2 is connected to the counter.

[0063] In one embodiment, the quantization circuit module uses a configurable constant current IMS (i.e., the second quantization switch S2 and the second quantization current source IMS2) to quantize the integral voltage Vcap. When the integral voltage Vcap is greater than the reference voltage VCM, the comparator CMP2 outputs a high level, the first NOT gate INV1 outputs a low level, and the second NOT gate INV2 outputs a high level, causing the third quantization switch S3 to open and the fourth quantization switch S4 to open. At this time, the second quantization current source IMS2 discharges the integral capacitor through the second quantization switch S2, and the discharge rate is determined by the current value of the second quantization current source IMS2. ​​The amount of charge discharged per clock cycle is IMS × tclk, which corresponds to 1 LSB. As the discharge proceeds, the integral voltage Vcap gradually decreases until it falls below the reference voltage VCM. At this time, the comparator CMP2 output flips to a low level, the first NOT gate INV1 outputs a high level, and the second NOT gate INV2 outputs a low level, causing the third quantization switch S3 to open and the fourth quantization switch S4 to open. The first quantization current source IMS1 begins to charge the integral capacitor, and the integral voltage Vcap begins to rise again.

[0064] During quantization, after the integral voltage Vcap is discharged to the reference voltage VCM, because Vcap is very close to VCM at this point, comparator CMP2 will alternately output high and low levels, and the constant current IMS will alternately charge and discharge the integrating capacitor Cint. Consequently, the integral voltage Vcap will fluctuate around the reference voltage VCM. This method in this embodiment ensures that the integral voltage Vcap remains stable near the reference voltage VCM, guaranteeing sufficient voltage margin for each quantization and improving quantization accuracy and stability.

[0065] As those skilled in the art will know, the quantization current and clock cycle can be set according to actual needs. The quantization circuit module only requires one IMS current and one comparator CMP2 and the corresponding logic circuit. Therefore, the actual layout area occupied is small and the power consumption is low, which can improve the system integration and energy efficiency ratio.

[0066] In this embodiment, the counter includes an upward counting module and a downward counting module; both the upward counting module and the downward counting module are connected to the quantization circuit module. When the integral voltage Vcap is higher than the reference voltage VCM, the upward counting module counts; when the integral voltage Vcap is lower than the reference voltage VCM, the downward counting module counts.

[0067] In one embodiment, the counter counts based on the output signal of comparator CMP2. When the output of comparator CMP2 is high, the counter counts up; when the output of comparator CMP2 is low, the counter counts down. When the integral voltage Vcap drops to near the reference voltage VCM, the integral voltage Vcap fluctuates around the reference voltage VCM, and the output of comparator CMP2 alternates between high and low levels. The counter's count value also alternates between +1 and -1, canceling each other out, so the overall count value does not change. This embodiment ensures that the count value accurately reflects the size of the touch capacitance, providing a reliable basis for subsequent touch state judgment.

[0068] Furthermore, this embodiment also proposes a capacitive touch detection method, using the capacitive touch detection circuit as described above, specifically including the following:

[0069] S1. Perform charge and discharge compensation on the touch capacitor to adjust the amount of charge on the touch capacitor to a predetermined charge range corresponding to the reference voltage VCM;

[0070] S2. Convert the remaining charge on the touch capacitor after charge / discharge compensation into current;

[0071] S3. Integrate the current to obtain the integrated voltage Vcap;

[0072] S4. Compare the integrated voltage Vcap with the reference voltage VCM; and

[0073] S5. Charge and discharge the integrating capacitor Cint according to the comparison result, and count the results to obtain a digital code representing the value of the touch capacitor.

[0074] Furthermore, this embodiment also includes: in the self-capacitance scanning mode, before performing charge and discharge compensation on the touch capacitor, pre-charging the self-capacitance to VDDCS or VSSA; configuring the charge and discharge compensation time and current according to the size of the self-capacitance; or, in the mutual capacitance scanning mode, not performing the pre-charging operation, and directly performing charge and discharge compensation on the mutual capacitance.

[0075] Furthermore, the charge / discharge compensation for the touch capacitor specifically includes: charge / discharge compensation for self-capacitance / mutual capacitance, with the amount of charge compensated being Q = ICOM × tclk; where Q is the amount of charge compensated, ICOM is the magnitude of the constant current, and tclk is the charge / discharge time. This step is implemented through a charge compensation module, compensating for the vast majority of the charge, thus improving the processing efficiency and accuracy of subsequent circuits. The amount of charge compensated is precisely adjusted by controlling the magnitude of the constant current ICOM and the charge / discharge time tclk. ICOM can be configured according to the size of the touch capacitor, and tclk can be set according to the system clock frequency and compensation accuracy requirements. Precise control of the amount of charge compensated allows the system to adapt to touch capacitors of different sizes, improving the system's versatility and scalability. At the same time, precise compensation reduces the dynamic range requirements of subsequent processing, lowers system complexity, and improves energy efficiency.

[0076] In this embodiment, converting the residual charge on the touch capacitor after charge-discharge compensation into current specifically includes: in self-capacitance scanning mode, absorbing the residual charge on the compensated self-capacitance through a voltage-to-current conversion module; or, in mutual capacitance scanning mode, absorbing the residual charge after mutual capacitance coupling and compensation through the voltage-to-current conversion module; converting the absorbed charge into current according to a configurable ratio, and inputting it to the integrating capacitor Cint through the conversion switch of the voltage-to-current conversion module, so that the current output in each scan is positive for the integrating capacitor Cint.

[0077] In this embodiment, comparing the integrated voltage Vcap with the reference voltage VCM specifically includes: when the integrated voltage Vcap is higher than the reference voltage VCM, the comparator CMP2 outputs a high-level signal; when the integrated voltage Vcap is lower than the reference voltage VCM, the comparator CMP2 outputs a low-level signal.

[0078] Furthermore, the charging and discharging of the integrating capacitor Cint based on the comparison result and the counting process specifically includes: when the comparator CMP2 outputs a high-level signal, the integrating capacitor Cint is discharged through the second quantization current source IMS2, and the counter counts upward; when the comparator CMP2 outputs a low-level signal, the integrating capacitor Cint is charged through the first quantization current source IMS1, and the counter counts downward, so that the integrated voltage can be stabilized near the reference voltage, and the value of the counter reflects the size of the touch capacitor.

[0079] In this embodiment, such as Figure 1 and Figure 2As shown, in the self-capacitance scanning mode, first, the self-capacitance Cs is pre-charged through the pre-charge switch circuit. Specifically, the second pre-charge switch sw3 (TXUP) is turned on to quickly pre-charge the self-capacitance voltage to VDDCS, or the second pre-charge switch sw4 (TXDN) is turned on to quickly pre-charge the self-capacitance voltage to VSSA. This pre-charge process can reduce the time required for subsequent compensation and improve the scanning efficiency. Secondly, the charge compensation module performs charge and discharge compensation on the self-capacitance to adjust the amount of charge on the self-capacitance to within a predetermined charge amount range corresponding to the reference voltage VCM. When it is necessary to charge the self-capacitance, the first compensation switch sw1 is turned on and the second compensation switch sw2 is turned off, and the first compensation current source ICOM_SCR charges the self-capacitance; when it is necessary to discharge the self-capacitance, the first compensation switch sw1 is turned off and the second compensation switch sw2 is turned on, and the second compensation current source ICOM_SNK discharges the self-capacitance. The compensated charge amount is ICOM×tclk, and this step compensates for the vast majority of charges, reducing the dynamic range requirement for subsequent processing. Then, the voltage-current conversion module is enabled, the first conversion switch sw_int1 is turned on, and the second conversion switch sw_int2 is turned off, connecting the receiving electrode to the inverting input terminal of the transconductance operational amplifier CMP1. Since the non-inverting input terminal of the transconductance operational amplifier CMP1 is connected to the reference voltage VCM and the inverting input terminal is controlled to the same level as VCM, a virtual ground point is formed. At this time, the remaining charge on the self-capacitance after charge compensation is absorbed by the transconductance operational amplifier CMP1 and converted into a current that is output from the second output terminal to the integrating capacitor, generating an integrated voltage Vcap. Finally, the quantization circuit module quantizes the integrated voltage and controls the integrated voltage to be stable near the reference voltage, for example, within the range of the reference voltage VCM±10mV. The comparator CMP2 compares the integrated voltage Vcap with the reference voltage VCM. When Vcap>VCM, the comparator CMP2 outputs a high level, and the second quantization current source IMS2 discharges the integrating capacitor, and at the same time the counter counts up; when Vcap<VCM, the comparator CMP2 outputs a low level, and the first quantization current source IMS1 charges the integrating capacitor, and at the same time the counter counts down. As the comparison process progresses, Vcap gradually stabilizes near VCM, and the count value of the counter also tends to be stable. The final count value is the digital code representing the self-capacitance value, such as Figure 2 the timing diagram of each key signal during the self-capacitance working process shown in

[0080] As Figure 3 and Figure 4 shown, in the mutual-capacitance scanning mode, first, the mutual-capacitance scanning does not require a pre-charge link, and the pre-charge switch circuit is not enabled. The TX electrode outputs an excitation signal, such as Figure 4The square wave signal VTX shown is coupled to the RX electrode (receiving electrode) through mutual capacitance Cm. Next, the charge compensation module charges and discharges the mutual capacitance, adjusting the charge on the mutual capacitance to a predetermined range corresponding to the reference voltage VCM. Since the mutual capacitance Cm is usually small, compensation may not be necessary in some cases. When compensation is required, the operation is the same as in self-capacitance mode, using the first compensation switch sw1 and the second compensation switch sw2 to achieve charge and discharge compensation. Then, the voltage-to-current conversion module is activated, opening the first conversion switch sw_int1 and closing the second conversion switch sw_int2, connecting the receiving electrode to the inverting input of the transconductance operational amplifier CMP1. The transconductance operational amplifier CMP1 converts the remaining charge after mutual capacitance coupling and compensation into current and outputs it to the integrating capacitor, generating an integrated voltage Vcap. Finally, the quantization circuit module and counter operate in the same way as in self-capacitance scanning mode, quantizing the integrated voltage and controlling the charging and discharging of the integrating capacitor and the counting of the counter based on the comparison result, ultimately obtaining a digital code representing the mutual capacitance value, such as... Figure 4 The timing diagrams shown are for key signals during the operation of mutual capacitance.

[0081] In mutual capacitance scanning mode, the processing flow is simpler and scanning efficiency is improved because a pre-charging stage is not required. Meanwhile, since mutual capacitance is typically small, the system's ability to detect minute capacitance changes is particularly important. This embodiment achieves reliable detection of minute changes in mutual capacitance through high-precision charge compensation, stable voltage-current conversion, and accurate quantization counting.

[0082] Whether using self-capacitance scanning mode or mutual capacitance scanning mode, the capacitive touch detection circuit proposed in this embodiment has advantages such as high linearity, strong noise immunity, simple structure, and low power consumption, which can meet the needs of various touch applications; moreover, the overall circuit area is small, making it suitable for multi-channel integration. In particular, during the scanning process, the reference voltage VCM remains constant, allowing the voltage-to-current conversion module to operate only within a small swing range, significantly improving the linearity and accuracy of the system, and enhancing the accuracy of touch detection.

[0083] In summary, the capacitive touch detection circuit and method proposed in this invention have the following advantages:

[0084] A complete closed-loop detection chain is formed by a charge compensation module, a voltage-to-current conversion module, an integrating capacitor, a quantization circuit module, and a counter, enabling high-precision detection of touch capacitance. This architecture ensures that the transconductance operational amplifier always operates within a small swing range near the reference voltage, avoiding nonlinear distortion caused by large swing operation and maintaining high linearity of the output current, thereby improving detection accuracy and system stability. The integrating capacitor only needs to perform unidirectional integration to obtain a digital code that is monotonically related to the touch capacitance value, eliminating the need for complex bidirectional integration or multi-stage conversion circuits. This significantly simplifies the control logic and timing design, reduces chip area, and lowers power consumption. The charge compensation module uses a configurable constant current source and adjustable charge / discharge time, allowing flexible adjustment of the compensation amount according to different sizes of touch capacitance. This not only expands the dynamic range of the system but also effectively suppresses residual charge errors and improves the signal-to-noise ratio.

[0085] Furthermore, the switching switch in the voltage-to-current conversion module ensures that the current direction of the output remains consistent in each scan, realizing the unidirectional integration characteristic of the integrating capacitor and improving integration consistency and measurement repeatability. The quantization circuit module uses a single comparator with simple logic circuitry, requiring only one IMS current to achieve accurate quantization, occupying a very small layout area and consuming low power. Moreover, the closed-loop feedback structure formed with the counter enables the integrated voltage to converge quickly to near the reference voltage, shortening the detection cycle and meeting the high refresh rate requirements of multi-touch systems. This achieves a balance between high integration, low power consumption, and high noise immunity.

[0086] 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 capacitive touch detection circuit, characterized in that, It includes a pre-charge switching circuit, a charge compensation module, a voltage-to-current conversion module, an integrating capacitor, a quantization circuit module, and a counter; The pre-charge switch circuit is used to pre-charge the self-capacitor in self-capacitor scanning mode before performing charge-discharge compensation on the touch capacitor, pre-charging the voltage of the self-capacitor to VDDCS or VSSA, and configuring the charge-discharge compensation time and current according to the size of the self-capacitor; or, in mutual capacitance scanning mode, the pre-charge operation is not performed, and the mutual capacitance is directly charged-discharge compensated. The charge compensation module is used to compensate for the charge and discharge of self-capacitance or mutual capacitance, and to adjust the charge on the touch capacitor to a predetermined charge range corresponding to the reference voltage. The voltage-to-current conversion module is used to absorb the residual charge on the compensated self-capacitance in self-capacitance scanning mode; or, in mutual capacitance scanning mode, to absorb the residual charge after mutual capacitance coupling and compensation. The absorbed charge is converted into current according to a configurable ratio and input to the integrating capacitor, so that the current output in each scan is positive for the integrating capacitor. The integrating capacitor is used to integrate the current to obtain the integrated voltage. The quantization circuit module is used to quantize the integrated voltage and control the integrated voltage to be stable within a preset voltage range of the reference voltage. The counter is used to count the output of the quantization circuit module to obtain a digital code representing the touch capacitance value.

2. The capacitive touch detection circuit as described in claim 1, characterized in that, It also includes a receiving electrode. The charge compensation module includes a first compensation current source, a second compensation current source, a first compensation switch, and a second compensation switch. One end of the first compensation current source is connected to the power supply voltage, and the other end is connected to one end of the first compensation switch. The other end of the first compensation switch and one end of the second compensation current source are both connected to the receiving electrode. The other end of the second compensation current source is connected to one end of the second compensation switch, and the other end of the second compensation switch is grounded.

3. The capacitive touch detection circuit as described in claim 2, characterized in that, It also includes a receiving electrode; the charge compensation module is connected to the receiving electrode; in the self-capacitance scanning mode, the pre-charge switch circuit is disposed between the charge compensation module and the voltage-current conversion module, specifically including a first pre-charge switch and a second pre-charge switch; One end of the first precharge switch is connected to the power supply voltage, and the other end is connected to one end of the second precharge switch and connected to the receiving electrode; the first precharge switch is used to precharge the voltage of the self-capacitor to VDDCS; the other end of the second precharge switch is grounded, and the second precharge switch is used to precharge the voltage of the self-capacitor to VSSA.

4. The capacitive touch detection circuit as described in claim 1, characterized in that, It also includes a receiving electrode; the charge compensation module is connected to the receiving electrode; the voltage-to-current conversion module includes a first switching switch, a transconductance operational amplifier, and a second switching switch; One end of the first switching switch and one end of the second switching switch are both connected to the receiving electrode; the other end of the first switching switch is connected to the inverting input terminal of the transconductance operational amplifier; the non-inverting input terminal of the transconductance operational amplifier and the other end of the second switching switch are both connected to the reference voltage; the first output terminal of the transconductance operational amplifier is connected to the inverting input terminal, and the second output terminal is connected to the integrating capacitor, for outputting the current to the integrating capacitor.

5. The capacitive touch detection circuit as described in claim 1, characterized in that, The quantization circuit module includes a first quantization current source, a first quantization switch, a second quantization switch, a second quantization current source, a third quantization switch, a fourth quantization switch, a comparator, a first NOT gate, and a second NOT gate; One end of the first quantization current source is connected to the power supply voltage, and the other end is connected to one end of the first quantization switch and one end of the third quantization switch; the other end of the first quantization switch is connected to the integrating capacitor, one end of the second quantization switch, and the non-inverting input of the comparator; the other end of the second quantization switch is connected to one end of the second quantization current source and one end of the fourth quantization switch; the other end of the second quantization current source is grounded; the third quantization switch is connected to the output of the first NOT gate, and the other end of the third quantization switch is connected to the other end of the fourth quantization switch; the fourth quantization switch is connected to the output of the second NOT gate; the inputs of both the first and second NOT gates are connected to the output of the comparator; the inverting input of the comparator is connected to the reference voltage, and the output of the comparator is connected to the counter.

6. The capacitive touch detection circuit as described in claim 1, characterized in that, The counter includes an upward counting module and a downward counting module; both the upward counting module and the downward counting module are connected to the quantization circuit module. When the integrated voltage is higher than the reference voltage, the upward counting module counts; when the integrated voltage is lower than the reference voltage, the downward counting module counts.

7. A capacitive touch detection method, using the capacitive touch detection circuit as described in any one of claims 1-6, characterized in that, Specifically, it includes the following: The touch capacitor is charged and discharged to compensate, and the amount of charge on the touch capacitor is adjusted to a predetermined amount of charge corresponding to the reference voltage. The remaining charge on the touch capacitor after charge-discharge compensation is converted into current. Integrating the current yields the integrated voltage; The integrated voltage is compared with the reference voltage; Based on the comparison results, the integrating capacitor is charged and discharged, and the count is performed to obtain a digital code representing the value of the touch capacitance.

8. The capacitive touch detection method as described in claim 7, characterized in that, Also includes: In self-capacitance scanning mode, before performing charge-discharge compensation on the touch capacitor, the self-capacitance is pre-charged to VDDCS or VSSA; the charging-discharge compensation time and current are configured according to the size of the self-capacitance; or, in mutual capacitance scanning mode, the pre-charging operation is not performed, and the mutual capacitance is directly charged-discharge compensated.

9. The capacitive touch detection method as described in claim 7, characterized in that, The charging and discharging compensation of the touch capacitor specifically includes: charging and discharging compensation of self-capacitance / mutual capacitance, wherein the amount of charge compensated is Q=ICOM×tclk; where Q is the amount of charge compensated, ICOM is the magnitude of the constant current, and tclk is the charging and discharging time.

10. The capacitive touch detection method as described in claim 7, characterized in that, The step of converting the residual charge on the touch capacitor after charge-discharge compensation into current specifically includes: In self-capacitance scanning mode, the voltage-to-current conversion module absorbs the remaining charge on the compensated self-capacitance; or, in mutual capacitance scanning mode, the voltage-to-current conversion module absorbs the remaining charge after mutual capacitance coupling and compensation. The absorbed charge is converted into current according to a configurable ratio and input to the integrating capacitor through the switching of the voltage-to-current conversion module, so that the current output in each scan is positive for the integrating capacitor.

11. The capacitive touch detection method as described in claim 7, characterized in that, The step of comparing the integrated voltage with the reference voltage specifically includes: when the integrated voltage is higher than the reference voltage, the comparator outputs a high-level signal; when the integrated voltage is lower than the reference voltage, the comparator outputs a low-level signal.

12. The capacitive touch detection method as described in claim 7, characterized in that, The charging and discharging of the integrating capacitor based on the comparison result and the counting process specifically includes: when the comparator outputs a high-level signal, discharging the integrating capacitor through the second quantization current source and causing the counter to count up; When the comparator outputs a low-level signal, the integrating capacitor is charged through the first quantization current source, causing the counter to count down.

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