CN-121070200-B - Capacitive touch detection circuit and method

CN121070200BCN 121070200 BCN121070200 BCN 121070200BCN-121070200-B

Abstract

The invention relates to the technical field of sensors, and discloses a capacitive touch detection circuit and a capacitive touch detection method, wherein the capacitive touch detection circuit comprises a charge compensation module, a voltage-current conversion module, an integration capacitor, a quantization circuit module and a counter; the touch control circuit comprises a voltage-current conversion module, an integration capacitor, a quantization circuit module and a counter, wherein the voltage-current conversion module is used for converting residual charges on the touch control capacitor after the compensation of the charge compensation module into currents and outputting the currents, the integration capacitor is used for integrating the currents to obtain integrated voltages, the quantization circuit module is used for quantizing the integrated voltages and controlling the integrated voltages to be stabilized in a preset voltage range of the reference voltage, and the counter is used for counting the output of the quantization circuit module to obtain digital codes representing the touch control capacitance. The invention can realize the touch detection performance with high linearity, low power consumption, small area and high noise immunity.

Inventors

KONG LONG
CHEN JIANQIU
ZHOU XIAOYA
WANG JIANJUN
LIU HUA

Assignees

上海海栎创科技股份有限公司

Dates

Publication Date: 20260505
Application Date: 20251106

Claims (12)

1. The capacitive touch detection circuit is characterized by comprising a pre-charge switch circuit, a charge compensation module, a voltage-current conversion module, an integration capacitor, a quantization circuit module and a counter; The pre-charge switch circuit is used for pre-charging the self-capacitance before the self-capacitance is subjected to charge-discharge compensation in the self-capacitance scanning mode, pre-charging the self-capacitance to VDDCS or VSSA according to the self-capacitance, and configuring the charge-discharge compensation time and current according to the self-capacitance; The charge compensation module is used for carrying out charge-discharge compensation on the self-capacitance or the mutual capacitance, and adjusting the charge quantity on the touch capacitance to be within a preset charge quantity range corresponding to the reference voltage; the voltage-current conversion module is used for absorbing residual charges on the self-capacitance after compensation through the voltage-current conversion module in a self-capacitance scanning mode, or absorbing residual charges after mutual capacitance coupling and compensation through the voltage-current conversion module in a mutual capacitance scanning mode; the integrating capacitor is used for integrating the current to obtain an integrated voltage; the quantization circuit module is used for quantizing the integrated voltage and controlling the integrated voltage to be stabilized in a preset voltage range of the reference voltage; the counter is used for counting the output of the quantization circuit module to obtain a digital code representing the touch capacitance value.
2. The capacitive touch detection circuit of claim 1, further comprising a receiving electrode, wherein the charge compensation module comprises a first compensation current source, a second compensation current source, a first compensation switch and a second compensation switch, wherein one end of the first compensation current source is connected with a power supply voltage, the other end of the first compensation current source is connected with 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 with the receiving electrode, the other end of the second compensation current source is connected with one end of the second compensation switch, and the other end of the second compensation switch is grounded.
3. The capacitive touch detection circuit of claim 2, further comprising a receiving electrode, wherein the charge compensation module is connected to the receiving electrode, wherein the precharge switch circuit is disposed between the charge compensation module and the voltage-to-current conversion module in a self-capacitance scan mode, and specifically comprises a first precharge switch and a second precharge switch; One end of the first pre-charging switch is connected with a power supply voltage, the other end of the first pre-charging switch is connected with one end of the second pre-charging switch and is connected with the receiving electrode, the first pre-charging switch is used for pre-charging the voltage of the self capacitor to VDDCS, the other end of the second pre-charging switch is grounded, and the second pre-charging switch is used for pre-charging the voltage of the self capacitor to VSSA.
4. The capacitive touch detection circuit of claim 1, further comprising a receiving electrode, wherein the charge compensation module is connected to the receiving electrode, wherein the voltage-to-current conversion module comprises a first transfer switch, a transconductance operational amplifier, and a second transfer switch; one end of the first transfer switch and one end of the second transfer switch are both connected with the receiving electrode, the other end of the first transfer switch is connected with the inverting input end of the transconductance operational amplifier, the non-inverting input end of the transconductance operational amplifier and the other end of the second transfer switch are both connected with the reference voltage, the first output end of the transconductance operational amplifier is connected with the inverting input end, and the second output end of the transconductance operational amplifier is connected with the integrating capacitor and is used for outputting the current to the integrating capacitor.
5. The capacitive touch detection circuit of claim 1, wherein the quantization circuit module comprises a first quantization current source, a first 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 with a power supply voltage, the other end of the first quantization current source is connected with 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 with the integrating capacitor, one end of the second quantization switch and the in-phase input end of the comparator, the other end of the second quantization switch is connected with 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 with the output end of the first NOT gate, the other end of the third quantization switch is connected with the other end of the fourth quantization switch, the fourth quantization switch is connected with the output end of the second NOT gate, the input ends of the first NOT gate and the second NOT gate are connected with the output end of the comparator, the reverse input end of the comparator is connected with the reference voltage, and the output end of the comparator is connected with the counter.
6. The capacitive touch detection circuit of claim 1, wherein the counter comprises an up-counting module and a down-counting module, wherein the up-counting module and the down-counting module are both connected to the quantization circuit module, the up-counting module counts when the integrated voltage is higher than the reference voltage, and the down-counting module counts when the integrated voltage is lower than the reference voltage.
7. A capacitive touch detection method using the capacitive touch detection circuit according to any one of claims 1 to 6, comprising the following steps: charging and discharging compensation is carried out on the touch capacitor, and the charge quantity on the touch capacitor is adjusted to be within a preset charge quantity range corresponding to the reference voltage; converting the residual charge on the touch capacitor after charge-discharge compensation into current; Integrating the current to obtain an integrated voltage; Comparing the integrated voltage with the reference voltage; and charging and discharging the integrating capacitor according to the comparison result, and counting to obtain a digital code representing the touch capacitance value.
8. The method of claim 7, further comprising pre-charging the self-capacitance before the charge-discharge compensation of the touch capacitance in the self-capacitance scan mode, pre-charging the self-capacitance to VDDCS or VSSA, configuring the charge-discharge compensation time and current according to the self-capacitance, or directly performing the charge-discharge compensation of the mutual capacitance without performing the pre-charge operation in the mutual capacitance scan mode.
9. The method of claim 7, wherein the compensating for charging and discharging the touch capacitor comprises compensating for charging and discharging the self/mutual capacitor with an amount of charge of q=icom× tclk, wherein Q is an amount of charge compensated, ICOM is a constant current, and tclk is charging and discharging time.
10. The method of claim 7, wherein the converting the residual charge on the touch capacitor after charge-discharge compensation into a current comprises: In the self-capacitance scanning mode, residual charges on the self-capacitance after compensation are absorbed through a voltage-current conversion module, or in the mutual-capacitance scanning mode, residual charges after mutual-capacitance coupling and compensation are absorbed through the voltage-current conversion module; And converting the absorbed charge into current according to a configurable proportion, and inputting the current into the integrating capacitor through a change-over switch of the voltage-current conversion module, so that the current output by each scanning is positive to the integrating capacitor.
11. The method of claim 7, wherein comparing the integrated voltage with the reference voltage comprises outputting a high signal from the comparator when the integrated voltage is higher than the reference voltage, and outputting a low signal from the comparator when the integrated voltage is lower than the reference voltage.
12. The method for detecting capacitive touch control according to claim 7, wherein the step of charging and discharging the integration capacitor according to the comparison result and counting the integration capacitor comprises discharging the integration capacitor through the second quantization current source and counting up the counter when the comparator outputs the high level signal; When the comparator outputs a low level signal, the integrating capacitor is charged by the first quantizing current source, and the counter is counted down.

Description

Capacitive touch detection circuit and method Technical Field The invention relates to the technical field of sensors, in particular to a capacitive touch detection circuit and a capacitive touch detection method. Background Technological progress is continuously pushing the innovation of man-machine interaction modes, wherein the touch sensor is one of key interaction means by virtue of the design concepts of simple operation, visual feedback and accordance with ergonomics. Among many touch technologies, the capacitive sensing technology has established a dominant role in the field of electronic products such as smart phones, tablet computers, wearable devices, and even personal computers and public display devices by virtue of its excellent durability, support for multi-touch and the comprehensive advantages such as miniaturization requirement of adaptive devices, and gradually replaces resistive, infrared and ultrasonic touch schemes. As such, capacitive sensing technology is also the preferred solution for performing precision sensing tasks in the leading edge field of biological tactile sensing and the like. Touch sensing performance is a core factor influencing touch experience, and the sensitivity, positioning accuracy and anti-interference capability of the system are directly determined. However, the currently mainstream capacitive detection technology still has several technical bottlenecks, in which the improvement of signal-to-noise ratio (SNR) is particularly critical—that is, the effective signal is maximized under limited conditions, while various noise interferences are suppressed. Research shows that the capacitive touch system mainly faces challenges such as LCD driving noise, charger coupling noise, power frequency grid noise, fluorescent lamp stroboscopic noise, radio Frequency (RF) interference and the like, and all interference sources have specific frequency spectrum distribution and amplitude characteristics. The existing noise reduction scheme generally adopts two strategies, namely, a filter is introduced to inhibit or attenuate noise, and the frequency band range of main noise is actively avoided by reasonably planning the working frequency point of the system. In order to obtain better noise immunity, the above strategies are often used in combination in practical applications, and the signal strength is optimized synchronously to maintain a signal-to-noise level of high stability and reliability. However, the environmental noise amplitude in practical application scenarios often significantly exceeds the effective signal, often requiring the use of signal pre-shrinking techniques or relying on measurement systems with extremely large dynamic ranges in order to accurately measure and effectively filter out such strong noise, which inevitably increases the cost of the overall solution. Therefore, a capacitive touch detection circuit and a capacitive touch detection method are needed to solve the above problems. Disclosure of Invention The invention aims to provide a capacitive touch detection circuit and a capacitive touch detection method, which can realize high linearity, low power consumption, small area and high noise-resistant touch detection performance. In order to solve the technical problems, the invention provides a capacitive touch detection circuit, which comprises a charge compensation module, a voltage-current conversion module, an integration capacitor, a quantization circuit module and a counter; The charge compensation module is used for carrying out charge and discharge compensation on an external touch capacitor, and adjusting the charge quantity on the touch capacitor to be within a preset charge quantity range corresponding to a reference voltage; The voltage-current conversion module is used for converting residual charges on the touch capacitor after the charge compensation module is compensated into current and outputting the current; the integrating capacitor is used for integrating the current to obtain an integrated voltage; the quantization circuit module is used for quantizing the integrated voltage and controlling the integrated voltage to be stabilized in a preset voltage range of the reference voltage; the counter is used for counting the output of the quantization circuit module to obtain a digital code representing the touch capacitance value. The charge compensation module comprises a first compensation current source, a second compensation current source, a first compensation switch and a second compensation switch, wherein one end of the first compensation current source is connected with a power supply voltage, the other end of the first compensation current source is connected with 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 with the receiving electrode, the other end of the second compensation current source is connected with