Capacitive Touch Sensing Circuit for Fast Dual-Mode Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing capacitive touch sensors face challenges in efficiently switching between self-capacitance and mutual capacitance modes, leading to increased power consumption, complex circuitry, and reduced response speed, especially when dealing with large touch panels.
Innovation Solution
A capacitive touch sensor design that allows switching between self-capacitance and mutual capacitance modes using a single sensing circuit with a commonly used touch panel, eliminating the need for additional current sources and incorporating a differential mode to enhance noise interference and accuracy, while optimizing scan time by combining scan results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If self-capacitance mode is used, then scan time is reduced, but measurement precision deteriorates due to ghost points and misjudgment in multi-touch
Solution Approach 1:
The patent combines self-capacitance and mutual capacitance modes in a single touch sensor system, allowing the sensor to switch between modes or use both simultaneously. This merging enables the system to benefit from the fast scanning of self-capacitance while maintaining the accuracy of mutual capacitance for multi-touch detection, resolving the contradiction between scan time and measurement precision.
2Measurement precision
If mutual capacitance mode is used, then measurement precision is improved for multi-touch, but loss of time increases due to M*N scans required
Solution Approach 1:
The patent implements dynamic mode switching between self-capacitance and mutual capacitance modes based on touch detection needs. The system can dynamically select the appropriate mode or combine both modes, allowing fast self-capacitance scanning for general detection and switching to mutual capacitance mode only when multi-touch is detected, thereby reducing overall scan time while maintaining precision.
3Adaptability or versatility
If separate voltage source and current source are provided for self-capacitance and mutual capacitance modes, then adaptability is improved, but use of energy increases power consumption
Solution Approach 1:
The patent designs a unified sensing circuit that can operate in both self-capacitance and mutual capacitance modes using the same voltage source and current source. This universal circuit design eliminates the need for separate power sources for each mode, reducing power consumption while maintaining the adaptability to switch between modes as needed.
4Adaptability or versatility
If M*N traces are connected to switch circuit and sensing circuit, then adaptability is improved for mode switching, but device complexity increases greatly
Solution Approach 1:
The patent merges the sensing circuits for self-capacitance and mutual capacitance modes into a single unified circuit structure. By combining the functions and sharing common components such as voltage sources, current sources, and trace connections, the patent significantly reduces circuit complexity while maintaining the ability to switch between modes and support both self-capacitance and mutual capacitance sensing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces power consumption, simplifies circuitry, and enhances response speed by saving scan time, particularly for large touch panels with multiple channels.
Implementation Method 1
A capacitive touch sensor used as an input tool for a human-machine interface is generally divided into self-capacitance and mutual capacitance. The so-called self-capacitance means that the driving electrode and the sensing electrode are the same one, and the change of the equivalent capacitance value of the electrode is detected to determine the touch effect. The mutual capacitance means that the driving electrode and the sensing electrode are two separated electrodes, and the change of the equivalent capacitance value between the driving electrode and the sensing electrode is detected to determine the touch effect.
Data Source
AI summary
A capacitive touch sensor includes a touch interface, a switch, and a sensing circuit. The switch circuit switches based on sensing conditions of self-capacitance and mutual capacitance. The sensing circuit is used for both the self-capacitance mode and the self-capacitance mode to simplify circuit structure and save circuit area and power consumption. The output sensing voltage from the sensing circuit is stable. A differential mode is designed to improve noise interference and enhance accuracy of judging the touch effect. Then, the self-capacitance mode is utilized for the areas of possible touches to save operation time for the capacitance mode.