Capacitive Multi-Touch Sensing Mode Switching for Power and Accuracy
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Solution Overview
Problem
Capacitive multi-touch systems face issues with high power consumption and instability due to drifting self and mutual capacitance, especially in portable devices, and struggle with accurate touch detection in varying environments and multi-touch scenarios.
Innovation Solution
A low power switching mode driving and sensing method that alternates between self and mutual capacitance modes using a controller to initialize and configure driving and sensing devices, storing base image data and detecting touch points to switch between idle and active modes, reducing power consumption and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If self capacitance sensing is used continuously, then power consumption is reduced, but touch detection accuracy deteriorates due to drifting capacitance values
Solution Approach 1:
The patent implements periodic switching between self-capacitance sensing mode (low power) and mutual-capacitance sensing mode (high accuracy). The system alternates between these modes based on detected drift conditions, using periodic calibration routines to maintain accuracy while minimizing power consumption. This resolves the contradiction by not relying on a single continuous sensing method but rather alternating between complementary approaches.
Solution Approach 2:
The patent changes the sensing parameters by switching between self-capacitance and mutual-capacitance measurement modes. When drift is detected, the system changes from using self-capacitance values to using mutual-capacitance values between adjacent conductor lines. This parameter change allows the system to adapt to drifting conditions while maintaining both low power consumption and high accuracy.
2Measurement precision
If mutual capacitance sensing is used continuously, then touch detection accuracy is improved, but power consumption increases
Solution Approach 1:
The system uses periodic action by alternating between mutual-capacitance sensing (for high accuracy) and self-capacitance sensing (for low power). Instead of continuously using the more power-consuming mutual capacitance mode, the patent implements periodic calibration and only activates mutual capacitance sensing when drift correction is needed, thus reducing overall power consumption while maintaining accuracy.
Solution Approach 2:
The system performs self-service by using self-capacitance sensing to detect drift conditions and automatically triggering mutual-capacitance calibration when necessary. This self-service mechanism allows the system to maintain accuracy without continuously consuming high power, as it only activates the more demanding sensing mode when its services are actually needed.
3Measurement precision
If capacitor coupling is increased for better signal strength, then signal-to-noise ratio improves, but electromagnetic disturbance and noises increase
Solution Approach 1:
The patent applies local quality by using mutual capacitance sensing between adjacent conductor lines rather than increasing overall capacitor coupling. This localized approach creates capacitor coupling only where needed (between adjacent lines) without generating widespread electromagnetic disturbances across the entire touch panel. The harmful factors are confined to local areas rather than propagating system-wide.
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 method reduces power consumption, enhances touch detection accuracy, and prolongs the use life of portable devices by efficiently switching between modes based on touch events and environmental conditions.
Implementation Method 1
a capacitive touch panel uses a capacitance change generated in an electrostatic combination of the arranged transparent electrodes with the touching part of a human body to generate a current or voltage for detecting the coordinate of the touching part
Implementation Method 2
The self capacitance sensing indicates that a capacitance coupling is generated between a touch object and a conductor line
Implementation Method 3
the driving and sensing devices 110 in a first direction drive the conductor lines in the first direction in order to further charge the self capacitance of the conductor lines in the first direction
Implementation Method 4
a change of the grounded capacitance is used to determine whether an object is toward the capacitive touch panel
Data Source
AI summary
A low power switching mode driving and sensing method for capacitive multi-touch systems is used in a capacitive multi-touch system with a capacitive touch panel. When the capacitive touch system operates in an idle mode, the method uses a self-capacitance driving and sensing technology to detect touch points. When the touch points are detected on the capacitive touch panel, the capacitive touch system is switched to an active mode and uses a mutual-capacitance driving and sensing technology to detect touch points for accurately acquiring the positions related to the touch points detected. During a predetermined time interval in which there is no touch point detected, the method automatically performs a calibration to update a mutual-capacitance base image raw data and a self-capacitance base image raw data, so as to overcome the drifting of sensors of the capacitive touch system.