Self-Capacitance Touch Pixel Driving for Floating Ground Suppression
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Solution Overview
Problem
Capacitive touch sensor panels often experience undesirable changes in touch sensing signals due to floating ground references, which can lead to inaccurate touch detection and performance issues.
Innovation Solution
Implementing techniques such as driving and sensing specific touch pixels while coupling others to a reference voltage, configuring routing to reduce parasitic capacitances, and utilizing dynamic touch pixel driving schemes to mitigate the effects of floating ground references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If touch pixels are driven and sensed using self-capacitance method, then touch sensing capability is achieved, but floating ground effects cause undesirable changes in touch sensing signals
Solution Approach 1:
The touch sensor panel is divided into multiple independently controllable touch pixels or groups of touch pixels. By segmenting the sensing area, the controller can selectively drive and sense specific regions while keeping other regions in a different state, thereby isolating floating ground effects to specific segments and preventing them from affecting the entire panel.
Solution Approach 2:
Different regions of the touch sensor panel are assigned different operational states: some touch pixels are driven and sensed while others are coupled to reference voltage. This local differentiation allows the system to maintain accurate touch sensing in active regions while suppressing floating ground effects in inactive regions through reference voltage coupling.
2Measurement precision
If routing is configured to reduce parasitic capacitances, then routing-to-routing parasitic effects are minimized, but device complexity increases
Solution Approach 1:
Routing lines are configured to maintain equipotential relationships where possible, reducing voltage differences between adjacent routing lines. This minimizes parasitic capacitance effects without requiring complex routing patterns, as the equipotential configuration naturally reduces the electric field coupling between lines.
Solution Approach 2:
Reference voltage coupling is introduced as an intermediary mechanism to manage parasitic capacitance effects. By coupling inactive touch pixels to reference voltage, the system creates a stable electrical reference that mediates the parasitic capacitance between active and inactive regions, reducing their mutual interference.
3Reliability
If dynamic touch pixel driving schemes are implemented, then floating ground effects are reduced, but control complexity increases
Solution Approach 1:
The touch controller implements periodic switching between different driving modes: during certain time intervals, touch pixels are driven and sensed; during other intervals, they are coupled to reference voltage. This periodic action allows the system to dynamically manage floating ground effects by alternating between sensing mode and reference coupling mode, stabilizing the ground reference over time.
Solution Approach 2:
The touch pixel driving scheme is made dynamic rather than static. The controller can adaptively switch the operational state of touch pixels based on sensing requirements, allowing the system to optimize between touch detection accuracy and floating ground suppression in real-time, thereby improving ground reference stability.
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
These methods enhance the accuracy and reliability of touch sensing by stabilizing the ground reference and reducing errors in current flow, thereby improving the overall performance of capacitive touch screens.
Implementation Method 1
Touch events can be sensed on the above touch sensor panels by detecting changes in the self-capacitance of the conductive plates
Implementation Method 2
fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface
Data Source
Figure 1A~1D
Figure 2
Figure 3A~3B
AI summary
A touch controller is disclosed. In some examples, the touch controller can include sense circuitry configured to be coupled to a first touch pixel and a second touch pixel on a touch sensor panel. In some examples, the sense circuitry can be configured to drive and sense the first touch pixel during a first time period while coupling the second touch pixel to a reference voltage. In some examples, the sense circuitry can be configured to drive and sense the second touch pixel during a second time period while coupling the first touch pixel to the reference voltage. In some examples, the reference voltage can be a system ground of the touch controller. In some examples, the sense circuitry can be configured to drive and sense pluralities of touch pixels in a similar manner.