Touch Controller Self-Capacitance Compensation for Ungrounded Signals
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Solution Overview
Problem
Capacitive touch sensor panels face attenuation of self-capacitance touch signals due to ungrounded interactions, which complicates the detection of touch events, especially in partially bootstrapped systems where not all pixels are driven and sensed simultaneously.
Innovation Solution
The solution involves obtaining both self-capacitance and mutual capacitance measurements on the touch sensor panel and scaling the self-capacitance measurements based on these values to reduce attenuation, allowing for effective detection of touch events by compensating for the ungrounded interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a partially bootstrapped touch sensor panel is used to reduce manufacturing complexity and cost, then device complexity is reduced, but self-capacitance touch signal attenuation increases
Solution Approach 1:
The system performs preliminary mutual capacitance measurements and calculations before processing self-capacitance touch signals. By pre-calculating the attenuation factor based on mutual capacitance data, the system compensates for signal attenuation in advance, allowing the partially bootstrapped design to maintain reliable touch detection without requiring full bootstrapping of all pixels.
Solution Approach 2:
The system uses mutual capacitance measurements as feedback to determine the attenuation factor, which then adjusts the interpretation of self-capacitance touch signals. This feedback mechanism allows the system to compensate for the reduced signal strength caused by the partially bootstrapped configuration, maintaining detection reliability while keeping the design simpler.
2Device complexity
If self-capacitance measurements are taken without compensation for ungrounded interactions, then measurement process is simpler, but measurement precision deteriorates
Solution Approach 1:
The system introduces mutual capacitance measurements as an intermediary element that mediates between the simple self-capacitance measurement process and the need for precise touch detection. The mutual capacitance data serves as a reference that helps correct the self-capacitance measurements, improving precision without significantly complicating the overall measurement process.
Solution Approach 2:
The system changes the parameter used for measurement interpretation by calculating an attenuation factor based on mutual capacitance values. Instead of directly using raw self-capacitance measurements, the system adjusts the measurement parameters by applying the attenuation correction, thereby improving measurement precision while maintaining a relatively simple measurement process.
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 approach enhances the accuracy and reliability of touch signal detection, reducing signal attenuation and improving the ability to sense touch events on partially bootstrapped touch sensor panels, making it easier to identify touch activity.
Implementation Method 1
Touch events can be sensed on the touch sensor panels by detecting changes in the self-capacitance of the conductive plates (touch pixels)
Implementation Method 2
In some capacitive-type touch sensing systems, 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
AI summary
A touch controller is disclosed. The touch controller can include sense circuitry configured to sense, during a self-capacitance portion of a touch frame, first one or more self-capacitances associated with a first plurality of touch pixels on a touch sensor panel, and sense, during a mutual capacitance portion of the touch frame, first one or more mutual capacitances associated with the first plurality of touch pixels. A touch processor can be configured to, based on the first one or more self-capacitances and the first one or more mutual capacitances, sense a single touch event associated with the touch frame.