Force Touch Sensing via Capacitance Gap
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Solution Overview
Problem
Existing touch screen devices face challenges in accurately sensing touch forces above a certain threshold and require additional electrode channels, leading to increased data processing time and potential damage from external impacts.
Innovation Solution
An electronic device with a force touch function that utilizes a change in capacitance between a metal structure and a touch electrode on the display panel, without an additional force touch panel, to sense touch forces, incorporating a panel moving part and a driving circuit to generate force raw data based on the distance between the image display module and the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoresistive material is used to sense touch force, then touch force can be sensed, but it is difficult to sense touch force above a predetermined threshold value
Solution Approach 1:
The patent replaces the mechanical piezoresistive sensing system with a capacitive sensing system. Instead of measuring resistance changes in piezoresistive material under mechanical stress, the invention uses a driving electrode and sensing electrode configuration that measures capacitance changes. This substitution enables accurate sensing of touch forces across a wider range, including forces above predetermined thresholds that piezoresistive materials cannot detect.
Solution Approach 2:
The invention changes the sensing parameter from electrical resistance (in piezoresistive materials) to electrical capacitance. By applying a driving voltage to the driving electrode and measuring the capacitance between the driving electrode and sensing electrode, the system can detect touch forces more accurately across different magnitude ranges, resolving the limitation of piezoresistive saturation above threshold values.
2Adaptability or versatility
If a touch screen panel is disposed on a display panel, then touch input is enabled, but the touch screen panel may be damaged by external impact
Solution Approach 1:
The patent merges the touch sensing function with the display panel structure itself. The display panel includes a driving electrode (such as the common electrode or data line) and a sensing electrode (such as the transparent conductive layer), eliminating the need for a separate touch screen panel. This integration maintains touch input capability while removing the vulnerable separate touch panel layer that would be damaged by external impacts.
Solution Approach 2:
The display panel components serve multiple functions: the common electrode and data lines function both as display driving elements and as touch sensing electrodes. The transparent conductive layer serves both as a display electrode and as a force sensing element. This multi-functionality enables touch input without requiring an additional dedicated touch panel layer.
3Measurement precision
If a touch processor is connected by one-to-one correspondence to each sensing electrode, then touch sensing is achieved, but the number of electrode channels is increased and data processing time is increased
Solution Approach 1:
The patent combines multiple sensing functions into existing display driving channels. Instead of creating separate processor connections for each sensing electrode, the invention utilizes the existing data line and common electrode structures as sensing electrodes. The same driving circuits and data processing pathways handle both display driving and touch sensing signals, reducing the number of electrode channels and processing time.
Solution Approach 2:
The data lines and common electrodes serve dual purposes: driving the display and sensing touch forces. The existing display driving processor and control circuits process both display refresh data and touch sensing data through the same channels, eliminating the need for separate dedicated processing pathways and reducing overall data processing time.
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
Enables accurate sensing of touch forces above the threshold value without additional electrode channels, reducing data processing time and protecting the touch screen from external impacts by using a capacitance-based sensing mechanism.
Implementation Method 1
a driving circuit for sensing a touch force based on a distance between the image display module and the hosing which are spaced from each other with the panel moving part interposed in-between
Data Source
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AI summary
An electronic device having a force touch function enables it to sense a touch force through a change of capacitance. An image display module (100) is bendable in at least a center portion in response to a force applied to it or to a cover window (200) attached to the front surface. A mutual capacitance is formed across at least a portion of the gap between a rear surface of the image display module (100) and a housing plate of a housing (300) supporting the image display module (100) and cover window (200). A driving circuit (500) senses a change in the mutual capacitance caused by a change in a size of the gap in response to the force and generates force data estimating the force applied to the image display module (100).