Piezoelectric Touch Panel Pressure Sensing via Switch Network
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Solution Overview
Problem
Projected capacitance touch panels lack the ability to sense pressure, failing to differentiate between light taps and heavy presses, which limits user interaction and feedback.
Innovation Solution
A touch panel system incorporating a layer of piezoelectric material between sensing electrodes and a common electrode, with a capacitive touch controller and switch networks to generate pressure signals and distinguish between capacitance and pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a projected capacitance touch panel is used, then touch location detection is enabled, but pressure sensing capability is lost
Solution Approach 1:
The patent combines projected capacitance sensing electrodes with piezoelectric pressure sensing material in a single touch panel structure. The sensing electrodes are positioned in electrical contact with the piezoelectric material, allowing simultaneous detection of both touch location (through capacitance changes) and pressure (through piezoelectric voltage generation) without requiring separate sensing systems.
2Measurement precision
If piezoelectric material is added to the touch panel, then pressure sensing is enabled, but device complexity increases
Solution Approach 1:
The piezoelectric material serves multiple functions simultaneously: it acts as both the pressure sensing element (generating voltage under mechanical stress) and the dielectric layer for the capacitance sensing electrodes. This multi-functionality eliminates the need for separate dielectric and pressure sensing layers, reducing overall device complexity despite adding pressure sensing capability.
Solution Approach 2:
The touch panel employs a composite structure where piezoelectric material is integrated with conductive sensing electrode layers. This composite design allows the piezoelectric material to fulfill dual roles as both structural/dielectric component and active pressure sensing element, streamlining the overall device architecture.
3Measurement precision
If sensing electrodes are connected to ground during pressure measurement, then pressure signal accuracy is improved, but capacitance measurement capability is reduced
Solution Approach 1:
The patent implements dynamic switching of electrode connections based on measurement mode. During capacitance measurement, sensing electrodes are connected to readout circuitry to detect capacitance changes. During pressure measurement, the same electrodes are switched to ground connection to eliminate capacitive interference and optimize piezoelectric signal detection. This dynamic reconfiguration allows the system to adapt to different measurement requirements.
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 the detection of pressure applied to the touch panel, providing additional interaction data and enhancing user experience by differentiating between various touch inputs.
Implementation Method 1
a layer of piezoelectric material disposed between a number of sensing electrodes and at least one common electrode
Data Source
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AI summary
A touch panel (10) including a layer of piezoelectric material (16) disposed between a number of sensing electrodes (14, 20) and at least one common electrode (15). The apparatus (73) including a capacitive touch controller (69) connected to the sensing electrodes and a switch network (74) including a number of inputs connected to some or all sensing electrodes, and an output connected to system ground or a common mode voltage (VCM). The apparatus also includes a controller (25) and a second circuit (24, 44) receiving signals from the at least one common electrode and generating, based thereon, a second pressure signal (30) indicative of a total pressure applied to the touch panel. The controller is configured to control the switch network to couple any connected sensing electrodes to system ground or the common mode voltage during a pressure measurement period, and to estimate the total pressure based on the second pressure signal during the pressure measurement period.