Piezoelectric Touch Panel Signal Processing
Find Innovative SolutionsGenerate Solutions
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 requires complex and costly systems for combined capacitance and pressure sensing.
Innovation Solution
A device with a layer of piezoelectric material between electrodes that generates both capacitance and pressure signals from input signals, using an amplifier and analog-to-digital converter to synchronize sampling with the capacitance signal's ground or minimum value, allowing for simultaneous capacitance and pressure measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate force sensors are used to sense pressure, then pressure detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines pressure sensing and capacitance sensing into a single integrated system using piezoelectric material. The piezoelectric layer generates electrical signals in response to applied pressure, while the same layer can be read out through capacitive sensing circuits. This merging eliminates the need for separate force sensors and their associated electronics, reducing device complexity and cost while maintaining pressure detection capability.
Solution Approach 2:
The piezoelectric material serves multiple functions: it acts as both a pressure sensing element and a capacitive sensing element. The same material layer and electrode structure are used for both pressure measurement and capacitance measurement, allowing the system to perform multiple sensing functions without requiring separate dedicated components for each function.
2Measurement precision
If piezoelectric material is integrated with capacitive electrodes, then pressure sensing is enabled, but signal separation becomes difficult
Solution Approach 1:
The patent employs periodic sampling of the piezoelectric signal at specific phases of the capacitive drive cycle. By sampling the piezoelectric output at times when the capacitive drive signal is at known states (e.g., when transfer capacitors are disconnected), the system can separate the pressure signal from the capacitance signal in the time domain, avoiding the need for complex simultaneous signal separation.
Solution Approach 2:
The patent uses transfer capacitors as intermediary elements that couple the piezoelectric material to the readout circuitry. These transfer capacitors allow the piezoelectric signal to be transferred to the sensing nodes without directly interfering with the capacitive sensing operation, providing a mechanical/electrical mediation that simplifies signal separation.
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 touch panels without separate pressure sensors, simplifying the system and improving user interaction by integrating pressure and capacitance sensing into existing touch panels.
Implementation Method 1
a layer of piezoelectric material disposed between a plurality of first electrodes and at least one second electrode
Data Source
AI summary
A device (116) for processing signals from a projected capacitance touch panel (43) is described. The projected capacitance touch panel (43) includes a layer of piezoelectric material (9) disposed between a number of sensing electrodes (7, 27) and at least one counter electrode (8). The device (116) includes a capacitive touch controller (84) having a number of measurement ports (122). The device (116) also includes a number of charge amplifiers (123). The device (116) also includes a number of terminals (C1, . . . , C5, D1, . . . , D5) for connection to the sensing electrodes (7, 27) of the projected capacitance touch panel (43). Each terminal (C1, . . . , C5, D1, . . . , D5) is connected to one of the measurement ports (122). Each terminal (C1, . . . , C5, D1, . . . , D5) is also connected to an input of one of the charge amplifiers (123) via a corresponding switch (SW) of a number of switches (117a, 117b). The device (116) also includes a controller (121) configured to synchronise the capacitive touch controller (84) and the number of switches (SW, 117a, 117b) so that during a first portion ([t1, t2]) of a cycle the capacitive touch controller (84) outputs a capacitance measurement signal (91) to one or more of the terminals (C1, . . . , C5, D1, . . . , D5), and the plurality of charge amplifiers (123) are disconnected from the terminals (C1, . . . , C5, D1, . . . , D5) by the respective switches (SW, 117a, 117b). The controller (121) is also configured to synchronise the capacitive touch controller (84) and the number of switches (SW, 117a, 117b) so that during a second portion ([t2, t7]) of the cycle the capacitive touch controller (84) does not output the capacitance measurement signal (91), and one or more of the charge amplifiers (123) are connected to the corresponding terminals (C1, . . . , C5, D1, . . . , D5) by the respective switches (SW, 117a, 117b).