Touch Controller Signal Processing for Pressure Sensing
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Solution Overview
Problem
Projected capacitance touch panels lack the ability to sense pressure, failing to distinguish 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 touch controller with a layer of piezoelectric material between electrodes, generating pressure and capacitance signals by sampling amplified signals at specific amplitudes of the capacitance signal, allowing for simultaneous processing of pressure and capacitance information without separate electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If projected capacitance touch panels use separate electronics for capacitance and pressure sensing, then pressure sensing capability is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines capacitance sensing and pressure sensing into a single integrated system using one set of electrodes and one analog-to-digital converter. The touch controller processes both capacitance and pressure information simultaneously by analyzing different aspects of the same signal, eliminating the need for separate sensing systems and reducing overall system complexity.
Solution Approach 2:
The analog-to-digital converter is designed to perform multiple functions: it processes both capacitance measurement signals and pressure-sensitive piezoelectric signals through the same electrode structure. This multi-functional approach allows a single component to handle both sensing modalities, reducing the number of required components and simplifying the overall system architecture.
2Measurement precision
If separate electrodes are applied onto piezoelectric film for pressure sensing, then pressure sensitivity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the capacitance electrodes and piezoelectric pressure sensing electrodes into a single electrode structure. The same electrodes that detect capacitance changes also detect piezoelectric signals generated by pressure, eliminating the need for separate electrode layers and simplifying the manufacturing process.
Solution Approach 2:
The electrodes are designed to serve dual purposes: they function as capacitance sensing elements and as piezoelectric signal collection elements. This universal design allows a single electrode structure to perform both sensing functions, significantly reducing manufacturing steps and material requirements compared to separate electrode systems.
3Device complexity
If a single signal is used for both capacitance and pressure sensing, then system complexity is reduced, but signal separation accuracy may be compromised
Solution Approach 1:
The patent employs periodic sampling of the combined signal at specific phases of the capacitance measurement cycle. By sampling at predetermined time points when the capacitance signal is at known states (e.g., when the driving signal is at zero crossing or at peak), the system can effectively separate pressure information from capacitance information in the time domain, maintaining accuracy while using a single signal path.
Solution Approach 2:
The patent uses the phase relationship between the capacitance driving signal and the piezoelectric response signal as an intermediary for separation. The analog-to-digital converter analyzes the phase-differentiated components of the combined signal, using phase information as a mediator to distinguish between capacitance changes and pressure-induced piezoelectric effects, thereby achieving accurate signal separation without requiring separate physical sensing paths.
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 pressure sensing and capacitance measurement in a single touch panel system, reducing complexity and cost while enhancing user interaction capabilities.
Implementation Method 1
a layer of piezoelectric material disposed between a plurality of first electrodes and at least one second electrode
Implementation Method 2
generate a pressure signal and a capacitance signal
Data Source
Figure 1~2
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AI summary
A device (42) is provided for processing signals (10) from a projected capacitance touch panel (43), the touch panel (43) including a layer of piezoelectric material (9) disposed between a plurality of first electrodes (7, 27) and at least one second electrode (8). The device is configured, in response to receiving input signals (10) from a given first electrode (7, 27), to generate a pressure signal (15a, 15b) indicative of a pressure applied to the touch panel (43) proximate to the given first electrode (7, 27) and a capacitance signal (54a, 54b) indicative of a capacitance of the given first electrode (7, 27). The device (42) includes an amplifier (52) configured to generate an amplified signal (14a, 14b) based on the input signals (10). The device (42) also includes an analog-to-digital converter (50a, 50b) configured to be synchronised (53) with the capacitance signal (54a, 54b), and to generate the pressure signal (15a, 15b) by sampling the amplified signal (14a, 14b) at times corresponding to the amplitude of the capacitance signal (54a, 54b) being substantially equal to a ground, common mode or minimum value.