Touch Sensing Noise Isolation via Differential Signals
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Solution Overview
Problem
Traditional touch sensing methods for integrated panels, such as those with OLEDs or Mini LEDs, face interference from display and fingerprint recognition operations, making it difficult to achieve effective touch sensing due to noise interference, especially when time-division driving is not feasible.
Innovation Solution
A touch sensing method that selects specific touch sensing units to apply excitation signals, obtaining differential sensing signals to isolate capacitance changes, and uses a reference signal to reduce noise interference, allowing for accurate capacitance value acquisition and improved touch position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If time-division driving is used to separate touch sensing from display operations, then interference between circuits is reduced, but display driving cannot be stopped for integrated panels like OLEDs/Mini LEDs, making time-division driving difficult to achieve
Solution Approach 1:
The touch sensing units are divided into two groups: to-sense units that receive excitation signals for touch detection, and reference units that receive reference signals for noise cancellation. This segmentation allows simultaneous operation of display and touch sensing circuits without mutual interference, resolving the contradiction between continuous display driving and clean touch signal acquisition.
Solution Approach 2:
A reference sensing signal is introduced as an intermediary to represent the noise component from display operations. By subtracting this reference signal from the touch sensing signals, the harmful noise is eliminated while allowing continuous display driving, thus resolving the contradiction without requiring display driving to be stopped.
2Object-affected harmful factors
If analog or digital filters are used in touch sensing circuits to increase sampling time, then noise from display operations is reduced, but power consumption increases
Solution Approach 1:
Instead of using power-consuming filters to remove noise, a reference sensing signal is used as an intermediary to represent and subtract the noise component directly from the touch sensing signals. This signal processing approach eliminates noise without requiring additional filtering hardware or increased sampling time, thus reducing power consumption while maintaining noise reduction effectiveness.
Solution Approach 2:
The patent replaces the mechanical/filter-based noise reduction approach with an electrical signal processing approach. By using reference signals and differential processing, noise is removed through mathematical subtraction rather than physical filtering, eliminating the need for additional filtering components and reducing overall power consumption.
3Area of stationary object
If touch excitation signals are applied to all touch sensing units simultaneously, then touch detection coverage is maximized, but noise interference from display and fingerprint recognition operations cannot be effectively isolated
Solution Approach 1:
The touch sensing units are segmented into to-sense units and reference units. The to-sense units maintain full coverage for touch detection, while the reference units are strategically positioned to capture noise from display and fingerprint recognition operations. This segmentation allows simultaneous achievement of full touch coverage and effective noise isolation through differential processing.
Solution Approach 2:
Reference sensing signals serve as intermediaries that capture the noise component from display and fingerprint recognition operations. By subtracting these reference signals from the touch sensing signals, noise interference is effectively isolated and removed while maintaining full touch detection coverage across all to-sense units.
4Measurement precision
If multiple touch sensing units are used to improve touch detection accuracy, then measurement precision increases, but the complexity of signal processing and noise cancellation increases
Solution Approach 1:
The multiple touch sensing units are segmented into to-sense units and reference units with clear functional differentiation. This segmentation simplifies signal processing by organizing multiple signals into two distinct groups that can be processed through systematic differential equations, reducing the complexity that would otherwise arise from handling all signals individually.
Solution Approach 2:
Reference sensing signals act as intermediaries that represent the common noise component across multiple touch sensing units. By using these reference signals, the patent simplifies noise cancellation for multiple units through unified differential processing, avoiding the need to individually process and cancel noise for each unit, thus reducing overall signal processing complexity.
Data Source
AI summary
A touch sensing method for a touch panel and an electronic device are provided. The touch sensing method includes: selecting a portion of multiple touch sensing units as to-sense touch sensing units, applying first touch excitation signals to the those to obtain multiple first touch sensing signals, and obtaining multiple differential sensing signals based on multiple first touch sensing signals; selecting a touch sensing unit as a reference touch sensing unit, and applying a touch reference signal to it to obtain a reference sensing signal; selecting a to-sense touch sensing unit as a preprocessing touch sensing unit, and applying a second touch excitation signal to it to obtain a second touch sensing signal; obtaining a capacitance sensing signal from the reference sensing signal and the second touch sensing signal; and acquiring capacitance values of multiple to-sense touch sensing units according to the differential sensing signals and the capacitance sensing signal.