Walsh Code Driving for On-Cell Touch Panel Noise Reduction
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Solution Overview
Problem
On-cell type touch panels, especially those integrated with thin active matrix organic light emitting diode (AMOLED) displays, suffer from noise interference and decreased sensitivity due to the influence of upper electrodes on the sensing electric field and electrical imbalance caused by panel bending, leading to poor detection accuracy.
Innovation Solution
A driving device and method utilizing Walsh codes from a Walsh matrix as driving signals to reduce noise interference between sensing signals, improving the signal-to-noise ratio (SNR) by using a signal processing circuit and readout circuit to demodulate sensing signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If on-cell type touch panel is used to integrate driving and sensing electrodes on display panel surface, then touch function is provided, but noise interference from lower panel display and upper electrodes affects sensing accuracy
Solution Approach 1:
The patent introduces a signal processing circuit as an intermediary between the sensing electrodes and the control system. This circuit applies orthogonal Walsh codes to drive the sensing electrodes and processes the resulting sensing signals to eliminate noise interference from display signals and upper electrodes, thereby maintaining touch detection accuracy while preserving the integrated on-cell structure
Solution Approach 2:
The patent changes the driving signal parameters by using orthogonal Walsh codes instead of conventional driving signals. This parameter change allows the sensing system to distinguish between touch signals and noise interference through correlation processing, improving detection accuracy without requiring structural modifications to the integrated on-cell design
2Length of moving object
If panel thickness is reduced below 100 μm to achieve thinner display, then flexibility and modern design are improved, but influence of upper electrodes on sensing electric field increases causing poor sensing
Solution Approach 1:
The signal processing circuit acts as an intermediary that processes sensing signals through Walsh code correlation. This intermediary processing stage separates the weak sensing signals from the dominant upper electrode interference, enabling accurate touch detection even in ultra-thin panels where the sensing electric field is heavily influenced by upper electrodes
Solution Approach 2:
The patent replaces conventional sensing methods with a signal processing approach based on Walsh code modulation and correlation. Instead of relying solely on physical electric field separation, the system uses mathematical signal processing to extract touch information from noisy signals, effectively compensating for the reduced physical separation in ultra-thin designs
3Reliability
If self-capacitance value increases to improve touch sensitivity, then touch response is enhanced, but ratio between mutual capacitance and self-capacitance decreases reducing detection accuracy
Solution Approach 1:
The patent employs periodic Walsh code sequences to drive the sensing electrodes. This periodic action creates distinct signal patterns that can be correlated with the expected touch response, allowing the system to maintain high sensitivity while accurately distinguishing true touch signals from noise even when self-capacitance values are high
Solution Approach 2:
The signal processing circuit serves as an intermediary that performs correlation processing between the sensed signals and reference Walsh codes. This intermediary processing enhances the signal-to-noise ratio by exploiting the orthogonality of Walsh codes, thereby maintaining detection accuracy despite the reduced mutual-to-self capacitance ratio
4Adaptability or versatility
If flexible display touch panel is bent to achieve flexible form factor, then adaptability is improved, but electrical imbalance phenomenon occurs affecting touch point detection accuracy
Solution Approach 1:
The patent uses Walsh code modulation as a parameter change technique that transforms the sensing approach from direct voltage measurement to correlation-based detection. This transformation makes the system robust against electrical imbalance caused by bending, as the orthogonal code structure maintains signal distinguishability even when capacitance values fluctuate due to mechanical deformation
Data Source
AI summary
The present disclosure provides a driving device for driving a sensing device having a plurality of driving electrodes and a plurality of sensing electrodes. The driving device includes a signal processing circuit and a readout circuit. The signal processing circuit is electrically connected to the plurality of driving electrodes of the sensing device. The signal processing circuit is configured to generate a plurality of driving signal to drive the sensing device. The signal processing circuit selects a plurality of Walsh codes from a plurality of rows or columns of a Walsh matrix to serve as a plurality of driving signals. The readout circuit readouts the sensing device to generate a plurality of sensing signals and provides the plurality of sensing signals to the signal processing circuit, so that the signal processing circuit demodulates the plurality of sensing signals. In addition, a driving method is also provided.