Capacitance Touch Sensor Noise Elimination via Timing Control
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Solution Overview
Problem
Existing capacitance type touch sensors in liquid crystal display devices face challenges in accurately detecting objects without using a shield layer, as noise from image-signal writing operations interferes with detection signals, leading to reduced detection accuracy and increased power consumption.
Innovation Solution
A display device with a capacitance type touch sensor that utilizes a common electrode and a touch detection electrode to form a capacitor, where the touch detection circuit performs detection operations based on detection signals obtained before and after the inversion timing of the common drive voltage, effectively eliminating post-inversion noise without a shield layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shield layer is added to block noise from image-signal writing operations, then detection accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and removes the shield layer from the touch sensor structure, achieving noise elimination through alternative means (timing-based noise removal and circuit design) rather than physical shielding, thereby reducing device complexity while maintaining detection accuracy
Solution Approach 2:
The patent changes the timing parameters of signal writing and reading operations, performing touch detection during periods when image signal writing is suspended or minimized. By adjusting the temporal parameters of operation sequencing, the system achieves noise-free detection without requiring additional shield layers
2Measurement precision
If a shield layer is added to block noise from image-signal writing operations, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The patent removes the power-consuming shield layer by implementing software/timing-based noise elimination strategies, reducing overall power consumption while maintaining detection accuracy through intelligent operation scheduling
Solution Approach 2:
The patent implements periodic touch detection operations that are synchronized with the display refresh cycle, performing detection only during specific time windows when image signal writing is minimized. This periodic action reduces average power consumption compared to continuous detection with shield layers
3Adaptability or versatility
If the touch detection electrode is placed deep inside the liquid crystal display element, then design flexibility is improved, but detection accuracy deteriorates due to noise from image-signal writing operations
Solution Approach 1:
The patent performs preliminary timing-based separation of touch detection operations from image signal writing operations. By scheduling detection during specific time periods before or after image writing, the system enables deep electrode placement without noise interference, achieving both design flexibility and detection accuracy
Solution Approach 2:
The patent implements dynamic timing control that adapts the touch detection operation timing based on the display refresh cycle and image signal writing schedule. This dynamic scheduling allows flexible electrode placement while maintaining accurate detection by avoiding noisy periods
4Measurement precision
If independent circuit sections for touch panel drive and coordinate detection are provided, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the touch panel drive circuit and coordinate detection circuit into a single integrated circuit section. By combining these functions and using timing-based noise elimination, the system achieves accurate detection without the complexity of independent circuit sections
Solution Approach 2:
The patent designs a multi-functional circuit that performs both touch panel driving and coordinate detection functions. This universal circuit reduces overall device complexity while maintaining detection accuracy through intelligent timing control and noise elimination algorithms
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
This approach enhances the accuracy of object detection in the display device by eliminating noise from image-signal writing operations, improving detection precision without the need for a shield layer and reducing power consumption.
Implementation Method 1
a capacitance type touch sensor having a new configuration... a capacitor is formed between the touch detection electrode and a common electrode
Data Source
AI summary
The display device with high detection accuracy includes: display pixel electrodes; a common electrode; a display function layer; a display control circuit performing image display control by applying a pixel voltage to each of the display pixel electrodes and applying a common drive voltage to the common electrode, the common drive voltage inverting in synchronization with a drive cycle of the image display control; a touch detection electrode cooperating with the common electrode to form a capacitor; and a touch detection circuit detecting an external proximity object, based on a detection signal obtained from the touch detection electrode in response to the common drive voltage applied to the common electrode. The touch detection circuit performs the detection operation in a inversion period following an inversion timing of the common drive voltage, based on both first and second detection signals obtained before and after the inversion timing, respectively.