Dynamic Impedance Control for Touch Detection Electrodes
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Solution Overview
Problem
Wearable devices with touch detection functions face challenges in balancing display quality and operability, particularly in achieving effective touch detection while minimizing power consumption and maintaining a simple structure.
Innovation Solution
A display device with a self-capacitive touch detection system, featuring a first detection electrode in the display area and multiple second detection electrodes in the peripheral area, where the first detection electrode is set to a high-impedance state or connected to a predetermined potential with 50 kΩ or higher impedance when not in use, allowing for efficient touch detection and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the first detection electrode is continuously connected to a low impedance during display period, then touch detection sensitivity is improved, but power consumption increases
Solution Approach 1:
The impedance of the first detection electrode is dynamically changed between display period and non-display period. During display period, low impedance (50Ω or higher) maintains touch detection sensitivity, while during non-display period, high impedance (50 kΩ or higher) reduces power consumption. This dynamic impedance adjustment resolves the contradiction between maintaining detection sensitivity and reducing power consumption.
Solution Approach 2:
The detection electrode impedance is periodically switched between two states: low impedance during display period for accurate touch detection, and high impedance during non-display period for power saving. This periodic impedance switching aligns with the display operation cycles and effectively balances detection performance with power efficiency.
2Use of energy by moving object
If the detection electrode impedance is set high during non-display period, then power consumption is reduced, but touch detection capability deteriorates
Solution Approach 1:
The system dynamically adjusts the impedance of the first detection electrode based on operational state. During non-display period, high impedance (50 kΩ or higher) is applied to reduce power consumption, while during display period, low impedance (50Ω or higher) is applied to ensure touch detection capability. This dynamic adjustment ensures that touch detection capability is maintained when needed while minimizing power consumption when display is active.
Solution Approach 2:
The impedance switching follows the display period cycle, periodically transitioning between high impedance (power-saving mode during non-display) and low impedance (detection mode during display). This periodic action ensures that touch detection capability is restored at appropriate intervals when display operation requires it.
3Measurement precision
If multiple detection electrodes are disposed throughout the display area, then touch detection coverage is improved, but device complexity increases
Solution Approach 1:
The detection electrode system is segmented into two functional zones: first detection electrodes disposed in the display area for primary touch detection, and second detection electrodes disposed in the peripheral area for additional detection coverage. This segmentation allows comprehensive touch detection coverage while maintaining a relatively simple overall structure by strategically placing electrodes only where needed rather than uniformly distributing them throughout the entire display area.
Solution Approach 2:
Different regions of the display device are assigned different detection electrode configurations tailored to their specific functions. The display area receives first detection electrodes optimized for touch interaction, while the peripheral area receives second detection electrodes for edge detection or additional functionality. This local quality approach achieves comprehensive coverage without uniformly increasing complexity across the entire device.
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 configuration enables both high display quality and excellent operability by touch, while reducing power consumption and maintaining a relatively simple structure, effectively addressing the balance between display and touch detection functions.
Implementation Method 1
a liquid crystal layer held between the first substrate and the second substrate, at least one first detection electrode disposed in a display area... during a display period in which images are displayed in the display area, a predetermined voltage for driving the liquid crystal layer
Implementation Method 2
in a period in which the liquid crystal layer is not driven, the first detection electrode is set to a state of being not electrically connected to anywhere or to a state of being connected to a predetermined potential with an impedance of 50 kΩ or higher
Data Source
AI summary
According to one embodiment, a display device includes a first substrate, a second substrate opposing the first substrate, a liquid crystal layer, at least one first detection electrode disposed in a display area and a plurality of second detection electrodes disposed in a peripheral area. In a display period in which images are displayed on the display area, a predetermined voltage is applied to the first detection electrode to drive the liquid crystal layer, and in a period in which the liquid crystal layer is not driven, the first detection electrode is set to a state of being not electrically connected to anywhere or being connected to a predetermined potential with an impedance of 50 kΩ or higher.