Touch Panel Sensing Unit Circuit Topology for Aperture Ratio
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Solution Overview
Problem
Conventional liquid crystal display devices with touch functions require a large number of transistors and capacitors, which reduce the aperture ratio and output voltage due to increased parasitic capacitance, leading to signal attenuation.
Innovation Solution
A touch panel with a sensing unit comprising only two transistors and two capacitors, where the transistors are configured to receive different potentials when switched on, allowing for reduced parasitic capacitance and a larger output voltage range, thereby minimizing the impact on the display's aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sensing unit uses three transistors and two capacitors (3T2C structure), then the touch detection function is achieved, but the aperture ratio is reduced and output voltage range is limited due to increased parasitic capacitance
Solution Approach 1:
The patent extracts and removes one transistor from the conventional 3T2C sensing unit structure, reducing it to a 2T2C configuration. This is achieved by optimizing the circuit architecture where the first transistor's drain electrode is directly connected to the second transistor's gate electrode, eliminating the need for an additional transistor while maintaining touch detection functionality.
Solution Approach 2:
The patent merges the functions of multiple components by directly connecting the drain electrode of the first transistor to the gate electrode of the second transistor. This direct connection combines the signal output function and the control function into a single node, reducing the total component count while preserving the sensing capability.
2Reliability
If excessive transistors are used in the sensing unit, then the touch detection capability is improved, but parasitic capacitance increases causing signal attenuation
Solution Approach 1:
The patent removes the harmful factor of excessive parasitic capacitance by extracting one transistor from the circuit. This reduction in component count directly decreases the parasitic capacitance between components, thereby reducing signal attenuation while maintaining adequate touch detection capability through the optimized 2T2C structure.
3Reliability
If a larger sensing unit size is used to accommodate more components, then the touch detection function is achieved, but the aperture ratio of the display is reduced
Solution Approach 1:
The patent extracts one transistor from the conventional sensing unit, reducing the component count and allowing for a smaller sensing unit footprint. This size reduction minimizes the area occupied by the sensing unit, thereby preserving a larger aperture ratio for the display while maintaining full touch detection functionality.
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
The solution achieves a smaller sensing unit size with reduced parasitic capacitance, enhancing the output voltage range and maintaining the display's aperture ratio, allowing for effective touch detection with fewer electronic components.
Implementation Method 1
the liquid crystal capacitor 16 has a capacitance value altered in compliance with the pressed degree of the sensing unit 10
Data Source
AI summary
A touch panel includes multiple sensing units and each thereof includes a first transistor, a reference capacitor, a liquid crystal capacitor and a second transistor. ON/OFF states of the first transistor are determined by a potential provided by a corresponding scan line. The reference capacitor and the liquid crystal capacitor are coupled in series between another scan line adjacent to the corresponding scan line and a common potential. A capacitance value of the liquid crystal capacitor changes with a pressed degree of the sensing unit. ON/OFF states the second transistor are determined by a potential at a connection node between the reference capacitor and the liquid crystal capacitor. The first transistor transmits a first potential to the connection node when the first transistor is turned on, and the second transistor transmits a second potential different from the first potential to a readout line when the second transistor is turned on.