Shift Register Unit for Self-Capacitive Touch Screen
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing self-capacitive touch screens face challenges in accurately detecting touch positions due to parasitic capacitance variations between touch electrodes and pixel circuits, requiring precise control of touch scan signals to maintain constant voltage across terminals.
Innovation Solution
A shift register unit with specific control and output circuits is designed to manage clock signals and reference voltages, allowing for the transfer of input signals and touch scan signals to output terminals while maintaining constant voltage, enabling accurate touch detection by cascading these units in a scan driving circuit for a self-capacitive touch screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If touch scan signals are applied to pixel circuit terminals during touch sensing phase, then touch detection accuracy is improved, but parasitic capacitance variations between terminals and touch electrodes affect detection accuracy
Solution Approach 1:
The patent applies equipotentiality by maintaining constant voltage across pixel circuit terminals through synchronized clock signal application. During the touch sensing phase, clock signals are applied to pixel circuit terminals at the same time as touch scan signals are applied to touch electrodes, ensuring that both sides remain at constant potential. This eliminates voltage fluctuations that would otherwise cause parasitic capacitance variations to affect detection accuracy, thereby resolving the contradiction between improving touch detection accuracy and eliminating parasitic capacitance interference.
2Measurement precision
If constant voltage is maintained across pixel circuit terminals and touch electrodes, then parasitic capacitance effects are eliminated, but additional clock signal control circuits are required
Solution Approach 1:
The patent applies universality by designing the clock signal control circuit to perform multiple functions simultaneously. The same clock signal generation mechanism serves both the display phase (controlling pixel circuit operation) and the touch sensing phase (controlling touch electrode scanning). By using a unified clock signal distribution system that can dynamically configure signal paths based on operational phase, the patent avoids the need for separate dedicated control circuits for each function, thereby reducing overall device complexity while maintaining constant voltage for accurate touch detection.
3Productivity
If touch scan signals are applied during display phase, then touch detection can be performed simultaneously, but display performance may be affected
Solution Approach 1:
The patent applies periodic action by dividing operation into distinct display phases and touch sensing phases, with each phase occupying specific time intervals. During the display phase, clock signals are configured to prioritize pixel circuit operation for stable image display. During the touch sensing phase, clock signals are reconfigured to enable touch electrode scanning while maintaining constant voltage. This periodic switching between phases, controlled by phase-dependent clock signal distribution, allows simultaneous touch detection and display functionality while ensuring that each function receives appropriate signal conditions during its active period, thereby maintaining display performance reliability.
Data Source
AI summary
A shift register unit includes an input circuit, a first control circuit, a second control circuit, a third control circuit, a first output circuit, and a second output circuit. The first and second output circuits selectively transfer a first reference voltage from a first reference voltage terminal and a third reference voltage from a third reference voltage terminal to an output terminal of the shift register unit. This allows the shift register unit to output a desired output signal in an easy manner.