Touch Detection Circuit With In-Phase Amplifier
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Solution Overview
Problem
Mutual capacitive touch technology in touch display panels faces challenges with high stray capacitance between touch electrodes and common electrodes, leading to reduced touch detection accuracy and increased production costs due to the need for cutting the common electrode into smaller pieces and applying time-sharing technology, which hinders display resolution and quality.
Innovation Solution
A display device with high touch detection sensitivity is achieved by using a thin film transistor (TFT) substrate layer, a common electrode layer, and a touch electrode layer, where the touch control circuit employs an in-phase amplifier to drive the touch sense signal to the common electrode, eliminating the current loop and maintaining high impedance between the display and touch control circuits, thereby reducing background parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the common electrode is placed close to the touch electrodes to reduce panel thickness, then the panel structure becomes more compact, but the parasitic capacitance between the common electrode and touch electrodes increases significantly
Solution Approach 1:
The common electrode is divided into multiple segments (first common electrode and second common electrode) that are spatially separated from the touch electrodes. This segmentation reduces the overlapping area between the common electrode and touch electrodes, thereby reducing parasitic capacitance while maintaining the thin panel structure.
Solution Approach 2:
An insulating layer is introduced between the common electrode and the touch electrodes as an intermediary element. This insulating layer increases the distance between conductive surfaces, reducing parasitic capacitance coupling while allowing the electrodes to remain in close proximity for thin panel design.
2Object-affected harmful factors
If the common electrode is cut into many pieces to reduce parasitic capacitance, then the stray capacitance problem is mitigated, but the display resolution deteriorates and production difficulty increases
Solution Approach 1:
The common electrode is segmented into multiple parts positioned at different locations, with each segment serving both as a common electrode for display driving and as a touch electrode for touch detection. This segmentation reduces parasitic capacitance while maintaining continuous coverage for high display resolution and simplifying production.
Solution Approach 2:
The segmented common electrode serves dual functions: it acts as the common electrode for display driving and simultaneously functions as touch electrodes for touch detection. This multi-functionality eliminates the need for separate touch electrode structures, maintaining display quality while reducing parasitic capacitance and production complexity.
3Object-affected harmful factors
If the common electrode is cut into many pieces and time sharing technology is applied to reduce parasitic capacitance, then the stray capacitance is reduced, but the device complexity increases
Solution Approach 1:
The common electrode is divided into multiple independent segments that can be independently controlled. Each segment functions as both a common electrode and a touch electrode, allowing simultaneous touch detection on multiple regions without requiring complex time-multiplexed switching circuits.
Solution Approach 2:
Each segment of the common electrode serves dual purposes as both display common electrode and touch sensing electrode. This eliminates the need for separate touch electrode layers and complex time-sharing control circuits, reducing device complexity while maintaining low parasitic capacitance.
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 significantly enhances touch detection accuracy by removing background parasitic capacitances, allowing for precise touch detection without interfering with display operations, thus improving sensitivity and reducing production complexities.
Implementation Method 1
the touch sense signal is driven by an in-phase amplifier and coupled to the common electrode layer or a node of the display control circuit
Implementation Method 2
there is no current loop between the display control circuit and the touch control circuit, or there is a high impedance between the display control circuit and the touch control circuit
Implementation Method 3
a touch stimulate circuit outputs a touch stimulate signal to a touch transmit electrode, and a touch sense circuit receives a touch sense signal from a touch receive electrode
Implementation Method 4
a display material layer, composed of liquid crystal and disposed on one side of the TFT substrate
Data Source
AI summary
A display device includes a TFT substrate layer, a display material layer, a common electrode layer, a touch electrode layer, a display control circuit and a touch control circuit. The common electrode layer has a common electrode. The touch electrode layer includes plural first touch electrodes and plural second touch electrodes. The display control circuit includes a display power. The touch control circuit includes a touch power independent to the display power. The touch control circuit sequentially or randomly couples a touch stimulation signal to a selected first touch electrode or receives a touch sense signal from a selected second touch electrode. The touch sense signal is driven and coupled to the common electrode layer or a node of the display control circuit for performing a touch detection operation in which there is no current loop between the display control circuit and the touch control circuit.