Current-Driven OLED Pixel Circuit for Integrated Touch Sensing
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Solution Overview
Problem
Current-driven OLED display panels lack effective touch sensing capabilities due to the absence of common electrodes connected only to capacitive loads, necessitating additional circuit elements and routing traces for integrated touch sensing solutions.
Innovation Solution
Incorporating a touch sensing-adapted pixel circuit with a current-driven element, drive transistor, hold capacitor, and sense capacitor in each pixel, where the drive transistor supplies current to the current-driven element and sense current to a sense line based on the capacitance variation of the sense capacitor, allowing for contact detection and pressure sensing without increasing the number of circuit elements and routing traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional sensing elements are incorporated into current-driven display panels for touch sensing, then touch sensing capability is achieved, but the number of circuit elements and routing traces increases
Solution Approach 1:
The drive transistor is designed to perform dual functions: driving the current-driven element during normal display operation and sensing capacitance changes during touch sensing. By making the drive transistor universal, the patent eliminates the need for separate sensing circuit elements, thereby achieving touch sensing capability without increasing device complexity
Solution Approach 2:
The patent merges the drive function and sense function into a single pixel circuit structure. The drive transistor and hold capacitor are used for both driving the display element and sensing touch input, combining multiple functions into one integrated circuit to avoid adding separate sensing elements
2Adaptability or versatility
If common electrodes are used as sense electrodes for touch sensing in liquid crystal display panels, then touch sensing is achieved without separate touch panels, but this approach cannot be applied to current-driven OLED display panels
Solution Approach 1:
Instead of using common electrodes throughout the display panel, the patent introduces sensing functionality locally at each pixel level by incorporating a sense capacitor and modifying the drive transistor to sense mode. This localized approach enables touch sensing in OLED panels where common electrode architecture is not applicable
Solution Approach 2:
Rather than using the conventional LCD approach of common electrodes connected to capacitive loads, the patent inverts the approach by using the drive transistor's capacitance to sense touch input directly in the pixel circuit, converting the sensing problem into a capacitance measurement problem that can be solved with existing OLED pixel structures
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 efficient touch sensing and pressure detection on OLED display panels by utilizing existing circuit elements for both drive and sense functions, reducing the complexity and number of additional components required for touch sensing, thereby enhancing user interaction while maintaining panel design simplicity.
Implementation Method 1
A capacitance of the sense capacitor varies in response to a contact of an object with the current-driven display panel in a vicinity of the touch sensing-adapted pixel circuit
Data Source
AI summary
A display panel includes a plurality of pixel circuits; and a sense line. The plurality of pixel circuits includes a touch sensing-adapted pixel circuit including a current-driven element, a drive transistor; a hold capacitor configured to hold a voltage corresponding to a data voltage and a sense capacitor. A capacitance of the sense capacitor varies in response to contact of an object with the current-driven display panel in a vicinity of the touch sensing-adapted pixel circuit. The drive transistor is configured to supply a current to the current-driven element in response to the data voltage and supply a sense current to the sense line in response to the capacitance of the sense capacitor.