OLED Pixel Circuit for Direct Operating Voltage Sensing
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Solution Overview
Problem
Existing display devices face challenges in sensing the operating voltage of light-emitting elements directly, which hinders effective compensation for deterioration due to the inability to sense the deterioration tendency of organic light-emitting diodes (OLEDs) and driving elements, leading to afterimages on the screen.
Innovation Solution
A pixel circuit design incorporating switch elements and a capacitor that allows direct sensing of the operating voltage of light-emitting elements by applying different data voltages to selected and non-selected pixel circuits, enabling the extraction of characteristics without affecting the driving element's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an operating point relationship method is used to sense OLED deterioration, then deterioration information can be obtained, but the driving element characteristics cannot be completely excluded requiring additional compensation work
Solution Approach 1:
The patent extracts the OLED operating voltage sensing function from the conventional operating point relationship method by introducing a dedicated sensing switch element (fifth switch element) that directly connects the sensing line to the OLED operating voltage node. This separation allows independent sensing of OLED voltage without being influenced by driving element characteristics, eliminating the need for additional compensation work while maintaining high measurement precision.
2Measurement precision
If a sensing switch element is added to directly sense OLED operating voltage, then driving element characteristics can be completely excluded, but the pixel circuit complexity increases
Solution Approach 1:
The fifth switch element serves multiple functions: it acts as a sensing switch during the sensing period to directly connect the sensing line to the OLED operating voltage, and can be integrated with the existing switch element array structure. This multi-functionality approach enables precise OLED voltage sensing while minimizing the increase in pixel circuit complexity by reusing existing structural frameworks.
Solution Approach 2:
The sensing switch element operates periodically during specific sensing periods within the display refresh cycle. During these designated time windows, the fifth switch element is activated to perform voltage sensing, while during other periods it remains inactive and the pixel circuit operates in normal display mode. This periodic operation allows precise measurements without continuously increasing circuit complexity or interfering with normal display functionality.
3Use of energy by moving object
If selective sensing is implemented to reduce power consumption, then power efficiency improves, but additional control mechanisms are required
Solution Approach 1:
The patent implements selective sensing by activating the fifth switch element only during specific sensing periods within the display refresh cycle, rather than continuously. This periodic activation significantly reduces power consumption associated with OLED voltage sensing while maintaining accurate deterioration monitoring. The sensing operation is synchronized with the display timing, ensuring that selective sensing occurs at optimal moments without requiring complex continuous control mechanisms.
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
Enables direct sensing of the operating voltage of light-emitting elements, allowing for complete exclusion of the driving element's characteristics and facilitating low-power driving with selective sensing capabilities.
Implementation Method 1
a capacitor connected between the first node and the second node
Implementation Method 2
a light-emitting element connected between the second node and the third node
Data Source
AI summary
A pixel circuit includes a driving element including a first electrode connected to a first power line, a gate electrode connected to a first node, and a second electrode connected to a second node; a first switch element configured to apply a data voltage to the first node in response to a first gate signal; a second switch element configured to connect a third node to the second node in response to a reset signal or the first gate signal; a third switch element configured to connect a sensing line to the third node in response to a second gate signal; a fourth switch element configured to connect a second power line to the third node in response to a third gate signal; a capacitor connected between the first node and the second node; and a light-emitting element connected between the second node and the third node.