Dual-Transistor Pixel Circuit With Sensing for OLED Aging Compensation
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Solution Overview
Problem
The electrical characteristics of driving elements in active matrix type electroluminescent displays, such as threshold voltage and mobility, are not uniform due to process conditions and environmental factors, leading to deterioration over time.
Innovation Solution
A pixel circuit with first and second driving transistors and sensing parts that alternately drive and sense the electrical characteristics of these transistors, allowing for real-time monitoring and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single driving transistor is used to drive the light-emitting element, then the circuit structure is simple, but the electrical characteristic deteriorates over time due to stress and process variations
Solution Approach 1:
The patent divides the single driving transistor into two separate driving transistors (first driving transistor and second driving transistor). Each transistor independently drives the light-emitting element during different time periods, reducing the stress on each individual transistor and slowing down electrical characteristic deterioration while maintaining manageable circuit complexity through systematic arrangement.
Solution Approach 2:
The patent implements dynamic switching between the first and second driving transistors using control signals. The transistors alternately drive the light-emitting element during different time periods within each frame, creating a dynamic system that distributes operational stress and enables real-time sensing of electrical characteristics to further compensate for degradation.
2Ease of operation
If driving transistors are operated continuously without sensing, then the display operation is simple, but the electrical characteristic deterioration cannot be compensated
Solution Approach 1:
The patent incorporates sensing parts that continuously monitor the electrical characteristics (such as threshold voltage and mobility) of the first and second driving transistors. The sensed information is fed back to the control circuit, which adjusts the driving signals to compensate for detected deterioration, creating a closed-loop system that maintains display quality despite transistor aging and process variations.
Solution Approach 2:
The patent implements periodic sensing operations where the sensing parts measure the electrical characteristics of the driving transistors at specific time intervals during frame periods. This periodic measurement approach enables continuous monitoring and compensation while minimizing interference with the normal display operation, balancing simplicity with reliability.
3Reliability
If two driving transistors are used with sensing parts, then the electrical characteristic deterioration is slowed and compensated, but the circuit complexity increases
Solution Approach 1:
The patent designs the first and second driving transistors to be structurally identical and functionally interchangeable, with each capable of both driving the light-emitting element and being sensed by the sensing parts. This universal design allows the same circuit topology to be reused twice, reducing overall circuit complexity compared to using two different types of transistors with different functions.
Solution Approach 2:
The patent merges the driving and sensing functions into a unified circuit architecture where the first and second driving transistors share common control circuits, sensing parts, and compensation mechanisms. By combining these functions systematically rather than implementing them separately, the patent reduces redundant components and simplifies the overall circuit structure while maintaining the benefits of dual-transistor operation with sensing.
Data Source
AI summary
The present disclosure relates to a pixel circuit and a display device including the same. The pixel circuit includes: a first driving transistor including a first electrode connected to a first node to which a driving voltage is applied, a gate electrode connected to a second node, and a second electrode connected to a third node; a second driving transistor including a first electrode connected to the first node, a gate electrode connected to a fifth node, and a second electrode connected to a sixth node; and a sensing part configured to sense electrical characteristics of the first driving transistor and the second driving transistor.