Pixel Circuit Segmentation for Threshold and Mobility Compensation
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Solution Overview
Problem
Display devices face challenges in compensating for the threshold voltage and mobility variations of driving transistors due to process variations, which affect the display quality.
Innovation Solution
A pixel circuit is designed with an internal compensation circuit to adjust the threshold voltage of a first driving transistor and an external compensation circuit to sense the driving current of a second driving transistor, thereby compensating for the threshold voltages and mobility of both transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an internal compensation circuit is used to compensate for threshold voltage, then threshold voltage compensation is improved, but mobility compensation is not achieved
Solution Approach 1:
The patent divides the compensation function into two separate circuits: an internal compensation circuit for threshold voltage compensation and an external compensation circuit for mobility compensation. This segmentation allows each circuit to specialize in one type of compensation, achieving both threshold voltage and mobility compensation effectively without the limitations of a single integrated circuit.
2Device complexity
If only internal compensation circuit is implemented, then device complexity is reduced, but compensation completeness deteriorates
Solution Approach 1:
The compensation system is segmented into internal and external circuits with distinct functions. The internal circuit handles threshold voltage compensation while the external circuit handles mobility compensation, achieving complete compensation without excessive complexity.
Solution Approach 2:
The patent introduces a sensing transistor as an intermediary element that enables the external compensation circuit to sense the driving current. This intermediary component facilitates mobility compensation by providing a mechanism to detect and compensate for current variations without significantly increasing overall circuit complexity.
3Reliability
If external compensation circuit is added for mobility sensing, then compensation completeness is improved, but device complexity increases
Solution Approach 1:
The sensing transistor serves multiple functions: it senses the driving current for mobility compensation, acts as a switch for initializing the light emitting element, and participates in the overall compensation mechanism. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the sensing function with the existing transistor structure in the pixel circuit. The sensing transistor is integrated into the compensation circuit architecture, combining mobility sensing with the driving function, which reduces overall complexity compared to using separate dedicated sensing components.
Data Source
AI summary
A pixel circuit and a display device including the pixel circuit compensates for a threshold voltage of a first driving transistor using an internal compensation circuit and senses a second driving current of a second driving transistor through sensing transistor using an external compensation circuit to compensate for threshold voltages and mobility of the first and second driving transistor.