Pixel Leakage Current Compensation via Transistor Segmentation
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Solution Overview
Problem
Threshold voltages of transistors in display pixels can be altered by frictional electricity or high temperature conditions, leading to leakage currents that degrade display quality.
Innovation Solution
A pixel design that includes a light emitting element, a driving transistor, a data writing transistor, and a leakage current compensator. The leakage current compensator, which can include an eighth transistor, operates to maintain the turned-off state of the driving transistor during emission waiting periods by equalizing the voltage of its electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel structure is used, then the device complexity is low, but leakage current occurs due to threshold voltage changes, degrading display quality
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a driving transistor for current control, a data writing transistor for voltage input, and a leakage current compensator for threshold voltage compensation. This segmentation allows each component to address specific issues independently, improving display quality without requiring complete redesign of the entire pixel structure.
Solution Approach 2:
The leakage current compensator is activated during a compensation period before the emission period to pre-adjust the threshold voltage of the driving transistor. By performing this compensation action in advance, the system prevents leakage current from affecting the emission phase, thereby maintaining display quality without adding continuous complexity throughout the operating cycle.
2Reliability
If threshold voltage compensation is implemented, then leakage current is reduced, but the pixel circuit complexity increases
Solution Approach 1:
The leakage current compensator serves multiple functions: it compensates for threshold voltage changes, maintains the turned-off state of the driving transistor during emission waiting periods, and stabilizes the control electrode voltage. By designing a single multi-functional component rather than separate circuits for each function, the patent reduces overall circuit complexity while achieving comprehensive leakage current control.
Solution Approach 2:
The leakage current compensator automatically activates during the emission waiting period when the driving transistor should remain turned off. The compensator self-regulates the voltage levels based on the operational state, maintaining proper voltage at the control electrode without requiring external intervention or complex control logic, thereby simplifying the overall control architecture.
3Ease of operation
If the driving transistor is kept on during emission waiting period, then the circuit operation is simple, but leakage current degrades luminance control
Solution Approach 1:
The leakage current compensator applies a counteracting voltage during the emission waiting period to prevent the driving transistor from entering an unintended on-state due to leakage current. By anticipating and counteracting the leakage effect before it degrades luminance control, the system maintains precise control without requiring continuous complex monitoring or adjustment mechanisms.
Data Source
AI summary
A pixel includes a light emitting element, a driving transistor, a data writing transistor and a leakage current compensator. The driving transistor applies a driving current to the light emitting element. The data writing transistor applies a data voltage to the driving transistor in response to a first writing signal and connected to a first electrode of the driving transistor. The leakage current compensator is connected to a second electrode of the driving transistor and operates in a way such that a turned-off state of the driving transistor is maintained in an emission waiting period in response to a second writing signal different from the first writing signal. The leakage current compensator includes an eighth transistor and the turned off state of the driving transistor is maintained in the emission waiting period by the eighth transistor connected to the second electrode of the driving transistor.