Pixel Circuit Reset Mechanism for Micro-OLED Mura Reduction
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Solution Overview
Problem
Micro-OLED panels face issues with brightness non-uniformity due to threshold voltage offsets, leading to the Mura effect, where different pixels exhibit uneven brightness caused by variations in threshold voltage during the manufacturing process.
Innovation Solution
A novel pixel circuit design that includes a driving transistor, capacitors, and reset transistors to initialize and control the light emitting device, allowing for simultaneous initialization of the driving transistor and light emitting device, and utilizing control signals to synchronize and store threshold voltage information, thereby canceling the offset effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pixel circuit design is used, then device complexity is low, but brightness non-uniformity occurs due to threshold voltage offsets
Solution Approach 1:
The reset operation is segmented into two independent stages: first resetting the driving transistor gate voltage, then resetting the light emitting device anode voltage. This segmentation allows each component to be reset independently, eliminating threshold voltage offset effects while maintaining manageable circuit complexity through modular operation
Solution Approach 2:
The driving transistor gate voltage is reset before the light emitting device anode voltage is reset. This preliminary action ensures that the driving transistor is in a known state before the light emitting device is activated, preventing threshold voltage offsets from affecting the display uniformity
2Reliability
If sequential reset operation is used, then initialization is complete, but current consumption increases during reset phase
Solution Approach 1:
The reset operation uses periodic control signals (first reset signal and second reset signal) that are activated only when needed. The first reset transistor is activated during the first reset period to reset the driving transistor gate, and the second reset transistor is activated during the second reset period to reset the light emitting device anode. This periodic activation reduces current consumption compared to continuous reset operations while ensuring complete initialization
Data Source
AI summary
A pixel circuit of a display panel includes a light emitting device, a driving transistor, a capacitor, a first reset transistor and a second reset transistor. The driving transistor has a gate terminal. A first terminal of the capacitor is coupled to the gate terminal of the driving transistor, and a second terminal of the capacitor is coupled to a reset input terminal of the pixel circuit. A first terminal of the first reset transistor is coupled to the gate terminal of the driving transistor, and a second terminal of the first reset transistor is coupled to the reset input terminal. A first terminal of the second reset transistor is coupled to the light emitting device, and a second terminal of the second reset transistor is coupled to the reset input terminal.