Pixel Circuit Segmenting Driving Transistors to Reduce Voltage Stress
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Solution Overview
Problem
In Active Matrix Organic Light-Emitting Diode (AMOLED) displays, the non-uniformity of luminance caused by threshold voltage drift in driving transistors leads to mura phenomena and image sticking, due to limitations in crystallization processes of Low Temperature Poly Silicon (LTPS) TFTs and threshold voltage drift under voltage stress or light illumination.
Innovation Solution
A pixel unit with multiple driving sub-circuits and a timing sequence control module that switches among them according to timing sequence phases, reducing the time of voltage stress on individual driving transistors and ensuring uniform driving of light-emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTPS TFTs or Oxide TFTs are used to drive OLED elements, then mobility and stability are improved, but threshold voltage drift under voltage stress or light illumination causes luminance non-uniformity and image sticking
Solution Approach 1:
The pixel circuit is divided into multiple sub-pixel circuits, each with its own driving transistor. By segmenting the driving function across multiple transistors, the patent reduces the voltage stress on each individual transistor, thereby minimizing threshold voltage drift and preventing luminance non-uniformity and image sticking phenomena.
2Reliability
If multiple driving sub-circuits are introduced to reduce voltage stress on driving transistors, then threshold voltage drift is reduced, but device complexity increases
Solution Approach 1:
Multiple driving transistors are merged into a single pixel circuit to share the driving burden. This combining approach allows the circuit to achieve better threshold voltage stability through distributed stress while maintaining a compact structure that does not excessively increase pixel area or complexity.
Data Source
AI summary
Provided is a pixel unit, a pixel circuit comprising the pixel unit and a driving method thereof. The pixel unit comprises a light-emitting element and n driving sub-circuits; wherein n is a natural number and n>1; each of the driving sub-circuits comprises a scan signal line for control-electrode, a switching transistor and a driving transistor; the switching transistor has a control electrode connected to the scan signal line for control-electrode, a first electrode connected to a data line, and a second electrode connected to a control electrode of the driving transistor; the driving transistor has a first electrode connected to a power supply line and a second electrode connected to a first electrode of the light-emitting element; and a second electrode of the light-emitting element is connected to a reference voltage terminal.