Voltage Programmed Pixel Circuit for AMOLED Threshold Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing AMOLED display pixel circuits are sensitive to threshold voltage shifts in driving transistors, leading to image distortion and reduced display quality, with conventional solutions either requiring extra transistors, increasing complexity and reducing yield, or experiencing overhead due to large line capacitance.
Innovation Solution
A locally referenced voltage programmed pixel circuit with a programming transistor that adjusts pixel current during the programming cycle, using a stable biasing condition to minimize the impact of threshold voltage shifts and OLED aging, while keeping the programming transistor on for only a small fraction of time to avoid threshold shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If voltage programmed pixel circuit is used to compensate threshold voltage shifts, then image distortion is reduced, but device complexity increases due to extra transistors
Solution Approach 1:
The patent merges the programming transistor with the existing driving transistor structure, using the same transistor to perform both driving and programming functions at different time periods, thereby eliminating the need for separate extra transistors while still achieving threshold voltage compensation
Solution Approach 2:
The patent employs periodic action by operating the programming transistor only during specific programming periods and keeping it off during other periods, allowing the same transistor to serve multiple functions (driving and programming) at different times, thus reducing overall device complexity while maintaining compensation capability
2Stability of the object's composition
If programming transistor is kept on continuously to adjust pixel current, then current stability is improved, but threshold voltage shift occurs due to prolonged stress
Solution Approach 1:
The patent applies periodic action by controlling the programming transistor to operate only during specific programming periods and remain off during other periods, thereby providing current adjustment when needed while minimizing prolonged stress that causes threshold voltage shift
Solution Approach 2:
The patent performs preliminary action by adjusting the pixel current during programming periods before the actual display period begins, compensating for threshold voltage shifts in advance, which allows the transistor to be turned off during display periods to avoid continuous stress
3Manufacturing precision
If current programmed pixel circuit is used to reduce threshold voltage sensitivity, then image distortion is reduced, but programming overhead increases due to large line capacitance charging time
Solution Approach 1:
The patent substitutes the mechanical charging process (current-based programming that requires charging large line capacitance) with a voltage-based programming approach, where voltages are applied to control the programming transistor, thereby significantly reducing programming time and overhead
Data Source
AI summary
A voltage programmed pixel circuit, display system having the pixel circuit and driving method thereof is provided. The pixel circuit includes a light emitting device, a driving transistor connected to the light emitting device and a programming circuit. The programming circuit adjusts a pixel current during a programming cycle of the pixel circuit.