AMOLED Pixel Circuit Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The change in threshold voltage of the driving transistor in AMOLED pixel circuits leads to non-uniform light emitting luminance, affecting the display effect of organic light emitting display panels due to manufacturing process variations and device aging.
Innovation Solution
A pixel circuit comprising a charging module, a driving module, and an initializing module, where the initializing module initializes the driving module and light emitting device, the charging module writes and loads reference signals, and the driving module drives the light emitting device to emit light, thereby compensating for threshold voltage changes and ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional AMOLED pixel circuit with driving transistor, switching transistor, storage capacitor and light emitting device is used, then the display panel can operate with basic functionality, but the threshold voltage drift of the driving transistor causes non-uniform light emitting luminance over time
Solution Approach 1:
The patent applies preliminary action by introducing an initializing module that performs threshold voltage compensation before the light emitting phase. The initializing module writes compensation data to the driving transistor in advance, establishing a corrected threshold voltage baseline that prevents luminance non-uniformity during subsequent operation. This proactive compensation approach addresses threshold voltage drift before it affects display quality.
Solution Approach 2:
The patent implements feedback through a compensation mechanism that continuously monitors and adjusts for threshold voltage changes. The initializing module reads the actual threshold voltage of the driving transistor and writes compensation values back to correct the drift, creating a closed-loop system that maintains luminance uniformity over time despite device aging and manufacturing variations.
2Device complexity
If the threshold voltage of the driving transistor changes due to manufacturing process and device aging, then the circuit structure remains simple, but the current flowing through OLED becomes non-uniform affecting display effect
Solution Approach 1:
The patent introduces an initializing module as an intermediary component between the data signal input and the driving transistor. This module acts as a mediator that compensates for threshold voltage variations by writing correction values to the driving transistor, thereby decoupling the simple circuit structure from the need for high manufacturing precision. The intermediary handles the complexity of threshold voltage compensation without requiring fundamental changes to the basic pixel circuit architecture.
3Device complexity
If no initialization module is added to compensate for threshold voltage changes, then the pixel circuit remains simple with fewer components, but the light emitting luminance becomes non-uniform over time
Solution Approach 1:
The initializing module performs preliminary threshold voltage compensation by writing correction data to the driving transistor before the display operates. This advance action establishes accurate voltage levels that prevent luminance non-uniformity during normal operation, accepting the added circuit complexity as necessary to ensure long-term display reliability and uniformity.
Data Source
AI summary
There are provided a pixel circuit, a method for driving the light emitting device (04) and an organic light emitting display panel. The initializing module (03) is added to the pixel circuit. In the initializing phase, the initializing module (03) initializes the driving module (02) and the light emitting device (04); in the writing phase, the charging module (01) writes the data signal inputted from the data signal terminal into the control terminal of the driving module (02); and in the light emitting phase, the charging module (01) loads the first reference signal inputted from the data signal terminal (Data) to the control terminal of the driving module (02), and the initializing module (03) connects the output terminal of the driving module (02) with the input terminal of the light emitting device (04) so that the driving module (02) drives the light emitting device (04) to emit light. The pixel circuit initializes the driving module (02) and the light emitting device (04) in the initialization phase, which eliminates the influence of the voltage difference in a previous phase on a subsequent phase, provides a compensating voltage and a driving voltage for the driving module (02) in the writing phase, which avoids the influence of change of the threshold voltage on the light emitting luminance of the light emitting device (04), so that the quality of the display picture is ensured.