Pixel Driving Circuit for AMOLED Threshold Voltage Drift Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The threshold voltage drift of Drive Thin Film Transistors (DTFTs) in Active Matrix Organic Light Emitting Diodes (AMOLEDs) due to manufacturing deviations and aging leads to errors in driving current, resulting in degraded display effects.
Innovation Solution
A pixel driving circuit with a compensating unit, data writing unit, energy storage units, and a driving unit that compensates for the threshold voltage by storing and managing voltages across nodes, allowing the driving current to be independent of the threshold voltage, ensuring consistent grayscale display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional DTFT is used to drive OLED, then the circuit structure is simple, but the threshold voltage drift causes errors in driving current and degraded display effect
Solution Approach 1:
The pixel circuit is divided into multiple functional units: a compensating unit with multiple transistors (second, third, fourth transistors) to measure and store threshold voltage, a data writing unit to write display data, and a driving unit to output driving current. This segmentation allows independent compensation of threshold voltage drift while maintaining overall circuit functionality.
Solution Approach 2:
The compensating unit performs preliminary measurement and storage of the driving transistor's threshold voltage before the driving phase. The first capacitor stores the threshold voltage information in advance, enabling subsequent compensation during the driving phase to eliminate display errors caused by threshold voltage drift.
2Manufacturing precision
If threshold voltage compensation is implemented, then display uniformity is improved, but circuit complexity increases
Solution Approach 1:
The compensating unit uses multiple transistors (second, third, fourth transistors) that work together with capacitors to perform multiple functions: measuring threshold voltage, storing compensation data, and enabling compensation during driving. This multi-functional design achieves display uniformity improvement while controlling circuit complexity through integrated operation.
Solution Approach 2:
Capacitors serve as intermediary elements to store threshold voltage information and compensation data. The first capacitor stores the threshold voltage measured during the compensating phase, acting as a mediator between the measurement process and the driving phase, enabling accurate compensation without direct real-time measurement during driving.
3Ease of operation
If the driving current depends on threshold voltage, then the circuit operation is straightforward, but manufacturing deviations and aging cause current errors
Solution Approach 1:
The compensating unit implements a feedback mechanism by measuring the actual threshold voltage of the driving transistor and storing it in the first capacitor. This feedback information is then used during the driving phase to compensate for threshold voltage variations, ensuring stable driving current despite manufacturing deviations and aging effects.
Solution Approach 2:
The circuit changes the operating parameters by introducing compensation voltages that counteract threshold voltage drift. The compensating unit adjusts the gate-source voltage of the driving transistor based on stored threshold voltage information, effectively changing the electrical parameters to maintain constant driving current despite threshold voltage variations.
Data Source
AI summary
The embodiments of the present disclosure relate to display technology and provide a pixel driving circuit and an associated driving method, a display panel and a display apparatus, capable of avoiding influence of a drifting threshold voltage of a driving transistor on a driving current of an active light emitting device. The pixel driving circuit comprises a compensating unit, a data writing unit, a driving unit, a first energy storage unit, a second energy storage unit and a display unit. The embodiments of the present disclosure are applicable to display manufacture.