Pixel Circuit Feedback Compensation for Uniform Display Brightness
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Solution Overview
Problem
Existing pixel circuits for display apparatuses using light-emitting devices face issues with non-uniformity in display brightness due to threshold voltage variations in driving transistors, leading to prolonged data voltage writing times and limitations in high-frequency driving.
Innovation Solution
A pixel circuit design incorporating a coupling control circuit, signal writing circuit, and threshold compensation circuit, which separate the paths for threshold voltage compensation and data voltage writing, allowing for independent processes that stabilize voltages and improve driving frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If threshold voltage compensation is performed using conventional pixel circuits, then display uniformity is improved, but data voltage writing time is prolonged and driving frequency is limited
Solution Approach 1:
The pixel circuit is divided into distinct functional modules: a threshold voltage compensation circuit that operates independently from a data writing circuit. The compensation circuit includes compensation transistors and capacitors that function separately from the data writing transistors, allowing simultaneous or independent operation of threshold compensation and data writing processes, thereby resolving the time conflict in conventional circuits
Solution Approach 2:
The threshold voltage compensation is performed in advance during a dedicated compensation phase before the data writing phase begins. The compensation circuit writes the threshold voltage to the storage node ahead of time, allowing the subsequent data writing process to proceed without waiting for compensation to complete, thus enabling high-frequency driving while maintaining display uniformity
2Illumination intensity
If data voltage is written to the pixel circuit, then display brightness is achieved, but threshold voltage variations cause non-uniformity in the displayed image
Solution Approach 1:
The compensation circuit uses feedback mechanisms where the threshold voltage of the driving transistor is sensed and compensated through dedicated compensation transistors and capacitors. The circuit writes the threshold voltage value back to the storage node, creating a feedback loop that corrects for transistor variations and ensures uniform display brightness across all pixels despite manufacturing variations
Data Source
AI summary
A pixel circuit, a display panel, a display apparatus and a driving method are provided. The pixel circuit includes: a light-emitting device; a driving transistor configured to generate a driving current for driving the light-emitting device to emit light according to a data voltage; a coupling control circuit configured to stabilize voltages at the first node, and the gate electrode and the second electrode of the driving transistor; a signal writing circuit configured to provide a signal from a data signal terminal to the first node in response to a signal from a scan signal terminal, and to provide a signal from a first power terminal to the first electrode of the driving transistor in response to a signal from a light-emitting control signal terminal; and a threshold compensation circuit configured to write a threshold voltage of the driving transistor to the gate electrode of the driving transistor.