OLED Pixel Driving Circuit Brightness Flickering
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Solution Overview
Problem
The existing pixel driving circuits in OLED display panels exhibit brightness differences between resetting and maintaining light-emitting states, leading to display effects issues, particularly in low grayscale and low frequency display states, causing flickering problems.
Innovation Solution
A pixel driving circuit with an operating sequence including multiple cycles, featuring a driving module, threshold voltage capturing module, and coupling module, which adjusts the control terminal's potential to correct the bias state of the driving transistor, ensuring consistent light-emitting current generation across stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel driving circuit is used, then the circuit structure is simple, but brightness difference occurs between resetting and maintaining light-emitting stages causing flickering
Solution Approach 1:
The light-emitting stage is divided into two separate stages: a first light-emitting stage for resetting the display panel and a second light-emitting stage for maintaining light-emitting. This segmentation allows independent control of each stage's characteristics, enabling the circuit to address brightness differences by treating resetting and maintaining operations differently rather than using a single unified driving approach
Solution Approach 2:
The circuit dynamically adjusts the driving current characteristics for different light-emitting stages. The driving module provides different current profiles for the first light-emitting stage (resetting) versus the second light-emitting stage (maintaining), adapting the electrical characteristics to match the specific requirements of each stage to eliminate brightness differences and flickering
2Manufacturing precision
If the driving transistor operates in conventional mode, then the operation is simple, but current ramping speed difference causes brightness inconsistency
Solution Approach 1:
Before the light-emitting operation, the circuit performs preliminary actions including threshold voltage capturing during a setup stage and bias state correction. These preliminary operations prepare the driving transistor in advance by establishing appropriate voltage levels and correcting threshold voltage shifts, ensuring that the subsequent light-emitting stage operates with consistent brightness without requiring complex real-time adjustments
3Reliability
If data writing is performed without correction, then the operation speed is fast, but threshold voltage shift affects display quality
Solution Approach 1:
The circuit implements periodic correction actions within the operating cycle. A correcting stage is periodically inserted between the first and second light-emitting stages to capture threshold voltage and correct bias state. This periodic intervention maintains display quality by continuously compensating for threshold voltage shifts without requiring constant correction, thus balancing display quality with operational efficiency
Data Source
AI summary
A pixel driving circuit, a method for driving the same, and a display panel are provided. An operating sequence of the pixel driving circuit includes a first light-emitting stage and a second light-emitting stage after the first light-emitting stage. The first light-emitting stage includes a data writing stage and a light-emitting stage after the data writing stage. The second light-emitting stage includes a correcting stage and a light-emitting stage after the correcting stage. The pixel driving circuit includes a driving module, a threshold voltage capturing module configured to be turned on during the data writing stage and to write a data voltage to a control terminal of the driving module, and a coupling module configured to adjust a coupling voltage of the control terminal of the driving module during the correcting stage and the light-emitting stage of the second light-emitting stage.