Pixel Driving Circuit Compensation for OLED Display Uniformity
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Solution Overview
Problem
Organic light-emitting display devices face issues with inhomogeneous displays and reduced image quality due to transistor variations, IR drops, and aging of light-emitting devices, leading to inconsistent driving currents across pixels.
Innovation Solution
A driving method for pixel driving circuits that includes a data writing stage, a light-emitting stage, and a compensation stage, where the compensation stage overlaps with the light-emitting stage and starts after it, using a first power signal voltage to adjust the gate electrode voltage of the driving transistor, thereby compensating for voltage drops and ensuring uniform driving currents across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel driving circuits use transistors to generate driving currents, then the light-emitting devices can be controlled to emit light, but transistor variations and aging cause inconsistent driving currents between different pixels leading to inhomogeneous display
Solution Approach 1:
The patent applies preliminary action by introducing a compensation stage before the light-emitting stage. In this compensation stage, a compensation transistor is activated to adjust the gate voltage of the driving transistor, compensating for threshold voltage variations and IR drops before the actual light emission occurs. This preliminary compensation ensures that despite manufacturing variations in transistor parameters, each pixel receives the correct driving voltage to achieve uniform display across all pixels.
2Measurement precision
If the compensation stage is implemented separately after the light-emitting stage, then transistor variations can be compensated, but the compensation cannot address real-time voltage drops during light emission
Solution Approach 1:
The patent merges the compensation stage with the light-emitting stage by overlapping their time intervals. The compensation transistor is activated during the light-emitting stage rather than separately after it, allowing real-time compensation of voltage drops that occur during actual light emission. This temporal merging ensures that the compensation is applied precisely when needed, addressing both threshold voltage variations and dynamic IR drops during the light-emitting process.
3Reliability
If the compensation transistor is activated during the light-emitting stage, then real-time voltage compensation is achieved, but the circuit complexity increases
Solution Approach 1:
The patent applies universality by designing the compensation transistor to serve multiple functions within the pixel circuit. The same compensation transistor structure is used across all pixels in the display, providing a universal solution for threshold voltage compensation and IR drop compensation. This multi-functional approach achieves display uniformity without requiring entirely separate compensation circuits for each pixel, thereby limiting the increase in circuit complexity.
Data Source
AI summary
Driving method for driving circuit, display panel, and display device are provided. The method includes: in a data writing stage, transmitting data signal voltage to a gate electrode of the driving transistor in response to a scan signal in a first scan signal line; in a light-emitting stage, turning on a driving path connecting the driving transistor to the light-emitting device, and making the driving transistor generate a driving current based on the voltage of the gate electrode in the driving transistor to drive the light-emitting device to emit light, in response to a light-emitting signal in a light-emitting signal line; and in a compensation stage, compensating the voltage of the gate electrode in the driving transistor by using a first power signal voltage. The light-emitting stage and the compensation stage overlap with each other, and a starting time of the compensation stage is after a starting time of the light-emitting stage.