7T1C OLED Pixel Circuit Reset Scheme for Flicker and Afterimage
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Solution Overview
Problem
Existing OLED display panels face issues with threshold voltage drift of driving transistors due to manufacturing processes and long-term operation, leading to hysteresis and afterimage phenomena, which affect display quality and screen flicker.
Innovation Solution
A pixel circuit with a 7T1C configuration, including a driving circuit, data writing circuit, compensation control circuit, energy storage circuit, and initialization circuits, is designed to reset and compensate the control and second terminals of the driving circuit, eliminating the influence of hysteresis and afterimage by applying initialization voltages under controlled signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional driving circuit is used in OLED display panels, then the device structure remains simple, but threshold voltage drift occurs due to manufacturing processes and long-term operation, leading to hysteresis and afterimage phenomena
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: a driving circuit for controlling the light-emitting element, a compensation control circuit for threshold voltage compensation, an energy storage circuit for maintaining control terminal voltage, and initialization circuits for resetting terminals. This segmentation allows each module to address specific reliability issues independently, resolving threshold voltage drift without requiring a complete circuit redesign.
Solution Approach 2:
The compensation control circuit performs threshold voltage compensation in advance before the driving circuit operates, and the initialization circuits reset the control and second terminals to predetermined voltages at the beginning of each frame period. These preliminary actions prevent hysteresis and afterimage phenomena from occurring, rather than correcting them after they manifest.
2Reliability
If initialization voltages are applied to reset terminals, then hysteresis and afterimage phenomena are eliminated, but additional circuits and control signals are required
Solution Approach 1:
The compensation control circuit serves multiple functions: it compensates for threshold voltage drift in the driving circuit, transmits initialization voltages from the initialization circuits to the control and second terminals, and maintains proper biasing during operation. This multi-functionality reduces the need for separate dedicated circuits, minimizing the increase in device complexity while achieving reliable display quality.
Solution Approach 2:
The energy storage circuit acts as an intermediary between the compensation control circuit and the driving circuit, storing the control terminal voltage and maintaining it during the light emission phase. This intermediary component ensures stable operation without requiring continuous active control, reducing the complexity of the overall control system.
3Stability of the object's composition
If the control terminal and second terminal are reset to predetermined voltages, then screen flicker is reduced, but additional control signals and circuit paths are needed
Solution Approach 1:
The initialization circuits are activated periodically at the beginning of each frame period to reset the control and second terminals to predetermined voltages. This periodic resetting ensures consistent bias states across frames, eliminating screen flicker, while the regular timing allows for efficient use of control signals that can be synchronized with the display refresh rate.
Data Source
AI summary
A pixel circuit and a driving method thereof, and a display panel. The pixel circuit includes a driving circuit, a data writing circuit, a compensation control circuit, an energy storage circuit, a first light-emitting control circuit, a second light-emitting control circuit, a first initialization circuit, a second initialization circuit, and a transmission circuit. The driving circuit includes a control terminal, a first terminal and a second terminal, and is configured to control a driving current flowing through the first terminal and the second terminal and used for driving a light-emitting element to emit light. The first initialization circuit is configured to apply a first initialization voltage to the control terminal of the driving circuit; the second initialization circuit is configured to apply a second initialization voltage to the first electrode of the light-emitting element.