OLED Pixel Driving Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
Conventional Organic Light-Emitting Diode (OLED) displays experience a short-term afterimage due to the hysteresis effect of the driving transistor, particularly when switching from a black-and-white image to a gray image, caused by the drift of the threshold voltage.
Innovation Solution
A pixel driving circuit comprising a driving circuit, initialization circuit, compensation control circuit, and light-emission control circuit, which applies an initial voltage to the light-emitting element and controls the driving transistor to prevent afterimages by maintaining an on-bias state and compensating for threshold voltage drift through a series of electrical connections and voltage writings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional OLED display uses a driving transistor without initialization, then the device complexity is low, but short-term afterimages occur due to threshold voltage drift
Solution Approach 1:
The patent applies preliminary action by initializing the driving transistor before normal operation. The initialization circuit writes an initial voltage (e.g., 0V) to the control end of the driving circuit at the beginning of each frame period, ensuring the transistor starts in a known state. This prevents threshold voltage drift from causing afterimages, while the initialization control line enables this action without adding permanent circuit complexity.
Solution Approach 2:
The patent uses an intermediary approach by introducing a compensation control circuit that mediates between the driving circuit and the light-emitting element. This circuit includes compensation transistors that can electrically connect or disconnect the control end of the driving circuit to the second end, allowing threshold compensation without fundamentally changing the driving circuit structure. The compensation control line acts as an intermediary control signal.
2Measurement precision
If threshold voltage compensation is implemented continuously, then display accuracy improves, but energy consumption increases
Solution Approach 1:
The patent implements periodic action by performing threshold voltage compensation at specific moments rather than continuously. The compensation occurs during designated time periods within each frame period when the compensation control signal is activated. This periodic compensation maintains luminance accuracy while significantly reducing energy consumption compared to continuous compensation operations.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining the initialized state of the driving transistor throughout the frame period. Once initialized, the transistor remains in a stable state with minimal threshold voltage drift, allowing normal operation to proceed without interruption. This continuous stable state ensures display accuracy while avoiding the energy costs of frequent re-initialization.
Data Source
AI summary
A pixel driving circuit, a pixel driving method and a display device are provided. The pixel driving circuit includes a driving circuit, an initialization circuit and a compensation control circuit. The compensation control circuit is configured to control a control end of the driving circuit to be electrically connected to a second end of the driving circuit under the control of a compensation control line. The initialization circuit is configured to write an initial voltage into the second end of the driving circuit under the control of an initialization control line.