OLED Pixel Circuit Threshold Voltage Compensation
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Solution Overview
Problem
In OLED display panels, driving transistors exhibit varying threshold voltages over time and between pixels, leading to uneven display brightness due to differences in driving currents, causing issues with luminous efficiency and afterimage phenomena.
Innovation Solution
A pixel circuit and driving method that stabilize the potential of the data line at fixed potentials to compensate for threshold voltage variations, using a capacitor and transistors to adjust the operating voltage and threshold voltage of the driving transistor, ensuring consistent light emission across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If driving transistors are used in OLED display pixels, then the display can be driven to emit light, but the threshold voltage of the driving transistor drifts over time, causing uneven display brightness
Solution Approach 1:
The patent applies preliminary action by measuring and compensating for the threshold voltage of the driving transistor before the actual display stage. The circuit performs threshold voltage compensation in advance during the initialization phase, storing the compensated value in a capacitor. This preliminary compensation ensures that subsequent display operations occur with corrected threshold voltage values, preventing brightness uniformity issues caused by threshold drift.
2Ease of manufacture
If the threshold voltage of driving transistors varies between pixels, then manufacturing can proceed with standard processes, but the driving currents become different, resulting in uneven display brightness
Solution Approach 1:
The patent implements self-service by enabling each pixel's driving transistor to automatically measure and compensate for its own threshold voltage through an integrated compensation circuit. The driving transistor itself participates in the compensation process by having its threshold voltage measured during initialization and then used to adjust its own operating parameters. This self-compensation mechanism eliminates the need for external calibration equipment while ensuring each pixel adjusts for its specific threshold characteristics, achieving brightness uniformity across all pixels manufactured with standard processes.
3Manufacturing precision
If a compensation circuit is added to stabilize threshold voltage, then display brightness uniformity improves, but the circuit complexity increases
Solution Approach 1:
The patent applies merging by integrating the compensation circuit functions directly into the existing pixel circuit structure. The compensation circuit shares transistors and capacitors with the driving circuit, combining multiple functions (threshold voltage measurement, compensation, and light emission control) into a unified circuit architecture. This integration approach reduces the number of additional components needed compared to separate compensation circuits, thereby limiting the increase in circuit complexity while still achieving threshold voltage stabilization and brightness uniformity.
Data Source
AI summary
The present disclosure provides a pixel circuit and a driving method thereof, and a display device. The pixel circuit includes: a light emitting element including an anode and a cathode; a first switching circuit; a driving circuit and a second switching circuit. The driving circuit includes: a first transistor, of which a control terminal, a first terminal, and a second terminal are electrically connected to the first switching circuit, a first voltage terminal, and the anode respectively; and a capacitor, of which a first terminal and a second terminal are electrically connected to the first voltage terminal and the first switching circuit respectively. The second switching circuit is configured to stabilize a potential of the data line at a first fixed potential that makes the light emitting element emit light and a second fixed potential that makes the first transistor be turned off respectively.