Pixel Circuit Threshold Compensation for Uniform OLED Brightness
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Solution Overview
Problem
The non-uniformity of threshold voltage in driving transistors of OLED display panels due to process variations and aging causes inconsistent current flow through light-emitting elements, leading to uneven display brightness and quality.
Innovation Solution
A pixel circuit with a 5T1C structure and a pixel driving method that includes a capacitor structure, driving transistor, and switching elements, utilizing scan signals to control charging, discharging, and compensation phases to produce a voltage containing the threshold voltage at the gate of the driving transistor, thereby offsetting threshold voltage drift and improving display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pixel circuits are used without compensation, then the circuit structure is simple, but the threshold voltage drift causes non-uniform display brightness
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before the light-emitting phase. The compensation transistor and capacitor are configured to pre-adjust the gate voltage of the driving transistor, offsetting threshold voltage drift effects before they impact display uniformity. This ensures that the driving transistor operates with corrected voltage regardless of subsequent aging or process variations.
Solution Approach 2:
The patent introduces a compensation transistor and capacitor as intermediary elements between the data line and the driving transistor. These intermediary components facilitate the threshold voltage compensation process by storing and transferring compensation voltages, enabling precise control of the driving transistor's gate voltage without directly modifying the driving transistor itself.
2Reliability
If threshold voltage compensation is implemented, then display uniformity is improved, but the circuit complexity increases
Solution Approach 1:
The compensation mechanism performs preliminary adjustment of the gate voltage to offset threshold voltage drift before the light-emitting phase. The compensation transistor and capacitor are configured to pre-correct voltage variations, ensuring consistent current flow through the light-emitting element regardless of aging or process variations.
Solution Approach 2:
The patent implements feedback by using the compensation transistor to sense and counteract threshold voltage drift effects. The capacitor stores compensation voltages that are applied to the driving transistor's gate, creating a feedback loop that continuously corrects for voltage variations and maintains reliable current consistency.
3Illumination intensity
If aging and temperature changes occur, then the threshold voltage drifts, but the display brightness remains sensitive to current changes
Solution Approach 1:
The compensation circuit performs preliminary correction of threshold voltage drift caused by aging and temperature changes. By adjusting the gate voltage of the driving transistor before the light-emitting phase, the system compensates for environmental variations and maintains stable luminous brightness despite threshold voltage instability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the gate voltage parameter of the driving transistor to compensate for threshold voltage drift. The compensation transistor and capacitor modify the electrical parameters (voltage levels) in response to aging and temperature variations, ensuring that the luminous brightness remains uniform despite changes in transistor characteristics.
Data Source
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AI summary
Disclosed are a pixel circuit, a pixel circuit driving method and a display device. The pixel circuit includes a light-emitting element, a capacitor structure, a driving transistor, and first to fourth switching elements. The first switching element connects a data line for providing a data signal to a first terminal of the capacitor structure in response to a first scan signal. The second switching element connects a first terminal of the driving transistor to a control terminal of the driving transistor and a second terminal of the capacitor structure respectively in response to a second scan signal. The third switching element connects a second terminal of the driving transistor to a first terminal of the light-emitting element in response to a third scan signal. The fourth switching element connects a first power signal terminal to the first terminal of the driving transistor in response to a fourth scan signal.