7T1C Pixel Circuit Timing for TFT Threshold Shift Compensation
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Solution Overview
Problem
LED light emission causes threshold voltage shift and infrared drop, leading to brightness degradation in display panels, particularly affecting thin film transistor (TFT) devices.
Innovation Solution
A 7T1C pixel circuit is designed with specific timing to detect and compensate for threshold voltage and infrared voltage drops, incorporating a driving transistor, light-emitting element, storage capacitor, and compensation transistors to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LED light emission is used to achieve high-color gamut and high-contrast displays, then display performance is improved, but threshold voltage shift and infrared drop occur causing brightness degradation
Solution Approach 1:
The pixel circuit performs preliminary detection and storage of the driving transistor's threshold voltage during the writing phase before the light-emitting phase. The detection transistor measures the threshold voltage and stores it in a storage capacitor, enabling the circuit to compensate for threshold voltage shift before it affects display brightness.
Solution Approach 2:
The pixel circuit implements a feedback mechanism where the detected threshold voltage is used to adjust the driving current. The storage capacitor holding the threshold voltage information feeds back to the driving transistor through the emission control transistor, automatically compensating for threshold voltage variations without external intervention.
2Illumination intensity
If LED light emission is used to achieve high-color gamut and high-contrast displays, then display performance is improved, but infrared drop occurs causing brightness degradation
Solution Approach 1:
The pixel circuit implements a feedback mechanism where the detected threshold voltage is used to adjust the driving current. The storage capacitor holding the threshold voltage information feeds back to the driving transistor through the emission control transistor, automatically compensating for threshold voltage variations without external intervention.
Solution Approach 2:
The circuit changes the operating parameters by adjusting the driving current based on the detected threshold voltage. By modifying the current magnitude according to the stored threshold voltage information, the circuit compensates for both threshold voltage shift and infrared drop effects on display brightness.
3Device complexity
If a simple pixel circuit is used to reduce device complexity, then manufacturing cost is reduced, but compensation for threshold voltage shift and infrared drop is insufficient
Solution Approach 1:
The detection transistor serves multiple functions: it detects the threshold voltage during the writing phase, and its stored information is used for compensation during the light-emitting phase. The storage capacitor also serves dual purposes by storing both the threshold voltage information and enabling current holding during emission, reducing the need for separate dedicated components.
Solution Approach 2:
The pixel circuit performs preliminary detection and storage of the driving transistor's threshold voltage during the writing phase before the light-emitting phase. The detection transistor measures the threshold voltage and stores it in a storage capacitor, enabling the circuit to compensate for threshold voltage shift before it affects display brightness.
Data Source
AI summary
A pixel circuit and a display panel are disclosed. The pixel circuit includes a first and a second power supply lines, a light-emitting element, a driving TFT, a storage capacitor, a writing TFT, a first, a second, and a third compensation TFTs. The storage capacitor is electrically connected to the driving TFT, the writing TFT is electrically connected to the driving TFT, the first compensation TFT is electrically connected to the driving TFT, the storage capacitor, and the driving TFT, the second compensation TFT is electrically connected to the storage capacitor and the first compensation TFT, the third compensation TFT is electrically connected to the storage capacitor, and the third compensation TFT is electrically connected to the light-emitting element.