OLED Pixel Compensation Circuit Stabilizes Threshold Voltage Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current OLED displays experience unstable current and uneven brightness due to threshold voltage drift in driving transistors, caused by factors like oxide semiconductor lighting and voltage stress.
Innovation Solution
A pixel compensation circuit utilizing a double-gate thin-film transistor with a specific configuration of switches and a storage capacitor to stabilize the threshold voltage, ensuring even brightness by isolating the current from threshold voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional driving transistor is used to control current through the OLED, then the display can operate with simple structure, but the threshold voltage drifts due to lighting and voltage stress causing unstable current and uneven brightness
Solution Approach 1:
The driving transistor is segmented into a dual-gate structure with separate first control terminals and second control terminals, allowing independent control of each gate. This segmentation enables the first control terminal to receive compensation signals while the second control terminal receives normal drive signals, thus stabilizing the threshold voltage against drift while maintaining current control functionality.
Solution Approach 2:
A compensation circuit is introduced as an intermediary component that generates compensation signals to counteract threshold voltage drift. The compensation circuit includes compensation transistors and capacitors that work together to detect and correct threshold voltage variations, thereby stabilizing the driving current without requiring changes to the OLED structure.
2Reliability
If the threshold voltage of the driving transistor drifts, then the circuit remains simple, but the current through the OLED becomes unstable and brightness becomes uneven
Solution Approach 1:
The compensation circuit implements a feedback mechanism where the state of the driving transistor (threshold voltage) is continuously monitored and corrected. The compensation transistors are configured to sense threshold voltage drift and generate compensating signals that are fed back to the first control terminals, creating a closed-loop system that maintains stable current and uniform brightness.
Solution Approach 2:
The invention changes the electrical parameters (voltage signals) applied to the first control terminals dynamically to compensate for threshold voltage drift. By adjusting the compensation signals in response to detected threshold variations, the system maintains stable operating parameters for the OLED current despite changes in the transistor's threshold voltage.
Data Source
AI summary
A pixel compensation circuit, method and flat display device are disclosed. The pixel compensation circuit includes a first control terminal of a driving switch connected with a reference voltage terminal, control terminals of a first and second controllable terminal connected with a first and second scanning line; a first terminal of the second controllable switch connected with a second terminal of the driving switch; an anode of an OLED connected with the second terminal of the second controllable switch, a cathode is grounded; control terminals of a third and fourth controllable terminals connected with a third scanning line; the second control terminal of the driving switch is grounded through a capacitor; a first terminal of the fourth controllable switch connected with a second terminal of the driving switch and the second terminal connected with a data line. The present invention can avoid unstable current of OLED by a voltage drift.