Hybrid Compensation Circuit for OLED Pixel Threshold Voltage Drift
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Solution Overview
Problem
Traditional AMOLED pixel driver circuits lack effective compensation for threshold voltage drift caused by aging, leading to instability and uneven brightness due to the limitations of internal and external compensation methods.
Innovation Solution
A hybrid compensation circuit combining internal and external compensation techniques, utilizing a 4T1C structure with a pixel internal driver circuit and an external compensation circuit that includes an ADC, current comparator, control module, memory, and DAC, to detect and correct current differences, ensuring fast and wide-range compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If internal compensation is used to compensate threshold voltage drift, then compensation operation speed is fast, but compensation range is limited
Solution Approach 1:
The patent combines internal compensation and external compensation into a hybrid compensation circuit. The internal compensation uses a compensation TFT to quickly compensate for threshold voltage drift, while the external compensation uses an IC to provide a broader compensation range. This merging allows the system to achieve both fast operation speed and wide compensation range simultaneously.
2Adaptability or versatility
If external compensation is used to compensate threshold voltage drift, then compensation range is large, but compensation operation speed is slow
Solution Approach 1:
The hybrid compensation circuit merges internal and external compensation methods. The internal compensation path provides fast response for immediate threshold voltage drift, while the external compensation path provides comprehensive coverage for various drift conditions. Both paths work together to overcome the speed limitation of external compensation alone.
3Device complexity
If traditional 2T1C pixel driver circuit is used, then circuit structure is simple, but threshold voltage drift cannot be compensated
Solution Approach 1:
The patent segments the compensation function into two parts: internal compensation handled by a compensation TFT within the pixel circuit, and external compensation handled by an IC. This segmentation allows the circuit to achieve threshold voltage compensation while maintaining relatively simple structure, resolving the contradiction between simplicity and reliability.
Data Source
AI summary
The invention discloses a hybrid compensation circuit and method for OLED pixel, by using a pixel internal driver circuit (100) of 4T1C structure to compensate threshold voltage of driving TFT using the source follow approach to achieve fast compensation; and in driving light-emitting phase, using an external compensation circuit (200) to detect the current flowing through the OLED (D1), comparing, computing and storing the difference between the current flowing through the OLED (D1) and a pre-defined current; when the corresponding row of pixel internal driver circuits (100) entering the threshold voltage programming design phase again, performing compensation on the data signal (Data), correcting compensation result so that the current flowing through the OLED (D1) is closer to the pre-defined current to achieve large compensation range.