OLED Pixel Compensation Circuit Fixing Source Voltage
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Solution Overview
Problem
The existing OLED driving circuits experience errors in driving current due to the substrate effect, which causes variations in the threshold voltage of transistors, leading to inaccuracies in image output.
Innovation Solution
A pixel compensation circuit with six transistors and two capacitors is designed, where the source voltage of the driving transistor is fixed, using a specific timing sequence for transistor operations to eliminate the substrate effect and ensure accurate voltage division across capacitors, thereby stabilizing the OLED driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source voltage of the driving transistor is not fixed (conventional design), then the circuit operation is simpler, but the threshold voltage varies due to substrate effect causing driving current errors
Solution Approach 1:
The patent applies preliminary action by fixing the source voltage of the driving transistor to a reference potential before the actual driving operation. This is achieved by configuring the source terminal of the driving transistor to be connected to a reference voltage node, ensuring that the source voltage remains constant during threshold voltage detection and light emission phases. This preliminary stabilization of the source voltage prevents substrate effect-induced threshold voltage variations, thereby improving driving current accuracy without requiring complex dynamic compensation circuits.
2Measurement precision
If six transistors and two capacitors are used (invention design), then substrate effect is eliminated and driving current accuracy improves to 0.5% error rate, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the pixel circuit into distinct functional modules: a driving transistor for current control, multiple transistors (first through sixth) for sequential threshold voltage detection and data signal transmission, and capacitors for voltage storage. Each transistor is assigned a specific function in the sequential operation cycle, allowing independent optimization of each component's role. This modular segmentation enables precise threshold voltage detection and eliminates substrate effect while maintaining manageable circuit complexity through clear functional separation.
Solution Approach 2:
The patent implements periodic action through a sequential operation cycle that repeats each frame: the transistors are switched in a specific sequence (first transistor for data transmission, second for reference voltage, third for threshold detection, fourth for compensation, fifth for light emission) with each phase occupying a specific time slot. This periodic sequential switching ensures that threshold voltage detection is performed under controlled conditions free from substrate effect, while the regular repetition of the cycle maintains stable display operation. The timed sequence of transistor operations enables accurate measurement and compensation without requiring simultaneous complex interactions.
Data Source
AI summary
The present invention relates to an OLED pixel compensation circuit for removing a substrate effect. The pixel compensation circuit according to the present invention uses six transistors and two storage batteries to fix both a source voltage and a body voltage of a driving transistor that drives an OLED, thereby having the effects of eliminating errors due to a substrate effect and presenting more accurate pixel compensation results.