Organic Light Emitting Display Signal Generation for Threshold Compensation
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Solution Overview
Problem
In organic light emitting display devices, variations in threshold voltages of driving transistors lead to inconsistent current supply to OLEDs, affecting brightness, and the shortened horizontal scanning period due to increased display panel resolution makes it challenging to secure sufficient sampling time for compensating these variations.
Innovation Solution
The organic light emitting display device employs a scan signal and emission control signal generation system that synchronizes signals across multiple horizontal lines, allowing for extended sampling periods without reducing data write time by overlapping initialization and sampling periods with previous horizontal line scan periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the horizontal scanning period is shortened to increase display panel resolution, then the display resolution is improved, but the sampling period for compensating threshold voltage variations becomes insufficient
Solution Approach 1:
The patent applies preliminary action by performing the sampling operation for threshold voltage compensation during the initialization period of the current horizontal line, which overlaps with the data write period of the previous horizontal line. This allows the sampling to occur before the emission period begins, ensuring sufficient time for compensation without extending the overall horizontal scanning period. The emission control signal is generated based on this preliminary sampling result, enabling timely compensation for threshold voltage variations.
2Reliability
If the sampling period is extended to compensate for threshold voltage variations, then the brightness consistency is improved, but the data write time is reduced
Solution Approach 1:
The patent resolves the time conflict by operating in another dimension - overlapping the sampling period of the current horizontal line with the data write period of the previous horizontal line in the temporal dimension. This dimensional shift allows the sampling operation to occur concurrently with data writing in adjacent lines, effectively extending the available sampling time without encroaching on the data write time of the current line. The emission control signal generation is synchronized to occur during this overlapping period.
3Reliability
If the emission control signal is delayed to allow sufficient sampling, then the threshold voltage compensation is improved, but the synchronization with scan signal is disrupted
Solution Approach 1:
The patent implements feedback by using the sampled threshold voltage information to generate an emission control signal that is fed back to control the emission period timing. The sampling result directly influences when the emission control signal is asserted, creating a closed-loop system where the emission timing is adjusted based on the actual threshold voltage measurements. This feedback mechanism ensures that the emission control signal remains synchronized with the scan signal while incorporating the necessary compensation timing.
Data Source
AI summary
An organic light emitting display device according to an embodiment includes a display panel including n (n is a natural number) number of horizontal lines, an ith (i is a natural number satisfying a condition of 1<i<n−2) scan signal generating unit and an ith emission control signal generating unit. The ith scan signal generating unit generates an ith scan signal and provides the generated ith scan signal to an ith horizontal line and an (i+2)th horizontal line. The ith emission control signal generating unit generates an ith emission control signal to be provided to the ith horizontal line.