OLED Driving Device Precharge Currents Reduce Programming Time
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Solution Overview
Problem
The current driving methods for light emitting displays, particularly OLEDs, face challenges in achieving high gray scale representation due to manufacturing non-uniformities and prolonged data programming times, especially near black levels, where parasitic capacitance and voltage differences on data lines prolong the programming time.
Innovation Solution
A driving device and method that utilize multiple drivers to manage selection signals and data signals, including precharge currents, to quickly charge data lines and reduce data programming time by optimizing signal pulses and intervals, thereby improving gray scale representation and reducing programming time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current programming method is used to drive OLED display, then uniform display characteristics are achieved, but data programming time is prolonged due to parasitic capacitance on data lines
Solution Approach 1:
The patent applies preliminary action by pre-charging data lines to the target voltage level before actual data programming begins. The scan driver includes a precharge unit that charges data lines in advance, so when data programming starts, the lines are already at the correct voltage level, eliminating the time-consuming charging phase and reducing overall programming time while maintaining display uniformity
Solution Approach 2:
The patent segments the data programming process into distinct phases: a precharge phase where data lines are charged to target voltage levels, and a programming phase where actual data is transferred. This segmentation allows the precharge operation to be optimized separately, using multiple precharge currents based on gray level requirements, thereby reducing the time penalty imposed by parasitic capacitance without compromising display uniformity
2Device complexity
If voltage programming method is used to drive pixel circuits, then simpler circuit structure is achieved, but high gray scale representation becomes difficult due to threshold voltage deviations
Solution Approach 1:
The patent employs parameter changes by utilizing multiple precharge currents with different magnitude levels corresponding to different gray levels. Instead of using a single voltage level for all pixels, the system adjusts the precharge current parameters based on the target gray level, allowing precise control of final display brightness while compensating for manufacturing variations in threshold voltage and carrier mobility
Data Source
AI summary
A driving device for a light emitting display, which includes a plurality of scan lines for transferring a selection signal, comprises: a first driver for shifting a first signal having a first integer multiple of first pulses by a first period, and sequentially outputting the first signal; a second driver for shifting a second signal having a second pulse by a second period, and sequentially outputting the second signal; and a third driver for sequentially outputting the selection signal having a second integer multiple of third pulses corresponding to at least one of the first integer multiple of first pulses, and a fourth pulse corresponding to the second pulse, in response to the first signal and the second signal.