OLED Driving Method for Brightness Uniformity
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Solution Overview
Problem
Current organic light emitting diode (OLED) display devices face challenges in controlling the brightness of the screen due to variations in the electrical characteristics of the switch element, leading to uneven brightness across the display, particularly in row-by-row scanning methods.
Innovation Solution
The method involves a timing controller that simultaneously enables scanning signals and sets data-voltages to a reference-voltage in a reset period, then enables system-high-voltage and sets data-voltages to reference-voltage in a threshold voltage cancelling period, and finally sets data-voltages according to displaying data in a scanning period, ensuring non-overlapping enabling periods of scanning signals to compensate for the electrical characteristics of the switch element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If row-by-row scanning method is used to drive OLED display panel, then the display can be updated sequentially, but the brightness distribution becomes uneven (lighter at top, darker at bottom)
Solution Approach 1:
The patent implements periodic action by dividing the display refresh into distinct phases: reset period, threshold voltage cancelling period, and scanning period. During the threshold voltage cancelling period, all pixels are updated simultaneously with reference voltage, while during the scanning period, pixels are updated sequentially. This periodic alternation between simultaneous and sequential updates compensates for the brightness non-uniformity caused by row-by-row scanning while maintaining display refresh functionality.
Solution Approach 2:
The patent applies preliminary action by performing threshold voltage cancellation before the actual display scanning. In the threshold voltage cancelling period, all pixels are given a reference voltage to compensate for threshold voltage variations and mobility differences. This preliminary compensation ensures that when the actual display data is scanned row-by-row in the subsequent scanning period, the brightness uniformity is maintained despite the sequential update method.
2Device complexity
If conventional driving method without threshold voltage compensation is used, then the device complexity is lower, but the display quality and brightness uniformity deteriorate
Solution Approach 1:
The patent segments the display refresh cycle into three distinct periods: reset period, threshold voltage cancelling period, and scanning period. This segmentation allows the threshold voltage compensation to be performed as a separate, dedicated phase before the actual display data is written. By dividing the refresh cycle in this way, the patent achieves improved display quality through threshold voltage compensation without requiring complex additional hardware, as the compensation is achieved through temporal separation of operations.
3Manufacturing precision
If threshold voltage compensation is implemented through additional compensation circuits, then the display quality improves, but the device complexity increases
Solution Approach 1:
The patent achieves threshold voltage compensation without additional compensation circuits by utilizing periodic action. The display refresh is divided into phases, with the threshold voltage cancelling period dedicated to compensation operations. During this period, all pixels are updated simultaneously with reference voltage to cancel threshold voltage effects. This temporal phase approach enables effective threshold voltage compensation using the existing pixel circuitry and driving signals, avoiding the need for complex additional compensation circuits while maintaining high display quality.
Data Source
AI summary
An organic light emitting diode (OLED) display device and a method for driving an OLED display panel are provided. The method includes the following steps. In a reset period, a plurality of scanning signals received by a plurality of pixels of the OLED display panel is simultaneously enabled, and a plurality of data-voltages received by the pixels are set to a reference-voltage. In a threshold voltage cancelling period, a system-high-voltage received by the pixels and the scanning signals are simultaneously enabled, and the data-voltages are set to the reference-voltage. In a scanning period, the scanning signals are sequentially enabled, and the data-voltages are set according to the corresponded displaying data within a plurality of displaying data.