Electrowetting Display Voltage Pulse Duration Control
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Solution Overview
Problem
Electrowetting display devices in active matrix configurations face challenges in effectively reducing backflow and achieving desired display states due to the resistance of the conductive second fluid, which affects the electrical properties and the efficacy of reset pulses.
Innovation Solution
The implementation of a longer pulse duration for voltage application, exceeding the RC time of the display elements, ensures that the desired voltage is maintained across the interface, reducing backflow and improving the attainment of intended display states by extending the frame period or using simultaneous addressing of rows with varying pulse durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard voltage pulse is applied to the display element, then the display element can be addressed within the frame period, but the desired voltage is not maintained across the interface due to fluid resistance, resulting in ineffective backflow reduction
Solution Approach 1:
The patent applies parameter changes by extending the pulse duration beyond the standard RC time constant. This modification allows the voltage to be maintained across the interface long enough to effectively reduce backflow, directly addressing the reliability issue while accepting a longer action duration as the necessary trade-off.
Solution Approach 2:
The patent implements preliminary action by applying a reset pulse with extended duration before the main display voltage is applied. This preliminary extended pulse ensures that backflow is reduced in advance, preparing the display element for accurate voltage application and improving the overall effectiveness of subsequent addressing.
2Reliability
If the frame period is extended to accommodate longer pulse durations, then the desired voltage can be maintained across the interface, but the productivity of the display device decreases
Solution Approach 1:
The patent applies segmentation by dividing the frame period into distinct phases: an extended reset pulse phase for reliable backflow reduction, followed by the main display phase. This segmentation allows the extended pulse duration to be concentrated where needed without proportionally extending the entire frame period, thereby maintaining higher productivity while achieving reliable voltage maintenance.
Solution Approach 2:
The patent implements periodic action by applying reset pulses at specific intervals within the frame period rather than continuously extending the entire frame. This periodic application of extended pulses achieves the necessary voltage maintenance while keeping the overall frame rate manageable, balancing reliability with productivity.
3Productivity
If simultaneous addressing of rows is implemented with varying pulse durations, then the desired display states can be achieved without extending the overall frame period, but the device complexity increases
Solution Approach 1:
The patent applies dynamics by implementing variable pulse durations for different rows during simultaneous addressing. The pulse duration is dynamically adjusted based on the specific row being addressed, allowing each row to receive the appropriate extended pulse duration needed for effective backflow reduction while maintaining overall frame rate productivity. This dynamic approach manages device complexity through programmable control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the effectiveness of reset pulses in reducing backflow and ensures that the display elements achieve the desired display states, improving image quality by maintaining the intended voltage levels across the interface.
Implementation Method 1
The display element includes a first and a second, immiscible fluid, the configuration of which can be controlled by a voltage applied to the display element
Implementation Method 2
application of a certain voltage to a display element in an active matrix configuration does not result in the desired effect, such as an effective reduction of backflow in the display element or the attainment of a desired display state
Data Source
AI summary
A method of controlling an electrowetting display device with display elements arranged in a matrix with n rows. In examples each display element is addressable with a voltage pulse having a pulse duration longer than Tf/n, where Tf is a pre-determined frame period for addressing the n rows. In examples the pulse duration may be longer than ReCe, with Re being an electrical resistance of an electrically conductive fluid of a display element and Ce being an electrical capacitance of a capacitor of the display element.