Electrophoretic Display Driving Method Using Stirring and Compensation Pulses
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Solution Overview
Problem
Electrophoretic display devices suffer from afterimages, ghosting, and the display of inverted images during image updates due to accumulated DC components and the need for radical changes in voltage potentials, which degrade display quality and user experience.
Innovation Solution
An electrophoretic display device and driving method that utilize a stirring pulse, compensation pulse, and set pulse with specific voltage waveforms to zero the total DC component, prevent inverted image display, and reduce power consumption by minimizing radical changes in voltage potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage waveforms are used to update images in electrophoretic display devices, then image update functionality is achieved, but afterimages and ghosting occur due to accumulated DC components
Solution Approach 1:
The patent extracts and eliminates the harmful DC component from the voltage waveform by introducing a compensation pulse that specifically targets and removes the accumulated DC charge, while preserving the useful image update function through the set pulse
Solution Approach 2:
The voltage waveform is segmented into distinct functional components: a stirring pulse to initialize particle distribution, a compensation pulse to eliminate DC components, and a set pulse to update the image. This segmentation allows each component to perform its specific function without causing harmful effects
2Object-generated harmful factors
If reset periods with inverted images are used to cancel history effects, then afterimages are reduced, but inverted images are displayed causing user discomfort
Solution Approach 1:
The patent converts the harmful DC component into a measurable parameter that can be compensated. By calculating the DC component from the voltage waveform and applying a compensating pulse, the previously harmful effect becomes a controllable variable that can be eliminated without displaying inverted images
3Productivity
If voltages with radical changes in potential are applied to update images, then image update speed is improved, but power consumption increases
Solution Approach 1:
The patent uses periodic voltage application with specific timing characteristics. The voltage is applied in controlled pulses rather than continuously, and the duration and frequency are optimized to achieve image update while minimizing energy consumption through the relationship between pulse width, amplitude, and duty cycle
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
The solution effectively eliminates afterimages and ghosting, maintains high image quality, and reduces power consumption by ensuring zero total DC components and preventing inverted image display during updates, enhancing user experience.
Implementation Method 1
a liquid cell (electrophoretic layer) containing charged particles is sandwiched by transparent electrodes, and the reflectance of the display surface changes by migration of the charged particles caused by adding a voltage
Data Source
AI summary
An electrophoretic display device is provided, in which an image update period is constituted with a reset period including at least a stirring pulse for stirring electrophoretic particles and a compensation pulse for suppressing accumulation of the residual DC component and with a set period including a set pulse for applying, to intended pixels, a voltage of polarity for making transition to black or white for a prescribed amount of time according to a next image. The voltage waveforms for each display gradation are so designed that a period where a positive voltage is applied to a counter electrode and a period where a negative voltage is applied do not overlap with each other, and a compensation pulse is applied after the stirring pulse which sets all the pixels of the display unit to a white or black base state. Thereby, changes in the display state are not visually recognized.