Electrophoretic Display Driving Using Pulse Amplitude Modulation
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Solution Overview
Problem
Electrophoretic display apparatuses face challenges in achieving effective gradation display due to limitations in pulse width modulation and reset operations, leading to deteriorated display quality and inability to control charge voltage levels efficiently.
Innovation Solution
A method and apparatus for pulse amplitude modulation (PAM) driving in electrophoretic display apparatuses, utilizing a driving unit that outputs source signals with limited levels, adjusting pulse widths and voltage levels for gradation and reset periods to control the state of electrophoretic cells, and applying common voltages to achieve gradation display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse width modulation is used for gradation display, then display control capability is improved, but parasitic capacitance charging causes display quality deterioration
Solution Approach 1:
The gradation period is divided into multiple sub-gradation periods, allowing the display to express gradation through temporal segmentation of voltage application rather than relying on pulse width modulation that charges parasitic capacitance. This segmentation enables precise control of electrophoretic cell states without the harmful side effects of PCM.
Solution Approach 2:
The patent implements periodic gradation periods with multiple sub-gradation periods, where source signals are applied in a periodic manner to control the state of electrophoretic cells. This periodic action allows gradation display while avoiding the parasitic capacitance charging issue associated with continuous pulse width modulation.
2Ease of operation
If reset operations are performed to control electrophoretic cell states, then display state control is improved, but charge voltage level control efficiency deteriorates
Solution Approach 1:
The patent changes the approach from binary reset operations to multi-level source signal voltage control. By applying source signals with different voltage levels (first voltage level, second voltage level, third voltage level) during gradation periods, the system can efficiently control both the state and charge voltage levels of electrophoretic cells in a unified manner, improving productivity.
Solution Approach 2:
The source signal lines are designed to perform multiple functions: they can apply reset voltages during reset periods and apply gradation voltages during gradation periods. This multi-functionality eliminates the need for separate control mechanisms, improving charge voltage level control efficiency while maintaining display state control capability.
3Device complexity
If source signals with limited levels are used, then driving unit complexity is reduced, but gradation display capability deteriorates
Solution Approach 1:
The patent adds a temporal dimension to the control scheme by introducing multiple sub-gradation periods within gradation periods. By controlling the duration and sequence of source signal application across these sub-periods, the system achieves fine-grained gradation control using only a limited set of voltage levels, thereby maintaining simple driving unit design while preserving gradation display capability.
Solution Approach 2:
The patent implements dynamic control of source signal application by adjusting the duration of signal application in each sub-gradation period and by selectively applying different voltage levels (first, second, third levels) based on the desired gradation. This dynamic temporal control enables rich gradation display with a limited set of voltage levels.
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
Enables efficient gradation display by controlling the number of sub-gradation periods and voltage levels, improving display quality and allowing for precise control of electrophoretic cell states, thereby enhancing the overall performance of electrophoretic display apparatuses.
Implementation Method 1
Electrophoretic display apparatuses use electrophoretic cells to display input images. Electrophoretic display apparatuses, which display images using the movement of charge carriers in a magnetic field
Implementation Method 2
each of the gate pulses having a pulse width and a first voltage level that are set not to fully charge a parasitic capacitance component of a switching transistor of a corresponding pixel
Data Source
AI summary
An electrophoretic display apparatus and a method of driving the same. Gradation display using pulse amplitude modulation (PAM) may be achieved using a gate pulse having a pulse width and a voltage level that are set not to fully charge a parasitic capacitance component of a switching transistor included in each pixel.