LCD Driving Method Using Three-Level Scan Signals
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Solution Overview
Problem
Conventional liquid crystal display (LCD) apparatuses face high power consumption due to significant voltage swings in data lines required for positive and negative polarity operations, which increases energy usage and heat generation.
Innovation Solution
The LCD apparatus employs a driving method with scan signals having three distinct voltage levels, allowing the pixel electrode to achieve larger voltage levels with reduced voltage swings, by using a switch element and coupling capacitance to manage voltage levels effectively, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional two-voltage-level scan signals are used to drive pixels, then the switching operation is simple, but the voltage swing of data lines becomes large causing high power consumption
Solution Approach 1:
The patent changes the parameter of scan signal voltage levels from two levels to three levels. The second scan signal includes a first voltage level, a second voltage level, and a third voltage level, which are different from one another during a frame time. This parameter change enables the pixel electrode to achieve both positive and negative polarity operations with reduced voltage swings on data lines, thereby reducing power consumption of the data driving circuit.
Solution Approach 2:
The patent segments the voltage control into multiple stages by using three distinct voltage levels in the second scan signal. The voltage levels are switched at different times to achieve different polarity operations: when the second scan signal switches to the third voltage level from the second voltage level, the pixel electrode is negative polarity; when the second scan signal switches to the second voltage level from the third voltage level, the pixel electrode is positive polarity. This segmentation allows independent control of voltage swings for different polarity operations.
2Reliability
If larger voltage levels are applied to pixel electrode for proper operation, then the display performance is maintained, but the voltage swing on data lines increases leading to higher power consumption
Solution Approach 1:
The patent introduces the second scan signal with three voltage levels as an intermediary to control the pixel electrode voltage. Instead of directly applying large voltage swings through the data line, the second scan signal acts as a mediator that couples to the pixel electrode through coupling capacitance, enabling the pixel electrode to achieve larger voltage levels (positive and negative polarities) while the data line maintains smaller voltage swings, thus reducing energy loss in the data lines.
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 reduces the power consumption of the data driving circuit by minimizing voltage swings, achieving power saving while maintaining image quality and resolution requirements for portable electronic devices.
Implementation Method 1
a coupling capacitance electrically coupled to the pixel electrode and the second scan line
Implementation Method 2
the scan signal G3 down to −7V from 22V at the time t2 will cause a feedthrough effect to the pixel electrode VA
Data Source
AI summary
An LCD apparatus has a first scan line transmitting a first scan signal, a second scan line transmitting a second scan signal, a data line intersecting the first and second scan lines, a switch element electrically coupled to the first scan line and the data line, a pixel electrode electrically coupled to the switch element, a coupling capacitance electrically coupled to the pixel electrode and the second scan line. The second scan line has three different voltage levels. When the first scan line enables the switch element, the pixel electrode receives a data signal through the data line. When the second scan signal switches to the third voltage level from the second voltage level, the pixel electrode is negative polarity, and when the second scan signal switches to the second voltage level from the third voltage level, the pixel electrode is positive polarity.