Electro-optical Drive Circuit Common Electrode Feedback Control
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Solution Overview
Problem
In electro-optical devices like liquid crystal devices, display unevenness occurs due to high ON resistance of transistors connecting common electrodes to a power supply line, which also increases the size of transistors and non-display contributing areas in the device substrate.
Innovation Solution
A drive circuit configuration that includes scanning line drive, common electrode drive, and data line drive circuits, with common signal output circuits that buffer and control voltages for common electrodes, allowing feedback control to maintain reference voltages and reduce noise, thereby suppressing display unevenness without increasing transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ON resistance of the transistor for connecting the common electrode to the power supply line is reduced, then display unevenness is suppressed, but the size of the transistor is increased and the area of the device substrate which does not contribute to the display is also increased
Solution Approach 1:
A detection line is introduced as an intermediary element to sense the potential of the common electrode. This allows the system to detect voltage variations without requiring the transistor to have low ON resistance, thereby suppressing display unevenness while maintaining a compact transistor size that contributes to display area.
Solution Approach 2:
The patent implements a feedback mechanism where the detection line monitors the common electrode potential and this information is used to adjust the data line signals. This feedback loop compensates for voltage drops caused by transistor ON resistance, eliminating display unevenness without needing to increase transistor size.
2Power
If common electrodes are individually driven for each scanning line, then voltage amplitudes of data lines are suppressed, but transistors are needed to connect common electrodes to power supply lines
Solution Approach 1:
The detection line serves multiple functions: it detects the potential of the common electrode, provides feedback information for signal adjustment, and enables compensation for voltage drops. This multi-functionality allows individual common electrode control while managing the complexity of transistor configuration efficiently.
Solution Approach 2:
The patent replaces the need for large, low-resistance transistors with an electrical feedback system. Instead of mechanically enlarging transistors to reduce resistance, the system uses detection lines and feedback control to achieve the same effect, substituting a compact electrical solution for a larger physical component.
Data Source
AI summary
A drive circuit of an electro-optical device includes: plural rows of scanning lines; plural columns of data lines; a plurality of common electrodes; pixel switching elements, pixel capacitors; and pixels. Here, the drive circuit includes a scanning line drive circuit; and first transistors corresponding to the plurality of common electrodes. Each of the first transistors includes: a common electrode drive circuit for connecting the common electrode to a power supply line, to which a predetermined voltage is applied, when the scanning line is selected, a common signal output circuit having a voltage for allowing a detection voltage of the common electrode corresponding to a scanning line to become a reference voltage when the scanning line is selected, and a data line drive circuit having a voltage according to the gray scale level of the pixel to the pixel corresponding to the selected scanning line via the data line.