Field Inversion Control Circuit for LCD Leakage Uniformity
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Solution Overview
Problem
The field inversion driving method in liquid crystal display devices leads to uneven leakage current distribution across the screen, causing shading and mottled patterns due to varying leakage periods and amounts among different pixels, which deteriorates image quality.
Innovation Solution
A control circuit that performs active matrix driving using a field inversion method, ensuring the vertical effective display period is close to the start of the field period, with a display resolution of 200 μsec or lower, to uniformize the in-plane leakage distribution and reduce current leakage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field inversion driving method is used to prevent DC deterioration and burning, then liquid crystal cell reliability is improved, but leakage current becomes uneven across the screen causing shading and mottled patterns
Solution Approach 1:
The patent applies periodic polarity inversion to the counter electrode at a frequency of 100 Hz or higher (shorter period than the field period). This periodic action equalizes the leakage current characteristics across different pixels by ensuring that pixels at different positions experience similar time-averaged electric field conditions, thereby preventing shading and mottled patterns while maintaining the protective benefits of field inversion driving
Solution Approach 2:
The patent changes the driving parameter by introducing a high-frequency polarity inversion signal to the counter electrode in addition to the conventional field inversion. This parameter change (adding a 100 Hz or higher frequency component) modifies the temporal distribution of electric fields across the display, transforming the uniform leakage pattern into a more uniform distribution and eliminating image quality degradation
2Stability of the object's composition
If conventional field inversion driving is used, then polarity is inverted for each field period, but leakage period varies across the screen leading to non-uniform leakage current distribution
Solution Approach 1:
The patent superimposes a periodic polarity inversion signal on the counter electrode with a period of 10 ms or shorter (100 Hz or higher frequency). This additional periodic action ensures that the leakage current characteristics become uniform across the screen by making the effective leakage period consistent for all pixels, thereby achieving both stable polarity inversion and uniform leakage current distribution
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 significantly suppresses image quality deterioration by minimizing shading and mottled patterns, improving display uniformity across the screen.
Implementation Method 1
a liquid crystal cell as an electrooptical element
Data Source
AI summary
A control circuit according to an embodiment of the disclosure performs control of active matrix driving by a field inversion driving method to cause a vertical effective display period in one field period to be close to a start time of the one field period upon observation of a waveform of a signal outputted from the control circuit with display resolution of 200 μsec or display resolution lower than display resolution of 200 μsec. The one field period is defined by a vertical start signal.