Electro-optical Device Drive Circuit Crosstalk Reduction
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Solution Overview
Problem
Passive matrix liquid crystal devices experience crosstalk issues during grayscale display, leading to luminance differences due to noise between black and white image segments, which degrade display quality.
Innovation Solution
An electro-optical device with a scanning line drive circuit and signal line drive circuit that synchronizes pulse width modulation, setting the period for the longest OFF voltage interval longer than the longest ON voltage interval, and employing right-adjust left-adjust pulse width modulation or line inversion drive methods to reduce common noise and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If passive matrix drive type is used to reduce power consumption and manufacturing cost, then power consumption is reduced and manufacturing cost is lowered, but crosstalk occurs between black color image and white frame image resulting in luminance differences
Solution Approach 1:
The patent changes the timing parameters of the drive waveform by adjusting the selection period and non-selection period durations. Specifically, it sets the selection period to 1/3 to 1/20 of the frame period and the non-selection period to 2/3 to 19/20 of the frame period, optimizing the balance between power consumption and crosstalk reduction
Solution Approach 2:
The patent employs periodic drive waveforms with specific selection and non-selection periods. By making the non-selection period longer than the selection period in a periodic cycle, the liquid crystal molecules have sufficient time to return to their initial state, thereby reducing cumulative crosstalk effects while maintaining acceptable power consumption
2Adaptability or versatility
If pulse width modulation grayscale display is performed, then grayscale display capability is achieved, but noise occurs in the common waveform resulting in luminance differences due to difference in noise level between segments
Solution Approach 1:
The patent modifies the pulse width modulation parameters by adjusting the duty cycle and timing of the drive waveform. By optimizing the selection period ratio and synchronizing the grayscale display timing with the extended non-selection period, it reduces noise accumulation while preserving grayscale display capability
Solution Approach 2:
The patent applies a longer non-selection period before the selection period in each cycle, preparing the liquid crystal molecules to return to their initial state before the next grayscale display cycle begins. This preliminary recovery action prevents noise accumulation that would otherwise degrade display quality
Data Source
AI summary
An electro-optical display device includes an electro-optical panel, a scanning line drive circuit for scanning the scanning lines of the panel during a selection period, and a signal line drive circuit for outputting a data signal to a predetermined pixel through the corresponding data line of the panel in synchronization with the scanning of the scanning line drive circuit. During the selection period during which the data signal is output to the predetermined pixel, the duration of the ON voltage interval corresponding to a grayscale level having the longest OFF voltage interval is longer than the duration of the OFF voltage interval corresponding to a grayscale level having the longest ON voltage interval.