Electro-optical Device Polarity-Dependent Signal Timing Control
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Solution Overview
Problem
In high-definition electro-optical devices using polarity inversion driving, it is challenging to secure sufficient writing time to signal lines, leading to display unevenness due to insufficient writing, particularly at positive polarity times.
Innovation Solution
The electro-optical device incorporates a control circuit that adjusts the length and timing of image signal supply periods based on the polarity of the image signal, using multiple selection signals to sequentially select sampling switches and ensure adequate writing time for each signal line, thereby optimizing the writing process across both positive and negative polarity periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarity inversion driving is used to prevent electrical degradation, then reliability is improved, but writing time to signal lines becomes insufficient causing display unevenness
Solution Approach 1:
The patent applies dynamics by making the supply period duration variable rather than fixed. The control circuit dynamically adjusts the supply period length based on the polarity of the image signal being written. For positive polarity signals, a longer supply period is allocated, while negative polarity signals use a standard period. This dynamic adjustment ensures sufficient writing time for both polarities while maintaining the polarity inversion driving scheme for reliability.
Solution Approach 2:
The patent changes the time parameter of the supply period based on the polarity parameter of the image signal. By detecting whether the incoming image signal has positive or negative polarity, the control circuit modifies the duration parameter of the supply period accordingly. This parameter change approach resolves the contradiction by ensuring that positive polarity signals, which require more time, receive extended writing periods while negative polarity signals maintain standard timing.
2Manufacturing precision
If high definition is pursued to increase pixel density, then image quality is improved, but writing time to signal lines becomes insufficient
Solution Approach 1:
The patent applies local quality by providing different supply period durations for different signal lines based on their polarity requirements. Instead of using a uniform time allocation for all signal lines, the control circuit identifies which signal lines carry positive polarity signals and extends their supply periods locally. This allows high definition pixel density to be maintained while ensuring that specific signal lines requiring more time receive adequate writing duration.
3Device complexity
If N-channel transistor is used as sampling switch, then device complexity is reduced, but writing time for positive polarity becomes insufficient
Solution Approach 1:
The patent applies preliminary action by extending the supply period for positive polarity signals in advance, before the actual writing process begins. The control circuit detects the polarity of the incoming image signal and proactively allocates a longer time slot for positive polarity signals. This preliminary time allocation ensures that when the N-channel transistor sampling switch operates, it has sufficient time to complete the writing process without rush, maintaining both circuit simplicity and adequate writing time.
Data Source
AI summary
An electro-optical device is provided that includes a pixel circuit disposed corresponding to each of intersections of a scanning line and eight signal lines, an image signal circuit, and a control circuit. The image signal circuit includes a write switch provided for each of the eight signal lines, and in a horizontal scanning period, an image signal is sequentially supplied to the eight signal lines in eight supply periods based on selection signals sequentially selecting eight writing switches. The control circuit controls the selection signals so that a time length of a supply period at a positive polarity time of an image signal is longer than a time length of a supply period at a negative polarity time.