Active Matrix Display Voltage Control for Non-Rectangular Shapes
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Solution Overview
Problem
Active matrix display devices with non-rectangular display units, such as circular units, experience display unevenness due to varying capacitance of data and scanning signal lines, leading to inconsistent voltage distribution and poor display quality.
Innovation Solution
The implementation of a field effect transistor-based analog switch with a connection control circuit that generates a predetermined time for voltage change from an on-state to an off-state, allowing for continuous or stepwise voltage transitions, thereby reducing voltage variations across data and scanning signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a non-rectangular display unit is used, then the display device can achieve diverse shapes and designs, but the varying capacitance of data and scanning signal lines causes display unevenness
Solution Approach 1:
The patent applies local quality by providing different compensation values to different pixel elements based on their specific positions and line characteristics. The compensation value calculation is performed individually for each pixel element, taking into account the specific capacitance values of the data signal line and scanning signal line connected to that element, thereby achieving uniform display quality across the non-rectangular display unit
Solution Approach 2:
The patent changes the voltage parameter dynamically by applying compensation voltages to pixel elements based on their position. The compensation value is calculated as a function of the capacitance values and adjusts the voltage level accordingly, transforming the uniform voltage input into position-dependent compensated voltages that offset the capacitance variations caused by the non-rectangular geometry
2Ease of operation
If analog switches are used to provide video signals to data signal lines, then signal routing is achieved, but voltage variations occur due to parasitic capacitance during switching
Solution Approach 1:
The patent applies preliminary action by calculating and storing compensation values in advance for each pixel element based on the known capacitance characteristics of the signal lines. Before the actual display operation, the compensation values are prepared and stored in a memory structure, enabling immediate application during signal writing without real-time calculation delays
Solution Approach 2:
The patent implements feedback by using the known capacitance values of the data and scanning signal lines to calculate compensation values that are then applied to correct the voltage variations. This creates a closed-loop system where the capacitance characteristics are measured, compensation is calculated, and the compensation is applied to achieve the desired voltage stability
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 ensures uniform voltage distribution across non-rectangular display units, reducing display unevenness and maintaining favorable display quality by controlling the charge transfer through the parasitic capacitance, regardless of line length.
Implementation Method 1
a parasitic capacitance Cgd formed between a gate terminal of this Nch transistor SWk and one conductive terminal thereof which is connected to the data signal line SLk
Data Source
AI summary
The present invention provides an active matrix display device capable of producing a favorable display on a non-rectangular display unit, such as a circular display unit. In an active matrix liquid crystal display device with a circular display unit, a control signal Sck is generated so as to reduce a decrease amount ΔVsl of a data signal line voltage Vsl due to a parasitic capacitance Cgd, as a control signal of an Nch transistor (SWk) that is a switching element of a sample-and-hold circuit for sampling a video signal Svi and holding the sampled signal in a data signal line capacitance. That is, at the time of turning off the Nch transistor (SWk), a connection switch control signal Sck is generated such that the control signal Sck changes from an H-level connection control voltage VCH as an on-voltage to an L-level connection control voltage VCL as an off-voltage through a period TCI for an intermediate level voltage VCI.