Display Driver Charge Sharing EMI Reduction
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Solution Overview
Problem
Liquid crystal display devices experience significant Electro Magnetic Interference (EMI) during charge sharing drive, which can lead to erroneous operations in touch-panel-type devices due to the proximity of touch panels to the display screens, causing incorrect positional recognition.
Innovation Solution
A driver circuit design that includes multiple circuits with alternating polarity inversion and controlled conduction phases to approximate output signal potentials to a reference potential, dispersing the timing of charge sharing across the display screen to reduce EMI generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If charge sharing drive is implemented to suppress electricity consumption for inversion of charge, then power consumption is reduced, but EMI is generated which can cause erroneous operations in touch-panel-type devices
Solution Approach 1:
The driver circuit is divided into multiple independent circuit blocks (first circuit block, second circuit block, third circuit block, fourth circuit block), each responsible for driving different regions of the display panel. By segmenting the charge sharing operation across multiple circuit blocks that operate at different timings, the patent reduces the simultaneous current discharge that causes EMI, while still achieving power savings through charge sharing in each segment.
2Use of energy by moving object
If output signals with different polarities are short-circuited at predetermined timing to achieve charge sharing, then power consumption is reduced, but EMI is generated from the liquid crystal display screen
Solution Approach 1:
The patent implements charge sharing operations in a periodic and staggered manner across different circuit blocks. Each circuit block performs charge sharing at different time intervals rather than simultaneously, creating a periodic pattern of current discharge. This temporal distribution reduces the peak EMI intensity while maintaining the power-saving benefits of charge sharing.
Solution Approach 2:
The circuit includes conduction means that is activated at predetermined timings to short-circuit output signals before they can generate excessive EMI. By preliminarily controlling the discharge timing and using conduction means to manage the charge sharing process, the patent prevents EMI generation while achieving power savings.
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
The solution effectively minimizes EMI by dispersing the charge sharing timing, thereby reducing the risk of erroneous operations in touch-panel-type liquid crystal display devices and enhancing overall operational reliability.
Implementation Method 1
a preceding conduction means which approximates a potential of an output signal line of the first circuit and a potential of an output signal line of the second circuit to a reference potential by making the output signal line of the first circuit having either one of positive polarity which is a potential higher than a reference potential and negative polarity which is a potential lower than the reference potential and the output signal line of the second circuit having the other polarity electrically conductive with each other
Data Source
AI summary
In a driver circuit which controls the supply of charge to cells each of which can store a charge, the EMI (Electro Magnetic Interference) which occurs at the time of performing the charge sharing driving can be reduced. A preceding conduction means (SW13) which is controlled in response to a clock signal (CLK1) makes an output signal line corresponding to a first circuit which has positive polarity of a potential higher than a reference potential and an output signal line corresponding to a second circuit which has negative polarity of a potential lower than the reference potential electrically conductive with each other. After a lapse of a predetermined time, a succeeding conduction means (SW23) which is controlled in response to a clock signal (CLK2) makes an output signal line corresponding to a third circuit which has the positive polarity and an output signal line corresponding to a fourth circuit which has the negative polarity electrically conductive with each other.