Driver Circuit for Display Charge Sharing EMI Reduction

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Solution Overview

Problem

Liquid crystal display devices using charge sharing driving methods generate electromagnetic interference (EMI), which can affect the operation of nearby electronic devices, particularly in touch panel types, leading to potential malfunctions due to erroneous recognition of position coordinates.

Innovation Solution

A driver circuit design that divides the TFT array substrate into regions and controls the supply of charges using a driver circuit with multiple output signal lines and switch mechanisms, allowing for sequential and staggered electrical connections to reduce EMI by dispersing the timing of charge sharing operations across these regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If charge sharing driving is used to reduce power consumption, then power consumption is reduced, but electromagnetic interference (EMI) is generated

Engineering Contradiction:

Improvepower consumptionVSAvoidelectromagnetic interference

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The display panel is divided into multiple regions (first region and second region) with different driving schemes applied to each. The first region uses conventional driving while the second region uses charge sharing driving, thereby segmenting the EMI generation sources in space and reducing overall EMI impact.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The driver circuit alternates between different driving modes for different regions in a periodic manner. By controlling the timing of charge sharing operations in the second region to follow those in the first region, the system creates a periodic pattern that reduces simultaneous EMI generation across the entire display.

Inventive Principle:

Principle #19Periodic action

2Use of energy by moving object

If charge sharing driving is used, then power consumption is reduced, but malfunction of adjacent electronic devices occurs

Engineering Contradiction:

Improvepower consumptionVSAvoidoperation reliability of adjacent electronic devices

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The display is segmented into regions with different driving modes, isolating the charge sharing operations to specific areas. This spatial segmentation prevents EMI from affecting the entire display area, thereby protecting adjacent electronic devices from malfunctions while still achieving power savings in the segmented regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

By implementing periodic charge sharing operations that are staggered between regions, the system reduces the intensity and duration of EMI exposure to adjacent electronic devices, maintaining operational reliability while achieving power consumption reduction.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If charge sharing driving is used in touch panel, then power consumption is reduced, but position coordinate recognition errors occur

Engineering Contradiction:

Improvepower consumptionVSAvoidposition coordinate recognition accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The touch panel is divided into regions with different driving schemes. By applying charge sharing driving only to the second region while using conventional driving in the first region, the system reduces EMI-induced measurement errors in touch coordinate recognition while maintaining power savings in the segmented area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The staggered periodic charge sharing operations reduce the intensity of EMI interference during touch detection, thereby improving the accuracy of position coordinate recognition while still achieving power consumption reduction through periodic charge sharing in the second region.

Inventive Principle:

Principle #19Periodic action

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 reduces EMI generated during charge sharing driving, minimizing the risk of malfunctions in adjacent electronic devices and improving the reliability of touch panel operations.

Implementation Method 1

electro magnetic interference (EMI) is generated from the liquid crystal display screen during the charge sharing driving

Methodology Applied

Scientific EffectElectromagnetic interference: Electromagnetic Induction

Data Source

PatentUS9070337B2Display device with improved driver for array of cells capable of storing charges

Publication Date: 2015.06.30 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

Provided is a display device including a driver circuit for controlling supply of charges to an array of cells capable of storing the charges. In the driver circuit, a preceding electrically connecting part (SW221) controlled by a clock signal (CLK1) electrically connects an output signal line of a first circuit (211) having a positive polarity which is a potential higher than a reference potential and an output signal line of a second circuit (212) having a negative polarity which is a potential lower than the reference potential. After a predetermined time period has elapsed, a subsequent electrically connecting part (SW222) controlled by a clock signal (CLK2) electrically connects an output signal line of a third circuit (213) having the positive polarity and an output signal line of a fourth circuit (214) having the negative polarity.