Membrane Switch Resistance Sensing for Ghost Key Prevention

Solution Overview

Problem

Densely arranged membrane switches in keyboard devices often experience signal interference, leading to the 'ghost key phenomenon where adjacent switches can trigger incorrectly, and the use of diodes to mitigate this increases costs and assembly complexity.

Innovation Solution

A membrane switch design featuring a first and second circuit layer with a spacer layer, where the conductive patterns form a conductive contact surface with a specific resistance value when pressed, allowing the processor to accurately determine key presses based on resistance rather than signal transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If diodes are added near membrane switches to prevent ghost key phenomenon, then reliability is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveaccuracy of key press detectionVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the ghost key prevention function into the membrane switch structure itself by using a conductive contact surface with specific resistance characteristics. Instead of adding separate diodes, the invention integrates the detection mechanism directly into the switch contact area, combining multiple functions into a single structural element.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses parameter changes by controlling the resistance value of the conductive contact surface. By adjusting the resistance characteristics of the contact area, the system can distinguish between genuine key presses and interference signals, achieving ghost key prevention through electrical parameter differentiation rather than additional components.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If diodes are added near membrane switches to prevent ghost key phenomenon, then reliability is improved, but manufacturing cost increases

Engineering Contradiction:

Improveaccuracy of key press detectionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent merges the ghost key prevention function into the membrane switch structure itself by using a conductive contact surface with specific resistance characteristics. Instead of adding separate diodes, the invention integrates the detection mechanism directly into the switch contact area, combining multiple functions into a single structural element.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses parameter changes by controlling the resistance value of the conductive contact surface. By adjusting the resistance characteristics of the contact area, the system can distinguish between genuine key presses and interference signals, achieving ghost key prevention through electrical parameter differentiation rather than additional components.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If membrane switches are densely arranged on keyboard circuit, then productivity is improved, but signal interference increases causing ghost key phenomenon

Engineering Contradiction:

Improvekey densityVSAvoidsignal accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by giving the conductive contact surface specific resistance characteristics that differ from other parts of the circuit. The contact area is designed with controlled resistance properties that enable it to distinguish genuine presses from interference, creating a localized detection zone with unique electrical characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses parameter changes by controlling the resistance value of the conductive contact surface. By adjusting the resistance characteristics of the contact area, the system can distinguish between genuine key presses and interference signals, achieving ghost key prevention through electrical parameter differentiation rather than additional components.

Inventive Principle:

Principle #35Parameter changes

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 design effectively reduces the ghost key phenomenon by providing a reliable method for determining key presses through resistance values, enhancing accuracy and reducing costs by eliminating the need for diodes.

Implementation Method 1

After the first conductive pattern is penetrated through the perforation and the first conductive pattern is contacted with the second conductive pattern, a conductive contact surface is formed between the first conductive pattern and the second conductive pattern, and the conductive contact surface has a resistance value

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS12131876B2Membrane switch

Publication Date: 2024.10.29 PRIMAX ELECTRONICS LTD

AI summary

A membrane switch includes a first conductive pattern, a second conductive pattern and a processor. The first circuit layer is aligned with the second conductive pattern. The first conductive pattern and the second conductive pattern have different shapes. When the second conductive pattern is contacted with and covered by the first conductive pattern, a conductive contact surface is formed. The conductive contact surface has a resistance value corresponding to an area of the conductive contact surface. A processor judges whether a key signal is generated according to the resistance value.