Membrane Keyboard Ghosting Prevention via Segmented Circuit Boards
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Solution Overview
Problem
Conventional keyboard devices face the 'ghosting' problem when multiple keys are pressed simultaneously, leading to incorrect key registration due to the complexity and cost of using diodes or the difficulty in managing numerous output wires.
Innovation Solution
The keyboard device employs a membrane switch circuit member with multiple independent boards to create key matrices, allowing for distinct conducting lines for each key, eliminating the need for diodes and simplifying the wiring, thus preventing ghosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional keyboard matrix with shared row and column lines is used, then the wiring is simple and cost is reduced, but ghosting occurs when multiple keys are pressed simultaneously
Solution Approach 1:
The membrane switch circuit member is divided into multiple independent boards, each handling a specific key or key group. This segmentation allows each key to have its own dedicated conducting lines, eliminating the shared lines that cause ghosting while maintaining manufacturing simplicity through modular construction.
Solution Approach 2:
The patent transitions from a planar keyboard matrix to a three-dimensional stacked configuration with multiple boards at different levels. This dimensional change allows conducting lines to be routed through vertical spaces between boards, providing dedicated pathways for each key without requiring complex lateral routing or additional diodes.
2Reliability
If diodes are added to prevent ghosting in a keyboard matrix, then key registration accuracy improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and removes the diodes from the circuit design entirely. Instead of adding diodes to prevent ghosting, the invention uses a fundamentally different architecture with independent conducting lines for each key, eliminating the need for current-directional components and their associated complexity.
Solution Approach 2:
Rather than modifying the conventional matrix approach by adding diodes to existing shared lines, the patent inverts the problem-solving approach by redesigning the conducting line structure itself to be key-specific from the outset, making ghost prevention inherent to the design rather than an added feature.
3Reliability
If diodes are added to prevent ghosting, then key registration accuracy improves, but manufacturing cost increases
Solution Approach 1:
The patent removes diodes from the bill of materials, directly reducing component costs. The independent board structure achieves ghost-free operation without requiring these additional expensive components, simplifying both the design and the manufacturing bill of materials.
Solution Approach 2:
The patent combines the functions of multiple components into the board structure itself. The conducting lines are integrated directly into the board layers rather than being separate wired components, reducing assembly steps and manufacturing complexity while eliminating the need for additional diode components.
4Reliability
If multiple independent boards are used to create key matrices, then ghosting is prevented and key registration accuracy improves, but device complexity increases
Solution Approach 1:
The patent arranges multiple boards in a stacked, nested configuration where each board is positioned at a different vertical level. This nesting approach consolidates what would otherwise be a spread-out complex structure into a compact vertical arrangement, reducing the overall footprint and making the multi-board structure more manageable.
Solution Approach 2:
The patent uses vertical stacking of boards to resolve the complexity issue. By moving from a two-dimensional planar layout to a three-dimensional stacked configuration, the conducting lines can be routed through the vertical dimension, simplifying the lateral routing complexity that would otherwise be required to provide dedicated lines for each key.
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 solution reduces costs and complexity by avoiding the need for diodes and simplifying the wiring, effectively preventing key registration errors when multiple keys are pressed simultaneously.
Implementation Method 1
the elastic element 103 is subjected to deformation to push the membrane switch circuit member 11 and trigger the corresponding key switch 114
Implementation Method 2
When one keycap is triggered, the keyboard device starts to scan the keyboard matrix and recognizes which keycap is depressed
Data Source
AI summary
A keyboard device includes plural keys, a supporting plate and a membrane switch circuit member. The membrane switch circuit member includes a first board, a second board, a third board and a fourth board. The first board includes plural first contacts. The second board includes plural second contacts and plural first openings. The third board includes plural third contacts and plural second openings. The fourth board includes plural fourth contacts. The plural first contacts, the plural first openings and the plural third contacts are collaboratively defined as a first key matrix. The plural second contacts, the plural second openings and the plural fourth contacts are collaboratively defined as a second key matrix.