Multi-Layer Membrane Keyboard Ghosting Prevention
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Solution Overview
Problem
Conventional keyboard devices face the 'ghosting' problem when three keys are pressed simultaneously, leading to erroneous key recognition due to the inability to distinguish between keys, and existing solutions either increase cost with diodes or complicate wiring with numerous output wires.
Innovation Solution
A keyboard device with a multi-layered membrane switch circuit member featuring two key matrices with different arrangements, where a control unit generates a key signal only when both key codes from the matrices are received, eliminating the need for diodes and simplifying wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are installed near key intersections to prevent ghosting, then ghosting problem is solved, but device cost and complexity increase
Solution Approach 1:
The patent transitions from a single-plane keyboard matrix to a three-dimensional stacked matrix structure with upper and lower layers. Each key press activates corresponding contacts on both layers, creating a spatial dimension for key identification that eliminates ghosting without requiring diodes. The control unit recognizes valid key presses by detecting simultaneous activation patterns across both layers.
Solution Approach 2:
The keyboard matrix is segmented into two independent layers (upper and lower), each with its own set of row and column contacts. This segmentation allows the system to distinguish between genuine key presses (which activate contacts on both layers) and ghosting conditions (which would only activate contacts on one layer), thereby solving the reliability issue without adding diodes.
2Reliability
If diodes are installed near key intersections to prevent ghosting, then ghosting problem is solved, but manufacturing cost increases
Solution Approach 1:
The patent transitions from a single-plane keyboard matrix to a three-dimensional stacked matrix structure with upper and lower layers. Each key press activates corresponding contacts on both layers, creating a spatial dimension for key identification that eliminates ghosting without requiring diodes. The control unit recognizes valid key presses by detecting simultaneous activation patterns across both layers.
Solution Approach 2:
The patent combines two keyboard matrices into a single integrated structure where the upper and lower layers work together as one system. This merging eliminates the need for separate diode components and their associated wiring, reducing both manufacturing cost and complexity while maintaining ghosting prevention functionality.
3Reliability
If numerous output wires are used to connect each key, then key recognition accuracy is maintained, but device complexity and wiring increase
Solution Approach 1:
The patent transitions from a single-plane keyboard matrix to a three-dimensional stacked matrix structure with upper and lower layers. Each key press activates corresponding contacts on both layers, creating a spatial dimension for key identification that eliminates ghosting without requiring diodes. The control unit recognizes valid key presses by detecting simultaneous activation patterns across both layers.
Solution Approach 2:
The row and column contacts on both upper and lower layers share common signal lines with the control unit. This multi-functional wiring approach allows the same conducting lines to serve multiple keys across different layers, significantly reducing the total number of wires needed compared to individual 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
Effectively solves the ghosting issue by accurately recognizing key presses without increasing cost or complexity, maintaining a slim design and reducing the number of conducting lines.
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
Implementation Method 2
the membrane switch circuit member 11 generates a corresponding key signal
Data Source
AI summary
A keyboard device includes plural keys, a control unit and a membrane switch circuit member. The membrane switch circuit member includes a first upper key switch and a first lower key switch. When the first upper key switch is triggered by the first key, a first key code corresponding to the first key is generated by the first upper key switch. When the first lower key switch is triggered by the first key, a second key code corresponding to the first key is generated by the first lower key switch. The control unit is connected with the membrane switch circuit member. If both of the first key code and the second key code are received by the control unit, a key signal is outputted. If either the first key code or the second key code is received by the control unit, the key signal is not outputted.