Keyboard Matrix Current Sensing to Eliminate Ghost Keys
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Solution Overview
Problem
Conventional keyboard apparatuses designed with a key matrix are prone to the ghost key phenomenon, which increases manufacturing costs when solutions like increasing matrix size or separating keys with diodes are implemented to avoid this issue.
Innovation Solution
A keyboard apparatus with a key module and detection circuit that uses crossed scan and return lines, coupled with a selection circuit and current-to-voltage converter to detect current flowing through return lines, indicating key switch states without the need for excessive wiring or costly modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a key matrix is used to reduce wiring, then manufacturing cost is reduced, but ghost key phenomenon occurs
Solution Approach 1:
A detection circuit is introduced as an intermediary component between the key matrix and the control system. This detection circuit includes current-to-voltage converters that accurately measure the current state of each key, serving as a mediator that resolves the ghost key issue without requiring changes to the key matrix structure or increased wiring complexity.
Solution Approach 2:
The patent changes the detection parameter from simple voltage level detection to precise current measurement using current-to-voltage converters. By monitoring the actual current flow through each key switch rather than relying on voltage states alone, the system can accurately distinguish between genuine key presses and ghost key signals, thereby resolving the reliability issue while maintaining the simplified key matrix structure.
2Measurement precision
If matrix size is increased to avoid ghost key, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical approach of increasing matrix size with an electronic detection solution. Instead of physically expanding the matrix to improve detection accuracy, the system uses current-to-voltage converters and sophisticated current measurement techniques to achieve accurate key detection while maintaining the original compact matrix dimensions.
3Reliability
If diodes are added to separate keys, then ghost key is avoided, but manufacturing cost increases
Solution Approach 1:
Instead of adding diodes as physical separators between keys, the patent introduces a detection circuit with current-to-voltage converters as an intermediary electronic system. This intermediary approach achieves ghost key avoidance through intelligent current measurement and state detection, eliminating the need for additional physical components like diodes and thereby reducing manufacturing cost.
Solution Approach 2:
The patent employs cost-effective current-to-voltage converter circuits that provide reliable ghost key prevention without the expense of adding diodes to every key. These converter circuits offer an economical solution that maintains reliability while minimizing manufacturing costs.
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 avoids the ghost key phenomenon while reducing manufacturing costs by accurately detecting key states using a detection circuit with current-to-voltage converters, outperforming traditional solutions in cost-effectiveness.
Implementation Method 1
The current-to-voltage converter converts the detection current into a detection voltage, and accordingly indicates that a switch of each of the keys coupled to the selected return line is in an on state or in an off state
Data Source
AI summary
A keyboard apparatus including a key module and a detection circuit is provided. The key module includes a plurality of keys, a plurality of scan lines, and a plurality of return lines. The scan lines and the return lines are crossed to each other and coupled to the keys respectively. The detection circuit is coupled to the return lines and configured to detect a current flowing through each of the return lines and indicate that a switch of each of the keys is in an on state or in an off state according to a value of the current.