Force-Sensing Keyboard Circuit for Single-Key Functions Without Ghosting

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Solution Overview

Problem

Conventional keyboard circuits require simultaneous pressing of multiple keys for control functions, which is inefficient for fast operations and prone to errors, and existing solutions using capacitive or optical sensing technologies are costly and complex, complicating the keyboard structure.

Innovation Solution

A composite function keyboard circuit with a matrix circuit, bias resistor circuit, and controller, utilizing ink-type force sensing switches and anti-ghosting units to generate divided conduction voltages based on pressure-related resistance, allowing single-key operation for various functions while preventing ghost keys.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If simultaneous pressing of multiple keys is used for control functions, then composite key functions can be executed, but operating time increases and error probability increases

Engineering Contradiction:

Improvecomposite key functionVSAvoidoperating time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent makes a single key perform multiple functions by detecting different pressing depths. The same key can trigger different control functions based on whether it is pressed lightly or deeply, eliminating the need for multiple keys or combination keys while maintaining functional versatility

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent changes the detection parameter from binary (pressed/not pressed) to continuous (pressing depth). By measuring the varying resistance values caused by different pressing depths, the system can distinguish between different operational intentions using a single key, thereby reducing operating time and errors

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If capacitive or optical sensing technology is used for single-key multi-function operation, then various key functions can be executed by single key, but device cost increases and structure becomes complicated

Engineering Contradiction:

Improvesingle-key multi-functionVSAvoidkeyboard structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces complex capacitive or optical sensing systems with a simple resistive sensing mechanism using ink-type force sensing switches. This mechanical-resistive approach achieves single-key multi-function capability without requiring expensive or complex electronic components, thereby reducing device complexity and cost

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses inexpensive ink-type force sensing switches that rely on simple resistive changes rather than expensive capacitive or optical components. This approach achieves the desired functionality using low-cost materials and simpler construction methods

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Adaptability or versatility

If ink-type force sensing switch is used to detect key press, then single-key operation for multiple functions is enabled, but ghost key phenomenon may occur

Engineering Contradiction:

Improvesingle-key multi-functionVSAvoidghost key prevention

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the controller reads the resistance value of the ink-type force sensing switch and compares it against threshold values to determine the appropriate control function. This feedback loop ensures accurate detection of pressing depth and prevents false triggering, thereby eliminating ghost key phenomena while maintaining single-key multi-function capability

Inventive Principle:

Principle #23Feedback

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

Enables efficient, cost-effective single-key operation for multiple functions and prevents ghost key phenomena by accurately identifying key presses through variable resistance and voltage thresholds.

Implementation Method 1

A pressure-related resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Implementation Method 2

When the ink-type force sensing switch is electrically conducted, a divided conduction voltage is generated by the electrical connection path

Methodology Applied

Scientific EffectVoltage division: Ohm's Law

Data Source

PatentUS20260058077A1Composite function keyboard circuit

Publication Date: 2026.02.26 PRIMAX ELECTRONICS LTD

AI summary

A composite function keyboard circuit includes a matrix circuit, a bias resistor circuit and a controller. Each switch unit in the matrix circuit includes an ink-type force sensing switch and an anti-ghosting unit. A pressure-related resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action. An electrical connection path is defined by the ink-type force sensing switch and the corresponding bias resistor of the bias resistor circuit. When the ink-type force sensing switch is electrically conducted, a divided conduction voltage is generated by the electrical connection path. According to a level of the divided conduction voltage, the controller generates a corresponding key control instruction, and the controller judges whether the switch unit in the switch unit group is effectively turned on. Consequently, a ghost key phenomenon is avoided.