Pressure-Sensing Keyboard Circuit With Ghost Key Prevention
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Solution Overview
Problem
Existing keyboard circuits are inefficient for fast operation speeds, as they require simultaneous key presses to execute control functions, leading to increased operating time and error probability. Additionally, current solutions for preventing ghost keys are costly and complex, making them unsuitable for cost-effective and reliable applications.
Innovation Solution
A composite function keyboard circuit with a pressure sensing function and a ghost key preventing function is developed. This circuit includes a first and second matrix circuit, bias resistor groups, and a controller. The second matrix circuit uses ink-type force sensing switches, allowing a single key press to execute various key functions based on pressure mode, while the first matrix circuit prevents ghost keys through a bias resistor and switch unit configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single key is operated to execute various types of key function instructions according to capacitive sensing technology or optical sensing technology, then the operation speed is improved, but the cost and device complexity are largely increased
Solution Approach 1:
The patent replaces complex capacitive sensing technology or optical sensing technology with a simple mechanical force sensing switch. The force sensing switch detects key press depth through mechanical force, enabling single-key multi-function operation without requiring expensive sensors. This mechanical approach maintains fast operation speed while dramatically reducing device complexity and cost.
Solution Approach 2:
The patent utilizes different pressing depths (pressure parameters) of a single key to generate different key control instructions. By detecting the force sensing switch's resistance changes at different press depths, the system distinguishes between various functions triggered by the same key, thereby improving operation speed without increasing device complexity.
2Reliability
If diodes are arranged near the corresponding key switches to prevent ghost key phenomenon, then the reliability is improved, but the cost is largely increased
Solution Approach 1:
The patent extracts the ghost key prevention function from the traditional diode-based approach and implements it through a software algorithm in the controller. The controller detects ghost keys by analyzing the timing and pattern of key signals, eliminating the need for additional physical diodes near each key switch. This reduces device complexity and cost while maintaining reliable ghost key prevention.
Solution Approach 2:
The patent introduces a software-based detection mechanism as an intermediary between the physical key switch and the key control instruction generation. The controller acts as a mediator that analyzes key press patterns and filters out ghost key signals, providing reliable ghost key prevention without requiring additional hardware components like diodes.
3Reliability
If two keys or a combination key are pressed down simultaneously to execute a specified control function, then the reliability is improved, but the operating time and error probability are increased
Solution Approach 1:
The patent transforms static key press detection into a dynamic process by detecting different pressing depths over time. A single key can trigger different functions based on how deeply and how quickly it is pressed, as detected by the force sensing switch. This dynamic approach maintains reliable control function execution while significantly reducing operating time compared to requiring simultaneous two-key presses.
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
The composite function keyboard circuit enables efficient execution of various key functions with a single key press, enhancing operation speed and reducing error probability. It also effectively prevents ghost keys without increasing costs, making it a reliable and cost-effective solution.
Implementation Method 1
Each of the second switch units of the second switch unit group is an ink-type force sensing switch. A resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action.
Data Source
AI summary
A composite function keyboard circuit includes a first matrix circuit, a first bias resistor group, a second matrix circuit, a second bias resistor group and a controller. Each switch unit in the first matrix circuit is an ink-type force sensing switch. A resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action. An electrical connection path is formed between the ink-type force sensing switch and the corresponding bias resistor of the second bias resistor group. When the ink-type force sensing switch is electrically conductive, a divided sensing voltage is generated by the electrical connection path, and the controller generates a corresponding key control instruction according to a level of the divided sensing voltage. Furthermore, the cooperation of the first matrix circuit and the first bias resistor group can achieve a ghost key preventing function.