Keyboard Matrix Circuit Using One Comparator for Ghost Key Suppression
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Solution Overview
Problem
Conventional input devices face issues with ghost key suppression, including increased costs, complex circuitry, and reduced precision, which lead to incorrect switch state determinations and longer operation times.
Innovation Solution
An input device with a switch module, comparator, exchange unit, bias voltage resistor, and processing module, where each switch unit has a resistor connected in series between strobe and sense lines, and a single comparator is used to determine switch states efficiently, eliminating the need for diodes and allowing for flexible board implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are added to switch units to eliminate ghost keys, then ghost key suppression is improved, but manufacturing cost increases and flexible board implementation is prevented
Solution Approach 1:
The patent removes diodes from the switch unit circuitry, extracting the problematic component that prevented flexible board implementation. Instead, it uses a centralized comparator-based detection system that achieves ghost key suppression without requiring diodes at each switch location, enabling flexible board manufacturing.
Solution Approach 2:
The patent introduces a comparator as an intermediary component that mediates between the sense lines and the processing module. This comparator-based intermediary provides intelligent detection capability, replacing the need for passive diodes and enabling both ghost key suppression and flexible board implementation.
2Reliability
If resistors are connected in series with switches to determine switch states, then ghost key suppression is improved, but the number of comparators increases with the number of sense lines
Solution Approach 1:
The patent merges multiple detection functions into a single comparator. Instead of having one comparator per sense line, the exchange unit dynamically connects multiple sense lines to a single comparator, allowing one comparator to perform the work of multiple comparators and significantly reducing device complexity.
Solution Approach 2:
The comparator is designed as a universal component that can detect states on any sense line through the exchange unit's dynamic switching. This multi-functional approach allows a single comparator to replace multiple dedicated comparators, reducing overall system complexity while maintaining ghost key suppression capability.
3Reliability
If series-parallel resistor connections are used to determine switch states, then ghost key suppression is improved, but judgment errors occur due to equivalent circuit effects
Solution Approach 1:
The comparator acts as an intelligent intermediary that provides precise voltage comparison instead of relying on complex series-parallel resistor network analysis. This intermediary component accurately determines switch states by comparing voltages directly, avoiding the judgment errors that occur with equivalent circuit calculations in series-parallel configurations.
4Reliability
If conventional resistor-based switch detection is used, then ghost key suppression is improved, but operation time is extended due to sequential determination
Solution Approach 1:
The processing module uses periodic strobe signals to sequentially activate different rows of switches, and the exchange unit dynamically connects sense lines to the comparator during each period. This periodic action enables systematic detection of multiple switch states through a single comparator, significantly reducing operation time compared to conventional sequential determination methods.
Solution Approach 2:
The exchange unit is configured in advance to dynamically connect appropriate sense lines to the comparator based on the current detection phase. This preliminary configuration enables the single comparator to efficiently detect multiple switch states without requiring sequential processing of each switch individually, improving overall operation speed.
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 manufacturing costs, simplifies resistor connections, enables simultaneous determination of multiple switch states, tolerates wider resistance variations, and requires only one comparator, thereby improving operational speed and accuracy.
Implementation Method 1
The comparator includes a first input end, a second input end for receiving a reference signal, and an output end for outputting a comparison signal. The comparator is configured for comparing a signal received at the first input end with the reference signal for generating the comparison signal.
Implementation Method 2
Each of the switch units has a switch and a resistor connected in series between a corresponding one of the strobe lines and a corresponding one of the sense lines.
Data Source
AI summary
An input device with ghost key suppression includes a switch module, a comparator, an exchange unit, a bias voltage resistor, and a processing module. The switch module includes a plurality of strobe lines, a plurality of sense lines, and a plurality of switch units. Each of the switch units has a switch and a resistor connected in series between a corresponding one of the strobe lines and a corresponding one of the sense lines. The comparator is configured for comparing a signal received at an input end thereof with a reference signal for generating the comparison signal. The exchange unit is electrically connected to the sense lines and the comparator, and is operable in response to a control input for making and breaking electrical connection between each of the sense lines and the input end of the comparator. The processing module controls operation of the switch module and the exchange unit based on the comparison signal.