Capacitive Receiver Path Diagnosis Using Switchable Bypass Capacitance
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Solution Overview
Problem
Capacitive sensing devices face challenges in accurately diagnosing errors in receiver and transmitter paths, leading to inefficiencies in detecting user input and maintaining reliable operation within sensing regions.
Innovation Solution
A processing system with a bypass switch and selectable capacitance is used to couple receiver paths, allowing for the acquisition of measurement signals and determination of ohmic coupling between paths, thereby diagnosing errors and ensuring accurate capacitance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If receiver paths are coupled with capacitors for sensing, then sensing capability is improved, but error diagnosis capability deteriorates
Solution Approach 1:
The system dynamically switches between sensing mode (capacitor connected) and diagnostic mode (capacitor disconnected via bypass switch). The bypass switch enables the receiver path to be decoupled from the capacitor, allowing error diagnosis measurements to be taken without the capacitor's influence, while maintaining sensing capability when needed.
Solution Approach 2:
The bypass switch acts as an intermediary element that controls the connection between the receiver path and the capacitor. By opening or closing the bypass switch, the system can selectively isolate or connect the capacitor to the receiver path, enabling both sensing and diagnostic operations.
2Difficulty of detecting and measuring
If bypass switch is used to isolate capacitor for diagnosis, then error detection capability is improved, but device complexity increases
Solution Approach 1:
The bypass switch serves multiple functions: it enables error diagnosis by isolating the capacitor, and it allows normal sensing operation when closed. This multi-functionality justifies the addition of the switch, as it provides both diagnostic capability and maintains sensing functionality within a single integrated system.
3Measurement precision
If ohmic coupling is present between receiver paths, then signal measurement becomes inaccurate, but detecting the coupling is difficult
Solution Approach 1:
The diagnostic method extracts the effect of ohmic coupling from the overall signal by taking measurements with the capacitor isolated. By removing the capacitor from the circuit during diagnosis, the system can separately measure and identify ohmic coupling effects between receiver paths, distinguishing them from capacitive sensing signals.
Data Source
AI summary
An input device comprises a processing system coupled with a plurality of receiver paths. The processing system comprises a first capacitor and a bypass switch. The first capacitor is configured to be selectively coupled with the plurality of receiver paths. The bypass switch is configured for bypassing the first capacitor. The processing system is configured to selectively couple a first receiver path of the plurality of receiver paths with the first capacitor; acquire a measurement of a first resulting signal from at least one of the first receiver path or a second receiver path of the plurality of receiver paths while the first receiver path is coupled with the first capacitor and while the bypass switch is not bypassing the first capacitor; and determine whether the first receiver path is ohmically coupled with the second receiver path based on the measurement of the first resulting signal.