Current Monitoring for Stable Error Frame Detection in CAN-FD
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Solution Overview
Problem
Conventional CAN systems face challenges in stably detecting error frames due to unnormalized output impedance of transceivers, leading to unstable voltage levels and incorrect detection of signal collisions in the non-arbitration area of CAN-FD communications networks.
Innovation Solution
A communications device with a first and second transmitting part, current monitoring parts, and a checking part is used to detect signal collisions by monitoring power supply currents and comparing them to normal currents, allowing for stable detection of error frames even with unregulated transceiver output impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage level detection is used to detect error frames in CAN-FD non-arbitration area, then error detection is attempted, but unstable detection occurs due to unnormalized transceiver output impedance causing different potentials at collision
Solution Approach 1:
The patent introduces current monitoring as an intermediary measurement method. Instead of directly detecting voltage levels which are affected by unnormalized transceiver impedance, the system monitors the current consumed by the transmitting part. This current measurement serves as a mediator that indirectly indicates signal collision conditions without being directly influenced by the impedance variations of connected transceivers, thereby providing stable and reliable error frame detection.
2Adaptability or versatility
If conventional voltage-based error detection is used in high-speed non-arbitration area, then error detection capability is provided, but detection fails when transceiver impedance characteristics vary
Solution Approach 1:
The patent replaces the voltage-based detection mechanism with a current-based detection mechanism. The electrical measurement method is substituted from voltage sensing to current monitoring. This substitution changes the fundamental physical quantity being measured, moving from voltage (which is impedance-dependent) to current (which provides a more consistent indicator of collision conditions regardless of transceiver impedance variations), thereby improving adaptability across different transceiver characteristics.
Data Source
AI summary
In a communication device, when an enabling signal is at a high level and a transmit data is at a high level, that is, in a recessive period, both transistors turn off. Thus, potentials of signal lines are determined by power supply from a second transmitting part to a communications network. When an error frame arises in this state, that is, transistors in the other ECU turn on, excessive currents flow the signal lines. When current monitoring circuits detect error currents, an error signal is changed to a high level.