EV Charging Relay Welding Detection via Periodic Monitoring
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Solution Overview
Problem
In electric vehicles, relays connected to battery packs can weld due to over-current, leading to dangerous situations such as continuous over-charging, fires, or explosions, necessitating a method to detect welding and prevent unnecessary power consumption.
Innovation Solution
A charging system with a welding monitoring relay and a relay welding sensing unit, utilizing a photo coupler to determine welding presence by sensing current flow, and controlling the welding monitoring relay based on charge completion to minimize power consumption and ensure safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay welding sensing unit continuously monitors relay welding status, then welding detection reliability is improved, but power consumption increases unnecessarily during charging operations
Solution Approach 1:
The patent applies periodic action by controlling the welding monitoring relay to open during charging operations and close after charging completion. This periodic switching of the monitoring circuit allows welding detection only when necessary (after charging), thereby reducing power consumption during charging while maintaining reliability when monitoring is active.
Solution Approach 2:
The patent implements dynamics by making the welding monitoring relay controllable and switchable between open and closed states based on charging status. The relay transitions from a static always-connected state to a dynamic state where connectivity changes according to operational phase, optimizing both power consumption and detection reliability.
2Reliability
If the welding monitoring relay remains closed continuously, then welding detection capability is maintained, but unnecessary power consumption occurs during charging
Solution Approach 1:
The control unit implements periodic action by opening the welding monitoring relay during charging operations and closing it after charging completion. This creates a periodic monitoring pattern where the relay is active only when needed, eliminating continuous power consumption while maintaining detection capability during critical post-charging periods.
Solution Approach 2:
The patent applies the extraction principle by temporarily removing the welding monitoring relay from the circuit (opening it) during charging operations when welding detection is not required. This extracts the monitoring function from continuous operation, reducing energy loss while preserving the ability to detect welding when the relay is reconnected after charging.
3Loss of energy
If the relay opens during charging, then power consumption is reduced, but welding detection capability is lost
Solution Approach 1:
The patent resolves this contradiction through periodic action by scheduling relay opening during charging (when detection is unnecessary) and closing after charging (when detection is critical). This timing-based periodic operation ensures power reduction during low-risk periods while maintaining detection capability during high-risk post-charging periods.
Solution Approach 2:
The control unit performs preliminary action by opening the relay before charging completes and closing it immediately after charging ends. This preliminary switching ensures that the relay is in the correct state (open) during charging to save power, and transitions to the detection state (closed) before welding detection becomes necessary, preventing both energy waste and detection failure.
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
Effectively detects welding in relays, preventing over-charging and potential fires, while minimizing power consumption during non-charge states, thereby enhancing safety and efficiency in electric vehicle charging systems.
Implementation Method 1
a photo coupler to determine welding presence by sensing current flow
Data Source
AI summary
A charging device includes: a plurality of main relays forming a connection between an electric vehicle (EV)-side connector and an outlet-side connector; a relay welding sensing unit connected to the plurality of relays to sense the presence or absence of welding of the plurality of relays; a welding monitoring relay opening and closing between the relay welding sensing unit side node and a main relay side node; and a control unit controlling the open and close of the welding monitoring relay.