Charge Control Relay Fusion Detection for Safe DC Charging
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Solution Overview
Problem
Existing vehicle charging technologies do not account for the potential fusion of a contact relay between a charging station and an AC outlet during DC charging, leading to the risk of applying DC voltage to AC devices, which can cause failures.
Innovation Solution
A charge control device equipped with bi-directional charger, C-contact relay, and a processor that uses voltmeters to detect and diagnose the fusion of the C-contact relay by measuring voltages at specific points in the circuit, allowing for proactive prevention of DC charging when fusion is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DC charging is performed using a shared AC/DC input path, then charging functionality is improved, but the risk of applying DC voltage to AC devices increases when the contact relay is fused
Solution Approach 1:
The system performs preliminary diagnosis by measuring voltages at multiple points (inlet side, relay output side, and AC outlet side) before initiating DC charging. This advance detection allows the system to identify fused contact relays and prevent DC voltage from being applied to AC devices, thereby resolving the contradiction between maintaining charging functionality and preventing harmful voltage application.
Solution Approach 2:
The processor acts as an intermediary that mediates between the charging function and safety protection. By introducing voltage measurement points and diagnostic logic, the processor enables the system to distinguish between normal AC outlet conditions and fused relay conditions, allowing DC charging to proceed safely or be prevented when necessary.
2Reliability
If voltage measurement points are added for fusion detection, then safety is improved, but device complexity increases
Solution Approach 1:
The existing voltmeter in the charging system is made multi-functional by utilizing it for both normal charging operation and fusion detection. The same measurement infrastructure serves dual purposes: monitoring charging status and detecting relay fusion conditions, thereby improving safety without significantly increasing device complexity.
Solution Approach 2:
The system performs self-diagnosis by using its own measurement capabilities to detect fusion conditions. The processor analyzes voltage measurements taken during normal operation to identify abnormal conditions indicating relay fusion, enabling the system to monitor its own health without requiring separate dedicated detection hardware.
Data Source
AI summary
The charge control device includes an ECU. ECU obtains a first voltage from the first voltmeter, a second voltage from the second voltmeter, and a third voltage from the third voltmeter. ECU diagnoses welding of the C-contact relays based on the first voltage. the second voltage, and the third voltage.