Vehicle Relay Shutdown Timing for Charging and Contact Wear
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Solution Overview
Problem
Existing relay control systems in electric vehicles do not effectively manage the life of the relay by reducing the frequency of opening and closing, leading to premature wear and reduced efficiency in battery charging operations.
Innovation Solution
A relay control device and method that includes an end detection unit to recognize when vehicle travel has ended and a determination unit to control the timing of relay circuit shutdown based on the likelihood of external power supply, thereby minimizing the number of relay state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay circuit is turned off immediately after vehicle traveling ends, then battery safety is ensured by cutting off power, but the relay life is reduced due to frequent opening and closing operations
Solution Approach 1:
The determination unit checks whether external power supply is connected before controlling the relay circuit shutdown. If external power is detected, the relay is kept on longer to prevent battery damage, avoiding unnecessary relay operations. This preliminary check prevents premature relay switching that would reduce relay life while still ensuring battery safety.
Solution Approach 2:
The system continuously monitors the connection status of external power supply and uses this feedback to dynamically adjust relay circuit shutdown timing. When external power is detected, the relay shutdown is delayed; when no external power is present, the relay can shutdown immediately. This feedback mechanism ensures battery safety while minimizing unnecessary relay operations to extend relay life.
2Duration of action of stationary object
If the relay circuit is kept on longer after vehicle traveling ends, then relay life is extended by reducing switching frequency, but battery safety may be compromised if external power is not detected
Solution Approach 1:
Before extending the relay operation time to protect relay life, the determination unit performs a preliminary detection of external power supply connection. Only when external power is confirmed does the system extend the relay operation time. This preliminary action ensures that battery safety is not compromised while still achieving relay life extension through reduced switching frequency.
Solution Approach 2:
The system uses real-time feedback from the external power supply detection to control relay shutdown timing. When external power feedback is positive, the relay is kept on longer to reduce switching frequency and extend life. When external power feedback is negative, the relay shuts down immediately to ensure battery safety. This feedback-based control resolves the contradiction between relay life extension and battery safety.
3Duration of action of stationary object
If unnecessary relay operations are performed during charging, then relay life is reduced, but simple control logic is maintained
Solution Approach 1:
The determination unit provides feedback on external power supply status to the relay control logic. This single feedback signal enables the control system to distinguish between normal shutdown scenarios (where relay should turn off immediately) and charging scenarios (where relay should be kept on). The feedback mechanism adds minimal complexity while effectively preventing unnecessary relay operations during charging, thereby extending relay life.
Data Source
AI summary
A relay control device controls a relay circuit mounted on a vehicle and connecting an inverter circuit that drives a motor mounted on the vehicle and a battery, the relay control device including: an end detection unit that detects that traveling of the vehicle has ended; and a determination unit that determines a possibility that power is supplied to the battery from an outside, and controls a time taken from when traveling of the vehicle ends to when the relay circuit is turned off based on the determination.