EV Charging Circuit With DC Voltage Recognition for Contactor Safety
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Solution Overview
Problem
Existing charging systems for electrically operable vehicles struggle to meet the safety requirements of the NACS standard, particularly in recognizing and managing DC and AC voltages to ensure safe operation of charging contactors, leading to increased development costs and effort.
Innovation Solution
A circuit arrangement with a voltage detection module that recognizes DC or AC voltage types and controls charging contactors accordingly, using ASIL B qualified contactors to meet the ASIL D standard, ensuring safe operation by only closing contactors when DC voltage is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage detection module is added to recognize DC or AC voltage types and control charging contactors, then safety compliance with ASIL D standard is achieved, but device complexity increases
Solution Approach 1:
The voltage detection function is segmented into a separate modular voltage detection module that interfaces with both the charging connection and battery control unit. This modular approach allows the safety-critical voltage recognition logic to be isolated, enabling verification and validation of the safety function without redesigning the entire charging system, thus achieving ASIL D compliance while managing complexity through modularity.
Solution Approach 2:
The voltage detection module acts as an intermediary component between the charging connection and the battery control unit. It receives voltage type information from the charging connection and transmits controlled signals to the battery control unit, which then manages the charging contactors. This intermediary structure implements the safety logic in a dedicated component, achieving ASIL D compliance while keeping the overall system architecture manageable.
2Ease of manufacture
If existing charging contactors are used without upgrades, then development costs are reduced, but the ability to meet ASIL D standard is compromised
Solution Approach 1:
The voltage detection module performs preliminary detection and recognition of the voltage type (DC or AC) before any charging contactor activation occurs. By establishing this safety check in advance, the system ensures that DC charging contactors are only closed when DC voltage is confirmed present, thereby achieving ASIL D safety integrity while using existing contactor hardware without requiring costly upgrades.
Solution Approach 2:
The voltage detection module continuously monitors the charging connection and provides feedback signals to the battery control unit regarding the detected voltage type. This feedback mechanism enables the battery control unit to make informed decisions about contactor activation, ensuring that safety requirements are met through information-based control rather than hardware upgrades, thus reducing development costs while maintaining ASIL D compliance.
3Device complexity
If voltage type recognition is performed by existing systems without dedicated detection module, then device complexity is reduced, but measurement precision of voltage type is insufficient
Solution Approach 1:
The voltage detection module autonomously performs the voltage type recognition function by directly monitoring the charging connection. It self-determines whether DC or AC voltage is present and generates appropriate control signals without requiring complex external processing or additional sensing infrastructure. This self-service approach achieves precise voltage type recognition while maintaining relatively simple system architecture.
Data Source
AI summary
A circuit arrangement for a charging system of an electrically operable vehicle includes a charging connection having a first input line and a second input line, which are electrically coupled to a high-voltage battery of the vehicle via charging contactors and via a current interruption device, and a voltage detection module electrically coupled to the first input line and the second input line and to the two charging contactors. The voltage detection module recognizes whether a direct voltage or an alternating voltage is present as the voltage type on the first input line and the second input line and to close the two charging contactors only if a direct voltage is present as the voltage type.