Vehicle Power Supply Node Switching for Electric Shock Prevention
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Solution Overview
Problem
Existing vehicle power supply devices with high voltage systems above 60V risk electric shock accidents when a human touches the high voltage circuit, as they do not effectively isolate the high voltage from the vehicle body, and they suffer from inefficiencies in power conversion.
Innovation Solution
A power supply device that uses a series connection of power storage elements with a control mechanism to selectively switch nodes and detect leakage current, preventing electric shock by maintaining all switching means off when leakage current exceeds a threshold, and achieving efficient power conversion without the need for isolation transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC-DC converter with an isolation transformer is used to prevent electric shock, then safety is improved, but device complexity and weight increase
Solution Approach 1:
The patent extracts and removes the isolation transformer from the DC-DC converter structure, replacing it with a direct connection configuration where the secondary battery negative terminal is connected to the vehicle body. This eliminates the complex transformer component while maintaining safety through controlled potential reference.
Solution Approach 2:
The vehicle body serves as an intermediary reference potential (ground) between the high-voltage battery system and the low-voltage loads. By using the vehicle body as a common reference, the patent avoids the need for galvanic isolation while still preventing electric shock through controlled potential differences.
2Reliability
If a DC-DC converter with an isolation transformer is used, then electric shock prevention is improved, but weight increases
Solution Approach 1:
The isolation transformer, which is a heavy component, is completely removed from the system. The patent achieves safety without this heavy isolation component by using the vehicle body as a ground reference and controlling switch operations to prevent hazardous voltage exposure.
3Power
If traditional switching methods are used in high voltage systems, then power conversion is achieved, but switching losses increase reducing efficiency
Solution Approach 1:
The patent employs periodic switching of the switch element connected to different series-connected battery units. By cyclically switching between multiple battery units in series, the system achieves continuous power conversion while allowing each switch operation to occur at optimized moments, reducing switching losses through periodic rather than continuous switching.
Data Source
AI summary
A vehicle power supply device converts power from high voltage to low voltage by selectively connecting a predetermined power storage element group to a low voltage electric load from a high voltage power supply formed by connecting power storage elements in series. A leakage current from the high voltage power supply is measured during the dead time period when the power storage element group is not connected to the low voltage electric load. When the value exceeds a predetermined value, the connection between the power storage element group and the low-voltage electric load is interrupted, so that electric shock is prevented.