Shield Wire Grounding Layout to Prevent Vehicle Ground Loops
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Solution Overview
Problem
In electric vehicles, the connection of electrical/electronic components through shield wires and chassis-grounding creates a ground loop that generates radio noise, deteriorating EMC tolerance.
Innovation Solution
A wiring structure with shield wires having a center conductor and an outer conductor, where at least one end of the outer conductor is connected to an insulation part on the shield case, preventing the formation of ground loops by ensuring a single point ground connection between components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If shield wires are used to connect electrical/electronic components and both ends are connected to chassis ground, then electromagnetic shielding effect is improved, but ground loops are formed generating radio noise
Solution Approach 1:
The patent extracts the harmful ground loop path by disconnecting one end of the outer conductor from the chassis ground. The insulation part removes the electrical connection between the shield wire and chassis ground at one end, eliminating the closed loop while preserving the electromagnetic shielding effect through the remaining connected end.
Solution Approach 2:
The insulation part acts as an intermediary element between the outer conductor and the chassis ground. It physically separates these two components, preventing direct electrical contact and thereby blocking the formation of ground loops while allowing the shield wire to maintain its protective function.
2Object-affected harmful factors
If both ends of shield wire are connected to chassis ground, then shielding coverage is improved, but EMC tolerance deteriorates due to ground loop current
Solution Approach 1:
The patent extracts the problematic current path by removing the chassis ground connection at one end of the shield wire. This breaks the ground loop that causes EMC issues while preserving the essential shielding coverage provided by the connected end and the inner conductor.
Solution Approach 2:
Instead of connecting both ends to chassis ground as conventionally done, the patent inverts the approach by intentionally leaving one end insulated. This reversal of the conventional grounding practice eliminates ground loop currents while maintaining effective electromagnetic shielding.
3Object-generated harmful factors
If outer conductor is connected to insulation part instead of chassis ground, then ground loop formation is prevented, but shielding effectiveness may be reduced
Solution Approach 1:
The insulation part serves as an intermediary that prevents ground loop formation by blocking the electrical path to chassis ground. Simultaneously, the shield wire structure with one-end grounding maintains sufficient shielding effectiveness for practical applications by providing a reference potential at the connected end.
Solution Approach 2:
The patent changes the grounding parameter from dual-point grounding to single-point grounding. This parameter modification prevents ground loop currents while maintaining adequate shielding performance for the specific application requirements, balancing both concerns.
Data Source
AI summary
A wiring structure that can prevent generation of radio noise is provided. A wiring structure includes: two electrical/electronic components mounted in a vehicle, and including respective shield cases connected to a chassis ground; and a shield wire including a center conductor, and an outer conductor covering an outer periphery of the center conductor. Both ends of the shield wire are extended to the shield cases, at least one of the shield cases includes an insulation part, and the outer conductor of one end of the shield wire extended to the at least one of the shield cases is connected to the insulation part.