Battery Pack Wiring Path Geometry for EMI Reduction
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Solution Overview
Problem
Conventional battery packs with a circuit board on the exterior of a rectangular battery unit suffer from significant Electromagnetic Interference (EMI) due to the large current loop area, which is not effectively mitigated by existing solutions like electromagnetic wave shielding plates, especially in thin or small designs.
Innovation Solution
The battery pack design features first and second wiring paths that intersect at the sealing plate, with opposite current flow directions on the exterior and interior sides, reducing magnetic fields by canceling them out, and includes a configuration where the negative terminal is electrically insulated and positioned between the positive electrode tab and the sealing plate, and the interval between wiring paths is minimized to enhance insulation and reduce magnetic field strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the circuit board is arranged on the exterior surface of the battery unit, then the battery pack structure is simplified and ease of manufacture is improved, but the current loop area increases causing electromagnetic interference
Solution Approach 1:
The current loop is segmented into multiple smaller loops by routing the positive and negative wiring paths separately from the battery unit to the circuit board. The positive electrode tab connection and negative electrode tab connection are separated into distinct paths that do not form a large rectangular loop, thereby reducing the overall current loop area and electromagnetic interference.
Solution Approach 2:
The wiring paths are routed in three-dimensional space rather than forming a planar rectangular loop. The positive and negative connections utilize vertical and lateral routing through the battery unit structure, transforming the current path from a two-dimensional rectangular loop into a three-dimensional configuration that minimizes the enclosed area.
2Object-affected harmful factors
If electromagnetic wave shielding plate is used to prevent EMI, then electromagnetic interference is reduced, but the battery pack size increases and thin or small designs are compromised
Solution Approach 1:
The invention converts the harmful electromagnetic field generation into a beneficial cancellation effect by routing positive and negative wiring paths in close proximity with opposite current directions. The magnetic fields generated by these opposing currents cancel each other out, transforming the potential harm into a beneficial EMI reduction without requiring additional shielding components.
3Object-affected harmful factors
If the current loop area is reduced by changing wiring path arrangement, then electromagnetic interference is reduced, but the wiring path complexity increases
Solution Approach 1:
The positive and negative wiring paths are merged into a closely coupled configuration where they run parallel to each other from the battery unit to the circuit board. This merging of paths in close proximity allows the magnetic fields to cancel effectively while maintaining a relatively simple overall wiring structure that integrates well with the battery pack design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces the total strength of magnetic fields produced by the current loop, even without a shielding plate, making it suitable for thin or small battery packs, thereby minimizing EMI and enhancing performance.
Implementation Method 1
when electric power is supplied, a current loop is formed from the battery unit to the circuit board, and will produce flux linkage. The current loop will produce flux linkage. This flux linkage may cause EMI (Electro Magnetic Interference) on a mobile electronic device
Implementation Method 2
the current flow direction of a current loop part that is formed from the intersection position on the exterior side of the battery unit is opposite to the current flow direction of another current loop part that is formed from the intersection position on the interior side of the battery unit
Data Source
AI summary
In a battery pack (1),a current loop between the positive and negative electrode plates of an electrode assembly passes points P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12, P13 and P14 in this order. A line that connects P2 to P3 intersects a line that connects P11 to P12 in the part where the loop passes a sealing plate (12), which is arranged on the top of a battery unit (10). The loop can be divided into loop parts B1 and B2. The part B1 is formed on the exterior side of the battery unit, and extends from the intersection A through a circuit board (20) back to the intersection A. The part B2 is formed on the interior side of the battery unit relative to the intersection A. The current flows counterclockwise and clockwise in the parts B1 and B2, respectively.