Bobbin Design for Conduction-Cooled Magnetic Components
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Solution Overview
Problem
Existing coil bobbins for conduction-cooled magnetic components with air gaps face challenges in efficiently removing heat from the core and windings, leading to increased power losses and reduced power density.
Innovation Solution
The design of a coil former with an increased diameter and ribs/splines to center the winding, allowing thermally conductive silicone-based encapsulant to fill the voids between the bobbin, core, and windings, facilitating conduction cooling and reducing air pockets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the bobbin diameter is increased to allow encapsulant to fill voids for conduction cooling, then heat removal efficiency is improved, but the device dimensions increase
Solution Approach 1:
The patent implements nesting by placing the core with air gap inside the bobbin structure, and further nesting the windings around the core. The encapsulant is then injected into the void spaces between these nested components, creating thermal conduction pathways without requiring significant external volume increase. This nested arrangement allows efficient heat removal while maintaining compact overall dimensions.
2Manufacturing precision
If ribs/splines or tabs are added to center the winding, then winding positioning precision is improved, but device complexity increases
Solution Approach 1:
The bobbin is segmented by adding ribs, splines, or tabs that divide the internal space into specific regions. These segments serve as mechanical guides and positioning features that precisely locate the windings and core during assembly. The segmentation approach provides accurate positioning without requiring complex external fixtures or assembly procedures.
Solution Approach 2:
The ribs, splines, and tabs are integrated directly into the bobbin structure, allowing the bobbin itself to provide the centering function. This self-service approach eliminates the need for separate centering mechanisms or additional assembly steps, reducing overall device complexity while maintaining positioning precision.
3Power
If thermally conductive encapsulant is used to fill voids, then power density is improved through better heat conduction, but manufacturing complexity increases
Solution Approach 1:
The bobbin is designed with pre-formed void spaces and access channels that are created during the injection molding process. These preliminary structural features guide the subsequent encapsulant injection process, ensuring complete void filling while simplifying the manufacturing sequence. The access channels are built-in from the start, eliminating the need for complex post-assembly encapsulation procedures.
Solution Approach 2:
The encapsulant serves as an intermediary material that fills the void spaces between the bobbin, core, and windings. It provides thermal conduction pathways while also acting as a mechanical bond between components. This intermediary approach allows heat transfer improvement without requiring direct thermal contact between hot components and external heat sinks, simplifying the overall thermal management structure.
4Temperature
If the bobbin design allows encapsulant to fill voids between bobbin and core, then conduction cooling efficiency is improved, but assembly precision requirements increase
Solution Approach 1:
The encapsulant material is used as a cushioning medium that compensates for minor dimensional variations and assembly tolerances. By designing the void spaces to be filled with this compliant material, the system accommodates small misalignments between the bobbin and core without compromising thermal contact. This beforehand cushioning approach reduces the stringency of assembly precision requirements while maintaining effective conduction cooling.
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 enhances power density by effectively managing heat and reducing winding losses while maintaining acceptable temperatures, with benefits including reduced stress on the core, ease of assembly, and compliance with thermal expansion requirements.
Implementation Method 1
allowing thermally conductive silicone-based or equivalent encapsulant to fill the voids between the coil former and the core, the coil former and the windings
Data Source
AI summary
A coil former, also referred to herein as a bobbin, is provided for use in conduction-cooled magnetic components that contain an air gap. The diameter of the disclosed bobbin is increased and ribs/splines or tabs are created to keep the winding centered about the core center post while allowing thermally conductive silicone-based or equivalent encapsulant to fill the voids between the coil former and the core, the coil former and the windings and/or both depending on the placement of the locating tabs. The disclosed bobbin may be fabricated from traditional injection molding resins or from high-thermal conductivity resins. As a result of the disclosed bobbin designs, the achievable power density is increased while maintaining acceptable temperatures.