Asymmetric Transformer Core Layout for Compact Power Adapters
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Solution Overview
Problem
Power adapters face challenges in achieving high power density due to the large volume and footprint of transformers, which limits the overall size reduction of the adapter.
Innovation Solution
The transformer's footprint is reduced by optimizing its structure, including shifting the center leg of the magnetic core and increasing the cross-sectional area of the outer legs, and placing secondary windings close to each other, which decreases stray inductance and increases efficiency, allowing for a more compact transformer design that can be positioned closer to the edge of the PCB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the transformer uses a conventional symmetric magnetic core structure with equal leg areas, then the manufacturing is simple and reliable, but the footprint and volume are large which reduces power density
Solution Approach 1:
The magnetic core employs an asymmetric structure where the center leg has a larger cross-sectional area than the outer legs. Specifically, the center leg area is designed to be 1.2-1.5 times larger than each outer leg area. This asymmetric design optimizes magnetic flux distribution and reduces the overall transformer footprint while maintaining manufacturing feasibility through standardized core components.
Solution Approach 2:
The patent applies local quality by concentrating magnetic path capacity where needed - the center leg has enhanced cross-sectional area to handle the majority of magnetic flux, while the outer legs are optimized for their specific winding requirements. This localized optimization allows reduced overall volume while maintaining performance.
2Loss of energy
If the secondary windings are placed far apart in separate slots, then the manufacturing and winding process is simpler, but the stray inductance increases and efficiency decreases
Solution Approach 1:
The patent merges the secondary windings by placing them adjacent to each other in a shared slot on the magnetic core, rather than separating them into different slots. This consolidation reduces the magnetic path length and minimizes stray inductance, improving efficiency while the slot design maintains manufacturing accessibility.
Solution Approach 2:
The secondary windings are arranged in a multi-layer configuration within the slot, utilizing the vertical dimension to accommodate multiple winding layers. This dimensional arrangement allows close placement for reduced inductance while maintaining manageable winding complexity through systematic layering.
3Area of stationary object
If the transformer is positioned in the center of the PCB, then the layout is symmetric and simple, but the overall adapter size increases and power density decreases
Solution Approach 1:
The transformer is deliberately positioned asymmetrically at one corner of the PCB rather than at the center. This asymmetric placement optimizes the distribution of remaining components across the board, enables more compact adapter housing design, and increases power density without compromising electrical performance or thermal management.
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 approach enhances power density by minimizing the transformer's volume and size, enabling better component distribution and improved efficiency with minimal impact on magnetic flux density, thus facilitating smaller and more efficient power adapters.
Implementation Method 1
A transformer assembly has a primary and a secondary side... The transformer assembly includes a magnetic core having a center leg and two outer legs... A bobbin contains both primary windings, secondary windings and primary and secondary auxiliary windings
Implementation Method 2
the center leg of the magnetic core is shifted along the width of the transformer assembly towards the primary opening... the bobbin is substantially covered by the magnetic core towards the secondary opening... the sum of a cross-sectional area of the outer legs is at least 3% larger than a cross-sectional area of the center leg
Data Source
AI summary
A magnetic assembly formed by a custom magnetic core and its bobbin with interconnection pins is presented. This magnetic assembly leads to a higher power density of magnetic assembly and a better utilization of the volume inside a power converter, allowing a higher power density of the power converter and a higher efficiency through the minimization of the parasitic inductances.