Multi-turn inductor with foil windings and under-core solder tabs
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Solution Overview
Problem
Existing switching power converters face challenges with high power losses in inductors due to winding resistive and core losses, particularly in battery-powered portable devices, where space and cost constraints are significant, and current multi-turn inductors are difficult and costly to manufacture with high winding resistance.
Innovation Solution
A multi-winding inductor design featuring a magnetic core with single-turn foil windings that are electrically connected in series, utilizing a foil interconnect to reduce resistance and facilitate surface mount soldering, allowing for a low resistance connection without the need for complex PCB traces, thereby reducing manufacturing costs and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-turn staple winding is used in a ferrite magnetic core, then winding resistance is reduced and cost is lowered, but inductance value is insufficient for applications requiring high efficiency and small size
Solution Approach 1:
The inductor is divided into multiple separate single-turn windings (first winding, second winding, third winding, fourth winding) instead of one complex multi-turn winding. Each winding is independently wound through the magnetic core, simplifying manufacturing while achieving the required inductance through series connection.
Solution Approach 2:
Multiple single-turn windings are electrically connected in series to combine their inductance values. The series connection of windings W1, W2, W3, W4 creates a total inductance that meets the application requirements while maintaining the manufacturing simplicity of individual single-turn windings.
2Reliability
If the number of turns is increased to two or more to increase inductance or decrease core losses, then inductance increases, but manufacturing complexity and winding resistance increase
Solution Approach 1:
Instead of creating complex multi-turn windings, the patent segments the winding function into multiple independent single-turn windings. Each winding has only one turn passing through the core, dramatically simplifying the winding process while achieving equivalent or superior inductance through series connection.
Solution Approach 2:
The conventional approach of increasing turns per winding is inverted by using multiple windings with one turn each. This reversal of the design strategy achieves the same inductance increase without the manufacturing complexity and resistance penalties of traditional multi-turn windings.
3Reliability
If core cross sectional area is increased to increase inductance or decrease core losses, then inductance and efficiency improve, but physical inductor size and cost increase
Solution Approach 1:
The inductance values of multiple windings are merged through series connection to achieve the required total inductance. This allows the use of a smaller core cross-sectional area compared to a single winding design, reducing the overall inductor size while maintaining the necessary inductance value.
4Reliability
If the gap thickness is decreased to increase inductance, then inductance increases, but core losses increase and saturation current decreases
Solution Approach 1:
The magnetic circuit is segmented into multiple paths through the use of multiple windings around different portions of the magnetic core. This segmentation allows for a larger effective gap distribution that reduces flux density and core losses while maintaining the required inductance value through the series connection of windings.
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
The design achieves a low resistance multi-turn inductor configuration that reduces power losses and manufacturing complexity, making it suitable for space-constrained portable applications while maintaining efficiency and cost-effectiveness.
Implementation Method 1
Switching power converters typically have a higher efficiency and a smaller size than linear power converters with corresponding power ratings. Accordingly, switching power converters are widely used in applications requiring small size and/or high efficiency
Implementation Method 2
The ferrite material also exhibits low core losses at high operating frequencies relative to other core materials, such as powdered iron
Data Source
AI summary
A multi-winding inductor includes a first foil winding and a second foil winding. One end of the first foil winding extends from a first side of the core and wraps under the core to form a solder tab under the core. One end of the second foil winding extends from a second side of the core and wraps under the core to form another solder tab under the core. Respective portions of each solder tab are laterally adjacent under the magnetic core. A coupled inductor includes a magnetic core including a first and a second end magnetic element and a plurality of connecting magnetic elements disposed between and connecting the first and second end magnetic elements. A respective first and second single turn foil winding is wound at least partially around each connecting magnetic element. Each foil winding has two ends forming respective solder tabs.