Multi-Leg Transformer Layout for Controlled Leakage Inductance

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Solution Overview

Problem

Transformers face challenges such as cooling issues in higher power applications, size concerns in LLC applications related to core gaps and fringing flux, and leakage inductance, which affect their suitability and require additional compensation with an inductor.

Innovation Solution

A multi-leg transformer design featuring a core with center posts, primary and secondary coils, and magnetic shunt material placed between them to tune leakage inductance, allowing for improved cooling and reduced fringing flux, eliminating the need for a separate resonant inductor in LLC circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magnetic shunt material is added to control leakage inductance, then leakage inductance is optimized, but device complexity increases

Engineering Contradiction:

Improveleakage inductance controlVSAvoidtransformer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Magnetic shunt material is placed in specific selected areas between primary and secondary coils rather than uniformly throughout, allowing localized control of leakage inductance where needed while maintaining simplicity in other regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Magnetic shunt material acts as an intermediary element between primary and secondary coils, mediating the magnetic flux distribution to achieve desired leakage inductance values without requiring complete redesign of the transformer structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If core gap size is increased to reduce fringing flux, then fringing flux is minimized, but transformer size increases

Engineering Contradiction:

Improvefringing fluxVSAvoidtransformer size

Core Design Contradiction:

Object-generated harmful factorsVSVolume of stationary object

Solution Approach 1:

The patent converts the potentially harmful fringing flux by using magnetic shunt material to redirect and contain it, transforming the harmful dispersed flux into useful controlled magnetic paths that improve performance without increasing size

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 multi-leg transformer design enhances cooling efficiency, minimizes leakage inductance, and optimizes transformer performance in high-power applications like LLC converters, battery charging, and server applications by providing better thermal management and reduced size, while maintaining effective coupling between coils.

Implementation Method 1

at least one magnetic shunt material disposed in one or more selected areas between the primary coil and the secondary coil

Methodology Applied

Scientific EffectMagnetic flux: Magnetic Field

Data Source

PatentUS20230402226A1Transformer with controlled leakage inductance

Publication Date: 2023.12.14 VISHAY DALE ELECTRONICS INC

AI summary

A multi-leg transformer includes a core having a plurality of center posts, a primary coil wound around at least one of the center posts, a secondary coil wound around at least one of the center posts and spaced apart from the primary coil, and at least one magnetic shunt material disposed in one or more selected areas between the primary coil and the secondary coil.