Planar Transformer Height Reduction via PCB Trace Merging

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Solution Overview

Problem

Conventional transformers occupy significant physical space in switched mode power supplies (SMPS), limiting power density, while planar transformers with windings on printed circuit boards offer a lower profile but face challenges in reducing height and cost due to the number of layers.

Innovation Solution

A planar transformer design utilizing a multilayer printed circuit board with a magnetic core, where primary windings are distributed across several layers with wider traces to minimize layer count, and secondary windings are solid wires to reduce DC and AC resistance, thereby enhancing efficiency and reducing the transformer's height and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If the number of layers of the PCB is reduced, then the height of the planar transformer is reduced, but the DC and AC resistance increases

Engineering Contradiction:

Improveheight of planar transformerVSAvoidDC and AC resistance

Core Design Contradiction:

Length of stationary objectVSLoss of energy

Solution Approach 1:

Multiple windings (primary and secondary) are merged onto a single PCB layer, eliminating the need for multiple separate layers. This consolidation reduces the overall transformer height while maintaining adequate winding turns through optimized trace routing patterns on the unified layer.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The winding traces utilize wider trace widths and optimized routing patterns in the planar dimension to compensate for the reduced number of layers. By expanding the trace width parameter in the 2D plane, the design maintains low resistance despite having fewer stacked layers, thus reducing height without sacrificing electrical performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of energy

If conventional wire windings are used, then the transformer has lower DC and AC resistance, but the physical size and height increase

Engineering Contradiction:

ImproveDC and AC resistanceVSAvoidheight of transformer

Core Design Contradiction:

Loss of energyVSLength of stationary object

Solution Approach 1:

Traditional mechanical wire windings are replaced with planar PCB trace windings. This substitution eliminates the need for bulky three-dimensional wire coiling, reducing transformer height and profile while achieving acceptable resistance levels through optimized PCB trace design with appropriate width and routing patterns.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The design changes key parameters of the winding structure by using wider PCB traces instead of thin wires, and by optimizing trace routing patterns. These parameter changes allow the planar traces to achieve resistance levels comparable to conventional wire windings while maintaining the compact planar form factor.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If more PCB layers are used, then the winding complexity increases allowing for more turns, but the manufacturing cost and height increase

Engineering Contradiction:

Improvewinding complexityVSAvoidmanufacturing cost

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

Multiple winding functions are merged onto a single PCB layer, reducing the total layer count required. This consolidation simplifies the manufacturing process and reduces costs associated with multi-layer PCB fabrication, while still achieving the necessary winding complexity through optimized trace routing and width design.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

A single PCB layer is designed to perform multiple winding functions (primary and secondary windings) simultaneously through carefully planned trace routing. This multi-functional approach eliminates the need for separate dedicated layers for each winding, reducing manufacturing complexity and cost while maintaining full winding functionality.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 lower DC and AC resistance, allowing for a thinner and more cost-effective planar transformer with improved power density in SMPS, while maintaining efficiency by distributing winding traces across multiple layers and using solid secondary windings.

Implementation Method 1

a primary winding of the planar transformer is formed by winding traces on several layers of the printed circuit board... A secondary winding of the planar transformer is also provided

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10510477B2Planar transformer with multilayer circuit board

Publication Date: 2019.12.17 SEMICON COMPONENTS IND LLC

AI summary

A planar transformer includes a magnetic core and a multilayer printed circuit board. A primary winding of the planar transformer is formed by winding traces on several layers of the printed circuit board. A layer of the printed circuit board that has a winding trace of the primary winding has a winding trace of another winding of the planar transformer, such as a winding trace of an auxiliary winding or a winding trace of a shield winding. The planar transformer further includes a secondary winding. The secondary winding can be a solid wire or a winding trace on a layer of the printed circuit board.