U-Shaped Core High-Voltage Transformer Design

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Solution Overview

Problem

Developing high-voltage transformers with small dimensions that maintain high power density and reliability, while minimizing manufacturing costs and parasitic inductances, is challenging due to the need for compact designs that balance magnetic core geometry, winding configurations, and compatibility with mobile and lighting applications.

Innovation Solution

A high-voltage transformer with a U-shaped core and three or more turns in the primary winding, where the windings are applied to one leg of the core, allowing for efficient manufacturing and reduced parasitic inductances, and a compact structure that achieves desired inductance and oscillation behavior.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the transformer size is reduced to achieve compact design, then the volume and weight are reduced, but the power density and reliability may be compromised

Engineering Contradiction:
Improvetransformer volumeVSAvoidtransformer reliability
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the geometric parameters of the magnetic core, specifically using a U-shaped core with optimized leg dimensions and a specific yoke thickness. This allows achieving compact volume while maintaining the magnetic path length and cross-sectional area necessary for reliable high-voltage operation. The core dimensions are carefully selected to balance volume reduction with maintaining adequate magnetic properties for reliability.

Inventive Principle:
Principle #35Parameter changes

2Volume of moving object

If the number of primary turns is reduced to fewer than 3, then the construction volume is reduced, but the inductance and oscillation behavior are adversely affected

Engineering Contradiction:
Improvetransformer volumeVSAvoidinductance characteristics
Core Design Contradiction:
Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent establishes that the primary winding must have at least 3 turns to achieve the desired inductance value and oscillation behavior. This parameter specification ensures that the transformer produces the required electrical characteristics while maintaining compact dimensions. The minimum turn requirement is derived from optimizing the balance between volume and electrical performance.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If the core length is increased to improve magnetic properties, then the inductance is improved, but the overall dimensions and volume increase

Engineering Contradiction:
Improvemagnetic propertiesVSAvoidcore length
Core Design Contradiction:
Device complexityVSLength of moving object

Solution Approach 1:

The patent employs an asymmetric U-shaped core design where the two legs have different dimensions. One leg is optimized for magnetic flux path while the other is optimized for winding accommodation and heat dissipation. This asymmetric configuration allows achieving good magnetic properties without proportionally increasing the overall core length, as the magnetic path is efficiently utilized within the available space.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

Instead of increasing core length in one dimension, the patent optimizes the core cross-sectional dimensions and yoke thickness. By adjusting the dimensional distribution across different axes (width, height, thickness) rather than simply extending length, the magnetic properties are improved while keeping the overall footprint and volume constrained.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

4Ease of manufacture

If standard ferrite cores are used, then manufacturing is simplified, but the precision control of inductance and oscillation behavior is limited

Engineering Contradiction:
Improvecore manufacturingVSAvoidinductance precision
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent specifies precise parameter ranges for the U-shaped core dimensions, including leg lengths, widths, and yoke thickness, to achieve the desired inductance and oscillation characteristics. By defining these geometric parameters within specific ranges, the patent enables precision control of electrical properties while maintaining compatibility with standard manufacturing processes for ferrite cores. The optimized dimension specifications allow standard cores to be selected or manufactured with controlled tolerances.

Inventive Principle:
Principle #35Parameter changes

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 solution enables a compact, high-voltage transformer with improved power density, reduced manufacturing costs, and controlled oscillation behavior, suitable for applications like gas discharge lamps and mobile devices, while maintaining mechanical and thermal properties.

Implementation Method 1

a first winding (140) with three or more turns (141, 142, 143)... a second winding (120)... U-shaped core (110)... transforms an input voltage of several 10 V to several 100 V to a relatively high output voltage

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3224841B1High-voltage transformer having a u-shaped core
Publication Date: 2020.12.02 SUMIDA COMPONENTS & MODULES GMBH
  • EP3224841B1 patent drawingFigure 1A~1C
  • EP3224841B1 patent drawingFigure 2A~2C
  • EP3224841B1 patent drawingFigure 3A~3C

AI summary

The transformer of the invention comprises a first coil that has three or four windings, preferably exactly three windings, a second coil, and a U-shaped core. The length of the transformer is 40 mm or less, resulting in a compact volume, for example for ignition units of luminaires, and production costs are reduced because a U-shaped core is used.