Shielded Transformer Layout for AC-DC Converter EMC Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Isolating AC-DC converters face reduced EMC performance due to common-mode loop channels in transformers, leading to increased size, weight, and cost.

Innovation Solution

Incorporating a first shielding layer between the primary and secondary windings of the transformer, connected to the PFC filter, forms a common mode loop to block interference signals from transferring to the secondary winding, eliminating the need for additional EMC filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional transformer structure is used in the isolating AC-DC converter, then the converter can achieve power conversion function, but a large common-mode loop channel is formed resulting in decreased EMC performance

Engineering Contradiction:

ImproveEMC performanceVSAvoidcommon-mode interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A first shielding layer is introduced as an intermediary component between the primary and secondary windings of the transformer. This shielding layer acts as a mediator to block the transmission of common-mode interference signals from the primary side to the secondary side, thereby improving EMC performance without affecting the normal power conversion function

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes the existing coupling capacitance between primary and secondary windings, which normally creates harmful common-mode loop channels, and converts it into a beneficial structure by connecting the shielding layer to form a controlled common-mode loop that directs interference signals away from the secondary winding, transforming the harmful effect into a protective mechanism

Inventive Principle:

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

2Reliability

If additional EMC filters are added to improve EMC performance, then interference signals can be blocked, but the size, weight, and cost of the converter increase

Engineering Contradiction:

ImproveEMC performanceVSAvoidconverter weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The shielding layer is integrated directly into the transformer structure, merging the EMC protection function with the existing power transformation component. This eliminates the need for separate external EMC filters, thereby maintaining converter weight, size, and cost while achieving improved EMC performance

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shielding layer serves multiple functions simultaneously: it blocks common-mode interference signals, provides electrostatic shielding, and can be used as a reference potential plane. This multi-functionality replaces what would traditionally require multiple separate components, preventing increases in converter weight and complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If additional EMC filters are added to improve EMC performance, then interference signals can be blocked, but the size and cost of the converter increase

Engineering Contradiction:

ImproveEMC performanceVSAvoidconverter structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of applying global EMC protection through system-wide filters, the patent applies localized shielding at the specific location where common-mode interference is generated (between primary and secondary windings). This localized approach achieves effective EMC protection with minimal additional complexity and cost

Inventive Principle:

Principle #3Local quality

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 EMC performance without increasing size or weight, effectively reducing common-mode current and interference, thus improving the overall converter efficiency.

Implementation Method 1

the first shielding layer is disposed between the primary winding and the secondary winding, and the first shielding layer is connected to the PFC filter to form a common mode loop, to block an interference signal from being transferred to the secondary winding

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS20250323570A1Isolated ac-DC converter, charging device, and power supply system

Publication Date: 2025.10.16 SUNGROW POWER SUPPLY CO LTD

AI summary

An isolated AC-DC converter, a charging device, and a power supply system are provided. The isolated AC-DC converter comprises: a PFC filter, wherein an input end of the PFC filter is connected to an alternating current; a PFC circuit, wherein an input end of the PFC circuit is connected to an output end of the PFC filter, and an output end of the PFC circuit is connected to an input end of a DC-DC circuit; and the DC-DC circuit, comprising a transformer, wherein the transformer comprises: a primary winding, a secondary winding, and a first shielding layer; the first shielding layer is arranged between the primary winding and the secondary winding; the first shielding layer is connected to the PFC filter for preventing an interference signal from being transmitted to the secondary winding.