Interleaved Shielding Windings for Transformer EMI Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inter-winding parasitic capacitive coupling between primary and secondary windings of transformers in power converters leads to common mode noise current flow, resulting in undesirable electromagnetic interference (EMI) that is challenging to mitigate with conventional low-value Y Capacitors.
Innovation Solution
The transformer design incorporates interleaved shielding windings that are symmetrically aligned on either side of the secondary winding, effectively blocking common mode noise current flow by ensuring no voltage difference between the shielding and secondary windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional transformer winding structure is used, then manufacturing is simple, but inter-winding parasitic capacitive coupling causes common mode noise current flow
Solution Approach 1:
A shielding winding is introduced as an intermediary element between the primary and secondary windings. This shielding winding acts as a mediator that blocks the parasitic capacitive coupling path, preventing common mode noise current flow while maintaining the functional relationship between primary and secondary windings.
Solution Approach 2:
The transformer winding structure is segmented into distinct regions: primary windings, shielding windings, and secondary windings. This segmentation isolates the primary and secondary circuits with an intermediate shielding layer, reducing inter-winding capacitance and common mode noise.
2Object-affected harmful factors
If low-value Y Capacitor is used for EMI filtering, then EMI requirements may be met, but capacitor value is limited and filtering effectiveness is reduced
Solution Approach 1:
The parasitic capacitive coupling that causes common mode noise is converted into a beneficial shielding effect. The shielding winding, positioned between primary and secondary windings, utilizes the same capacitive coupling mechanism to block noise propagation, transforming the harmful effect into a noise suppression benefit.
3Object-affected harmful factors
If shielding windings are added to block common mode noise, then EMI performance improves, but manufacturing complexity increases
Solution Approach 1:
The shielding winding is merged with the existing transformer winding structure, sharing the same magnetic core and physical space. This integration allows the shielding function to be added without requiring separate components or significant structural modifications, maintaining manufacturing simplicity.
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 design significantly reduces common mode noise current, allowing power converters to comply with EMI standard requirements even without the need for a low-value Y Capacitor, while also simplifying manufacturing and ensuring consistent performance.
Implementation Method 1
Inter-winding parasitic capacitive coupling occurs between primary windings of the transformer and secondary windings of the transformer. Such inter-winding capacitance allows a common mode noise current to flow from the primary-side of the power converter to the secondary-side of the power converter.
Data Source
AI summary
A transformer includes first and second primary windings serially electrically connected in a primary-side series combination. The transformer further includes a secondary winding disposed between the first primary winding and the second primary winding. The transformer further includes first and second shielding windings serially electrically connected in a shielding series combination. The first shielding winding is disposed between the first primary winding and the secondary winding, and the second shielding winding is disposed between the second primary winding and the secondary winding.