Transformer Shielding Winding Layout for Switching EMI Oscillation
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Solution Overview
Problem
Existing switching power supplies experience increased electromagnetic interference (EMI) due to oscillations caused by leakage inductance and coupling capacitance between the shielding winding and primary winding of the transformer, despite the use of shielding windings.
Innovation Solution
The introduction of an oscillation reduction unit connected to the shielding winding, utilizing capacitors and resistors to absorb oscillations and reduce EMI, effectively addressing the issue of increased EMI at critical points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shielding winding is added to reduce common mode current, then common mode EMI is reduced, but oscillations occur at certain conduction and radiation points causing EMI to increase
Solution Approach 1:
The patent introduces an oscillation reduction unit as an intermediary component connected to the shielding winding. This unit acts as a mediator that suppresses the harmful oscillations generated by the shielding winding's interaction with leakage inductance and distributed capacitance, while preserving the shielding winding's beneficial common mode EMI reduction effect.
Solution Approach 2:
The patent converts the harmful oscillations caused by the shielding winding into a controllable phenomenon by adding the oscillation reduction unit. The unit transforms the detrimental oscillation energy into harmless forms (typically heat through resistive damping), thereby converting the harmful effect into a manageable situation that maintains overall EMI reduction.
2Object-affected harmful factors
If shielding windings are wound in parallel with the first winding in the same layer, then common mode suppression is improved, but leakage inductance and coupling capacitance increase causing oscillations
Solution Approach 1:
The patent segments the winding structure into distinct functional components: the first winding for power transmission, the shielding winding for EMI suppression, and the oscillation reduction unit for stability. This segmentation allows each component to perform its specific function while minimizing negative interactions between them.
Solution Approach 2:
The patent applies local quality by positioning the oscillation reduction unit specifically at the locations where oscillations occur (certain conduction and radiation points). This targeted approach addresses the local oscillation problems without requiring changes to the entire winding structure, maintaining simplicity while achieving the desired effect.
3Power
If distributed capacitance and leakage inductance are present in the transformer, then power conversion function is achieved, but oscillations occur during switching causing EMI increases
Solution Approach 1:
The patent implements beforehand cushioning by pre-configuring the oscillation reduction unit to dampen oscillations before they can propagate and cause EMI issues. The unit is designed with appropriate damping characteristics to absorb and dissipate the oscillation energy generated during switching transitions, preventing the harmful effects before they occur.
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 significantly reduces EMI interference by absorbing oscillations caused by stray capacitance and leakage inductance, improving the power supply's ability to pass EMI tests and enhance radiation performance.
Implementation Method 1
oscillations will still occur at certain points of conduction and certain points of radiation
Implementation Method 2
The switching power supply must pass an electromagnetic interference (EMI) test
Implementation Method 3
adding a shielding layer (such as a shielding winding) inside the transformer to reduce the common mode current
Implementation Method 4
a transformer is usually used to achieve power conversion
Data Source
AI summary
A switching power supply and an electronic device includes a transformer, which includes a frame and a multi-layer winding structure arranged on the frame, different winding units are distributed at intervals along a target direction; at least one winding unit includes a first winding of the primary side of the transformer; at least one winding unit includes a second winding of the secondary side of the transformer; at least one winding unit includes a shielding winding; at least one group of shielding windings and the first winding are wound in parallel in the same layer, and/or: at least one group of shielding windings are distributed between the first winding and the second winding; the shielding winding is located on the primary side of the transformer; at least one end of the shielding winding is connected to an oscillation reduction unit for eliminating or weakening oscillation.