PCB Planar Transformer Windings for Common-Mode Noise Suppression
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Solution Overview
Problem
Switch-mode power supplies face significant challenges in suppressing common mode noise, which leads to electromagnetic interference (EMI) and affects the stability and efficiency of the power supply.
Innovation Solution
A planar transformer with a magnetic core and a printed circuit board (PCB) winding board is designed, featuring a primary winding, a secondary winding, a shielding winding to shield electric field coupling, and a compensation winding with multiple turns to cancel common mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional transformer structure is used, then the structure is simple, but the common mode noise suppression performance is poor
Solution Approach 1:
The transformer winding structure is segmented into primary winding, secondary winding, shielding winding, and compensation winding. Each winding serves a specific function: the shielding winding suppresses common mode noise by providing a low-impedance path for noise currents, while the compensation winding generates counter-phase magnetic fields to cancel out residual common mode noise. This segmentation allows the transformer to address EMI issues without requiring an entirely different structure.
Solution Approach 2:
The shielding winding acts as an intermediary element positioned between the primary and secondary windings. It provides a low-impedance path for common mode noise currents, preventing these currents from coupling between the primary and secondary sides. The compensation winding serves as another intermediary that generates opposing magnetic fields to neutralize residual common mode noise, thereby mediating the electromagnetic interaction between windings.
2Object-affected harmful factors
If the quantity of turns of the compensation winding is increased, then the common mode noise suppression is improved, but the manufacturing consistency becomes difficult to control
Solution Approach 1:
The patent optimizes the parameter of compensation winding turns to a specific range (5-15 turns) based on empirical analysis and theoretical calculations. This parameter optimization achieves an balance between noise suppression effectiveness and manufacturing feasibility. Within this range, the compensation winding generates sufficient counter-phase magnetic fields to cancel common mode noise while maintaining reasonable winding complexity that can be consistently manufactured using automated winding equipment.
Solution Approach 2:
Rather than using a very large number of compensation winding turns that would guarantee complete noise cancellation but create manufacturing difficulties, the patent employs a moderate number of turns (5-15) that provides sufficient noise suppression for meeting EMI standards while remaining practical for mass production. This partial action approach achieves adequate performance without excessive complexity.
3Object-generated harmful factors
If the shielding winding is added to reduce noise current, then the conducted emission is reduced, but the device complexity increases
Solution Approach 1:
The shielding winding is merged with the compensation winding into a single integrated winding structure on the transformer. Both windings are wound on the same magnetic core and share the same physical space, reducing the overall device volume. The shielding and compensation functions are combined in one component rather than requiring separate shielding structures and compensation windings, thereby reducing device complexity while maintaining noise suppression effectiveness.
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 effectively reduces noise currents between windings, minimizes common mode noise, and decreases conducted and radiated emissions, allowing for a more efficient and stable power conversion process.
Implementation Method 1
a shielding winding, disposed between the primary winding and the secondary winding, and configured to shield electric field coupling between the primary winding and the secondary winding
Implementation Method 2
Common mode noise generated by the compensation winding cancels common mode noise flowing to the secondary winding or the primary winding
Data Source
AI summary
A planar transformer, a power conversion circuit, and an adapter, is provided to improve noise suppression performance. The planar transformer includes a magnetic core and a printed circuit board (PCB) winding board, where the PCB winding board includes a primary winding, a secondary winding, a shielding winding, and a compensation winding. In embodiments of this disclosure, the shielding winding and the compensation winding that has a plurality of turns of coils are disposed between the primary winding and the secondary winding of the planar transformer. The shielding winding can shield electric field coupling between the primary winding and the secondary winding, thereby suppressing a noise current between the primary winding and the secondary winding. Common mode noise generated by the compensation winding cancels common mode noise flowing to the secondary winding or the primary winding, to minimize common mode noise of an entire system.