Partial Electrostatic Shield for Power Converter Common Mode Noise
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Solution Overview
Problem
Existing methods for reducing common mode noise in power converters are inadequate, particularly in high power density applications, as they fail to effectively address noise generated by voltage jumps on both the primary and secondary sides of the transformer, with conventional Faraday shields often increasing noise from the secondary side.
Innovation Solution
A transformer with a partial electrostatic shield between primary and secondary windings, featuring a length-orientation or width-orientation gap, and potentially replacing some shield material with a different permittivity, along with adjusting the distance and thickness of the shield, to balance parasitic capacitances and reduce common mode noise. Additionally, an additional balancing capacitor can be used to balance noise voltages between the primary and secondary sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a full Faraday shield is used between primary and secondary windings, then parasitic capacitance of primary side is reduced, but voltage jump on secondary side creates larger common mode noise
Solution Approach 1:
The patent divides the Faraday shield into multiple segments (first, second, and third Faraday shields) positioned at different locations between primary and secondary windings. This segmentation allows selective reduction of parasitic capacitance at different points, thereby reducing common mode noise from both primary and secondary sides simultaneously without the adverse effect of a full continuous shield.
Solution Approach 2:
The patent applies different shielding configurations at different locations: first Faraday shields near primary winding, second Faraday shields near secondary winding, and third Faraday shields at intermediate positions. Each segment is optimized for its local requirement, reducing parasitic capacitance where needed while maintaining voltage balance across the transformer structure.
2Object-affected harmful factors
If common mode inductor and Y capacitor are used to reduce common mode noise, then noise is suppressed, but device size increases
Solution Approach 1:
The patent implements noise reduction measures at the source by strategically placing Faraday shields between windings to prevent parasitic capacitance formation in the first place. This preliminary action reduces common mode noise generation before it requires external filtering, thereby minimizing or eliminating the need for bulky common mode inductors and Y capacitors.
Solution Approach 2:
The patent extracts the noise reduction function from external filter components and integrates it directly into the transformer structure through embedded Faraday shields. This eliminates the need for separate external noise suppression components, reducing overall device volume while maintaining noise suppression effectiveness.
3Object-affected harmful factors
If asymmetrical circuits are used for reverse-complement operation, then common mode noise is reduced, but circuit complexity increases
Solution Approach 1:
The patent introduces Faraday shields as intermediary elements between primary and secondary windings. These shields act as mediators that physically separate the windings and reduce parasitic capacitance coupling, thereby reducing common mode noise without requiring complex asymmetrical circuit operations or additional control circuitry.
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 effectively reduces common mode noise by balancing the parasitic capacitances between the primary and secondary sides, achieving lower noise levels by adjusting the shield geometry and adding a balancing capacitor, thereby meeting the requirement of minimizing total common mode noise.
Implementation Method 1
a transformer with a partial electrostatic shield between primary and secondary windings
Implementation Method 2
balance parasitic capacitances and reduce common mode noise
Implementation Method 3
an additional balancing capacitor can be used to balance noise voltages between the primary and secondary sides
Data Source
AI summary
The present invention discloses a power converter with low common mode noise. The power converter having a primary side and a secondary side, comprises a transformer having a primary winding and a secondary winding, and at least one electrostatic shield disposed between the primary winding and the secondary winding, wherein the electrostatic shield is configured with partial first region of the primary winding and partial second region of the secondary winding such that the electrostatic shield partially shields with the primary winding and the secondary winding to reach the purpose of suppressing the common mode noise. In addition, another method can be used to reduce the common mode noise of a power converter having primary side and secondary side, which is adding some additional impedance between the static points and jump points of the primary side and secondary side.