Balance Winding Scheme to Reduce Common-Mode Noise in Flyback Transformers

Kaining Fu; Wei Chen

Balance Winding Scheme to Reduce Common-Mode Noise in Flyback Transformers

Kaining Fu

Wei Chen

Vol. 19, No. 1, pp. 296-306, Jan. 2019

10.6113/JPE.2019.19.1.296

Balance winding

common-mode (CM) noise

EMI

Flyback

PCB transformer

PDF Full-Text

Abstract

The flyback topology is being widely used in power adapters. The coupling capacitance between primary and secondary windings of a flyback transformer is the main path for common-mode (CM) noise conduction. A Y-cap is usually used to effectively suppress EMI noise. However, this results in problems in space, cost, and the danger of safety leakage current. In this paper, the CM noise behaviors due to the electric field coupling of the transformer windings in a flyback adapter with synchronous rectification are analyzed. Then a scheme with balance winding is proposed to reduce the CM noise with a transformer winding design that eliminates the Y-cap. The planar transformer has advantages in terms of its low profile, good heat dissipation and good stray parameter consistency. Based on the proposed scheme, with the help of a full-wave simulation tool, the key parameter influences of the transformer PCB winding design on CM noise are further analyzed. Finally, a PCB transformer for an 18W adapter is designed and tested to verify the effectiveness of the balance winding scheme.

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Cite this article

[IEEE Style]

K. Fu and W. Chen, "Balance Winding Scheme to Reduce Common-Mode Noise in Flyback Transformers," Journal of Power Electronics, vol. 19, no. 1, pp. 296-306, 2019. DOI: 10.6113/JPE.2019.19.1.296.

[ACM Style]

Kaining Fu and Wei Chen. 2019. Balance Winding Scheme to Reduce Common-Mode Noise in Flyback Transformers. Journal of Power Electronics, 19, 1, (2019), 296-306. DOI: 10.6113/JPE.2019.19.1.296.