Y-capacitors are widely used in flyback converters to suppress common-mode (CM) noise to comply with the strict electromagnetic interference (EMI) standards. However, Y-capacitors increase the leakage current between the primary and secondary side, which is not allowed in the applications with high safety requirements. In this paper, the displacement current models of two conventional De-Y methods are quantitatively established to analyze their limitations for the flyback converter. Then, a hybrid EMI-optimized transformer is proposed to improve the limitations. The proposed structure can completely balance the CM noise between the primary and secondary sides, making the flyback converter comply with the EMI standard under the conditions of no Y-capacitor. Compared with the traditional methods, the proposed method has a better capability for CM noise suppression, higher universality and the same cost. Finally, the simulation and experimental results verify that the CM noise of the new transformer structure decreases about 10 dB compared with that of the conventional one. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

中文翻译：

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用于具有低共模噪声的 De-Y 反激式转换器的 EMI 优化变压器

Y 电容器广泛用于反激式转换器以抑制共模 (CM) 噪声以符合严格的电磁干扰 (EMI) 标准。然而，Y 型电容器会增加原边和副边之间的漏电流，这在安全要求较高的应用中是不允许的。在本文中，定量建立了两种常规 De-Y 方法的位移电流模型，以分析它们对反激式转换器的局限性。然后，提出了一种混合 EMI 优化变压器来改善这些限制。所提出的结构可以完全平衡原边和副边之间的共模噪声，使反激式转换器在没有Y电容器的情况下符合EMI标准。与传统方法相比，所提出的方法具有更好的CM噪声抑制能力、更高的通用性和相同的成本。最后，仿真和实验结果验证了新变压器结构的共模噪声比传统结构降低了约 10 dB。© 2021 日本电气工程师学会。由 Wiley Periodicals LLC 出版。