返馳型切換式電源的變壓器雜散電容分析

切換式電源傳導型電磁干擾可分為差模與共模雜訊兩種，在本文中我們只對共模雜訊做討論。共模雜訊主要是由線路上對地的雜散電容所造成，而變壓器初次級繞組間的雜散電容是其主要的路徑之一。本文主要是在分析切換式電源變壓器初次級繞組間的雜散電容對於傳導型電磁干擾的影響。首先，針對切換式電源的電磁干擾來源與路徑進行分析，將線路圖簡化與模型化。其次利用平板電容的計算公式，並且考慮繞組上的電位梯度分佈，計算得到電容值；同時也使用等效電路的量測方法去量測、比較與分析結果。最後使用目前常使用的三種不同繞線結構的變壓器，在一台12V 12W的電源轉換器上做傳導型電磁干擾的的量測與驗證，實驗結果與理論尚可符合。

關鍵字

傳導型電磁干擾；雜散電容；變壓器；返馳式轉換器

並列摘要

The Conducted Electromagnetic Interference (EMI) of the switching power supply can be divided into two types, the differential-mode noise and the common-mode noise. Only the common-mode noise was concerned in this study. The common-mode noise is caused by the stray capacitance of circuits, among which the capacitance between the primary and the secondary transformer windings is one of key paths. This paper presents the effect of the capacitance between the primary and the secondary transformer windings of the switching power supply on the conducted EMI. First, we analyzed the source and the path of EMI of the switching power supply, simplify and model it. Then we used the formula of the plate capacitor to obtain the calculated capacitance with the considering of the potential gradient at the transformer windings. We compared and analyzed the results Finally, we used three types of differently winded transformers to measure and verify the EMI on a 12V 12W adaptor. The results of these experiments are consistent with the modeling theory.

並列關鍵字

Transformer ； Flyback Converter ； Stray Capacitor ； Conducted EMI

參考文獻

[1] A. I. Pressman, Switching Power Supply Design, 2nd Edition, McGraw-Hill.

[5] C. A. Paul, Introduction to Electromagnetic Compatibility, 2nd

Edition, A John Wiley & Sons, INC. Publication.

[6] H. K.Patel, Flyback Power Supply EMI Signature and

[9] H. Y. Lu, J. G. Zhu, S. Y. R. Hui, Experimental Determination of Stray Capacitances in High Frequency Transformers, Power Electronics, IEEE Transactions on Volume 18, Issue 5, September 2003, P1105~P1112.

國際替代計量

返馳型切換式電源的變壓器雜散電容分析

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