傳導型電磁干擾的分析與濾波器設計

切換式電源供應器自1970年代發明以來，逐漸地廣泛使用在各式各樣的電子與家電產品內，諸如計算機、筆記型電腦、印表機、數位相機、行動電話，… 等等。各產品早已成為現代人生活與工作上不可或缺的必需品。綜觀切換式電源的技術發展，有幾個領域的突破，像高效率電路拓樸的提出，幾近理想的功率半導體器件，各種控制IC的進步，以及低損耗磁鐵心的發明等等，使得廣大的電力、電子、通訊產品使用者，得以享受便宜可靠的服務。　　然而隨著電路佈局的密集與高頻化，電子器件之間與印刷電路板的耦合問題越來越嚴重，電磁干擾(Electromagnetic Interference, EMI)早已變成電源產品開發中最令工程師頭痛的一環了。從干擾源的產生到耦合路徑，存在著許多不容易量化分析的電場與磁場交互影響的問題。由於對干擾的原因與途徑的無法量化掌握，濾波器的設計一直存在著試誤(cut and try)的過程，到現在都還沒有有效的系統化分析與解決方案。　　作者以其在電源產業實際參與設計的經驗來看，有效的探討EMI 雜訊的產生，耦合的途徑以及配合量測技術，有效的設計雜訊濾波器，不失為現階段克服EMI 問題的一個方向。本論文將以一個常規300W的主動功率因數改善電路為例，探討雜訊源的產生，並且分析不同型式的干擾途徑，然後配合量測方法與濾波器分析，設計出符合EMI規範的濾波器。

關鍵字

切換式電源供應器；電磁干擾；濾波器

並列摘要

Ever since the initial development in 1970’s, the switching mode power supplies have been widely adopted in various electronic apparatus, such as personal computers, laptop computers, printers, digital cameras , mobile phones, … etc. Switching power supplies become essential for modern human life. From the power supply technical point of view, there are several remarkable progresses in the past decades, such as high-efficiency topologies, high performance power semiconductors, various integrated control circuits, and low-loss magnetics, which make the power supply more efficient and reliable. However, accompanying with the technologies of high density PCB layout and high-frequency switching, the noise coupling problem between the PCB wirings and the components are getting more and more serious. The so-called “Electromagnetic Interference” (EMI) has always bothered the power supply engineers. In terms of noise generation and noise coupling, many uncertainties exist inside the power supply system. Most engineers can resolve the EMI issues only by try and error method. In this thesis, an analytic approach to identify the noise amount of an active power factor corrector is proposed, which is great helpful for designing the noise filter. Besides, a common/differential noise separator is adopted to distinguish the noise types, which can be used for efficient filter design. Measurement to identify parasitic parameters of filter components are also included, which illustrates the noise spectrum in different frequency range. Finally a systematic approach is proposed to design a suitable noise filter. Implementation of the noise filter in a 300W hardware is presented to verify the feasibility of the theoretical derivation.