了解開關(guān)電源的電磁兼容標準

　　由于其固有的設(shè)計特點，AC和DC和DC / DC開關(guān)電源（SMPS）產(chǎn)生由多個頻率的射頻信號組成的電磁干擾（EMI）。除了在安裝這些SMPS電源的系統(tǒng)中干擾電路元件和功能外，這種發(fā)射也會干擾源附近的其他設(shè)備。為了確保這種排放量保持在最低限度，國際監(jiān)管機構(gòu)制定了規(guī)章制度；符合這種標準的SMPS轉(zhuǎn)換模塊被稱為電磁兼容（EMC）電源。

　　電源制造商崔已經(jīng)發(fā)布了一份白皮書，題為“電磁兼容性考慮開關(guān)電源”1調(diào)查各種國際標準控制電磁調(diào)速，和更詳細的描述。在美國，負責(zé)調(diào)節(jié)這種干擾的政府機構(gòu)是聯(lián)邦通信委員會（FCC）。FCC的規(guī)則第15部分概述了電磁干擾的控制，規(guī)定任何大于10千赫的虛假信號都要受管制。此外，根據(jù)發(fā)射的類型，它還規(guī)定了必須控制這些雜散發(fā)射的頻帶。

　　There are two types of EMI emissions： radiated and conducted. While radiated emissions are those radiated and coupled through the air， conducted emissions are RF signals coupled by a direct path between the source and the receptor. Direct contact is provided by a transmission line， wire， cable， printed circuit board （PCB） trace or metal enclosure. It can appear in a common or differential mode on two conductors.

　　Also， per FCC Part 15， radiated emissions must be controlled between 30 MHz and 1000 MHz， and conducted emissions must be controlled in the frequency band between 0.45 MHz and 30 MHz.