Analyze the valid switch power supply electromagnetism interference represses the measureTake off to want: This text analyzes the switch power supply to produce the mechanism of the electromagnetism interference first, a few valid switches power supply electromagnetism interference measure carried on the analysis currently comparison, and put forward the reference suggestion for the further research of the switch power supply electromagnetism interferenceKeyword: The switch power supply electromagnetism interference represses the measure to matchCurrently, many universities and the research units all carried on the research of the switch power supply EMI( the Electromagnetic Interference), they win some mechanism that produces from the EMI to set out, some from the EMI produce of influence set out, all put forward many practical worthy projects.The here is analytical with compared a few valid projects, and repress the measure to put forward the new reference suggestion for the switch power supply EMI.One，the creation mechanism of the switch power supply electromagnetism interference Output interference of the switch power supply, press an interference of source category to divide, can is divided into the diapason an interference of the peak interference two kinds of; if match the thoroughfare according to the to divide, can is divided in to conduct the interference and radiation the interference is two kinds of.Press an interference of source to come to explain respectively now: 1, diode of anti- toward the interference that the instauration time cause The high commutates the back track in of commutate a hour of positive guide of diode to is bigger just flow through toward electric current, at it be subjected to anti- be partial to the electric voltage but change direction to close, because having to carry to flow the sub- backlog morely in the PN knot, as a result in carry flow sub- disappearance previously of a period of time, the electric current would be anti- toward fluxion, causing carry to flow the sub- disappearance anti- to reduce toward nasty play of the instauration electric current but take place the very big electric current variety( di/ dt). 2, an interference of that hour of work produce of tube of switch The power switch tube flows through the bigger pulse electric current while lead.For example just arouse the type and push a form of the importation electric current of the type of and the bridge type transformation machine at the load look like for the rectangle wave, among them imply a weight of abundant high .When adopt zero electric currents, zero electric voltage switcheses, an interference of this kind of will be very small.Moreover, the power switch take care of during the period of close, the high transformer of rounds an electric current mutation for leaking the feeling to cause, also will produce the peak interference. 3, exchanges importation interference of the back track creation The switch power supply importation that have no work transformer carries to commutate the tube at anti- will cause the high to reduce to flap to become bankrupt to living the interference toward period of instauration.Harmonious interference energy of the switch power supply output peak interference, the importation that passes the switch power supply outputs the line dissemination to go out but the formative interference call it as to conduct the interference; but wave of and live on the energy of flap the 荡 , pass the importation exportation line dissemination, will produce the electric field and magnetic fields in the space.This kind of is called the radiation interference through an output interference of the electromagnetism radiation.4, other reasonA machine piece lives on the parameter, the principle diagram of the switch power supply design not enough perfect, the printing circuit plank( PCB) walk the line usually adopts the handicraft to arrange, have very big at will sex, the PCB an interference is big, and print the plank up the gearing of the machine piece, place, and directions of not reasonable will result in the interference of EMI. Two, the characteristics of the switch power supply EMI Be the work in the energy conversion device of the switch appearance, the electric voltage, the electric current variety rate of the switch power supply is very high, the interference strength that produce compare greatly;The interference source main the concentration is in the power switch period and spread the hot machine and high and even transformers connect with each other with it, opposite compare in the position of the numerical electric circuit interference source clearly;The switch frequency is not high( from several:, and the few trillion Hertzs), the main interference form is to conduct the interference and an interferences; but the printing circuit plank( PCB) walk the line usually adopts the h