پياده سازي روش هاي مقابله با EMI در مبدل فلاي بك

چكيده انگليسي :

Impelementation of EMI Supprestion Method in Flyback Converter Zahra Emami Bistgani Zahra emami1765@yahoo com 03 15 2010 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan Iran Degree M Sc Language FarsiHosein Farzanehfard hosein@cc iut ac irAbstract Nowadays there is trend for increasing switching frequency of power devices in order to reducegeometrical dimensions and weight of power converters High frequency switch mode power supplies SMPS generate EMI noise due to their switching actions and parasitic elements which interferes with thenormal operation of the other devices or systems Consequently suppression of EMI is a very important issuein SMPS design In hard switching dv dt and di dt are the main sources of EMI noise In recent years various methods are used to reduce EMI noise such as grounding shielding filtering passive cancellation Moreover it is well known that various softswitching techniques can significantly reduce the dv dt or di dtthat decreases switching loss and EMI noise In this thesis sources of EMI noise several EMI standards and an EMI measurement method isintroduced Furthermore some of EMI reduction methods in switch mode power supply are discussed AnEMI measurement system in time domain is suggested along with the conventional frequency domainmeasurement system to extract more information on EMI noise without requiring a noise separator A LineImpedance Stabilization Network LISN is built for measuring the conducted EMI The measurements aredone in accordance with CISPR11 standards Since understanding and predicting the system EMI noise through an accurate EMI model at the designstage is necessary thus a precise modeling for active and passive elements and PCB is developed and exactsimulation is performed The experimental results confirm the simulation results Since softswitching techniques can significantly reduce the switching dv dt and di dt it is conceivable thatthe EMI noise generated by a hard switching flyback converter could be reduced by soft switchingtechniques In the last chapter of this thesis the overall performance and the measured results of theconducted EMI emission of a Zero Voltage Transition ZVT flyback converter is compared with its hard switched counterpart The ZVT converters are PWM controlled and have an auxiliary resonant circuit whichis only used during the switching instants to reduce the voltage or current to zero just before switching Theemployed ZVT converter provides soft switching condition for all switching elements This reduces theamount of high frequency harmonics generated by high dv dt and di dt Keywords Electromagnetic Interfrence EMI Flyback Converter Conducted EMI Measurement Soft Switching ZeroVoltage Transition ZVT

امامي بيستگاني، زهرا

پياده سازي روش هاي مقابله با EMI در مبدل فلاي بك

تداخل الكترومغناطيس , سوئيچينگ نرم , ZVT