15385

13789

كارشناسي ارشد

الكترونيك - مدارهاي مجتمع خطي

اصفهان : دانشگاه صنعتي اصفهان

1398

هشت،‌ 77ص. : مصور، جدول، نمودار

احسان اديب

حسين فرزانه فرد، سعيد گلشاه

حميدرضا كارشناس، اصغر غلامي

1398/10/14

كتابنامه

مهندسي برق

مهندسي برق و كامپيوتر

1398/10/14

2590908

76Investigation Improvement and Loss Reduction of High Step Down Converters With Self Driven Synchronous Rectifier Behzad Soleymani b soleymani@ec iut ac ir Department of electrical and computer Engineering Isfahan University of Technology Isfahan 84156 83111 Degree M Sc Language Persian Supervisor Dr Ehsan Adib E Adib@cc iut ac ir Adviser Dr Hosein Farzanehfard Hosein@cc iut ac ir Abstract Today with the increasing development of hybrid electric cars and the increasing use ofcomputers in home and industrial applications the issue of electric power supply of theseapplications has become one of the most challenging issues in the world These applicationsrequire high current DC DC converters which in cases that the input and output isolationis not required synchronous buck structure is used due to its simplicity low cost and lowcomponent count This structure uses a synchronous rectifier instead of the diode of the buck to reduce the conduction losses However synchronous buck converter in high current highstep down applications suffer from disadvantages such as high conductive losses ofMOSFETs narrow duty cycle switching losses due to hard switching condition of the mainswitch and reverse recovery loss of the synchronous rectifier body diode The narrow dutycycle increases the current stress of the main switch and control complexity of the converter The interleaved structure of the buck converter is used to improve the transient response ofthe converter reduce the conduction losses and also improve the efficiency over a widerange of output currents This method also reduces the output current ripple however interleaved structure has little effect on narrow duty cycles Another challenge is the propertiming for triggering the synchronous rectifier which might cause the short circuit of inputsource and damages switches of the converter Various methods have been proposed toimprove the performance of the high step down buck converters one of which is altering thestructure of buck in order to increase the duty cycle and if possible provide soft switchingconditions for the main switch The objective is to apply as little modification as possible tothe synchronous buck converter to eliminating its disadvantages while maintaining thesimplicity of the buck converter The general idea behind these methods is to create a voltagesource in reverse to the input to reduce the effective voltage For this purpose coupledinductors or capacitors are used in the power path In this thesis three non isolatedconverters based on the coupled inductor buck structure along with two isolated convertersbased on forward topology are introduced In the first proposed non isolated converter apartially zero voltage switching condition is provided at turn off time of the main switch byusing a lossless passive snubber circuit which results in the improved efficiency of theconverter In addition a self drive circuit with gate energy recovery is used to automaticallygenerate the synchronous rectifier control pulses and reduce the complexity of the converter In order to further reduce switching losses and reduce the number of converters a secondproposed non insulated structure was introduced In this converter ZCS condition of the

احسان اديب

حسين فرزانه فرد، سعيد گلشاه

حميدرضا كارشناس، اصغر غلامي