Lecture 4 - EEL 5245: Power Electronics I Lecture # 4...

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EEL 5245: Power Electronics I Lecture # 4 Non-Isolated Dc-dc Converters School of Electrical Engineering and Computer Science University of Central Florida Insturctor: Dr. Sam Abdel-Rahman
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2 DCM Buck Converter - In DCM, Vo/Vin= M= f (D,T,R,L) Vo/Vin= M= f(D,D 1 ) and D 1 = f (D,T,R,L) i Lmin = 0 Means inductor current starts at zero (i L (0)=0) , and ends at zero (i L (T)=0) For a certain inductor value, DCM occurs as load is low,, Io is small. Io<Io,critical
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3 Intuitive Concepts (All other variables are constant) Smaller L Larger inductor current slope Larger inductor current ripple More likely to go to DCM Smaller Io Smaller inductor average current (DC value) More likely to go to DCM Larger T Extended switching period allows more time for IL to reach zero Larger inductor current ripple More likely to go to DCM
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4 DCM Buck Analysis 0 DT DT D 1 TD 1 T T V L = Vin – Vo I L (0)=0 V L = -Vo V L = 0 I() L Vin Vo tt L = ( ) I( ) LL Vo t t DT DT L =− + I() 0 L t = Mode 1: S on, D off
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This note was uploaded on 10/05/2010 for the course EEL 5245 taught by Professor Abdel-rahman during the Fall '10 term at University of Central Florida.

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Lecture 4 - EEL 5245: Power Electronics I Lecture # 4...

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