Buck Converter + V in - + V OUT - Assumptions for First Order Analysis: All components are ideal, including voltage source Output ripple voltage is negligible (2 nd order effect) Continuous (nonzero) current through inductor We will examine the case where inductor current goes to zero for part of the cycle at a later time. However, we will identify the condition which causes this to happen. i L (t) = I OUT + i C (t) I OUT iCiC

iLiL ILIL i L,max i L,min I L = I O T S = t 1 +t 2 t 1 =DT S t 2 =(1-D)T S m2m2 m1m1 Inductor Current > 0

ILIL i L,max i L,min I L = I O m2m2 m1m1 Expressions for Inductor Current Variation

iLiL ILIL i L,max i L,min I LB = I OB I L = I O TSTS DT S Critical Inductor Current I O = I L = I L,crit =  I L /2

iLiL ILIL i C,max i C,min T S = t 1 +t 2 t 1 =DT S t 2 =(1-D)T S Capacitor Current +  Q T S /2

iLiL ILIL i L,max i L,min I SW = I D T S = t 1 +t 2 t 1 =DT S t 2 =(1-D)T S Switch Current = I D

iRiR ILIL i L,max i L,min IRIR T S = t 1 +t 2 t 1 =DT S t 2 =(1-D)T S Diode Current