iLiL 11 I L = I o TSTS D m2m2 m1m1 Buck Converter – Discontinuous Conduction 22

Determine D,  1,  2

iLiL 11 I L = I IN TSTS D m2m2 m1m1 Boost Converter – Discontinuous Conduction 22

Determine D,  1,  2

Summary for Discontinuous Conduction Mode ParameterBuckBoostBuck/Boost ILIL IOIO I IN I IN - I O I L (max) D DCM 11 22

ParameterModeBuckBoostBuck/Boost V O RangeC/D0 < V O /V IN < 1V O /V IN > 1V O /V IN < 0 I IN C/DI O (V O /V IN ) = P O /V IN = (V O /R O )(V O /V IN ) I L (max) CI L + I L,cr D I L (min)CI L - I L,cr C/D Boundary I IN,cr C/D(V O /V IN ) 2 (V IN - V O )/2Lf(V IN /V O )(V O - V IN )/2Lf(V O /(V O - V IN )) 2 (V IN /2Lf) I L,cr C/DI O,cr I IN,cr I IN,cr - I O,cr I O,cr C/D(V O /V IN )(V IN - V O )/2Lf(V IN /V O ) 2 (V O - V IN )/2Lf(V IN /(V O -V IN )) 2 (V O /2Lf) Duty Cycle CV O /V IN (V O -V IN )/V O V O / (V O -V IN ) DV O /V IN (V O -V IN )/V O V O / (V O -V IN ) 11 C(V IN –V O )/V IN V IN /V O V IN / (V IN -V O ) D (V IN - V O )/V IN V IN /V O V IN / (V IN -V O ) 22 D Reverse diode for V IN < 0 DCM if I O /I O,cr < 1 Switching Converter Parameters

Ripple Voltage: Buck Converter iLiL tQtQ I L = I o TSTS DT s QQ 11 22

Ripple Voltage: Boost/Buck-Boost Converter iLiL TSTS DT s tQtQ QQ 11 22

Buck Converter – Discontinuous Conduction With constant duty cycle, D, V O is constant if I O > I O,cr (CCM) If I O < I O,cr, V O increases as I O decreases! True for other converters also.