View attachment 150060

Duty Cycle of a square wave train is defined as Ton/(Ton+Toff) x 100 and is a percentage. Example : 10% Duty Cycle means short "ON" time of 10% and longer "OFF" time of 90%. ( Ton +Toff = 100%)

 

If that's meant to be a buck-regulator, then you need an inductor between C2 and D2, but the original question is 3 years old.