UCC28019 boost coil equation

MacIntoshCZ

Active Member
Hi,
i dont know why there is D(1-D) in equation. Duty/Frequency stays for time... But why 0,5*(1-0,5)...
L= V*t/Iripple

page 28
thanks

Pommie

Well-Known Member
If you plot a chart from d=0.1 to d=0.9 compared to d(1-d) you will see that 0.5 is where it peaks. They are simply using the worst case.

Mike.

MacIntoshCZ

Active Member
If you plot a chart from d=0.1 to d=0.9 compared to d(1-d) you will see that 0.5 is where it peaks. They are simply using the worst case.

Mike.
Thanks pommie for reply, now i get that d*(1-d) is biggest when duty is 0,5. But i still dont know why is there d*(1-d) in eq. instead of just d or (1-d).

rjenkinsgb

Well-Known Member
It symmetrically "shapes" the result to peak at 50% duty; eg. that give 0.25 while eg. 10% and 90% both give 0.09

ronsimpson

Well-Known Member
biggest when duty is 0,5. But i still dont know why is there d*(1-d) in eq. instead of just d or (1-d).
For that "biggest" equation it would be "0.5d". But for all duty cycles it is d*(1-d).
Worse case duty cycle = d/2=0.5d,,,, For any duty cycles d*(d-1)

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