Dear Sirs,
My Customer wants to use UCC2897A for 250W design.
The excel calculation result as attached.
The design requirement are:
AC19.2V ~31.2V , Vo=12V/21A (250W)
For transformer and secondary side inductor, customer will use PQ3220.
Here are the design calculation and some question need help.
Transformer:
Np=Vin(min)*ton/(ΔB*Ae) = (27*0.6*(1/250K))/(0.25*170) = 1.524Ts (N1=2)
Dmax = ( Vout * N ) / Vin_min = 0.6 = (12 * N )/27 = ratio = 1.33 (N2=1)
L = N1^2*AL = 2^2 * 7310 = 29uH
=============================
Secondary side Inductor:
L = Vout*T*(1-Dmin) / Id = ( 12V*(1/250K)*(1-0.35) )/21A = 1.49uH
N1^2*AL = N^2 * 7310 = 1.49uH………L is too small and cannot make it.
May I have a better suggestion for the transformer and inductor about customer design requirements?
Thanks.