A rule of thumb I have heard about and want to check its validity is that:
For a fan cooled forward converter transformer, employing feed forward should have a flux density lower than 250mT as not to saturate for TDK PC40.1) Is this a reasonable estimate of max flux density at say 100 Deg C 100KHz.
I know that in PSU terms (not described accurately mathematically)
therefore following integration etc...
V *dt =3D N *Ae * dB
dB =3D (V*dt)/N*Ae---(1)
and by similar methods
dB =3D (L*dI)/N*Ae----(2)
(d indicated change or delta)2) For a continuous forward converter, would this 250mT =3D (dB) limit be as a result of
a) the ripple current peak to peak in the coil (from low value to high value of the trapezoid) during the fet on time =3D (dT) or
b) the max current (from zero to the top of the trapezoid) during the fet on time =3D (dT)
I think a)
Have I the wrong idea?