In just about every design guide I saw, the formula for primary inductance of flyback is:
However in "SMPS Design" by Pressman/Billings the equation for CCM is:
To bring second equation to the first form Kr should be = Vin/(Vin-Vds), which is always > 1. Does not look right.
Question: Which equation should I use?
UPDATE: I'm accepting @andy-aka answer because it prompted me to verify the derivations in Pressman's book. Turns out that at some point they use DCM formula dI = 2 x Iedc (instead of CCM dI = 2 x Iedc x Kr) to substitute dI in Lp equation.
So, the answer is: First formula is correct, second is wrong. Although I suspect one of the two Vin(min) in it can be substituted for Vin(min) + Vds to account for voltage drop in a switch, like it is done in the book.