Multi-phase Buck Converter - Does the inductor breakdown during the startup transient?
My premise that "When the phase A first turns on (phase B is off) the current going through the inductor will be (50V-25)/1Ohm = 25A" is incorrect. Below is how you solve how much current will be flowing through the inductor.

Initially the inductor current is 0, inductor is rated at 15uH also my switching frequency per phase is 62500 Hz.

The change in current between the time when phase A first turns ON and when phase B turns ON is calculated as follows.

V = L*(dI/dt)

dI = (V/L)*dt

dI = ((Vin-Vout)/L)*dt

dI = ((50V-25V)/15uH)*dt

Note: dt = (1/62500)/4 = 4uS -> (With 4 phases phase B turns on after 1/4 of the switching period)

dI = ((50V-25V)/15uH)*(4uS)

dI = 6.67A

So when phase B first turns on the current going through the inductor in phase A will be 6.67A. Since 6.67A &lt; 15A (15A is the rating of the inductor) then inductor will not breakdown when the SMPS first turns on.