/diy/ - Do It Yourself

>>1204611
>what D1 is for
When Q1 is OFF the voltage across it (the drain-source voltage Vds) is V1, 25V. When Q1 switches ON, Vds goes (close to) zero and the current in L1 ramps (!) up to 70A or whatever current it reaches during the ON phase of Q1. Now the coil collects and stores energy in form of the magnetic flux it generates. When Q1 is now switched OFF, e.g. because Q2 switches ON, the stored energy has to go somewhere, else it would immediately destroy Q1. The fast diode D1 now offers a (current) path the stored energy can follow and 'discharge' the coil. The energy stored in a coil follows (the square of) the current that flows through it.

You may want to read this a few times because your assumptions are far from reality.