Hi folks, I'm reviewing a design about a power converter for driving an electromagnet (10A, 50V).

The substitution of a freeweeling diode with a N-channel enanchement mosfet it's a good choice for reducing dissipated power which is relevant on the diode.

I'm just wondering about the current direction in the N power mosfet: from Source to Drain in this arrangement. The flow is opposite respect to the "normal" one.

Ok, nothing strange in a planar mosfet which is geometrically simmetric (source and drain may be reversed if you want - ignoring that the sub is connected to the source) but what about a vertical power mos ?

When current flows from drain to source with Vgs > VT (enanchement N mos) the channel acts as a "low" value resitor if Vds remains far from the pinch-off condition Vgs-Vds >> VT.
Voltage channel drop from drain to source affect this condition.

How about the pinch off condition where the current flow in the opposite direction and the geometry of the VMOS is asimmetric?

I'm just curious about that.

Thanks !
Enzo