Smps Inductor Loss Reduction

Usually I spec a core that has enough worst case saturation reserves and then select a wire gauge that crams it pretty full but not to an extent that it makes production difficult.

Let's say it's a toroid... When you mean full..do you mean multilayer windings for a big fat donut? Or full single layer? D from BC

For switchers in the few hundred kHz class it's often the big fat donut, for RF filters it's single layer with an isolation layer on the core. Many times switchers will also contain a single layer winding but that is because there comes a point when increasing the wire diameter doesn't buy you much anymore, other than a hard time soldering it in.

Cool...Thanks.. I'll go multilayer on the toroid. To reduce Rdc, can I dodge ordering fatter magnet wire by doubling up thinner wire (#23) in some way? Maybe wind a twisted pair on the toroid? Ill effects? D from BC

I have doubled up wire without problems on switchers. But not for series production as that increases cost.