[as-j]

> Hasn't that problem mostly been solved already with switch mode power supplies that are pretty small.

I waste a ton of board space with power supplies. Not everything is personal electronics with custom ICs* in the volume of an iPhone. So this means on my current design there's power supplies for 1v, 1v8, 2v5, 3v3, ~4v, 5v. Each of these the biggest component is the inductor.

I've sometimes joked, I make power supplies with a computer attached.

Edit: since the volume is low we use off the shelf parts which means we tend to end up with a variety of voltage requirements. And yes...reduction of rails is something that's part of components selection, alas....

[tgflynn]

Are all of those drawing significant current though ? If you just have some small component with an odd voltage requirement that doesn't need much current couldn't you supply it with something a lot simpler than a dc-dc converter, like maybe a voltage divider or linear regulator ?

[mlyle]

Almost certainly not a voltage divider. Maybe a linear, if efficiency doesn't matter.