I put together a couple of simulations using LTSpice for +1.2v to +30v and -1.2v to -30v switching supplies, 2.5A that were really quite efficient; ~80% worst case. They both operate from a single +34v supply.

Very nice. You think it would be possible to find a controller that would support something like this?;

 

Your post was hijacking this thread.

Negative (low power) switching regulator oprtions? (For dual supply)

A thread belongs to the original poster. Now you have one of your own.

 

You'd need around 20A for the switching current, so you probably won't find a controller with an integrated switch that would handle that. One of the biggest problems is the low input voltage vs the Vf loss incurred in the diode; you'll lose ~0.6v or 0.6/3.5 = ~17% of your input power right there.

With as low as 2.9v in and requiring 6v @ 5A out, figuring ~50% maximum duty cycle, 6v*5a/2.9v/50% ~=20.68 Amperes required.