I am certainly interested in such a circuit.  Would be grand to be able to run 
off one cell, but also plug in a 9V power source, and the 'magic' buck-boost 
does what's necessary.  It would seem some of the chips are designed to do 
both, but not at the same time.  Does not seem that complex, though.  If you 
are under-voltage, then close the buck switch and toggle the boost, if you are 
over-voltage do the reverse.  

Good luck,
David

Quoting "William \"Chops\" Westfield" <westfw@mac.com>:

> 
> In the attached circuit I've overlaid a standard buck-mode converter  
> (SW2, CR2, L1), and a boost mode converter (SW1, CR1, L1) that shares  
> the same inductor.
> 
> Is there some reason that this doesn't work as a boost/buck variable  
> voltage regulator? (for boost, you leave SW2 ON continuously, for  
> buck you leave SW1 off all the time.)  I don't think I've ever seen  
> this sort of configuration.  (for that matter, I haven't seen many  
> switch-mode variable power supplies at all...)  I can forsee "issues"  
> trying to run this with a traditional analog feedback path, but if  
> I'm using a microcontroller as the regulating element anyway?
> 
> Thanks
> Bill W
> 
> 




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