Raising voltage from a single battery

[beerbaron]

Hi, I'm trying to raise a battery voltage from 0.9-1.5V to a stable 3.3V (20mA to 60mA).

I'm using a charge/pump inductor with a capacitor to smooth the whole thing.

I'm planning to use feedback voltage to keep the output stable. But I'm not sure how to proceed from here. I tough of using two different techniques.

-1st, I could use my feedback to modify my pulse width. And therefore change the output voltage.

-2nd, I could use my feedback to change the frequency and therefore adjusting the output voltage.

Cost is the most important here, what approach should I use? PIC? VCO? PWM?

See a simplified circuit that I built so far.

http://pages.infinit.net/f199/SimpleRaise.JPG

Thanks
BeerBaron

 

[MikeHalloran]

The simplest design involves three more cells and a regulator.



Mike Halloran
Pembroke Pines, FL, USA

 

[logbook]

There is another thread on EngTips discussing low voltage boost converters. I don't have time to look right now.

 

[geekEE]

What about just using an off-the-shelf chip like the MAX849 to do this? It would reduce your parts count and development time.

 

[logbook]

A MAXIM 1700, or any from this family will start at 0.9V typical, but run down to 0.7V once running (according to their data sheet). This is much better than trying to make one from "first principles". MAX849 is on the same data sheet page as the 1700, but occured earlier in the listing for some reason.