> It's not for sale. I'm teaching a class this summer on 
> alt. energy and
> sustainability for high school kids and part of the class 
> is to modify the
> golf cart. The kids are putting everything together, I've 
> just got to design
> the electronics. :)

That both tightens and loosens the spec.

Efficiency and minimum cost are not as important as 
bullet-proofness.

Many major IC manufacturers provide ICs that are well suited 
to this task and have application notes that cover it well. 
Linear Technology are a good place to start. It's not an 
overly hard task to do "well enough" and if you rate the 
components conservatively it should work quite well. With a 
single winding inductor you don't get the leakage inductance 
woes that beset some fancier moderate power designs.

If you wanted absolute minimum spec a (blush) 555 set at ~= 
50% duty cycle driving a FET with a simple gate driver and 
suitable inductor and output diode would do a "good enough" 
[tm] job. But, I'd recommend a dedicated IC driving a FET 
similar to the one I mentioned.

If a bit less efficiency is OK an eg IRFP250 in TO247 
package would do well enough for about $1.50 from Digikey.

Inductor can be a commercial one with the right specs or a 
self wound air cored one (RFI, what RFI?) of about 100 uH 
(or see app note for IC you are using) and fat enough wire 
to get resistance down to a loss level that is acceptable.



        Russell



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