[arnolde]

Remember, anything that gets hot, is actually wasting energy and reducing the efficiency. I'd try raising the pwm frequency if I were you, 20 khz is really pretty low, there's a good reason why smps's are usually between 50 and 200 khz. Maybe the switching losses will get higher then, but I assume the other losses (in coils and capacitors) will get lower and result in overall better performance.

I just kicked myself for ordering those expensive capacitors, thank god I only got 2. Later I found a surplus store that sells slightly smaller ones for 2$ each. I think I should have wound the coils myself, too, I'd just need to know how thick the wire is and how many turns, and what material to use for the core (if there is one). Well, next time I will.

Actually I think that with enough searching for low-cost parts, this thing can theoretically be built for under 100 EUR in parts (including µC, display and all). I wonder if there's any chance of getting it EMI certified...

Update: So, I finally got my final order sent out. Altogether about 150 EUR worth of parts, from 3 suppliers. I hope I didnt forget anything important :-) I decided to leave out the little 15V power supply for now, since I have lots of dc-regulated plug-casing-type PSU's around. I also looked at making a printed PCB but at over 40 EUR each, I'll save that for the next revision.

I'm still confident I can get everything into a PC power supply casing. From surplus stores I can get one with a temp-regulated fan... and just throw out the contents, and use the case and fan :-)

2.EDIT: Farnell sucks!!! They had the inductor listed as "min order 1 unit, in stock, delivery about 3 days, overseas processing fee 20 EUR". Now they called me and told me the min order is 10 units and it would take 8-9 weeks!!! Bah. I guess I'll have to wind my own, there's no way I'm gonna wait 8 weeks!