well still doing the smps part of my fan controller i encountered a little problem.....dont know if it's the transformer, that's why i'm here
, but something make my mosfet heat a lot and that means bad efficiency, aka sub 50% with little loads.
i used a smps transformer from a 200w atx psu, just the opposite way, so i switch the 12V input, and use the 200v input as my output, flyback alike.
pictures:
**broken link removed**
**broken link removed**
**broken link removed**
and the oscilloscope screenshots (gate voltage)
**broken link removed**
**broken link removed**
**broken link removed**
the sg3525 drives the mosfet directly, as you see about 130ns rise and fall, the grounds are super reinforced, from "main power" (12V 2A regulated psu) goes to LC and then to drain, source to ground, then secundary is rectified and referenced to ground....
the thing is, as said above, the mosfet gets hot, with a 12V 0,55A load (cant even handle 6W u.u), it drains about 1,34A from the 12V psu, the transformer doesnt get hot at all.
Tried varing the switching speed from 50k to 150, with very little change in efficiency, with less load it reahes about 74% (150mA 12V output)
is it all switching losses or am i doing something wrong, cause the atx psu i took the transformer from didn't had problems at all delivering 12V 5A. or is it because it doesn't work to rise the voltage?
i'm really lost here, even conecting it directly to a 12V 12Ah battery didnt change a thing, only increacing the frecuency to about 80khz seemed to make it output more power but even with the batery i coundln't get more output than with the 2A psu.....
the only thing i think could be a problem are the little bumps after opening the mosfet.....but is tit because of that?