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Maybe someone could show me a site where I can figure this out on my own... However, I have 37V out, and I need it to be 30V.... It's from a rectified AC circuit and I have a 12000uF capacitor in parallel... I saw this: I think now that the capacitor is helping regulate it as is, the regulator will help bring down the voltage to 30 and keep it extremely smooth.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I use LM338 quite a lot, and find them excellent. Take care you have a good greased heat sink mind!
Take care you read the section on protection diodes in the application notes, and just copy their reccommended circuit. Can't go wrong so long as you are happy with the 5A max - 7A peak that this device is able to provide.
It's always a good idea to post a circuit diagram - schematic - of what you have already done, or what you are thinking of doing, so other members can see more clearly what it is you're trying to do, and so give much better advice.
Ok, so this is the reason I am possibly needing the 37V to go down to 30V.
Harry - I cleaned the mosfet and its still burning somewhat... I can't see any problems as of yet, actually, no other parts are having the same troubles, and on the other side (as you can see, there is a replica of the whole arrangement) the other mosfet stays cool (does not warm up at all). I don't even understand WHY a mosfet would get hot? A quick look at the mosfet shows bubbles in the metal, like it was expanding. The weirdest part is that even replacing it with a BETTER completely new mosfet is giving me the same results.
Not to mention that this has not happened in the past 50 times testing this circuit.
I will have to examine more, but I would like some insight on why a mosfet would get hot (to the point of slight smoke, and expanded metal) and if lowering the voltage is really necessary?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
OMG, it's my old flyback driver back from the dead!
I don't see any reason why it shouldn't run off 37V, as long as your MOSFETs and diodes are all rated higher than that. If FETs have started burning up, it's probably because some other component has failed. Maybe D3 or D6 has failed short.
When you say "the metal expanded", FETs have some solder inside and on a really serious overload this can melt and run out.
OMG, it's my old flyback driver back from the dead!
I don't see any reason why it shouldn't run off 37V, as long as your MOSFETs and diodes are all rated higher than that. If FETs have started burning up, it's probably because some other component has failed. Maybe D3 or D6 has failed short.
When you say "the metal expanded", FETs have some solder inside and on a really serious overload this can melt and run out.
Haha, yeah I like it by the way, Should this circuit be efficient? Like for long periods of time? Thats what I am hoping for. Thnaks for the advice, I will check the diodes again, but they seem fine. something I just realized is that R3 was ALL the way up, I think the mosfet was not able to bare the 10V stress (even if its oscillating) I tuned it down to abotu a volt (for now, I will work it up slowly) just to see if that helps, I guess The mosfets could use a heatsink :P
As for "expanding" The metal was bubbly, on the exterior, nothing came out of it..... yet :P
P.S. - My mosfets and diodes are all rated double the recommended values... so :)
Edit - so that would make no sense though, the heart of the problem is the fact that the tl494 is not oscillating properly -_- Because of that, the mosfet is just getting redic hot... even when there is only 1V by lowering the R3 there is still heat. The other side of the circuit, its never producing anything, because there is no oscillations, therefore its never voltage to the other half -_- I checked... I double checked.... ARGH?
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Voltage Regulation/circuit question (updated)
