13.8V 15A offline SMPS w/ PFC - Page 2

Boris_The_Blade · 29th March 2008, 06:58 PM

iron powder cores are color coded so you can figure what material they are. Then go to the magnetics inc website and download there software and plug in the appropriate core part # (measure core size to find part #), number or turns and wire size. You can play with the output current to then see core and wire losses and saturation effects by the drops in permeability. The software will also tell you the expected lifespan.

switchmodepower · 29th March 2008, 08:18 PM

Quote:

Originally posted by djQUAN
it's the long term effects that I know of. I have read here many times that a hot running core loses its capacity to store energy or something like that.

maybe Eva or others could chime in if I'm wrong?

Yes running them hot reduces reliability so it's alway good to run them cool- just like anything else. I never said it's good to cook eggs on them.

djQUAN · 30th March 2008, 03:39 AM

Quote:

Originally posted by switchmodepower

Yes running them hot reduces reliability so it's alway good to run them cool- just like anything else. I never said it's good to cook eggs on them.

but you said...

Quote:

Originally posted by switchmodepower

The curie temp for magnetics is much higher so you can run them super hot. Try to find out what core is used and look at the specs.
It looks like a powered iron core and most likely it is since they are cheaper as compared other materials.

so I thought that's what you meant.

oh well, still at the bench. will probably keep the windings the same. just need to add a current limit at the output to keep it within 15A max.

switchmodepower · 30th March 2008, 01:53 PM

It depends on your goals. There are trade-off. If you want an efficient ps then you optimize for low losses. If you just care about not going "BAM" then you can run them hot. I personally would never go about 125C but in certain circumstances you may need to run close to the max rating of the wire/core.

Check out http://www.micrometals.com/material/Coreloss_aging.html

They discuss core loss vs time, temp, and operational hrs. In one instance they state that in that given circumstance, core, etc you can operate at 100,000hrs at 125C. Now you need to know all operational parameters especially what core you have and the flux density since the core losses change with temp as shown.

Good luck

djQUAN · 30th March 2008, 02:26 PM

core is #52 material (T106-52) with 24turns of #16 wire. wire is the type with insulation that burns off when soldered.

there is lots of airflow in the inductor area so I guess I could stay with the stock winding.

at 15A the inductor stays at about 50-60degC so I guess I'm safe here.

now, onto the current limiting circuit!

djQUAN · 30th March 2008, 03:55 PM

added a few resistors and a transistor and now I have a current limit.

set to 15A fixed.

just did a 10minute full load test and it got really hot. but it didn't blow up.

now, to look for my notes and post everything I did in this PS.

EWorkshop1708 · 31st March 2008, 02:44 AM

Very, very awesome. That power supply will be useful.

Have you tried adding caps for more output filtering?

What do you think it would take to modify one for +/-30V or so?

luka · 31st March 2008, 06:29 AM

Hi

Yes you can, supply doesn't care what it has to do, you change trafo and output stage, FB and you are done

djQUAN · 31st March 2008, 11:43 AM

it isn't that easy. I had little difficulty because I used an existing winding and didn't use the others. rewinding the trafo is another issue because this is a forward converter (or I think it is, or it's either a flyback type?

) and the transformer characteristics are critical.

if it is push pull, it is easier to change the output voltage by changing feedback circuit and trafo secondaries.

30th March 2008, 01:53 PM	#14
switchmodepower diyAudio Member Join Date: May 2007	It depends on your goals. There are trade-off. If you want an efficient ps then you optimize for low losses. If you just care about not going "BAM" then you can run them hot. I personally would never go about 125C but in certain circumstances you may need to run close to the max rating of the wire/core. Check out http://www.micrometals.com/material/Coreloss_aging.html They discuss core loss vs time, temp, and operational hrs. In one instance they state that in that given circumstance, core, etc you can operate at 100,000hrs at 125C. Now you need to know all operational parameters especially what core you have and the flux density since the core losses change with temp as shown. Good luck __________________ http://www.switchmodepowersupply.net

31st March 2008, 06:29 AM	#18
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	Hi Yes you can, supply doesn't care what it has to do, you change trafo and output stage, FB and you are done __________________ home page @ http://www.classdaudio.tk/ @ 24/7 all year long I FEEL SLOVENIA

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29th March 2008, 06:58 PM	#11
Boris_The_Blade diyAudio Member Join Date: Mar 2007	iron powder cores are color coded so you can figure what material they are. Then go to the magnetics inc website and download there software and plug in the appropriate core part # (measure core size to find part #), number or turns and wire size. You can play with the output current to then see core and wire losses and saturation effects by the drops in permeability. The software will also tell you the expected lifespan.

30th March 2008, 02:26 PM	#15
djQUAN diyAudio Member Join Date: May 2004 Location: manila	core is #52 material (T106-52) with 24turns of #16 wire. wire is the type with insulation that burns off when soldered. there is lots of airflow in the inductor area so I guess I could stay with the stock winding. at 15A the inductor stays at about 50-60degC so I guess I'm safe here. now, onto the current limiting circuit!

30th March 2008, 03:55 PM	#16
djQUAN diyAudio Member Join Date: May 2004 Location: manila	added a few resistors and a transistor and now I have a current limit. set to 15A fixed. just did a 10minute full load test and it got really hot. but it didn't blow up. now, to look for my notes and post everything I did in this PS.

31st March 2008, 02:44 AM	#17
EWorkshop1708 diyAudio Member Join Date: Nov 2004 Location: Florida	Very, very awesome. That power supply will be useful. Have you tried adding caps for more output filtering? What do you think it would take to modify one for +/-30V or so?

31st March 2008, 11:43 AM	#19
djQUAN diyAudio Member Join Date: May 2004 Location: manila	it isn't that easy. I had little difficulty because I used an existing winding and didn't use the others. rewinding the trafo is another issue because this is a forward converter (or I think it is, or it's either a flyback type? ) and the transformer characteristics are critical. if it is push pull, it is easier to change the output voltage by changing feedback circuit and trafo secondaries.