Electronics > Projects, Designs, and Technical Stuff
ATX Flyback Transformer
engrguy42:
Don't ya just love how these threads always seem to wander off into "I'm smarter than you" discussions of irrelevant pseudo-factiods? :D
Geez people. The ultimate manufacturer's name, wrapping tape color and perfectly accurate transformer type are irrelevant. At some point I'll probably reverse engineer this thing to find out how it's configured, but at this point it's irrelevant since I'm looking only for the transformer characteristics.
So, back to the question of the thread...
I think the reason why my coupled inductor/flyback transformer/whatever the f*** you want to call it is giving no secondary voltage output at low frequencies is due to the fact that the waveform generator output impedance is 50 ohms, and the inductive reactance of the inductor drops below around 1kHz. And around 400Hz the measured volts drops to about 50%, which implies that it's like a 20mH. Cool, so now I can model it.
Though I'm sure everyone already knew that... :D
wraper:
--- Quote from: engrguy42 on June 16, 2020, 10:29:14 am ---wrapping tape color and perfectly accurate transformer type are irrelevant. At some point I'll probably reverse engineer this thing to find out how it's configured, but at this point it's irrelevant since I'm looking only for the transformer characteristics.
--- End quote ---
It's very relevant. Because it directly affects how transformer was made. You cannot simply take it and use for different type of converter. Say flyback transformer is not suitable for bridge or forward topologies, even if you rewind it.
T3sl4co1l:
Close -- you want the 70.7% point, that's equal impedance magnitudes. At 50%, it's 1/sqrt(3), or 50/sqrt(3) ohms, or 11mH.
That's pretty high so I'm thinking this board had filter chokes on the secondary side, i.e. it's a forward converter. :-+
Tim
engrguy42:
Well after a bit of research I think I found a schematic for a very similar 450watt ATX power supply, and it appears that the two secondaries of this transformer are for the 12VDC and 5VDC, and they tap off the 5VDC to get the 3VDC. And a coupled inductor between the 12, -12, and 5VDC. :wtf:
FWIW, there's also a separate transformer listed as a flyback converter for the bias and 5VDC standby. And a 3rd transformer for the gate drive.
Anyway, as you can see the secondaries of this transformer have a crap-ton of Schottky's on a big heat sink. Anyone know what those are for?
These things are so freakin' complicated...
Buriedcode:
--- Quote from: engrguy42 on June 16, 2020, 02:10:20 pm ---Anyway, as you can see the secondaries of this transformer have a crap-ton of Schottky's on a big heat sink. Anyone know what those are for?
These things are so freakin' complicated...
--- End quote ---
Maybe start at the basics of the topology. The fact you used 60Hz on a ferrite transformer shows you've made assumptions that aren't true (and worked that out!).
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