A little tip on coupled inductors in group regulated PSUs
I was rummaging thru my inductor box for suitable candidates for a little project (a battery powered, blocking oscillator type SMPS - ie a joule thief). I'm too lazy to wind both of the windings myself, so i was looking for one with a suitable main winding already on it.
While measuring with my LC meter i noticed that all coils extracted from 3.3v outputs, regardless of size measured about the same - 30 to 40uH. I was curious about the coupled inductors too, so i measured all the coupled inductors i hadn't unwound yet, ranging from tiny ones from dirt cheap chinese knockoffs to large ones from properly built PSUs.
Guess what? All of them had the 5v winding at ~10uH and the 12v winding at ~60uH. That makes sense - the Chinese don't have the brains to reconfigure a design, they just copy the same thing in various sizes, depending on which segment they're marketing towards... Practically, the only difference between these inductors is the amount of current they will handle before saturating and becoming ineffective. That, and the tiny ones might burn up because of the high electrical resistance of the thin gauge wire they're wound with.
So there you have it - if you have some lying around, you CAN put in a larger coupled toroid inductor to upgrade a cheap PSU, without disturbing the control loop. Just keep in mind that ripple suppresion will remain the same at low power, (unless you upgrade the caps too), but the maximum power the PSU can deliver before ripple goes out of spec will be increased. You may find that something blows up before the ripple goes out of spec tho.
Happy swapping.
While measuring with my LC meter i noticed that all coils extracted from 3.3v outputs, regardless of size measured about the same - 30 to 40uH. I was curious about the coupled inductors too, so i measured all the coupled inductors i hadn't unwound yet, ranging from tiny ones from dirt cheap chinese knockoffs to large ones from properly built PSUs.
Guess what? All of them had the 5v winding at ~10uH and the 12v winding at ~60uH. That makes sense - the Chinese don't have the brains to reconfigure a design, they just copy the same thing in various sizes, depending on which segment they're marketing towards... Practically, the only difference between these inductors is the amount of current they will handle before saturating and becoming ineffective. That, and the tiny ones might burn up because of the high electrical resistance of the thin gauge wire they're wound with.
So there you have it - if you have some lying around, you CAN put in a larger coupled toroid inductor to upgrade a cheap PSU, without disturbing the control loop. Just keep in mind that ripple suppresion will remain the same at low power, (unless you upgrade the caps too), but the maximum power the PSU can deliver before ripple goes out of spec will be increased. You may find that something blows up before the ripple goes out of spec tho.
Happy swapping.
Well, that's where this Enermax Liberty ECO 400 Watt PSU came from. Like I mentioned, it had cut cables and many bulged caps on the DC output side. I stripped a few cables and did a quick temporary recap with whatever junk (but still reading OK) caps I could find, then performed a basic power test – the PSU passed. 
Thus, I knew I'd eventually go around to repairing it. One year later and we're here. 
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