Same model, different PPFC chokes. Are they real? (MPT-350P)

[Wester547]

Re: Same model, different PPFC chokes. Are they real? (MPT-350P)

Do power supplies that use general purpose caps have a problem using low ESR caps with a higher ripple rating (but capacitors that aren't polymer and thus possibly mismatching in capacitance)? Or does that go for half-bridge PSUs with older designs such as the aforementioned two-transistor 5VSB circuit?

Rather, if a power supply has general purpose capacitors in some outputs and low ESR ones in others, does it mean that only general purpose capacitors are ever suited for recapping general purpose capacitors that fail in any PSU?

[momaka]

Re: Same model, different PPFC chokes. Are they real? (MPT-350P)

Do power supplies that use general purpose caps have a problem using low ESR caps with a higher ripple rating

Depends on how low you go. If you take just entry-level low ESR caps (i.e. Panasonic FC, Nichicon PW, and Chemicon LXV/LXY/LXZ) or the next level lower ESR (Nichicon HE, Chemicon KY), it should be fine. Further lower ESR (Nichicon HD, Chemicon KZE, Rubycon ZL, Panasonic FR) will likely work fine too, but the output ripple may be higher than with the general purpose caps. And then there's Panasonic FM, which is just at the edge of what a PSU would accept as low ESR and still work. Anything with lower ESR than Panasonic FM is usually motherboard-grade low ESR and may cause problems in some PSUs.

2-transistor 5VSB circuits are a special case. They don't have a PWM controller and they *usually* work fine even with motherboard-grade caps.

Rather, if a power supply has general purpose capacitors in some outputs and low ESR ones in others, does it mean that only general purpose capacitors are ever suited for recapping general purpose capacitors that fail in any PSU?

No.
Like I mentioned above, SMPSs will work fine with low ESR caps most of the time as long as you don't go too low.

[goodpsusearch]

Re: Same model, different PPFC chokes. Are they real? (MPT-350P)

I think they are designed for (entry level) low esr caps. They put general purpose caps to reduce cost, but that's another story.

[momaka]

Re: Same model, different PPFC chokes. Are they real? (MPT-350P)

I think they are designed for (entry level) low esr caps. They put general purpose caps to reduce cost, but that's another story.

Very true, actually.

[Behemot]

Re: Same model, different PPFC chokes. Are they real? (MPT-350P)

Well, you call it entry-level, I call it PSU type. Many manufacturers actually talk about them being suitable for switching power supplies and sometiems even PSU-type

Below them are general purpose (many of which couldn't even handle 100 kHz so they should not even be in PSU!), above them VRM suitable. Sure, over time also caps fiting between these cathegories came.

As for the main cathegories, you usually are OK just with knowledge of which type goes where (well latelly that is also not true as they not only use general purpose caps on place of low-ESR, but they also DESIGN controlling circuits for GP crap from the very begining). As for the models between main types, you really better read datasheet and compare with what was inside before.