Doesn't cross-reg go negative on a typical flyback switcher? If you load the winding that makes the feedback, the drive goes up to the others.
Do PC supplies do some sort of averaged or compromise or nonlinear feedback?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Flybacks are a bit anomalous in that they won't work without a fair bit of leakage inductance--that's where the energy gets stored. With poor coupling, there's room for loading to affect different windings differently, sure.
Dunno. I only use them in PCs. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
In the leakage? Not magnetizing inductance?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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Well even with the dummy current on the 5V line, it has other problems. = The wire guage is too thin, the 12V is not as stable as some of the gra= phics cards like. One of them keeps dropping the clock speed, and anoth= er occasionally stops functioning. I may have to replace the three of t= hem with:
1 decent Corsair for the computer and one graphics card. 1 1kW 12V LED supply from China for the other two graphics cards.I'd prefer to buy it in the UK for speed of receiving it and more likely= to get something that actually works, but there aren't any here. There= are some in Germany but they've all sold out.
If anyone knows anywhere other than China that I can buy a 12V regulated= 1kW supply for a decent price, please let me know (the Chinese ones are= about =A338).
Mine is next to a PC, running one PC component. Which is why I sometimes feel like defenestrating it.
AIUI the energy is basically stored in the air gap, which is the source of the leakage inductance. But I've never designed a flyback, so I wouldn't want to be too dogmatic about that.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
In a flyback the energy is stored in the magnetizing inductance. You gap t he core to decrease the value of magnetizing inductance vs. the large, unre gulated value the magnetic material gives you. For a given FET ON time, V = L*dI/dt means that peak current increases proportional to the decrease in L. But since energy is 1/2*L*I^2, a smaller inductance means more store d energy.
The leakage inductance is the non-coupled inductance of each winding. For modeling the effect of leakage on transformers with multiple windings, Eric kson/Maksimovic have a really good paper:
Sure. But almost all the energy is stored in the gap, because the magnetic energy density is proportional to B*H. Perpendicular B is continuous across the interface, so H is 1/mu_R times higher in the gap. Since mu is in the thousands, the origin of the energy storage is the same as that of the leakage inductance.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
mu_R times higher.
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
*sigh*. Shouldn't post after having two glasses of wine. Magnetic energy density is |B|**2/mu, so since perpendicular B is continuous across the boundary, the energy density is mu_r times higher in the gap.
Cheers
Phil Hobbs (Still on vacation in a beach house on Anna Maria Island)
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I run many GPUs off a 4 way multiplexer card. There's nothing but 12V feeding those cards. There might be a small amount of current available through the USB cables to the cards, but it ain't for power. Maybe just communication.
A lot more in fact. The average decent CPU is 90W. The average decent GPU is 250W. That would be why they have 3 fans instead of 1.
Yeah the energy is mostly in the gap. The goal with the flyback transformer design is to have as much of this energy be transferred from one winding to another; by definition this is the mutual inductance.
Have a nice vacation. For warm weather I like to mix red wine with sprite and ice. Cheap wine of course...
The stock flyback is an irritating topology anyway and scales poorly. I don't think most beefy modern PC supplies use them anyway they use two-switch forward converters.
But the same statements wrt cross-regulation apply.
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Don't drink and derive. :^)
I'm going to pull out Erickson's book on SMPS's.. it got a long section on magnetics that I only skimmed. (who as a physics type, sees energy stored in the B-field... which is mostly in the gap..)
George H.
Thanks. When I have my druthers it's a G&T with Inverroche Verdant or Junipero gin and Fever Tree tonic, with a twist of lime holding a little umbrella. ;)
(My 15 minutes of fame arrived some years back when my flight-attendant daughter posted a photo of me in a Delta Sky Club with a little umbrella in my drink. The in-flight folks loved it.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
My MD suggested that quinine can prevent cramps, but she said that I'd have to drink a lot of tonic water to get much. A few bananas a week seems like a more pleasant therapy.
-- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
I haven't seen much from EVGA. I got a graphics card from them once and it was fine. They make other stuff then?
"Commander Kinsey" wrote in news:op.0gim98w6wdg98l@glass:
Motherboards, Graphics adapters, PSUs and a few other things. They actually took Nvidia and did some cards which were fully compliant wher other only had some of the elements. Look though their cards, they had some of the best and the other guys followed, and now all have high end cards with huge memoray arrays on them. EVGA was among the earliest to make high end Nvidia offerings.
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