Trying to understand a Cuk converter

[gbugh]

I can't see how this design allows 600W of power to transfer across a toroid transformer the size of a quarter when the switching frequency is only 68.5KHz:

**broken link removed**

Is this article in error?

Is it really having a lot of VHF or UHF ringing that gets the power through the transformer?

George

 

[ALERTLINKS]

It shows winding containing 14 turns only. Wire diameter looks appropriate for 3A current. The width of the core is not obvious. For only 14 turns of single layer, a small core can be used. For higher power, multiple cores can be stacked. You can calculate cross section area of toroid for inductor containing 14 turns and operating at 68KHz.

 

[schmitt trigger]

I can't explain either how the circuit works....But the article's author is none other than Dr. Slobodan Cuk, a world-renowned expert in the power conversion field.

I'm not saying that he couldn't be exaggerating some performance claims, but it is unlikely.

 

[mtwieg]

Yeah it's not actually a Cuk converter, but if the article is written by Cuk himself then odds are it's legit.

I'm sticking on one claim:

The Three-Phase Bridgeless PFC converter extension provides unity power factor operation, low total harmonic distortion, and eliminates the large output DC storage capacitor, yet results in small output ripple voltage

Pretty sure there's no physically possible way to trade off PF, output ripple, and output capacitance, regardless of the topology.

 

[schmitt trigger]

Actually the article is quite vague, I believe this is on purpose.

 

[gbugh]

He writes about a IXTH12N1200 and a IPW66R037C6 and I can't find either available anymore. I think they worked too well so they were asked to remove them from the market.

part 1 **broken link removed**
part 3 **broken link removed**

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"You can calculate cross section area of toroid for inductor containing 14 turns and operating at 68KHz."

Is there an online calculator for this?

Maybe the core can be so small because it has very high relative permeability and yet doesn't saturate?

I don't see a gap in it so it still seems strange to me.

 

[ALERTLINKS]

https://www.transphormusa.com/sites/default/files/transphorm/news/Totem-pole paper_0.pdf