Sepic converter and coupled inductors

[Flyback]

The following article states how adding leakage inductance to a coupled inductor sepic converter can reduce the RMS inductor currents…
Do you agree that the article is like telling people to get to the surface to breath when diving, without telling people that they must rise slowly in order to avoid the bends…in other words, no information is better than “not enough”?

https://www.powerpulse.net/techPaper.php?paperID=153

However, “A little knowledge is dangerous” and the article fails to mention that adding leakage alone is not enough, and indeed can cause more problems if not done properly.
-if significant leakage is added, then there is a danger that the leakage inductance and the sepic capacitor will cause severe ringing in the inductor current. Such ringing will need a RC snubber to be placed across the sepic capacitor. The R(snubber) should be sized as per SQRT{L(leakage)/C(sepic)}.
The C(sepic) should then be sized as 1/{2*pi*f*C(cepic)}
..where “f” is the resonant frequency of C(sepic) and L(leakage).
This particular ringing only occurs if the duty cycle exceeds 50%.
This ringing is related to the feedback loop, and does not occur if the sepic is run “openloop” (with a fixed duty cycle). If the L,C ringing frequency is too near the feedback loop frequency,then that’s what sets off this ringing.
The power rating of the R(snubber) depends on the amount of transient activity on the output…..with much transient activity, this resistor will need a higher power rating.
The sepic capacitor shown in the schematic of the above artcle is too small, and should be sized at 18uF, which ensures that the ripple voltage on the C(sepic) is less than 5% of the input voltage.

 

[ronsimpson]

I have only used coupled inductors that are tightly coupled. (coilcraft) or (hand wound)
For the SEPIC capacitor: I use a large cap (in part) because the cap needs to handle large current.

 

[Flyback]

Thanks,
I have written a document stating why the ti.com article below (and of the first post) is rather "wide of the mark", in its claim about the usefulness of loosely coupled sepic inductors.

Article concerning loosely coupled sepic inductors:
**broken link removed**

Attched is the document, as well as the LTspice simulations which prove what my document says is correct....they are the simulations of the sepic converters discussed in the ti.com article (both loosely coupled sepic, and tightly coupled sepic)

 

[WTP Pepper]

For tightly wound coils, use Litz wire.