Gate drive transformer for LLC with poor coupling?

[cupoftea]

Hi,
The attached pics show a Tridonic 100W LED driver (TALEX LCA)

Its a Boost PFC followed by a Synchronous half bridge LLC.

What is the little ferrite 2-coil device in approx. the middle of the board? (shown best in "LLC2__" picture)
("LLC5__" shows its pins on the bottom layer)
Sorry , I only had 5 mins with it and not enough time to rev eng it.

One of its pins connects to the source of the top primary side FET.

I presume its a high side gate drive transformer, and the poor coupling between the coils doesn't matter since its an LLC.?

Also, why are the Y caps not near the mains connector?...they can be seen downstream of the Boost PFC output caps, right by the two pllel resonant inductors.
Also, what is the Xitec DG2181AA?....no datasheet on the web.

We wish to possibly buy this product and so will be looking to gain a better understanding of it.

Talex 100W LED driver

https://resources.tridonic.com/PDB/Ressource/GroupPdf/en/Driver_LCA_100W_24V_one4all_SC_PRE_24789.pdf

 

[betwixt]

I think you may be thinking it uses a different topology.
The two blue 'Y' caps are I think part of the output stage, not mains filters. The real filters are on the left side of LLC1__.jpg btween the grey connector and choke.

Brian.

 

[cupoftea]

Thanks, though the 2 yellow things on the LHS of LLC1 are MOVs.
Not the two box caps, but the two blue radial caps in LLC2__ are Y caps, and have the Y cap demarkation on them.

 

[Easy peasy]

you need to take much clearer photo's of the magnetic you are interested in

 

[betwixt]

SMPS isn't my strong point but why shouldn't Y rated capacitors be used elsewhere?

What is the light blue box near the grey connector?
In my mind I see (in LLC1) AC enters on the left,
some filtering using the light blue/grey capacitors and choke,
PFC stage,
Some kind of switching supply with inductors and those Y capacitors at its output,
presumably rectifiers and big electrolytics at the right.

Brian.

 

[cupoftea]

What is the light blue box near the grey connector?

Its an X2 capacitor, and yes as you know, your explanation is correct of the general stuff in there.

you need to take much clearer photo's of the magnetic you are interested in

Thanks, yes ill see if i can get it back.....its a small transformer with a bobbin with winding width split equally by a "wall"...there are multiple turns either side....and it looks like the same number of turn in each section. I cant see any use for anything remotely like this in an LLC.....other than as mentioned, possibly its a gate drive transformer where the poor coupling doesnt matter because its LLC.....maybe its just cheaper to make them like this.?

Also, Y2 capacitors should preferably be as near the mains connector as possible...as they are part of the common mode filter, and one wouldnt want emissions "jumping round" the Y capacitor and avoiding it so to speak. In the position seen, the emisssions could use surrounding tracking and components to avoid the Y capacitor, and go back into earth without having been filtered down.
Not only that, but the Boost PFC, even though QR, is likely to generate more common mode noise than the LLC, so the y caps should be upstream of the PFC.

 

[FvM]

If the blue caps are not LLC caps, where are they?
If blue ceramic caps C46/Cxx are Y-capacitors, they are most likely connected between primary and secondary.

--- Updated Sunday at 9:55 PM ---

Also, what is the Xitec DG2181AA?....no datasheet on the web.

DGD2181 ?