smd transformer trouble

[kripacharya]

i need a 1:15 or higher ratio smd transformer. primary >=10uH, size ~ 5-6 mm or less.
of course the cost has to be zero ideally, or not more than $1.2 at most
operating freq is around 50-100Khz, and the voltages are of course around 100v, 1000v

All i can find is photoflash transformers which are always 1:10 ratio.

anyone with any ideas ? i'd be grateful...

 

[FvM]

The chances to find a catalog part with the requested specification are rather small, I think. Insulation strength will be most likely critical, I guess you'll want to be more specific than the sloppy specification "of course around 100v, 1000v".

I suggest to fully specify and calculate the imagined transformer to find out if it's feasible at all.

 

[kripacharya]

be more specific than the sloppy specification "of course around 100v, 1000v".

I suggest to fully specify and calculate the imagined transformer to find out if it's feasible at all.

Haha yes i see what you mean. The spec of ~ 100v/ 1000v was for primary/ secondary capability, and of course V-isolation has to be commensurate.

good news is that i think i found one which seems to fit the bill - Coilcraft CJ5143-AL. Pricing though only matchs if i go to 1000's of units bulk purchase, which is fine.

Now a 2nd source for something similar would be great. I also found Sumida #CEEH54/tw, which is lower on the max volts, but they don't have it off- the- shelf anyhow.

Would you have any other suggestions ?

 

[FvM]

The Coilcraft transformer isn't bad. It's not clear to me if 350 V operation voltage is sufficient for your application. The least, apart from existing insulation strength standards, would be to guarantee partial discharge free normal operation, otherwise the lifetime expectation is very poor.

 

[kripacharya]

350 V operation voltage is sufficient for your application. The least, apart from existing insulation strength standards, would be to guarantee partial discharge free normal operation, otherwise the lifetime expectation is very poor.

thats true. i'm running this upto 600-750v on the secondary and it's ok so far. but i know i'm pushing my luck, hence the search for a better component.

 

[FvM]

It's quite understandable why Coilcraft won't specify a higher dielectric strength of the transformer than needed in the dedicated application, even it can be possibly achieved.

So the first step would be to check with a test voltage appropriate for 700V operation voltage. As said, partial discharge free operation is essential for long term reliability, it can be easily determined for interwinding insulation, but not so easy for intra-winding.

I imagine, that class 1 enamelled wire (1UEW) or similar material must be used to guarantee the higher dielectric strength. Unfortunately, the copper fill factor is considerably lower and also the minimal conductor diameter is restricted.

 

[rera1000]

hello

i think u will get the required transformer in digikey.


https://www.tdk.co.jp/tefe02/e6813_atb3225.pdf

u can have a look the link above .

 

[kripacharya]

hello

i think u will get the required transformer in digikey.


https://www.tdk.co.jp/tefe02/e6813_atb3225.pdf


u can have a look the link above .

Thanks for your interest, but I wanted > 1:15 turns ratio. Digikey doesn;t have it in the size i need.