Small xformer with less than 6mm build height

Hi

I am looking for a small transformer (preferable SMD), than has a build height of less than 6mm and an isolation voltage of 2.5kV.

I am designing a 20V/3.3V 150mW forward converter and have very little space available.

I found these:

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(is less than 60cents)

But its a little to the tall side

Any other candidates?

Thanks

Klaus

Reply to
Klaus Kragelund
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of less than 6mm and an isolation voltage of 2.5kV.

available.

If you find nothing else, grind away the bottom to get your 6mm. I downloaded that PDF, used *400 to view, did a screen capture,print and measured. If that whole down-hanging "U" was removed so that it was co-planar with the rest of the bottom as shown in the side view, one would have a package about 5.68mm high.

Reply to
Robert Baer

That datasheet disclaims the isolation voltage. says not ask it to withstand more than 60V on a permanent basis.

available.

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(digikey)

it says 4A saturation current in the table but the graph dives at 10mA I'm not sure how to interpret that. And no claims of isolation.

why a forward converter at such low power?

-- ?? 100% natural

Reply to
Jasen Betts

Yes, but we may be able to talk to them to use triple isolated wire instead= , so the isolation voltage is increased.

space available.=20

I have looked at those, but I need 3 windings and a pot core like that will= most likely have poor coupling, so high leakage inductance. They are reall= y nice though for gate drivers etc.

10mA is the saturation of the magnetising inductance, the 4A figure is the = transferred current which does not increase magnetising current, but causes= temperature rise due to winding resistance (normally the limitation of a x= former is due to the temperature rise)

I need high efficiency, target is >90%

Regards

Klaus

Reply to
Klaus Kragelund

ad, so the isolation voltage is increased.

e space available.

ll most likely have poor coupling, so high leakage inductance. They are rea= lly nice though for gate drivers etc.

e transferred current which does not increase magnetising current, but caus= es temperature rise due to winding resistance (normally the limitation of a= xformer is due to the temperature rise)

I once had a similar requirement, they may have what you need: from their website

SUMIDA CORPORATION is a leading coil company. ... CDRH28D07,Low Profile ...

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There was a custom transformer house I used about three years ago, can't find them

At that voltage you may have trouble with creepage.

Reply to
Robert Macy

Planar transformer. You didn't mention your footprint requirements, but the smallest planar E cores from Ferroxcube are something like 14 mm wide. You can make as much creepage clearance as you want, and goop up the board with silicone or epoxy for extra insulation.

Come to think of it, getting enough turns for 20V input might be challenging (5 mil traces?), then again you won't need too many turns to get that step-down ratio, and you could run at a high frequency (>500kHz?) to keep the turns down again.

Downside is the cores are about 2mm thick, above and below the board, which is something like 2mm in the E shape, for an overall height of about 6mm, almost centered on the board axis. You might not have room underneath.

OTOH, you could make a teensy board with pins that fits into the core, and mount that on your main board. Now you get Hi

Reply to
Tim Williams

so the isolation voltage is increased.

available.

most likely have poor coupling, so high leakage inductance. They are really nice though for gate drivers etc.

transferred current which does not increase magnetising current, but causes temperature rise due to winding resistance (normally the limitation of a xformer is due to the temperature rise)

While triple build does give better overall stand-off, if you really need continuous HV standoff rating, then go for the following (from MWS Wire Industries): Temperature Class: 240° C Insulation Type: Polyimide-ML MWS Code: ML NEMA Specification: MW 16C Federal Specification: JW1177/15 IEC Specification: 317-7 Insulation Characteristics: ML is a film coated magnet wire made with polyimide resin. It is a Class

240° C thermal life insulation with exceptional resistance to chemical solvents and burnout. It will operate at a temperature up to 240° C. The outstanding cut-thru of over 400°C and its ability to withstand excessive overloads extends the use of magnet wire in extreme conditions. ML is unaffected by prolonged exposure to varnish solvents and it's compatible with virtually all systems. General Applications: Fractional and integral horsepower motors, high temperature continuous duty coils and relays, hermetic and sealed units, heavy duty hand tool motors, encapsulated coils.
Reply to
Robert Baer

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