Feasibility of a small custom 1W SMT DCDC transformer for qty 1000

[Psi]

I'm looking at the feasibility of replacing 4x isolated SIP package DCDC bricks with a small custom SMT DCDC transformer.
It would have 5 isolated windings, 1 in 4 out.

Just wondering how feasibility a custom transformer would be for a low volume product. We sell like 300 a year. but could maybe purchase 1000 transformers at a time. I know places like coilcraft can make custom transformers to order, but is that cost effective for this volume? 

What sort of price would you expect for a small SMT mount  5 winding 1W (total) power transformer. If I ordered say 1000?
The current DCDC bricks cost $1.5 each so we're spending $6 on them. 
Making the design simpler and more SMT less TH is an advantage, so having just one transformer instead of 4 SIP modules is an advantage even if it costs the same.  Probably not worth it if it costs more.

Thanks

[thm_w]

Get your rough specs together and ask for a few quotes on alibaba. https://www.alibaba.com/product-detail/ee10-smd-inductor-flyback-transformer-smps_1600529170703.html
https://www.coilcraft.com/de-de/products/transformers/dc-dc-transformer-worksheet/

I'm guessing coilcraft would be in the $3-8 range.
China <$2.

What is isolation voltage between secondaries?
Are you ok with possibly more losses if loads are imbalanced?

4 out means 8 wires which might require a larger core or maybe multiple small units?

[jbb]

Haven’t used them in a long time, but I think https://www.marquemagnetics.com/ is OK with moderate order quantities.

Magnetics manufacturers often have access to quite a large catalog of components like cores and bobbins and triple insulated wire that aren’t easily available in small quantities or from the usual distributors.

So I suggest you give them a briefing of what you want to accomplish (volume, operating freq, mag inductance, turns ratios, required isolation etc.) and see what they come back with instead of ‘please fabricate this exact design.’

[Psi]

so I suggest you give them a briefing of what you want to accomplish (volume, operating freq, mag inductance, turns ratios, required isolation etc.) and see what they come back with instead of ‘please fabricate this exact design.’

 

[tszaboo]

https://www.we-online.com/en/components/products/pbs/cm/pcd
I haven't used them for transformers yet and I don't know how good is the support outside the EU. Here its really good.

[temperance]

A Pulse P0585NL might work.

[Psi]

A Pulse P0585NL might work.

Yeah, that's the sort of thing I need, but could probably be lower power.  Also would need 1:2:2:2:2 winding ratio so i can do 5V to 12/12/12/12

[temperance]

A planar transformer will be a low cost solution. A small multi layer PCB will do the job.

Cores with the required size: less than €0.25 per piece, two required. Cores without air gaps are easy to obtain.
Core clamp: around the same price tag.
25 x 25 mm PCB, 6 layers: €0.55.
Or the same size with 8 layers : €0.7
Some pin headers (see next comment) to mount the transformer: €0.3
Mounting costs: unknown. But less work in comparison to the original solution if you ignore the driver and rectifiers. If you really want, you can make the transformer PCB into a surface mount component if it can fit onto a standard tray for TQFP's or something. (like a stamp with castellated sides)

Last but not least: some fun to implement.

It would have been nice if you stated the input/output voltage requirement. I think must people here where under the assumption that Vin=Vout.

[jbb]

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

[Psi]

It would have been nice if you stated the input/output voltage requirement. I think must people here where under the assumption that Vin=Vout.

In this case 5V in and multiple 12V out, but it is somewhat flexible. Could be 9V in and 10V out.   
But input has to be under 12V with some room for regulation and outputs needs to be 8-15V

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

[Jefferson.Lee]

It would have been nice if you stated the input/output voltage requirement. I think must people here where under the assumption that Vin=Vout.

In this case 5V in and multiple 12V out, but it is somewhat flexible. Could be 9V in and 10V out.   
But input has to be under 12V with some room for regulation and outputs needs to be 8-15V

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

Can you tell us about your detailed specifications, such as wire size, number of turns, core specification ER or EE and additional...
I might be able to help you in China.

[Psi]

It would have been nice if you stated the input/output voltage requirement. I think must people here where under the assumption that Vin=Vout.

In this case 5V in and multiple 12V out, but it is somewhat flexible. Could be 9V in and 10V out.   
But input has to be under 12V with some room for regulation and outputs needs to be 8-15V

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

Can you tell us about your detailed specifications, such as wire size, number of turns, core specification ER or EE and additional...
I might be able to help you in China.

Thanks for the offer, I don't have any spec yet, or looked into creating one.
I was just curious if it made sense to go down that path for lowish qty.

[jonpaul]

Planar cores are very fragile and costly. Long lead time.
Suggest find a stock transformer (Coilcraft, Pulse Engineering, Halo, etc. ) and adapt your ckt

If the app is to supply floating H br gate drivers, then both C-P-S and voltage rating between wdg are important

j

[mikeselectricstuff]

Planar cores are very fragile and costly. Long lead time.
Suggest find a stock transformer (Coilcraft, Pulse Engineering, Halo, etc. ) and adapt your ckt

If the app is to supply floating H br gate drivers, then both C-P-S and voltage rating between wdg are important

j

Quite a few in stock at Digikey

[temperance]

Planar cores are very fragile and costly. Long lead time.

I can obtain planar cores without an air gap in different sizes in >2K quantities for less than 30 cent @ Mouser. Here in the EU I can obtain the required size (oversized actually to make life easier) for less than 20  cent.

Fragile: just like any other ferrite core.

[temperance]

@ jonpaul

Dear Jonpaul, you often comment on various topics providing your opinion but you rarely provide useful information. If you read what has been been written, you will see that an off the shelf solution is probably not available and probably why the OP posted the question here.

[voltsandjolts]

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

Photovoltaic drive or SSR too slow?

[mikeselectricstuff]

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

Photovoltaic drive or SSR too slow?

Skyworks SI8751 is another very neat solution for isolated gate drive - faster than a PV isolator

[thm_w]

OP meant they are switching DC, eg DC-DC. 5V to 12V.
Nothing to do with gate driving.

[Psi]

If you’re making supplies for isolated gate drivers, then you’ll need to carefully consider winding-to-winding capacitance.

Yes, but only switching DC so na,

Photovoltaic drive or SSR too slow?

Skyworks SI8751 is another very neat solution for isolated gate drive - faster than a PV isolator

Is the Skyworks SI8751 actually useful for fast gate switching? I'm switching <200A split across 4 fets (DC load switch)

Looking at the datasheet, GATE On Impedance is 162k  and output voltage 10V.
Am I correct in assuming that using a SI8751 is equivalent to applying 10V to a FET gate through a 162k resistor ?

The price of the chip wouldn't save me much money but it would make things much simpler, which would be useful for other reasons.

[mikeselectricstuff]

Not super fast  - I use it for mains trailing-edge dimming of SOT-223 MOSFETS in a SSR configuration, for which it works brilliantly. For slow DC switching maybe it could be combined with a capacitor & voltage detector to get faster switching at the expense of latency

[voltsandjolts]

OP meant they are switching DC, eg DC-DC. 5V to 12V.
Nothing to do with gate driving.

I think the OP is looking for isolated DC-DC converters, for the purpose of making four floating power supplies for gate driving four high-power FETs at a low frequency (switching a DC 200A load). So discussion of other methods of gate driving is valid.

[Psi]

OP meant they are switching DC, eg DC-DC. 5V to 12V.
Nothing to do with gate driving.

I think the OP is looking for isolated DC-DC converters, for the purpose of making four floating power supplies for gate driving four high-power FETs at a low frequency (switching a DC 200A load). So discussion of other methods of gate driving is valid.

I have 4 DCDC modules powering 4 opto-fet gate drivers atm. Works great, just not very compact or elegant or cheap.  Also working on a discrete component non-isolated solution with one 12-24V DCDC. But always on the lookout for a new solution.

[voltsandjolts]

How much do your DCDC converters cost?
I see Mornsun have +15V/-9V DCDCs for IGBT gate drives at around GBP3.50
https://www.digikey.co.uk/en/products/detail/mornsun-america-llc/QA153-1509R3/16643920


How about reducing DCDC count from 4 to 1, by having just one 200A IGBT?
https://www.digikey.co.uk/en/products/detail/infineon-technologies/IKQB200N75CP2AKSA1/17399196
and a good gate driver...
https://www.digikey.co.uk/en/products/detail/infineon-technologies/1ED3121MC12HXUMA1/14311597

[mikeselectricstuff]

How much do your DCDC converters cost?
I see Mornsun have +15V/-9V DCDCs for IGBT gate drives at around GBP3.50
https://www.digikey.co.uk/en/products/detail/mornsun-america-llc/QA153-1509R3/16643920

Plenty of similar isolated DC-DCs at LCSC for under a dollar :
https://www.lcsc.com/products/Power-Modules_634.html