Planar transformer Question

I have to design a power supply with 600v isolation, 12 outputs are 15v at 10mA per channel.

I was wondering if the typical strategy with this type of construction is to use buried vias.

thank you Bob N9NEO

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600 volts isolation between the secondaries? At your power levels, you might be able to use single-turn secondaries. But you are probably talking 27 or so pins on one transformer, unless you use several transformers.

I do a lot of isolated-channel stuff, with individual DC/DC sips or transformers. Sometimes the power is also a clock for a delta-sigma ADC or something.

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A single planar transformer would be interesting next time.

Coilcraft makes some very pretty planar transformers, but I don't think they can do that many windings.

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They go up to something insane like 350 watts.

John Larkin         Highland Technology, Inc 
picosecond timing   laser drivers and controllers 
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John Larkin

Sounds like gate drivers... :)

I'd suggest limiting that to maybe 2-4 outputs per core, using more and smaller cores (they can be very small indeed at that power level).

You can dog-leg outside turns to avoid too much layer waste, but if cost is no object and space is critical, buried vias (and lots of layers -- upwards of 16 is easily encountered) will help with that.

UL rated FR-4 should handle that voltage with typical (10 mil?) prepreg layers, so the voltage shouldn't be a problem.


Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
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Tim Williams

I have looked into similar issue. We got the response that 0.4mm solid insulation (0.4mm prepeg) is needed for reinforced insulation, so unless you olan for very thick PCB 2 outputs is possible

If however you only need functional isolation for a gatedriver, that's another story



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Klaus Kragelund

Blind vias are something you try to avoid under most circumstances.

In thick stack-ups, they can be simulated by splitting the stack and introducing a thin-film layer, for a multiple stack, but creepage applies if the layer isn't impregnated.


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