On Wednesday, June 9, 2021 at 11:40:47 PM UTC+10, jla...@highlandsniptechnology.com wrote:
> This will have to work at up to 200 watts maybe; 48 in and out. 
> 
> Those surface-mount Coilcraft planar transformers are wonderful. 
> 
> https://www.coilcraft.com/en-us/products/transformers/planar-transformers/planar/pl300/ 
> 
> I suspect some air flow can sneak in between the flat kapton windings. 
> I guess I should include the leakage inductances, but they are tiny. 
> 
> The LTC gate drivers are a bit expensive but they work really nice. 
> And they have a Spice model! 

<snipped the .asc file>

The transformer model is a bit rudimentary.

The coupling between the winding is supposed to be perfect - "K1 L4 L5 1" when anything much better than 0.99 is a bit unlikely.

This does specify the leakage inductance.

It's relatively easy to measure leakage inductance - you just short one coil and measure the inductance of the other one.

It's actually in the data sheet  which says the primary inductance is 287uH (min) not 75uH and the leakage inductance 0.25uH (max).

For some odd reason, John hasn't included coil resistance - 7.2mR (max) - inside the inductance specification, and hasn't put in any parallel capacitance. The inter-winding capacitance is worth measuring too, and putting into the circuit model.

It's easy enough to measure the parallel capacitance - you just measure the self-resonant frequency of one of the coils. Most inductor data sheets include that.

The interwinding capacitance is even easier - a capacitance meter can measure it directly.

As a simulation, this does fall a bit short.

-- 
Bill Sloman, Sydney

This will have to work at up to 200 watts maybe; 48 in and out.

Those surface-mount Coilcraft planar transformers are wonderful. 

https://www.coilcraft.com/en-us/products/transformers/planar-transformers/planar/pl300/

I suspect some air flow can sneak in between the flat kapton windings.
I guess I should include the leakage inductances, but they are tiny.

The LTC gate drivers are a bit expensive but they work really nice.
And they have a Spice model!


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-- 

John Larkin      Highland Technology, Inc

The best designs are necessarily accidental.