# PMP8740: Transformer design and datasheet

Part Number: PMP8740

Hi,

Kindly provide detailed datasheet for T4(Main Fb Transformer) of PMP8740. Other thread contains datasheet, but that was not sufficient for making transformer.

It does not contains layer stackup, wire size and number of wires etc.

Also request you to help in design 60V & 110V (separate )output, 330V to 400V input transformer. I have excel design tool, but not have enough confidence to design on my own. it will help to have verification from you.

Regards.

Vikas Dabas

• Hi,

Power transformer details.

I need turn ratio like 19:2:2 or something like that. i do not know if secondary has two windings of 1 turn each or two turns each

19:2 = 19:2:2 or 19:1:1.

Please confirm. also kindly measure and provide exact primary and secondary and leakage inductance.

also confirm litz wire specification used in secondary. cross section area and strand size

VIkas Dabas

• Hi Vikas,

I believe here the optimum turn ratio, for your design, is 10:2:2, but must be verified. In my design it was 19:2:2 (each secondary winding has two turns). In fact, the minimum Vin in my case is 350V. If the turns ratio is 19:2, then the peak Vout at minimum Vin is 350V / 9.5 = 36.8V; considering the maximum duty cycle = 90%, then the maximum Vout is 36.8V * 0.9 = 33.12V. In my application Vout(max) was 32V, so this ratio was OK.

In your case, Vout(max) is 60V, therefore the ratio should be 350V / 60V * 0.9 (Dmax) = 5.25. Then you can select a ratio of 5.

Now, according to your output power (mine was 2KW, but you have 3.5KW), you should design a new transformer, capable of deliver 3.5KW. I am not sure you can transfer 3.5KW with PQ50-50 core....you have to check it and make your own calculations. In TI we don't design transformers, we sell silicon as you know. In case you want to design your own transformer, I suggest to go to Magnetics-Inc WEB site and access the "Design" tab, then click on Transformer design with magnetics ferrite cores"; this is a good design procedure, see:

https://www.mag-inc.com/Design/Design-Guides/Transformer-Design-with-Magnetics-Ferrite-Cores

There is another software I used to work with, in the past (several years ago). This software is very powerful and calculates all possible parameters of any transformer, for any type of topology (it also calculate the inductor, if needed). The name is Power 4-5-6, but you need to purchase a license, see details:

I hope that helps.

Best regards,

Roberto