• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 169 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS23755: PoE transformer - alternative part required

Johann Teufelhart MSc
Prodigy 20 points
Part Number: TPS23755

It's the first time I deal with a PoE Design. I decided to use the TPS23755 for my first design and as I continue drawing the circuit and selection the required components, unfortunately I have to realize that I do not have access to samples for the PoE transformer from LinkCom "LDT0950-50" used in the design.

I tried to find a replacement part but the two parts I found do not have exactly the same specifications.
  -) Wuerth Electronics: Part number: 7491199112
  -) Coilcraft; POE13P-12L

The parameters for the inductance value differs - 127µH instead of 150µH
and
Turn Ratio is also different 2:1:1 instead of 2.25 and 2.57.

What I can say is that it is not required for my design that the output voltage is exactly 12V. It is allowed for the design that the output voltage is in the range of 9V to 14V. However I do not the effect the different turns ratio applicable to the auxiliary winding used to supply the TPS23755.

Can you give me some hints what I can do using the TPS23755 and having no access to your transformer from the reference design?

I hope you can help me.
Best regards
Johann Teufelhart

  • 0
    TI__Mastermind 21741 points

    Hi Johann,

    Thanks for reaching out to us. We will reply you in 2-5 business days. 

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    TI__Mastermind 21741 points

    Hi Johann,

    Thanks for your patience.

    I believe you are doing a flyback converter using TPS23755. The original transformer in the TPS23755EVM-894 is LDT0950-50, which has PRI:SEC:AUX turns ratio is 2.57 : 1 : 1.14.

    Since a closed loop current mode Vout regulation control is applied in TPS23755, the turns ratio normally won't influence the output voltage as well as it is within a proper range. So does the inductance. 

    POE13P-12L and 7491199112 should both work here.

    One concern is if there two transformer are good for the primary side regulation:

    - Primary side regulation needs the AUX winding has a good coupling with SEC in the transformer

    - You need to adjust the voltage divider resistor consider the SEC : AUX is from 1 : 1.14 to 1 : 1

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    TI__Mastermind 21741 points

    Hi Johann,

    I will close this thread for now. Please rely or open a new thread if you have further questions.

    Best regards,

    Diang