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Highest efficiency possible with non-custom transformers for POE isolated power converter.

Karlis Tucs77
Intellectual 320 points
Other Parts Discussed in Thread: TPS23753, TPS23770, TPS23753A, TPS23750, TPS23757, TPS23757EVM, TPS2376-H

Hi.

I need to design a POE PD classification + isolated power converter stage for a load which is around 12 W at 5V.

As this is high load for class 0 POE , I really need high efficiency. I don't want this design to be POE+.

Which solution would be best for high efficiency but also without use of custom made transformers?

1. Separate isolated Power converter IC and Poe PD IC? I used TI Webench and it showed multiple power converter schematics, but almost all of them had custom made transformers...

2. One of the ICs which has combined POE PD functionality and flyback converter. I checked these too, but I have no idea which of all these TPS23753A , TPS23753 , TPS23750, TPS23770, TPS23757 would be most efficient.

Can you please advise?

Thanks in advance.

  • 0
    TI__Expert 3700 points

    Hi Karlis,

    Thank you for your question.

    1. For highest efficiency and a non-custom transformer and combined PoE PD + flyback converter, I recommend the TPS23757EVM. This design is able to achieve the below efficiency:

    The Nsupply efficiency line shown above is representative of the DC-DC converter efficiency only. In order to further improve the PoE efficiency by ~1-2%, you can modify the EVM design to use a full FET bridge or a half FET bridge/half diode bridge as opposed to a full diode bridge which is used in this design. 

    As examples:

    Here's a full FET Bridge TI Design example: TPS2373-4EVM-758

    Here's a half FET Bridge/half diode bridge TI Design example: TPS2372-3EVM-757

    2. For a stand alone PoE PD, I recommend the TPS2376-H. For a DC-DC converter to pair with this PoE PD to obtain your desired efficiency, please feel free to search through our TI Reference Designs Library: http://www.ti.com/reference-designs/index.html#search? 

    Best Regards, 

    Brett Colteaux

    Product Marketing Engineer | PoE Products

  • 0 in reply to Brett Colteaux
    Intellectual 320 points

    Hi Brett. Thank you for answer!

    I already started calculations for a design with  TPS23757.