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LM5156: Isolated DC-DC converter

Francesco Rizzotto
Prodigy 85 points
Part Number: LM5156

Tool/software:

Hi,

I'm currently in the process of designing an isolated DC-DC converter with the following specifications:

  • Input Voltage: 22-36V
  • Output Voltage: 20-200V
  • Output Power: 600W

I am considering using a flyback converter for this application.

Do you think the LM5156 would be a suitable choice for this design?

Additionally, are there any alternative topologies or microcontrollers you would recommend?

Thank you for your valuable insights!

Best regards,

Francesco

  • 0
    TI__Mastermind 30160 points

    Hi Francesco,

    For isolated Flyback topology, LM5156 should indeed be the best recommendation.
    However, I am concerned about the high power level requirements.

    Flybacks are well suited for low power application up to 50W or even 100W, but at 600W, current ratings will get higher, leading to strong losses at the diode on the secondary side.
    The output voltage range is also quite large, which makes finding a good compensation more challenging.

    Can you specify the following:
    - Is isolation required?
    - How many output rails are required?
    - Are 600W output power required over the full Vout range (20-200V)?

    Thanks and best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 85 points

    Hi,

    Thank you for your response.

    The converter needs to be fully isolated, and it must maintain the required output power across the entire output range.

    Additionally, the converter should generate only a single output voltage.

    Do you recommend any alternative topologies?

    Thank you

  • +1 in reply to Francesco Rizzotto
    TI__Mastermind 30160 points

    Hi Francesco,

    Thanks for the feedback.
    I am afraid a Flyback cannot support these requirements.
    I had an internal discussion for alternative topologies.

    An LLC topology or a push-pull could be possible options which are preferred for these power ratings.
    Unfortunately I have little experience with these designs and best suitable devices.

    For a good starting point, I would recommend looking into the UCC28951.
    This is a phase-shifted full bridge controller.
    I do not know who is the best engineer to forward you to, so instead, you can open a new thread with the UCC controller in the title and you should be assigned to the correct person automatically.

    Feel free to come back to me if you cannot find a suitable solution with this controller.

    Best regards,
    Niklas