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Original question:

LM5160-Q1: LM5160-Q1

LM5160-Q1: LM5160-Q1

AJAY CHOLE
Prodigy 210 points
Part Number: LM5160-Q1

Dear David and Team,

I have designed a Flybuck converter for 44Vin to 54Vin at 12Vout-iso, 1.2A using Webench. The design file is attached here ( WBDesign29.pdf). If we refer to Vout-iso curve in the design file then we can see that the Vout-iso is around 11.35V. While selecting the isolated output voltage I had entered 12V then why it is regulating the output at 11.35V?

Similar thing is happening for a 5Vout-iso, 1.4A output, Vout-iso is around 4.51 V. The design file for 5Vout is here (WBDesign30.pdf). 

I think these are approximate values? Where is the problem?

Thanks and Regards,

~Ajay M. Chole

  • 0
    TI__Mastermind 25590 points
    Ajay,

    Just below your schematic on your design files there's a note:

    1. Feedback Resistors may need to be further adjusted to get more precise regulation as ripple injection circuit will introduce some amount of
    DC offset. Use simulation to help adjust.

    Try changing Rfbt from 9.76k to 10.5k. That should bring your 11.35V to 12V.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 210 points

    Hi Sam,

    Thank you for your response. I hope there is no need of changing other components?

    The simulation is not available for this design.

    Ok I will use, Rfbt=10.5k (RT0402BRD0710K5L)

    Similarly, request you to suggest feedback resistor for 5 V output at secondary. i.e Viso=5 V. The design file is here (6076.WBDesign30.pdf).

    We will have to set around Vprimary=5.5V. For that I have referred the datasheet of LM5160-Q1.

    It says (Rfbt/Rfbb)=[(Vo-pri/Vref)-1]. Where Vref=2V. Vopri=5.5V. If Rfbb=2k, then appr. Rfbt=3.5k.

    Please let me know if standard Rfbt=3.48k (RT0402BRD073K48L) is okay?

    Is there any modification required other than feedback resistors in both the designs?

    This design will be used for auxiliary power supply for solar hybrid inverter.

    Thanks and Regards,

    ~Ajay M. Chole

  • 0 in reply to AJAY CHOLE
    TI__Mastermind 25590 points
    Ajay,

    Rfbt=3.5k is what I calculate as well.

    The feedback resistors should be the only component change.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 210 points

    Hi Sam,

    Thank you. I think I will now proceed for hardware implementation of both the designs.

    Regards,

    ~Ajay

  • 0 in reply to AJAY CHOLE
    TI__Mastermind 25590 points

    Ajay,

    Sounds good. I will close this thread. Feel free to create a new thread if you run into another issue which you cannot find a solution to.

    -Sam