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LM5116: Can LM5116 be used as Flybuck?

Duoduo Cheng
Expert 3050 points
Part Number: LM5116
Other Parts Discussed in Thread: LM5161, LM5180

I need a flybuck IC. The Vinmax is 65V. The non-isolated output current is 1A at least and isolated output current is 0.2A.

Do you have any suggestion about Flybuck IC?

Can LM5116 be used as Flybuck? Can all synchronous buck controller be used as Flybuck?

Thanks

  • 0
    TI__Mastermind 25590 points
    Duoduo,

    Yes, this can be used as a Fly-Buck. Fly-Buck require the ability to sink current as well as source it. LM5116 has diode emulation which would not work with a Fly-Buck but you can disable this feature.

    -Sam
  • 0 in reply to Samuel Jaffe
    TI__Expert 3050 points
    Thanks for your reply.
    LM5116 is emulated Peak Current Mode, so if the reflected current from secondary winding is large and the current of low-side MOS will reverse. Is this a problem for emulated Peak Current Mode?
    and normally the flybuck converter is COT control mode because this control mode is more tolerant to leakage.
    Whether emulated Peak Current Mode is sensitive to leakage of transformer and is there any risk to use LM5116 as flybuck or what I need to focus on when designing it?
  • 0 in reply to Duoduo Cheng
    TI__Mastermind 25590 points

    Duoduo,

    You are correct. I was missing some information.

    LM5116 may or may not operate properly due to the Fly-Buck current waveforms. We also typically need a negative current limit to provide OCP for the Fly-Buck output. For these reasons I'd recommend using LM5161 for this job. You could also use LM5180, our new low-power flyback. If you require more power than LM5161 can provide, you can check out more Flybacks or other isolated converters/controllers.

    -Sam