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TPS23734: TPS23734 with primary side regulation

Stefan Burstrom
Prodigy 130 points
Part Number: TPS23734
Other Parts Discussed in Thread: TPS23731

Hi!

I was planning to use TPS23731 in a 12V, 25W design, but when I noticed that the part was not available I realized that the TPS23734 would also work with the added benefit of supporting ACF.
Can you explain the tradeoffs using ACF vs the flyback mode? My TPS23731 design is using primary side regulation and I was hoping that I could do the same using TPS23734 but the EVK is using an opto coupler instead. Is primary side regulation not recommended in ACF mode or can those be combined to improve efficiency + eliminate the need for the opto coupler?
If the opto coupler is need in combination with ACF, is it possible to achieve the same functionality as TPS23731 simply by using the same schematic as the TPS23731  EVK and connect the DT pin to GND.

Stefan

  • 0
    TI__Mastermind 21320 points

    Hello, 

    At a high level ACF is the best performance at the highest cost. Flybacks are smaller solution size and lower cost. 

    Primary side regulation is not currently possible in ACF. 

    Yes the TPS23734 is essentially the same as TPS23731 except that it has the additional gate drive. So if you disable the second gate drive, they are the same. But then you are paying for a gate drive you are not using. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0
    Prodigy 130 points

    Thanks!
    Is it possible to explain why ACF is not possible combined with primary side regulation? I have been trying to read as much as I can on ACF vs regular flyback but I could not find any obvious reasons why ACF makes it harder to sense the secondary side voltage compared to the flyback configuration.

    Using TPS23734 over TPS23731 is simply a sourcing decision since TPS23731 does not seem to be available right now.

    Best regards,

    Stefan

  • +1 in reply to Stefan Burstrom
    TI__Mastermind 21320 points

    In order to have good regulation, the secondary side must be accurately represented on the primary side. There is not yet a plausible way to do this in ACF. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 130 points

    Undersood, thanks! The reason why I asked is that I have built a prototype of my own ACF DCDC using a microcontroller (to learn more about it) and I just wasn't sure what to expect when I power it on for the first time. Boards are still being fab'ed so I am very curious what result that I will see Slight smile

    Best regards,

    Stefan