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TPS23730: Flyback Self Driven Synchronous SSR vs ACF

RAMA MANIKANDAN
Prodigy 110 points
Part Number: TPS23730
Other Parts Discussed in Thread: PMP23253, PMP22477

We would like to use TPS23730 to design a 5V,51W O/P PoE Design. 
Leaving the Cost & Space tradeoff can you please provide us the difference in "Efficiency" & "Power Dissipation" between below two topologies for a 5V,10A PoE design.
1)Flyback Self Driven Synchronous SSR
2)Active Clamp forward
If any other performance related parameters plays a important role between the above two topologies please include them also.

And also please let us know whether using TPS23730 with "Flyback Self Driven Synchronous SSR" topology the below requirement can be met.
1)Output - 5V,10A
2)System Power Consumption - 45W
3)O/P ripple & Load regulation not exceeding 4.6-5.4V range(+/-400mV) for 5V typical DC O/P at PoE since we are directly supplying WiFi Front End Modules(VDD Range - 3.5-5.5V) from PoE O/P.

  • 0
    TI__Intellectual 770 points

    Hello Rama,
    Thank you for your interest in using TPS23730.

    In terms of efficiency, the results are similar, however the ACF topologies are slightly higher in efficiency.
    Here, I am comparing the graphs for PMP23253 (15V/3.3 A ACF)



    and PMP22477 (12V, 3.8A Flyback)


    TPS23730 has features that work well with either topology option you may choose to use in your design.

    As for your requirements,
    These certainly can be met.
    We have an existing reference design for a 5V/10 A output using the TPS23730, TIDA-050045
    This one uses Active Clamp Forward topology.
    For the same design, the output ripple was measure to have around only (+/- 50 mV)

    Hope this helps.

    Best,
    Sarah

  • 0
    Prodigy 110 points

    Hi Sarah,
    As per the shared data it seems like there will be approx difference of 3% efficiency between flyback & ACF with additional 2W achievable for ACF.
    But is the extra no of components, cost, space occupancy is just for this 2W difference in a 51W design?
    Is there any other performance related parameters in ACF having advantage over Flyback topology for its additional components, cost, space occupancy?
    Can you please let us know any particular application which can only be addressed with ACF topology and cannot by Flyback Self Driven Synchronous SSR?


  • 0 in reply to RAMA MANIKANDAN
    TI__Intellectual 770 points

    Hi Rama,

    Yes this is true.
    ACF will generally have higher efficiency than flyback, but will have a higher cost and larger size. Flyback is less efficient, but has lower cost and smaller size.

    There is not a difference in achievable power for the two topologies. Both are capable of achieving 51 W.

    ACF has larger size and requires 2 additional FETs at the secondary side( Q6 & Q8 ), and gate clamp.

    Secondary side for flyback may just be diode or singular output mosfet.
    This is the main difference in layout.
    Other components are design-dependent.

    If V_out is high, then ACF will have a large power loss for the gate driving circuit,
    and the efficiency will be lower, similar to the efficiency of a flyback.
    However at light load, ACF performs less efficient than flyback. The ACF's transformer loss & gate driving loss change less with load current.

    There are no applications that are exclusive to ACF that Flyback cannot also be used for.

    Thanks,
    Sarah