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TPS23734: Flyback design 12V output

Paul Zoehner
Prodigy 10 points
Part Number: TPS23734
Other Parts Discussed in Thread: TPS23755EVM-894, TPS23755, , PMP8803, TPS23753A

Looking for a flyback reference design 12V 13W output.

  • 0
    TI__Expert 3700 points

    Hi,

    Thank you for your question. 

    For Class 3 (13W) flyback design with 12V output, I recommend our TPS23755EVM-894: https://www.ti.com/tool/TPS23755EVM-894

    This design uses the TPS23755 in a primary side regulated flyback topology.

    Let me know if you have any questions about this. Thanks.

     

    Best Regards,

    Brett Colteaux

  • 0
    Prodigy 10 points

    Hi Brett,

    I'm looking at the TPS23755EVM-894 (REV A) and the one I have at least is putting out 13.1V with the LED on and 13.9V with the LED off. In both cases I see 13.5V at TP9 and TP10 and 1.75V at the junction of R16 and R21. I assume the light loads cause the PSR errors.

    The first design I implement with the TPS23734 will have a reasonably stable and consistent output load of about 200 mA. Do I use the same PSR loop compensation values with the '34 and if so what components should be adjusted to tune in the output voltage? 

    Thanks,

    Paul

  • 0 in reply to Paul Zoehner
    TI__Expert 3700 points

    Hi Paul,

     

    Are you performing your TPS23755EVM-894 testing with no load when you see 13.9V and then with only the LED on load when you see 13.1V? If so, this is expected behavior of the design given PSR topology at light load. You can see the expected EVM output voltage over output current (load regulation) in Figure 6-4 of the TPS23755EVM-894 user guide here: https://www.ti.com/lit/ug/slvubg8a/slvubg8a.pdf?ts=1623161158708&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FTPS23755EVM-894

    This behavior is common in all diode PSR topologies. If your design requires higher efficiency at light loads, then a secondary side regulated topology is recommend such as ACF. 

    For your design, could you confirm my understanding is correct, are you looking for a 12V design that is optimized for efficiency at 200mA load (2.4W) but can handle up to Class 3 (13W) power level transients? If so, I recommend taking a look at PMP8809.

       

     

    Best Regards,

    Brett Colteaux

  • 0 in reply to Brett Colteaux
    Prodigy 10 points

    I intend to use the TPS23734 in several designs but the active design is for a constant 2.4W load at 12V - no load transients higher than maybe 200mW. In other applications the load may run anywhere from 2.4W to 13W continuously.

    A Google search doesn't seem to find "PMP8809".

  • 0 in reply to Paul Zoehner
    TI__Expert 3700 points

     Hi Paul,

     

    Apologies the reference design number should have been PMP8803.

     

    The TPS23734 reference designs that the team has today are catered towards the Class 4 (25W) space so unfortunately I don't have a reference design to recommend that is optimized for the Class 1-3 space which uses TPS23734. Typically customers will use a device optimized for Class 1-3 (<13W) power levels if 13W is their max power, like the TPS23753A used in PMP8803 or the TPS23755. However, if you would like to use the TPS23734 for your Class 1-3 designs, that is no problem. I recommend you design a flyback topology with TPS23734 for <13W and you could reference the same power stage as in PMP8803 for your design. Just be sure to be mindful of the delay time since it is a flyback you will have to disable the delay time. 

     

    Thank you.

     

    Best Regards,

    Brett Colteaux