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Original question:

TPS23730EVM-093: Changing output voltage to 48V

TPS23730EVM-093: TPS23730EVM-093 reference_48VOUT design from 48VIN~56VIN workable ?

Ching-Fei Ho
Prodigy 140 points
Part Number: TPS23730EVM-093
Other Parts Discussed in Thread: TPS23730

Hello team,


My customer ask us to have the 48VOUT design from 48VIN~56VIN by TPS23730.
At first, we think it is not workable due to the duty cycle is only about 74.5%. However, I saw this discussion about changing output voltage to 48V and TI have some designs at 54VOUT by TPS23730.

The 48VOUT design from 48VIN~56VIN by TPS23730 is workable, right? And what is workable reason of 48VOUT under the duty cycle is only 74.5%?
And could you provide me the design guideline at 54VOUT by TPS23730 for reference?
Is there any design concern that I need to noitice on 48VOUT design of TPS23730?

Thanks.

  • 0
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    If you plan to use isolated flyback you should have Vout = D/(1-D)*Vin/Npri*Nsec. With a suitable turns ratio it should not to hard to design a flyback with 0- 74.5% duty cycle. 

    I can share with you the 54V design in email.

    Best regards,

    Diang 

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    Thanks for your sharing, they are very useful information about the reference design and the suggested transformer for me.
    Howerver, there are some question abou 54V reference schematic that I am not very clear understand.


    1. Does the circuit that used on secondary side of transformer be the application of RCD snubber(D16, D17, C15,R30, R31) which like the RCD snubber(R33,C23,D18) at primary side of transformer?

    2. There are many non-installed components at secondary side of transformer, is there any situation that I should make them installed?

    And could you help review the schematic of TPS23730 as attachment?
    Please let me know if you have any suggestion.
    I have sent my TPS23730 schematic by email.

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    I had sent you the review comments in email.
    1. Does the circuit that used on secondary side of transformer be the application of RCD snubber(D16, D17, C15,R30, R31) which like the RCD snubber(R33,C23,D18) at primary side of transformer?

    Yes, it looks like the passive clamping circuit with RCD (R33,C23,D18) on primary side. But it is placed on the secondary side. I think it is for the same purpose. 

    2. There are many non-installed components at secondary side of transformer, is there any situation that I should make them installed?

    These non-installed components are for optional sync FET, line filter, snubber circuits... Depending on your design preference and requirement, you can choose use them or not.  

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    Thanks for your feedback, I have updated my schematic base on your suggestion. However, there are some items that I don't clear understand that I list in the mail. And please let me know if the schematic that I send have any other concern.

    On the other hand, POE use lots of synchronous control on secondary side of transformer, but we don't very familiar with it. Does TI have some information for us to study?

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    Thanks for your updates.

    I received your email and I should be able to reply in 3 business days.

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    Sure, review schematic need to take times. I will wait your feedback, thanks so much.

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    You are welcome! I had replied you in email for your schematic.

    The paper below may be helpful. Usually for 48V and 51W output, the efficiency of sync FET flyback and diode flyback may not have significant difference.  

    Under the Hood of Flyback SMPS Designs Article (https://www.ti.com/seclit/ml/slup261/slup261.pdf)

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    I will provide you final schematic to review after the P/N transformer finished applied. However, the paper you provide that I cannot download, it seems that have the usage rights. Could you just send me the pdf file of this paper to me?
    Thanks so much.

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    Please try the link below:

    https://www.ti.com/lit/ml/slup254/slup254.pdf

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    Thanks, I could download the pdf file of this paper now.
    And I have sent you the final schematic to you for reviewing by email, please let me know if you have any design concern.

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    Confirm received the schematic. Will reply you in email.

    Best regards,

    Diang  

  • 0 in reply to Diang Xing
    Prodigy 140 points

    Hi Diang,

    Thanks so much about your reviewing, the SCDIS that you mention by mail I will discuss with my EE.

  • 0 in reply to Ching-Fei Ho
    TI__Mastermind 30621 points

    Hi Ching-Fei,

    No problem!

    As we already connected in email, I would prefer to closing this thread for now. If you have a different question please open a new thread. 

    Best regards,

    Diang