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UCC256304: LLC solution for use case of SiC FET (and UCC24612)

Satoshi
Guru 19645 points
Part Number: UCC256304
Other Parts Discussed in Thread: UCC27531, UCC24612

Please let me know about three points below for LLC + SiC FET solution. (IC; UCC256304 + UCC24612-2)

①Is LLC circuit no problem to use SiC FET solution? (Device are UCC256304 + UCC24612-2)

　About SiC = high speed switching, I think that first switching will increase and flow to body diode.

　Is UCC25630x have control mode for measure above switching? 

　If there the other problem for SiC, please let me know.

②Is there important point in the use case of UCC24612-2 for LLC with SiC solution?

③Is there recommended reference design and additional parts?

　(I found UCC27531. is there the other require device?)  

【Backgroung】

・AC: 200V, Vout: 48V / Pout: TBD(500W or over)

・The reason of LLC, customer's most priority is small board size. (LLC circuit can design small size Transformer)

・Fsw is 450kHz_max. But the future, customer will considering to increase fsw.

Best regards,

Satoshi

  • 0
    TI__Expert 7310 points
    Hi Satoshi,

    There is no problem for LLC with SiC FET. can you explain more about your question: Is UCC25630x have control mode for measure above switching?

    For UCC24612-2, I will ask my colleague to help you.

    Regards,
    Bosheng
  • 0
    TI__Expert 7395 points
    Satoshi,
    Can you share what SiC FET you are using? Are you using it on the primary or secondary? Only 1 or multiple of them in parallel? This information will help to determine if there will be any concerns with using UCC24612 with it.
    Regards,
    John
  • 0
    TI__Expert 7395 points
    Sotoshi
    I haven't heard from you here so i'm going to close the thread. Just take special note of the UCC24612 thermal capability if you are using a SiC rectifier MOSFET. In general also, we recommend that UCC24612 be used with FETs with 3mohms Rdson or higher for proper operation considering it is Vds-sensing SR controller with certain thresholds set for the target applications. With lower than 3mohms Rdson, it may not function as intended.

    If you are referrring to using SiC on the primary side, we haven't tested UCC24612 in that type of configuration so not sure on the voltage and current waveforms seen on the secondary and how UCC24612 would respond with that.

    I've asked the LLC team comment on your UCC256304 questions as well.

    Regards,
    John
  • 0 in reply to John Stevens
    TI__Mastermind 27135 points
    Hi Satoshi,

    Could you provide some more detail on your question "Is UCC25630x have control mode for measure above switching?". I want to make sure I understand your question correctly.

    You will likely need an external driver for both high side and low side if you plan to use SiC FET's on the primary side. We do not have a reference design showing UCC25630x controller + SiC FET's at the moment unfortunately.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Guru 19645 points
    John-san, Ben-Lough-san

    Thank you for reply,
    And sorry for my reply delay.

    About SiC FET, I confirming to customer and waiting for reply.
    I will feedback to you if there any update from customer.

    About "Is UCC25630x have control mode for measure above switching?";
    I think that SR controller is start to react turn off switching.
    At first turn on(switching), large current will through body diode.
    Especially in the case of SiC FET, high speed switching.


    Best regards,
    Satoshi
  • 0 in reply to John Stevens
    Guru 19645 points
    John-san

    Thank you for reply,
    And sorry for my reply delay.

    About SiC FET, I confirming to customer and waiting for reply.
    I will feedback to you if there any update from customer.
    Please wait a little longer

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Mastermind 27135 points
    Hi Satoshi,

    UCC25630x uses adaptive dead time and looks at the switch node and the Vcr pin to determine the turn on and turn off times. I think you will not have a problem if you use an appropriate SiC driver for the high side and low side primary FET's. You will need to make sure the HS pin can still sense the switch node for the adaptive dead time circuit to work.

    Best Regards,
    Ben Lough