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UCC28070: CRM vs CCM Interleaved

Mason Noh
Expert 2490 points
Part Number: UCC28070
Other Parts Discussed in Thread: UCC28064, , UCC28064A

Hi TI,

Datasheet shows that UCC28064 will be a very good choice for cost optimized applications in the 150W to 800W.

And UCC28070 also supports over 750W applications.

My customer has plan to design 750W power. and they prefer semi-bridgeless PFC for efficiency.

But peak current is too high in semi-bridgeless PFC. It means inductor size should be large. They also have to consider PCB size(slim).

Could you recommend topology? CrM(UCC28064) vs semi-bridgeless CCM (UCC28070)

  • 0
    TI__Genius 13660 points
    Hi Mason,

    I have contacted one of my colleagues to help here, but the response maybe delayed for a couple of days due to holiday.

    Regards,
    Teng
  • 0 in reply to Teng Feng
    TI__Genius 9140 points

    Hi Mason:

    Thanks for your interest in UCC28064 and UCC28070. Actually it is hard to say which controller is the best.

    If you use UCC28070 for bridgeless CCM pfc, the efficiency should be higher than CRM suppose using the same key devices. All the benefits are from cancelling the bridge. But here you should consider the drawbacks of using semi-bridgeless CCM PFC.

    1, You need fast recovery feature diode, for example ultra recovery diode or SIC to higher your efficiency

    2,Due to the common mode noise of this topology, the EMI is not easy to deal with, so input filter circuit is not likely to reduce the size.

    3, Cost will be higher compare with interleave CRM.

    And if you choose UCC28064A, mosfets are always working at zcs, and so here you can choose low cost diode.

    for your 750W project, both UCC28064A and UCC28070 can cover, if the efficiency is the most important, I would recommend UCC28070 for semi-bridgeless , if cost has higher priority, UCC28064A should be your better choice.

  • 0 in reply to David Huang33
    Expert 2490 points

    Hi David,

    Thanks for your kindly support.

    What about 850W? Why does TI recommend CCM for power over 800W? I wonder why the standard is 800W.

  • 0 in reply to Mason Noh
    TI__Genius 9140 points

    Hi Mason:

    TI has a recommend power level for controller, it is based on below items:

    1, Driving capability of the controller. If you need higher power level design, you need bigger current of mos or other switching devices, and usually higher current mos has higher Qg, which need more driving capability.

    2,How to handle the EMI? 

    3, System cost. TI recommend the power level in order to help customer compromise the cost and efficiency。

    So , according to your question, 850W is not a problem . actually we have customer use UCC18180 for 3.5kW project, we have customer using UCC28064A for 1200W .

    Keep in mind, when you want to higher the power level, please consider the three items to see whether it is a limitation.