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UCC28051: Inductor Selection

Bright Robert
Intellectual 300 points
Part Number: UCC28051

Hello dear, I want to enquire about the induction selection in section 8.2.2.1  of page 18 of the datasheet.  What is the maximum input power averaged over the ac line period in this case?  And how can you calculate/determine it?

Kind regards

Bright

  • 0
    TI__Guru 73685 points

    Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru 73685 points

    Hello,

    Section 8.2.1 gives design specifications for the applications.

    This design has an efficiency target at max load of 0.9.

    With this information you can calculate Pin as follows.

    Pin = Pout/efficiency =  100 W/0.9 = 111.11 W

    Regards,

  • 0 in reply to Mike O'
    Intellectual 300 points

    Hello Mike,

    Thanks for your switch response. 

    Regarding calculating the inductor value on 8.2.2.1 inductor selection, what is the switching frequency that should be used in the example. I understand that the switching frequency is determined automatically based on the mode of operation, for example CCM, DCM as mentioned in section 7.4.1. In this sense, how do you select the switching frequency to use to calculate for inductor selection on section 8.2.2.1. 

    Kind regards,

    Bright

  • 0 in reply to Bright Robert
    Intellectual 300 points

    Hello Mike,

    Thanks for your switch response. 

    Regarding calculating the inductor value on 8.2.2.1 inductor selection, what is the switching frequency that should be used in the example. I understand that the switching frequency is determined automatically based on the mode of operation, for example CCM, DCM as mentioned in section 7.4.1. In this sense, how do you select the switching frequency to use to calculate for inductor selection on section 8.2.2.1. 

    Do I need to use the minimum Switching Frequency of 5kHz?

    Kind regards,

    Bright

  • 0 in reply to Bright Robert
    TI__Guru 73685 points

    Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru 73685 points

    Hello,

    I think 5 kHz is too slow.  The typical target for this frequency is 25 to 50 kHz.  I have seen designs done with either 25 kHz or 50 kHz for selecting this inductor.  Either will work.

    Regards,

  • 0 in reply to Mike O'
    Intellectual 300 points

    Thank you very much.