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Original question:

UCC28180: About restart time

UCC28180: UCC28180: About restart time

Igor Mohoric Bonca
Prodigy 20 points
Part Number: UCC28180


Tool/software:

Hello Mr. Harish,

I have stumbeled upon your thread about brown out functionality being added to UCC28180 in case of more powerfull PFC circuit - I supose? Is that correct? 

Anyways, I am in desperate search for a solution of a restart problem on PFC design (https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1572915/ucc28180-pfc-fail-after-fast-restart-of-power-supply) It seems like it's the same thing you have answered two years ago.

 

I checked the LM8364BALMF30 and found out that of all the component variations regarding treshold values only LM8364BALMF20 is produced. So I'm wondering in the case of 2,0V treshold version if I was to use R1=1M, R2=18k, C1=2nF, R3= 1MoHm is this going to work? BTW I have VCC=17VDC on my board, please comment on R3=1M.

Please respond. 

  • 0 in reply to Igor Mohoric Bonca
    TI__Prodigy 480 points

    Hi Igor,

    Currently I am handling the queries related to UCC28180.

    It seems that the R1 and R2 calculation is correct according to 2V threshold version.

    In the previous thread, for 15V VCC the required pull up resistor (R3) was given as 1.15MoHm, so now for 17V VCC it needs to be 17*1.15/15 = 1.3MoHm.

    C1 as 2nF can reduce the band width of the sensing network than the recommended (47pF). It will be advantageous for noise reduction but at the same time it can increase the reaction time during input under-voltage.

    Regards,

    Soumya

  • 0 in reply to Soumya Kundu
    Prodigy 20 points

    Hello Mr. Soumya

    Thank you for your reply regarding R1, R2, R3. 

    About C1 I figured it is the RC constant of C1 and R2. So if I use 47pF it is O.K. if I understand correctly?

    Just to be certain this brown out function is necessary for PFC circuit that is more powerful. At which power/current does this happen? I'm asking because we have also a 120-230V 1100W 10A PFC circuit without brown out, that has not failed so far. That is why this issue on more powerful PFC of 110V 16A 1800W version is quite a surprise for us (not a pleasant one I would say).

    Regards,

                   IgOr

  • 0 in reply to Igor Mohoric Bonca
    TI__Prodigy 480 points

    HI Igor,

    The restart problem does not necessarily depend on the power level. The problem can occur when if the controller does not have brown out protection and the input voltage again goes high.

    As Harish has mentioned in the e2e thread: UCC28180: About restart time - Power management forum - Power management - TI E2E support forums 

    "The UCC28180 if the high voltage input drops out the gate drive goes to max duty cycle because the input voltage is not being monitored and all the UCC28180 see is that VOUT is low. Once the input voltage comes back online (meaning when you turn on), the converter will go to an over voltage condition because of the slow loop response of the pfc.This is could potentially damage the MOSFET when a heavy load step is applied. So it would be better to have a brownout detection circuit."

    Regards,

    Soumya