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UCC28070A: Power limitation at high line

Thibault ALBOUSSIERE
Prodigy 250 points
Part Number: UCC28070A
Other Parts Discussed in Thread: UCC28070, UCC28070EVM

Dear all,

 

Developing a 600W PFC with UCC28070 and searching into the TI forum without any success… (except Mark Walters 4 years ago, without any conclusion)

It seems to have a power limitation in high line. All parameters seems to be OK in Design tool, but I see Vrmo always at 3V and Vao near 4.6V @110Vac and 5V @230Vac. Irmo would change from 3V to 1V.

I have a doubt on C14 and C16 value.

 

I send you schematics, design tool and scope capture.

 

The scope legend is :

Yellow : C13 voltage

Pink : Vrmo (pikes ?)

Blue : Vcao

@110Vac Pout 400W => 438

@230Vac Pout 400W => 439

Thanks a lot,

  

Design Tool.pdf

  • 0
    TI__Genius 9790 points

    Hi, poster

    The replier of this post is out of office, please expect a response by this Friday.

    Yunsheng

  • 0 in reply to Yunsheng Qu
    TI__Genius 9140 points

    Hi Poster,

    C14/C16 is just used as a filter on the CT second winding. the Resistor in series with C14/C16 was set to be avoid CT saturation. C14 and C16 can be removed in some real case.

    The yellow scope looks normal with mosfet ID current sampling.

    so what is your concern?

  • 0 in reply to David Huang33
    Prodigy 250 points

    Hi David,

    My problem is a power limitation in high line (230Vac). Do you think C14/16 can make this problem ? or another parameter ?

    Regards,

  • 0 in reply to Thibault ALBOUSSIERE
    Prodigy 250 points

    Could you check my parameters ?

    First problem : power limitation, I don't manage to reach 600W (at 400W, Vout goes down. Less than 390V). 

    Second problem :the boost doesn't start à 230Vac sometimes. Still OK at 220Vac. VINAC value and filtering seems to be OK.

    As mentionned in my first message, Irmo has still the same value @110Vac or @230Vac, looking strange...

    Thanks,

  • 0 in reply to Thibault ALBOUSSIERE
    TI__Genius 9140 points

    Hi Poster,

    I am sorry the schematic you attached is not clear enough to review.

    one suggestion is VINAC resistor divider should be the same as Vsense resistor divider.

    For power limited issue, please check CSA/CSB and see whether it triggers PKLMT function.

    also you should check whether resistor on Imo pin with a  correct value.

    C14/C16 should not influence the high line power limited.(if you have a filter on CSA/CSB pin that can filter the noise.)

  • 0 in reply to David Huang33
    Prodigy 250 points

    Hi David,

    Sorry for my schematics...

    Divider resistors are the same between VINAC et VSENSE.

    I will check CSx and PKLMT, can I disable PKLMT by removing R9/R10?

    I would try to change the R12/R22 saturation resistors with diode+zener. Which values can you advise ?

    Thanks

  • 0 in reply to Thibault ALBOUSSIERE
    TI__Genius 9140 points

    Hi Alboussiere,

    you can try R9/R10 to set a high level power limit threshold.

    for the diode+zener, I suggest you follow the schematic with PMP4311.(diode: BAS16, Zenor:33V)

    www.ti.com/.../slur515.pdf

  • 0 in reply to David Huang33
    Prodigy 250 points

    Hi David,

    No more power by changing the reset resistor with diode+zener.

    Power limitation is not made by PKLMT.

    Could you take time to check my parameters in my Design Tools file ?

    Thanks,

  • 0 in reply to Thibault ALBOUSSIERE
    TI__Genius 9140 points

    Hi Alboussiere,

    It looks to me that the design tool parameter is ok.

    have you tried the Rimo resistor?

    I would suggest you can order an UCC28070evm as reference to see whether anything missing.

  • 0 in reply to David Huang33
    Prodigy 250 points

    Hi David,

    It seems to work better by changing current loop values.

    Vsense capacitor value is also critical.

    I see PFC has less power at 185Vac, I don't know why but I will investigate !

    Regrads,

  • 0 in reply to Thibault ALBOUSSIERE
    TI__Genius 9140 points

    Hi Alboussiere,

    Do you have any progress?

    so this time is low line power limitation issue? and high line power limitation issue already closes?

    lower line power limit may be influece by PKLMT pin threshold, please double confirm.

  • 0 in reply to David Huang33
    Prodigy 250 points

    Hi David,

    I still have less power between 150-185Vac (50W minus) and sometimes no PFC start at 230Vac.

    Regards,

  • 0 in reply to Thibault ALBOUSSIERE
    TI__Genius 9140 points

    Hi Alboussiere,

    I suggest you add more information about your issue. Other it is hard for me to guess what is happening.

    when you meet power limitation at 150-185Vac, Is it cause a suddenly drop of the power limitation or just decreasing output voltage?

    do you have any 230VAC no start up waveform to share with me?

    I suggest you can probe below signal in the same scope

    Voltage of csa/csb

    Voltage of PKLMT

    Voltage of Imo pin

    voltage of VCC pin