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UCC28782: On timing of PWML in ABM/AAM mode

TETSU
Prodigy 250 points
Part Number: UCC28782


Hello TI-Team,

I have a question regarding the on timing of PWML in ABM/AAM mode.
When in ABM/AAM mode, does PWML go high in the following two ways?
(1) If ZVS detection (below VTH(SWS)) is made at the SWS terminal within tz, it turns on at tz+tD(SWS-PWML).

(2) If ZVS detection (below VTH(SWS)) is not made at the SWS pin within tz, it turns on after ZCD detection at the VS pin + delay time tD(ZCD).

Also, is it necessary to delay the SWS pin more than ZCD because after ZVS detection at the SWS pin, ZCD detection is checked when PWML is made to go high? (Is it because there is a function to prevent the secondary side CCM mode from turning on if ZCD is not detected?)

Kind regards

TETSU

  • 0
    TI__Mastermind 24375 points

    Hi Tetsu-San,

    Thank you again for the query. 

    We are working on this and will get back to you on this query.

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    TI__Mastermind 24375 points

    Hi Tetsu-San,

    1. Yes, it will be optimized to turn on after tz with the propagation delay.

    2. If that does not happen, then it will correct by increasing the tdm in the next switching cycle so more negative magnetizing current helps pull Vsw within tz period other switching cycles will be ZCD detected through the AUX (Fig-8.27 illustrates this).

    Other questions:

    3. Yes, ZVS and ZCD timing is described in page26 paragraph 4 of datasheet..

    4. Yes, secondary rectifier CCM turn off effect as you mentioned is clearly mentioned in page 40 of the datasheet

    Please let us know if you have additional questions.

    Regards,

    Harish