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UCC28950/about master slave mode

Tsukui Yusuke
Guru 21930 points
Other Parts Discussed in Thread: UCC28950

Hi,

Could you tell me about UCC28950 master slave mode phase delay.
By timing to synchronize with SYNC clock, is the phase of master and slave delayed 270 degrees?



Best Regards,
Yusuke Tsukui

  • 0
    TI__Mastermind 25570 points

    The slave device will run 90deg behind the master. The output inductor sees twice the switching frequency so the two output inductors will run 180deg out of phase. The delay in Figure 20 shows the initial delay between applying the SYNC_IN signal and the slave starting to run.

    Colin

  • 0 in reply to Colin Gillmor
    Guru 21930 points

    Colin-san,

    Thank you for your support.
    Please let me reconfirm this to make sure.
    Is the following phenomenon not happen?



    Best Regards,
    Yusuke/Japan Disty

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  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 25570 points

    Hello Yusuke-san

    The 270deg is correct of course if you measure from the start of the SYNC_OUT waveform as you have shown in the diagram. It's most easily seen when the system starts synchronizing. This delay is of course preserved as the system operates in the steady state - you can measure 270deg from a given SYNC_OUT pulse at an OUTA pulse. because of the periodic nature of the system it is normally more convenient to think of the phase shift as a 90deg rather than 270deg (it's really the same thing).

    To further complicate matters, the output inductor currents are 180deg out of phase with one another - because the output inductor period is half that of the transformer primary. This ensures maximum cancellation of the ripple currents into the output filter of the PSU -

    Please feel free to ask again if this isn't clear.

    Regards

    Colin

  • 0 in reply to Colin Gillmor
    Guru 21930 points

    Colin-san,

    Thank you for your kind support.
    I sent you incorrect image in the previous e2e.
    I am attached to the following image again.
    Customer wants to fix phase in case of pattern1 and pattern2 to either.
    Could you tell me method to fix to either 90deg delay and 270deg delay?


    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    Guru 21930 points

    Hi,

    Can I get the information ?
    If you need more information or if  I should  clarify my comment ,
    please let me know.
     
    Best Regards,
    Yusuke/Japan Disty