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UCC24612: UCC24612-1

Hiroshi Doi35
Expert 2845 points
Part Number: UCC24612
Other Parts Discussed in Thread: UCC28631, UCC28630

Hi all,

Is it possible to use UCC24612-1 as S.R. for UCC28631 CC mode ?

www.tij.co.jp/.../ucc24612.pdf

Thank you!

  • 0
    TI__Genius 9130 points
    Doi-san,

    I assume you mean CCM mode, i.e. continuous conduction mode?

    Yes, UCC24612-1 can be used together with all UCC28630 family devices. The fast turn-off delay and proportional gate drive features ensure fast SR turn-off, even in CCM, and minimise CCM shoot-through current.

    Thanks,
    Bernard
  • 0 in reply to Bernard Keogh
    Expert 2845 points

    Bernard-san,

    My concern is rapidly load increase <--> decrease.

    Like this  increase -> decrease -> increase-> decrease  rapidly.

    Is it OK ?

    If it is ok,  W/W input 160W output with high efficiency can be acheaved?

    Thank you,

    H.DOI

    rapidly load increase -- decrease.pdf

  • 0 in reply to Hiroshi Doi35
    TI__Genius 9130 points

    Doi-san,

    The Flyback stage will behave in the same way with with diode or SR when the load increases into CC region and then back to CV region - there should be no difference.

    Here is a plot of the load step from 40-ohm (~0.5 A) to ~2.2-ohm (limited in CC mode to ~7 A, hence Vout drops to ~15 V), then back to 40-ohm.

    This was measured on UCC28630 EVM, modified with SR + UCC24612-1; (red is Vout, pink is Iout):

    However, there is one area that is affected by the SR driver - when the Fsw drops very low as load is decreased to a very low level, the SR driver stops driving the SR gate, then the SR FET body diode rectifies. The increased Vf drop causes Vout to regulate ~0.5 V lower at standby/no-load.

    At a certain range of load, where Fsw is close to the SR driver light-load enable/disable thresholds, the operating made can repeatedly cycle between SR driving and not-driving, causing Vout to cycle up & down by ~0.5 V (body diode Vf drop). On the EVM, this is seen at ~50-100 mA load range.

    Note that this is only happenning because of the PSR controller on the primary - the Vf drop change looks like a step-change in Vout and causes the primary loop to react accordingly. This would not be seen with SSR/opto feedback.

    Thanks,

    Bernard