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LM3429 flashing LED driver?

Discussion in 'LEDs and Optoelectronics' started by eem2am, Aug 13, 2012.

  1. eem2am

    eem2am

    414
    0
    Aug 3, 2009
    We are doing a ~2Hz flashing LED driver

    vin=12v
    vout= ~33v (max)
    iled = 0.45 (bit this is in the on state, oviously zero in off state)
    buckboost
    926khz

    We use LM3429 controller.

    We are flashing the leds and want them to come back on smoothly each time.

    Can we do this by shorting the comp pin to ground temporarily before flashing the leds back on?

    LM3429:
    http://www.ti.com/general/docs/lit/getlite...29&fileType=pdf
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,689
    Jan 21, 2010
    What do you mean by "come on smoothly"?

    I doubt that shorting the pins of a comparator to ground is a good idea.

    Your link is broken.
     
  3. eem2am

    eem2am

    414
    0
    Aug 3, 2009
    by coming on smoothly i mean no over shooting in the inductor current.

    For example, shorting the comp pin of the ucc28c43 to ground affects a soft start, ...is it the same with the LM3429.

    For the ucc28c43, adding a soft start circuit is done via the comp pin, as many of the old unitrode app notes testify
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    9,134
    1,843
    Nov 17, 2011
    Have a look at the LM3429's datasheet.
    Figure 5 shows an anlog dimmming circuit. You can use this to simulate a soft start. Read also the text, it describes various dimming methods.
     
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