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  1. #1
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    bflex driver switches off at 1A

    I am running a small head with 2 xpe leds and a seperate housing (plastic) for the bflex (running uib2) and the switch.

    All works well on 350, 500 and 750 milliamps but when i switch to 1000 it cuts out completely after a couple of seconds.

    I recall someone else on the forums having the same problem on high.

    My problem is that my driver is far removed from leds and thus cannot measure the temp of the led housing. bflex is also a step down driver and does not require a heatsink thus it is just sitting in the housing.

    I thought that when the voltage of the battery drops below medium and low the light will dim first before cutting out, although i am leaning towards the voltage dropping below the required voltage and the driver cuts out as the problem at the moment

    I have to disconnect power to get the light on again.

    I then set the power to 750mA and the light burns on without switching off.

    Anyone have any thoughts about this.

    This light will be a commuter light that will sit on the bar for heatsinking.

    some photos with lenses in. still needs faceplate screwed on.



    side view with concave bottom and top

  2. #2
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    I forgot to mention that the battery pack (li-ion) 4 cell 14.8 volt have a pcb built in.

    Could it be the pcb cutting the power and not the driver ?

  3. #3
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    Quote Originally Posted by fish.man
    I forgot to mention that the battery pack (li-ion) 4 cell 14.8 volt have a pcb built in.

    Could it be the pcb cutting the power and not the driver ?
    Yes, that's what I was about to suggest. The over current protection on some protection PCBs can be set off by the way a buck regulator draws current in pulses. The bflex has an input filter capacitor, but it doesn't totally smooth out the pulses.

    When it cuts out, measure the input voltage to the bflex before you unplug that battery. If it's very low, then the protection PCB has shutdown. If that's the case, try adding a capacitor to the output of the battery. Something in the range of a 47uf is usually enough. Tantalum is best, but an electrolytic cap will usually work. I put an additional filter capacitor in just about all my battery packs now before I shrink wrap the pack.

  4. #4
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    Yep, protection circuit of the battery pack is tripping due to the large current pulses that occur when the driver pulses the main LED(s).

    The driver (please read the manual....) does NOT dim down when the battery voltage drops to medium etc, what it does is flash the main LED(s) if enabled and the STAT LED (if connected). The large surge of flashing the main LED(s) is likely enough to trip the battery pack - must be a pretty wimpy protection circuit in your pack.

    As MTB stated, a largish value cap across the battery pack can help smooth the large pulses that are likely tripping your battery protection circuit.

    cheers,
    george.

  5. #5
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    fixed up

    Just an update on the problem i was having.

    It was indeed the protection circuit on the battery packs i was using.

    when connecting to an unprotected lipo battery pack no such problems were encountered.

    thansk to george and all the others that helped me with this issue.

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