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USB Apple-style clone power supplies

Discussion in 'Electronic Design' started by Spehro Pefhany, Sep 29, 2012.

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  1. I took one of those things apart- a clone that had failed due to a bad
    solder joint. It was marked cULus with a file number (surely fake).
    This is one of those things that's about a 1" cube.

    Some of these things are DEADLY bad in design. Do NOT NOT NOT give one
    to a child. Creepage distances are way too small for safety and there
    was debris inside that could short. As an aside regulation is dubious
    and a single-point failure could easily damage the attached device.

    If anyone's interested, I'll post photos and some analysis when I get
    a chance.


    Best regards,
    Spehro Pefhany
     
  2. So, 80% okay.

    The one I have is different from both of those ones. It has two
    boards, but a similar circuit to the "fake" above. Self-oscillating
    TO-92 "MJE13003", regulation is just a zener series with an opto IR
    LED. No input fuse, no input CM choke, limited output filter, no OVP.

    To trust your life or even a $600 iPhone or $300 iPod to such a
    circuit would be madness.


    Best regards,
    Spehro Pefhany
     
  3. DrParnassus

    DrParnassus Guest


    http://www.amazon.com/gp/product/B00439G3WS/ref=oh_details_o06_s00_i00

    Perfect for charging/feeding ANY USB battery/device requirement.
     
  4. miso

    miso Guest

    EMI from the charger to the touch screen? Supply noise, maybe, but EMI?

    "Apple's power adapter is clearly a high-quality power supply designed
    to produce carefully filtered power. Apple has obviously gone to extra
    effort to reduce EMI interference, probably to keep the charger from
    interfering with the touchscreen."
     
  5. There's CM filtering in the Apple supply. If the power supply has a
    lot of HF hash relative to the mains then that will appear on the
    capacitive touch screen inputs.


    Best regards,
    Spehro Pefhany
     
  6. Thanks for posting this, useful!


    Best regards,
    Spehro Pefhany
     
  7. Tim Williams

    Tim Williams Guest

    When programming our induction power supplies, we sometimes have the
    dongle connected to a laptop while in operation. The trackpad becomes,
    less useful shall we say :) That the connection can be made to actually
    work with "only" a couple ferrite beads is probably testament to the power
    supply's design.

    Tim
     
  8. miso

    miso Guest

    Well this all comes down to the question "How big is an inductor". There
    is the physical size, then there is the region that it effects.

    I have two touch screen devices, neither Apple, and no issues when used
    with the usb power supply connected. Maybe this is an Apple problem more
    than a power supply problem.

    I guess the next question is how clean is the 5V you get from a PC
    connection?
     
  9. miso

    miso Guest

    I guess I don't have any crappy USB power supplies. I can't see any
    difference, and I'm trying stuff like wrapping the power cord around my
    finger or the phone, holding the mains/cig-socket end, etc. Phone is a
    HTC Desire Z.

    Think about it. These phones have DC/DC inside and freakin' RF
    transmitters. That should be plenty of noise to cause problems.

    Maybe the iphone, in the desire to be thin, skimps on filtering the DC
    input. Caps and inductors require space.

    I thought for sure the cigarette lighter adapter would be noisy. It is
    some $5 Fry's special.

    Put me in the dubious camp on this one.
     
  10. Tim Williams

    Tim Williams Guest

    Probably not so bad since it's probably not isolated, and the voltages are
    smaller.

    Tim
     
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