USB Apple-style clone power supplies

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

 

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

 

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

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

 

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."

 

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

 

Thanks for posting this, useful!


Best regards,
Spehro Pefhany

 

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

 

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?

 

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.

 

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

Tim