
Searching for USB Power Supplies That Won't Explode - szczys
http://hackaday.com/2016/04/27/searching-for-usb-power-supplies-that-wont-explode/
======
mrob
Sometimes even a well designed and assembled power supply can be dangerous
because of defective components. Big Clive on Youtube does many teardowns of
cheap electronics, and here's one of a USB power supply that's dangerous
because of internal damage to the transformer:

[https://www.youtube.com/watch?v=3Hdn0MuCK_0](https://www.youtube.com/watch?v=3Hdn0MuCK_0)

Because this is an intermittent fault it's possible that non-destructive
testing would not find it.

~~~
Obi_Juan_Kenobi
That's not a random failure, though. The quality control for the transformer
manufacturing was inadequate. This wasn't some difficult to anticipate error,
either; maintaining the integrity of the winding insulation is basically the
most important thing to monitor. The machines were either poorly designed or
improperly operated.

Sourcing higher quality components would prevent such issues. I'll concede
that nothing can be perfect, but this type of error is preventable. It starts
to cost quite a bit when you move from 0.1% error to 0.01%, though.

~~~
tsomctl
It's not just quality control on the part of the transformer manufacturer. It
was a cheap design. They could've completely isolated the two transformer
windings, either with heavy tape, or wound them on two separate bobbins. That
way, if the enamel on the wire wears off, the two sides are still completely
isolated. I still agree with your conclusion, though.

------
LeoPanthera
I trust Anker's chargers more than anyone elses. (No association with them,
just a happy customer.)

In general, chargers from big brands (Apple, Amazon, Samsung, even Ikea) are
fine because they don't want to risk damage to their brand if one were to burn
down a house or something.

If your charger has a brand you've never heard of, beware!

~~~
swah
Me too - my Anker car charger delivers 1800 mAh as measured by an Android app
called Ampere - I can charge my phone only during commute and use it for 24
hours. A cable I have from them is also high quality.

OTOH some Ebay cables might drop it down to 500 mAh. It was a shock to me
because for years I exclusively bought Ebay chargers and cables (around 1/5 of
the price of Anker) thinking they would work as specified (or not at all)...

~~~
arantius
FYI: "mAh" or milli-amp-hours is a unit of capacity, in this case it makes no
sense. Perhaps you mean just "mA", a unit of current, which does make sense in
context?

~~~
swah
Sorry! You're right.. and the app is also right, I couldn't even copy from it
properly :(

------
tibbon
From what I've experienced, most power supplies are just awful and don't hold
up at all to their specs, especially current in excess of 500mA.

I've been working with LEDs recently (APA102s), and I attempted just doing
some testing with 4 meters (60 LEDs/m) and a cheap old 5VDC laptop power
supply that in theory was rated for 5A+. Didn't work so well. Overheating, not
providing enough current to keep the LEDs acting stable, power on spike,
etc...

To solve my problem, I've purchased two 5V 90A Meanwell power supplies, and
those seem to work pretty well. But needless to say, I cannot imagine
cheap/small power adapters working well at all.

At my day job, we have some hardware that requires 800mA at peak to run. Even
many 1A USB supplies we've found to offer nowhere near that current capacity.
And if they do, they frequently fail after a while.

~~~
Gibbon1
> we have some hardware that requires 800mA at peak to run. Even many 1A USB
> supplies

I've been doing this for 30 years now. My rule is. Power supplies? Derate by
50% or you will be sorry. That power IC that says it's good for 1.2A? Yeah
read that as 600ma.

Capacitors are the same way, rated for 16 volts? Try 10 volts. If you look at
capacitors specs you'll often see MTBF at rated voltage and temperature of
2000 hours which is three months.

~~~
gh02t
Usually I see a big voltage sag when you get near the rated voltage on most
wall wart type supplies. I try and stick to 50% or maybe 75% if I think it's
quality.

------
darkclarity
I think the best power supplies are those commissioned by big manufacturers to
go with their hardware. The HP Touchpad's power plug being a good example.
These brands don't want a poorly designed adapter killing their products.

~~~
manyxcxi
I was going to say something similar. I often use USB power supplies that came
from old phones/laptops for my various little robot/gizmo projects. I do this
with the (naive) assumption that If I'm Apple/Dell/Samsung/etc. I don't want
to taint my products because of bad power supplies.

Other than using my non-pro knowledge and tools to roughly test voltage
stability, sustained amperage, and output voltages on some of the power
supplies, I don't have any hard evidence that this is true- but if I'm
choosing between an Apple USB power supply or a no-name power supply from
Amazon for a project, I'm taking the Apple one because I can assume it's a
minimum level of quality that's good enough for my use. I've got a couple of
iPad USB power adapters that I guard pretty closely because the other USB
power supplies I have that say they're good for at least an amp or two are
from no-name suppliers.

------
fpgaminer
Makes me wonder if DC wiring will ever catch on in newer homes. We don't have
much need for AC anymore. The only places in a home where one needs AC is in
the kitchen for large appliances, and garage/laundry room. And really that's
just because of the motors. I'm not sure if those could be converted to DC
motors and what powerloss that might entail. But the point stands; you could
totally get away with building a new home where you drop AC to the kitchen and
garage, and then 12VDC+5VDC everywhere else (12V on the wires, put a regulator
to drop to 5V in the outlet for USB-C ports). The power-loss of DC in a home
won't be that large. The end result is that the AC to DC transformer will be
centralized to one location, where you can spend more money up front to get
higher reliability, cleaner power, better safety, and better efficiency. Plus,
if you have solar, you can avoid AC to DC conversation altogether, saving on a
good chunk of powerloss there.

The caveat, of course, is that lots of devices don't natively support DC
input. Phones, tablets, and modern USB-C laptops are fine. Lighting is easy;
just do permanent LED installations. The LEDs will last a very long time since
they won't have regulators in them. Desktops are an issue. I believe the only
desktops that support DC input are HTPC builds, using those micro PSUs.
Perhaps there's an HTPC PSU that's got enough beef to power a normal desktop?
You'd also have to find monitors that accept DC input, which do exist but that
will narrow your market significantly.

Rob Rhinehart is an early adopter (see:
[http://robrhinehart.com/?p=1331](http://robrhinehart.com/?p=1331)) of this
type of home. Sounds crazy, but it seemed like a glimpse at a hopeful future,
at least everything outside of the kitchen.

~~~
mmagin
Well, uh, AC vs DC and 100-250 volts versus 5-48 volts are two completely
different dimensions to the problem here.

For example, there has been some standardization of high voltage DC power
distribution for datacenters, seeing as that could simplify providing battery
backup, etc.

But back to the residential case: As soon as you go to lower voltage power
distribution, unless you spend a lot more on copper (larger conductors),
you're really hurting as far as power distribution losses: your load uses 10
times as many amps running on 12 volts DC as it did on 120 volts RMS AC. Thus
your loss due to the resistance of the wire is 100 times what it was, given
the same wiring. (i.e. the same series resistance -- your loss is P = V * I =
I^2 * R)

And no, you don't suddenly get much greater efficiency in the power supply of
the device - a lot of off-line power supply designs today are already 90%
efficient, and even if you provide 12 volts (or 12 and 5) to the plug, there's
going to be a lot of things you want to do in the device that does not
satisfy, and if you want _exactly_ 12, you're going to need some kind of DC-DC
converter with regulation, because you cannot predict how the 12 volt supplied
at the wall will go down due to other load at any given point in time -- so
just like a laptop has various DC-DC converters from the 18 volts supplied by
its power brick to the various internal circuits (Vcore logic, 1.8 volt logic,
3.3 volt, 5 volt USB, backlight circuits, etc) most devices will still have
that. They might not require as much safety isolation, but you're not going to
get them to be magically far more efficient than what we have today.

~~~
jws
Lets not forget we could change the frequency. Running at 400Hz like aircraft
do lets you shrink the capacitors, inductors, and transformers of your power
supplies and your electric motors can make 10 times the power for the same
weight.

Going to 3-phase instead of single phase probably also helps for power
supplies. The power delivered across time is uniform so a sufficiently clever
design doesn't need to store energy between cycles. Sure, its another
conductor, but they can be slightly smaller so you use the same amount of
copper in the end.

50/60Hz is better suited to long distance transmission, but you could put an
inverter to 400Hz for the last 50 meters. Smaller, lighter, cheaper devices
but with the efficiency loss in the inverter. I suspect it would be a win.

(Also, pick a new voltage, something in the ~100v+ range. High enough for
efficiency, but then do the lethality tradeoff on picking the ultimate
voltage. As long as its a new standard, build ground fault detection at the
inverter as part of the standard. There are about 400 household electrocutions
per year in the United States, so there is room to improve.)

------
nikanj
I've been searching for a good-quality usb hub. After a few years of intense
competition, there are basically two options on the market: cheap chinese
crap, and cheap chinese crap in an expensive designer enclosure.

~~~
paulmd
It's not like any of it's made in America, so...

I have one of these and it's been fine so far.

[http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-
Ultra...](http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-Ultrabooks-
Microsoft/dp/B00ID270ZU)

To reiterate everyone else, Anker is great. I've had good results with
TronSmart too. And the Amazon Basics lineup is universally reliable. They have
all sorts of chargers/hubs/cables at reasonable prices.

~~~
voltagex_
If anyone can shed some light on the supply chain for these I'd be interested
- I've seen Anker, Aukey and Tronsmart 5 or 6 port chargers that look
identical (performance has been almost identical too, luckily). I can't buy
Anker or Aukey in Australia (easily / for a reasonable price) but I can get
Tronsmart through Geekbuying.

------
eumoria
This is obvious to the point of not reiterating but don't ever plug your stuff
into cheap/unknown chargers. I've seen the AC jump across to the low power DC
side MANY times and it insta-destroys anything designed to just take the
+5vdc.

I work in the event industry and we supply recharging cabinets for corporate
events. We use Anker.

------
mmagin
I generally avoid anything that doesn't have legitimate safety certifications:
UL, ETL, TUV, etc. ("CE" as printed on random imported crap seems to mean
nothing in particular.)

Also, you can usually count on actual, non-counterfeit chargers from well-
respected phone and tablet vendors being just fine. I've never thrown out an
old USB charger from an iphone, samsung, motorola, asus, just put them in a
box for possible later use :)

~~~
sbierwagen

      "CE" as printed on random imported crap seems to mean 
      nothing in particular.
    

[http://www.icomuk.co.uk/News_Article/3794/17103/](http://www.icomuk.co.uk/News_Article/3794/17103/)

[https://en.wikipedia.org/wiki/CE_marking#China_Export](https://en.wikipedia.org/wiki/CE_marking#China_Export)

------
mrbill
After reading Ken Shirriff's review a few years ago, I bought a bunch of
Touchpad chargers off eBay (before the clones started appearing) and use them
for tons of stuff.

[http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-
ap...](http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-
is.html)

Otherwise I stick with Anker/Aukey; am a huge fan of the 6-port "charger
bricks" and have used one next to my bed (phone, two tablets, a couple of USB-
powered devices like a sleep monitor) for 3-4 years now.

------
binman
Here are some good analytical reviews of USB power hardware, including safety:
[http://www.lygte-info.dk/info/indexUSB%20UK.html](http://www.lygte-
info.dk/info/indexUSB%20UK.html)

In general I buy Anker stuff - decent pricing and solid
stability/quality/safety.

------
synaesthesisx
There's a difference between active and passive protection systems - similar
to certain Lithium-ion batteries. A lot of the cheaper manufacturers skimp out
on a lot of such components (hence why you hear of e-cigs blowing up, etc).

------
dublinben
I've been very satisfied with my charger from ChoeTech. I figure that if
something is Qualcomm Quick Charge Certified, then it is probably adequate to
charge my devices.

~~~
seanp2k2
For inexpensive USB power, Anker has been my go-to. They also do the Qualcomm
quick charge with many of their products. Related, I liked their stuff so
much, and was so impressed when ripping apart one to use for lots of 5V amps,
that I bought their LED desk lamp (Lumos A2) which I've been very satisfied
with. They also have the E1 out now, which is more powerful as lumens go.

Edit: tear down of the charger I like by Anker (thanks binman): [http://lygte-
info.dk/review/USBpower%20Anker%2040W%205-port%...](http://lygte-
info.dk/review/USBpower%20Anker%2040W%205-port%2071AN7105%20UK.html)

