Post a Comment On: Ken Shirriff's blog

How about you buy an off the wall (literally) charger from apple and break it open to compare?

March 14, 2012 at 2:14 AM

Hi Anonymous. Apple chargers are a bit too expensive for me to sacrifice one just for my curiosity.

Ladyada has a picture of inside an Apple charger; it's considerably more complex with two circuit boards, so it's clearly a better design.

March 14, 2012 at 8:24 AM

My real samsung charger messes up the touchscreen to the point that I cant use drawsomething when plugged in. Not just cheap adapters do it.

March 18, 2012 at 4:43 PM

Nice blog here very interesting, i found this page after my mate bought me a crappy blackberry charger and it blew up, but luckily it triggered the circuit breaker in my home.

April 21, 2012 at 7:48 AM

I bought a "cheap" Mac book magnasafe from Extreme Deal. It fried the mother boards of two Macbooks. I took it apart, it was an "official" apple logo mangasafe with junk inside. It was putting out twice the spec voltage. I learned my lesson!

April 28, 2012 at 10:22 PM

But it's not just a few dollars is it, Albeit I'm in the back of beyond, but an official iphone charger where I live is closer to $40, compared to $4-5 for the chinese variants.

April 28, 2012 at 10:32 PM

I used to work for a consultant who did UL Safety testing. One of the things I got to do was that when we got a new device in, the first thing to do was to take out the power supply, find the circuit traces for the high voltage primary and the low voltage secondary. I then got to take a pair of calipers and measure the distance between the traces.

This was almost 15 years ago, so I don't remember the exact separations required, but it was a hell of a lot more than 1mm.

Beside the measurments, we also did the HIPOT test. HIPOT stands for HIgh POtential. In the HIPOT test, you take a special power supply that is capable of at least 10KV. You clip one lead to the primary of the power supply and one lead the secondary. You then ramp the voltage up. For UL 1950, which is the standard for most any commecial IT type gear, the power supply had to withstand at least 1500 volts.

Product Safety testing paid my way through college and it was a fun job.

April 29, 2012 at 9:28 PM

This comment has been removed by the author.

April 30, 2012 at 6:08 AM

Well written, Shirriff. And here are pictures of just such a charger that blew up on me.

http://goo.gl/DRLyg

Anool : anool@wyolum.com

April 30, 2012 at 6:12 AM

In Denmark, we have very strict rules about high voltage electricity.

These rules says that for every 100V, you must have an isolated distance of 1mm.

So for 115V, I would make at least 1.5mm (because voltage may sometimes rise above 120V) and for 230V (which means voltages up to 260V), I would make at least 2.6mm (preferrably 3mm or more).

If you're smart and your PCB layout program can handle it, put a narrower width trace on the top-side of a PTH PCB, and the same width trace on the bottom-side of the PCB; this way, you'll get traces that can carry the same power on the traces, but you can make the spacing wider. Note: Please make sure that the trace is somewhere between half and full width of the original trace width, so it can carry the current that it should.

Now, there's a difference between an open pad and a trace closed by a solder mask. A trace closed by soldermask is isolating better than two open traces close to eachother. This is due to that "air" has a variable resistance.

Eg. Air is a very good isolator, but on a rainy day, the resistance drops very much, thus the isolation drops as well.

But back to the small power supply and the gap.
I believe that if the trace is isolated from the pad, the power supply will be safe enough for 115V, however, for 230V, it is not.

Anyway, I'd recommend anyone to buy an Apple charger (the small one), ofcourse because it's a real American product, which means they have to conform to certain rules and laws - so the product will be safer; second, you're supporting an American company, third: You already know that someone pulled the thing apart and verified that it's safe. :)

If you, on the other hand, are looking for a cheap power supply that you can sell, you should buy a bunch of different power supplies and disassemble them, to see whether or not they can be used.
-If you don't know how to determine it yourself, find someone you can rely on answering the question correctly.

Please note: There are cheap Apple-look-alike power-supplies available, and even though they look like Apple's, they might contain sloppy electronics like the one mentioned in the above article.

Thank you OP for the awesome and outstanding detailed article.

May 5, 2012 at 1:45 PM

I forgot to say:
If you have some liquid plastic spray, you can give the PCB a few doses, to make the insulation better.

@Anool: Have you found the cause of the failure in your power supply ?

One would think that 0.6mm safety would be enough safety distance for a circuit where the diode is placed before the transformer, however, I do not think that is so.
This is because the voltage difference between the two traces would be... 115V / 2 (say +60V and -60V).
Now, the diode does not divide the voltage by two, but instead, it only lets half of the periods through, which means either +60V or -60V.
That might be why the chinese manufacturers made a shorter distance.
Yes, the voltage is only the half, but the peak voltage is actually the same, if you think about it.

May 5, 2012 at 1:59 PM

@Jens, it blew up at switch on. We have 240V here. I'm guessing it would have survived longer under 110V conditions. The switch on surge at 240V was probably more than it was designed to handle. Didn't look like a creepage related issue. More like component failure.

May 18, 2012 at 10:21 PM

My powersupply for ADSL modem don't even have the optocoupler to regulate the output!. this one is far better.

May 19, 2012 at 12:32 AM

Anool: thanks for the very interesting pictures.

Jobin: some power supplies avoid the optocoupler by using primary-side regulation. An auxiliary transformer winding tracks the secondary output, and this is used for feedback. Or your power supply might use a linear regulator. Or maybe it's just unregulated :-)

May 19, 2012 at 10:27 AM

Did you know the last time this surfaced on Hacker News it was killed and the guy got hellbanned? Check Google on fake iphone charger and compare that post and the cached version.

I'm desperate to find someone who sees this and can help.

May 30, 2012 at 3:45 AM

The DC voltage will be equal to the (RMS) AC voltage. When we say that a wall outlet provides 240V AC, it means 240V RMS.

So, a 240V AC input will result in 240V DC inside the power supply, not 340V. Yes, the peak voltage of the AC waveform is sqrt(2)*V_rms, but the steady-state DC voltage is not.

June 1, 2012 at 9:26 AM

JST: your calculations would be right if the bridge didn't have a filter capacitor. But with a filter capacitor, the capacitor charges to the peak AC voltage and only drops slightly. Thus, the DC voltage is about the same as the peak AC voltage (minus small diode voltage drop and ripple).

A few references are Diode Bridge Rectifiers, Rectifying AC increases voltage, "Power Supply Cookbook" page 123, and Power Electronics (22.6.1).

June 1, 2012 at 10:24 PM

Got a news flash for people differentiating official from "Chinese" chargers. They are all made in China, some even in the same factory.

In the end for any cheap product, you get what you pay for. Some safety tolerances aside that $3 charger does work, but what do you expect it's $3! Take away the logistical and material expenses and the profit margin is less than a few pennies.

It's when you buy an overpriced Apple charger and it ends up the same smokey mess that irritates people. Wasn't because it was made in China, it was because Apple was too damn greedy to design something better.

July 18, 2012 at 9:58 AM

"it's considerably more complex with two circuit boards, so it's clearly a better design."

That has to be the most stupid comment ever. Electronics don't have to be complex to work. The design of the charger you took apart is electrically sound from an engineering point. The problem with cheap electronics is the assembly.
These are Class 1 IPC commercial electronics. Most problems come from poor solder assembly (missing, bridges and balls.)
Even name brand electronics can suffer this fate, it's just the nature of the beast when companies try to save pennies.

November 2, 2012 at 5:27 AM

https://www.dropbox.com/sh/hzrep9beuqi8s5i/QtYjD2tdYa

is this thing real or fake?

November 22, 2012 at 3:14 AM

Anonymous with the HTC charger pics on dropbox: That looks like a really poor charger, but at least they paid attention to safety.

Bad features: just a single rectifying diode instead of a bridge will make much more ripple. No control IC, just a ringing choke converter circuit. A zener diode for feedback instead of the TL431 almost everyone uses - worse regulation. A cheap electrolytic capacitor for output filtering - poor output filtering. It looks like they did everything they could to minimize cost.

On the plus side, they have a good isolation boundary - the gap in the PCB labeled HY-777B. They include a Y capacitor. There's extra insulation over the USB connector and transformer. So they are paying attention to safety

Overall, I don't know why anyone would make counterfeit HTC chargers, so I'm guessing that this is real but kind of nasty. I hope you didn't pay more than a couple dollars for it :-)

November 26, 2012 at 8:46 PM

Any thoughts on this charger of mine?
I bought it off of DealExtreme (http://dx.com/65368) for $2.30. Yes I know it is fake, but it does have a full bridge rectifier and a 13003A power BJT in a TO-126 package (better heat dissipation maybe?) and it sets the proper resistance values on the data lines for the USB out. However, there is no Y-cap, fuse or MCU.

https://www.dropbox.com/sh/4fxnhm2ykk9oqex/RqMicMwAjk

December 3, 2012 at 5:58 PM

Hi Jack! Thanks for the dropbox link with extremely detailed pictures of your charger.

The label is very interesting - it's build by "Flextronic" rather than "Flextronics", and they've invented their own CE-like safety marking.

The charger circuit looks pretty minimal, but I've seen worse. I didn't see any insulation between the two boards or between the input AC and the output board. The thick input wires and lack of a fuse suggest that it would probably fail spectacularly if something shorts.

It turns out that one of the chargers I've disassembled but haven't written up yet has the identical component layout as yours. However, the circuit board routing is slightly different and my power transistor is smaller. These are the most similar chargers I've come across though - it surprises me that these companies don't just rip off someone else's design but have unique designs.

December 3, 2012 at 8:52 PM

Thank you for the prompt reply! I believe that it is actually supposed to say "Flextronics" because I do have a second one here that has the 's' on the end so I think it must have just rubbed off on the one I disassembled.

I've done some measurements on this fake charger I own and I found that they output about 5.4V instead of 5V and when I have my phone plugged into them the touchscreen is intermittently responsive, probably due to the over-voltage.

I also probed it with an oscilloscope and found that the ripple was actually very low, thanks to the full bridge rectifier, but there were a lot of spikes going as large at 200mV all over the place. Needless to say I don't think that I'll be using these with my phone, not only because it means I can't use my touchscreen, but I also don't want to risk damaging it!

December 6, 2012 at 6:32 PM

Hi Ken, came across your article and found it really interesting. Could you comment on these 3 adapters on their safety? I'm concerned as they were bought off ebay (cheaply). Whats the risk of getting electrocuted if something goes wrong?

https://www.dropbox.com/sh/2evhxz275cu11aq/OvL4twNhkO

December 30, 2012 at 11:29 PM

I find this "SMD-rest-solder-Balls" in expensiv Devices. Like ABS and ..
Metal Cased BlueThooth Devices ect.
And the "automated device-tests" are ok, as long and
after a Time if a Solder-Ball gets loose, it plays Bimmel Bingo on the small TSSOP Pins
of the Mico...an have thomething strange happen with the Device.
Why magnificate inspect this by human eye in a important thing.

January 6, 2013 at 6:40 AM

@Jobin -- Many ADSL modems accept a wide range of power because they do the regulation internally. Chances are your power adapter either is just a transformer and nothing else (I've seen many ADSL modems happy with that) or it may be an unregulated DC supply (transformer -> diode bridge -> filter capacitors).

Both of those options are perfectly safe (assuming the transformer isn't junk) as long as the equipment receiving the power either does it's own regulation or doesn't need it anyways. In none of those cases would opto-isolators or any other feedback device be found.

It could also be linear, but that's far less likely nowadays.

February 6, 2013 at 10:21 AM

I just learned my lesson!! I bought several ipod chargers online from EBAY and I got a helluva whollop the other day. I was holding my ipod in my right hand with the metal back contacting my hand. I plugged the charger into the wall with my left hand. And bang, a huge jolt through my right hand and right foot. I took the offending charger apart and it defintely does not look the Apple insides.
I have ordered new chargers from Apple and throw out generic ones.

March 30, 2013 at 2:31 PM

@Jens Bauer

America is hardly the kind of country most non-Americans want to support. Apple are another thing entirely -- probably one of the most unethical companies in the world.

April 24, 2013 at 2:53 AM

I have a cheap charger that doesn't seem to cause any screen interference, but it does run awfully hot. Hot enough that I almost suspect they shoved in a transformer, diode and a 7805 regulator and called it a day.

May 5, 2013 at 11:01 PM

Did the fake Apple wart have the data pin iterlocks in place - put there to slow down people wanting to user more economic chargers than the Apple rip-off pricing?

June 28, 2013 at 10:23 PM

Anonymous: you asked about the data pin protocol. This charger just shorted the two data pins together, indicating a generic USB charger. There were empty spots for data pin resistors - R2, R3, R8, R10 - so they could easily make this look like an Apple charger by putting the right resistors there. Lots of USB chargers pretend to be Apple chargers because it's so easy.

Magsafe chargers are a whole different story - you need a special chip in the connector, so you can't easily make knockoffs. See my Magsafe article.

June 29, 2013 at 9:52 AM

Whether Apple charger is a better design using 2 circuit board is subjective, but objectively all power supply should have tested to approved certification which is what most manufacturer do.

This particular el cheapo looks illegal to me on the basis,
there are no safety marking i.e. CE or UL certification.

Which means it may not even complied with the IEC electrical safety standards.

The casing doesn't look adequate fireproof to me.

Stay away from this piece of crap!!! It's dangerous!!!

July 15, 2013 at 3:27 AM

It's better to stay clear of products from China, they are usually of a really low quality hence the low cost. Always purchase the branded quality product, look for the quality marks on the product also.
Cheap == poor quality.

July 17, 2013 at 7:34 AM

I wondered why at first why 340VDC... I'm not an expert but I would think that your 240VAC gets immediately stepped down to 5VAC (or a bit higher) and then rectified to 5VDC...

Seeing the schematics I thought at first, that the XFMR was right before the rectifier but it looks like its a filter?? Anyways, it rectifies the 240VAC first and, as somebody else said, with the capacitors the peak voltage is maintained thus having aprox 340VDC and at the end of all the control circuitry they use a XFMR to step it down to 5VDC...

So... What is the reason for having the rectifier first and then the XFMR? Why not step it down immediately and then rectify if 340VDC is can kill...?

Thanks for the feedback, I appreciate the help...

July 17, 2013 at 7:35 AM

This comment has been removed by the author.

July 17, 2013 at 7:37 AM

Hi Bebiro. These chargers are switching power supplies. First the 220V (in China) AC is converted to DC, which ends up sqrt(2) higher voltage because the rectifier circuit ends up with the peak voltage not the average (RMS) voltage. This is chopped up at high frequency and fed through the transformer. The transformer output is converted to DC and filtered, giving the final 5 volt output.

This sort of switching circuit is much more compact and efficient, which is why it is used. You can step down first and then rectify, which is what the older big wall-wart power supplies do. A 60(or 50)Hz transformer is much larger than a high frequency transformer. Also, it's more efficient to regulate the output by high-frequency switching than a linear regulator which turns excess power into heat. Finally, anything line-powered can be unsafe if don't care about safety - if the step-down transformer is built too cheaply, it could short out and give you 220V (which is better than 310V but still lethal).

To summarize, your suggestion of stepping down first works, but the power supply would be much larger, less efficient, and probably more expensive.

July 18, 2013 at 10:20 AM

Great explanation, thanks for taking the time Ken...

Fernando

July 18, 2013 at 12:00 PM

hey the case happened with me.i brought a cheap charger and it sparks when i was charging my mobile phone.i am fortunately saved from it

July 19, 2013 at 3:15 AM

A Flyback Transformer?!?! That is a component used on older anolog Television of the Vacuume tube era!
And you are what you call an expert?!?

July 19, 2013 at 10:11 AM

Ha ha, Anonymous. Old TVs also used resistors and capacitors. Needless to say, these components are all still in use today :-)

July 19, 2013 at 10:20 AM

Just wondering... if I take the cheap charger of my chinese tablet - which presumably has some sort of rudimentary switching power supply in its guts, and complement it with a 7805 and two filtering capacitors will I end up with a better supply in terms of ripple and noise?
(yes, now the capacitive screen has problems when the tablet is plugged in)

IIRC, the thing puts out much more than the required five volts, at least with no load.

July 19, 2013 at 4:09 PM

Hi Ken,

I'm curious as to how the ASUS eee Pad Slider charges at 18-20V using the official charger. It won't charge at all from 10W Apple iPad chargers.

July 25, 2013 at 12:27 AM

I've made a bunch of UL listed hardware. "HiPot" testing (high potential) is done on all devices to verify the leakage currents. The limits are small. The durations usually quite long, relatively speaking. (For instance, a functional test may be 5 seconds, and a hi-pot 30.) When the rating agencies' (UL, CSA, VDE) logos are on a product, it means that the design has been reviewed, the manufacturing and test inspected (routinely) and that you can count on the component being safe. Apple is not going to use non-UL adapters to power things people touch to their hands and ears. Can't speak for Samsung or the rest of the "I'm too cheap to buy quality" products, but Apple margins certainly support the extra tests. $20 for the amount of stuff inside, including the margins, packaging, labor is a small price to pay for a few more years on the planet, don't you think?

Pisses me off that Apple takes the hit for some fly-by-night asian wannabe engineer but will settle for being a murderer criminal.

August 6, 2013 at 6:23 AM

Anonymous Anonymous said...

A Flyback Transformer?!?! That is a component used on older anolog Television of the Vacuume tube era!
And you are what you call an expert?!?

AnonAnon... he didn't call himself an expert, (but he did use his name and not just insult and run like an adolescent!)

Flybacks are used in a lot of places. It's not just old TVs. I'd explain it to you, but your comment suggests you wouldn't understand my answer. I am an expert.

August 6, 2013 at 6:28 AM

People are always trying to do things on the cheap, so they're only getting what they deserve by getting injured when they've been told to buy the proper equipment. No point in losing one's life trying to save a few dollars. Apple is taking the heat for Chinese knock-off crooks and careless individuals, but of course, Apple is always at fault for supposedly charging too much for their products.

August 6, 2013 at 9:28 AM

you rock! Notation on a picture from an amazon review praised the AmazonBasics USB charger for

"feedback winding on the transformer"

not knowing better I assumed his electricialistic-balderdash was grand

Your writeup is evidence based, thanks.

December 17, 2013 at 12:10 AM

In response to @rpi4all's rather unscientific assertion. After looking at Amazon's chargers myself, I'd say that their power supplies have pretty good power quality, and safety for the money. Of course seeing that these are battery chargers, not built to be a dedicated power supply for say routers or a computer system. In reference to the "feedback winding", it's the same kind of triple insulated wire Apple uses. I think here, along with Apple, it is actually the output that feeds the power to the usb, not a feedback winding. Amazon uses a controller ic, which is a far better thing to watch out for than the type of feedback used. I seriously hope it is not a case of "oh a counterfeiter uses it, so the others that use it must be bad also". Knowing very little about power supply topology, that is not a good thing to be assuming. Furthermore, the reviewer pointed out some things about the charger, with plenty of pictures. Not owning a blog or website to post lengthy analysis I think that was good enough.

January 4, 2014 at 4:53 AM

An Apple charger blew up on me yesterday. Scared the hell out of me.

Picture 1
Picture 2
Picture 3

January 9, 2014 at 3:22 PM

Nobody has mentioned the solder flux.

That board is filthy with flux all over it. Flux is not a conductor but over time it can absorb ambient humidity. I've seen resistances as low as 10k between pins of a connector that were never properly cleaned.

February 11, 2014 at 4:20 AM

Can I use 1 amp fuse and MOV in ac input with these cheap charger to avoid any spark or danger. Please confirm level of safety after adding fuse and/ or MOV ;I am using this cheap 5v supply for my project design.

March 16, 2014 at 10:50 AM

@ Blogger

"There can be no direct electrical connection between the two sides, or else someone touching the output could get a shock. Any connection between the two sides must go through a transformer or opto-isolator" - You missed something.. well 2 other things!

Insulation can also be bridged from primary to secondary by the use of Y1 grade cap (for maintaining a reinforced)[or a "X1/Y1" grade] or a Y2 grade cap (for maintaining basic / supplementary.

This is quite common on SMPS style circuits for EMC purposes. This is also something to bear in mind as often cheap chargers do not use the correctly approved (IEC60384-14) grade capacitors and use regular caps instead! Ensure they are of correct grade, and bear safety markings (ENEC marking is sufficient for Europe, or individual recognised safety bodies individual marks such as VDE etc).

There are also digital-isolators now that do the same function as an opto-isolator however they use a substrate rather than a physcial gap between emiter and detectors in an opto-coupler.

Opto-couplers if used should also meet the required safety certification, IEC60950-1 and IEC60065 for reinforced insulation, worth checking that cheap non-compliant opto's haven't been put in instead.

@Jenny:

MOV / VDRs / varistors do not protect you from shock. Such a component sits across Live and Neutral and protects the circuit from overvoltages.

A fuse offers protection to the circuit also - not you.

Accessible metal parts (e.g. the shield of the USB port)could be sat at live but the fuse won't blow if live got bridged somehow over the reinforced insulation to the secondary SELV side.

A class I circuit under this condition MAY trip an external breaker at the fuse board detecting an earth leakage, but in a typical USB phone charger being a class II (Double insulated) device no earth leaking would be able to be detected.

Best way is by good circuit design, separation and ensuring you meet the requirements for reinforced insulation at the output with regards to the mains input, use good quality certified X and Y grade caps where appropriate, certified opto-couplers meeting safety standards.

April 10, 2014 at 12:31 PM

Can I also add to above, noted one commenter mentioning "CE" marking :-

"there are no safety marking i.e. CE or UL certification."

no..no..NO.

CE is NOT a safety mark! It does not infer any testing has been carried out.

The CE marking is the manufacturer's declaration that the product meets the requirements of the applicable EC directives.

CE marking is a self-certification scheme. Retailers sometimes refer to products as "CE approved", but the mark does not actually signify approval. Certain categories of products require type-testing by an independent body to ensure conformity with relevant technical standards, but CE-marking in itself does not certify that this has been done.

Please..please..be clear on what CE means!

Comments here also have spoken about circuit separation requirements - and, depending on the standard, this varies quite considerably.

Let's educate people - and use correct terminology for this - Creepages and clearances.

Creepage is the distance along the surface between two points.

Clearance is the distance between two points through air.

The values a circuit needs to meet are determined according to the standard used for assessing the product, and can vary between 3.0mm for reinforced to 5.0mm for reinforced

The values are determined from many factors. Working voltage, Pollution degree, Over voltage category and Material group (CTI/PTI).

There is also 3 types of insulation - basic, supplementary and reinforced. Basic insulation in some standards is split into functional and operational insulation, just to complicate it, but for all intents and purposes, these are "basic" insulations.

Basic insulation is (mostly) fine for sufficiently enclosed MAINS sides of circuits.

Secondary circuits should be at least Supplementary but preferably meet reinforced requirements.

IEC 60950-1 stipulates 2.5mm clearances for basic insulation, reinforced is twice basic at 5mm.

Creepages can never be less than clearances, so at least 5mm creepage also. Distance through insulation (applies to opto couplers with insulation completly filling the void inside) from gold wire on emitter to gold wire in detector should be minimum 0.4mm for reinforced.

Manufacturers often use slots on boards which increase creepages for compliance (a slot needs to be at least 1mm wide for the most part to be considered wide enough for the creepage path to go around it). Clearances are unaffected by the slots put on boards.

It's common place to see this on inverter boards for CCFL backlights, under optocouplers and sometimes under transformers.

There is alot to circuit design, and safety testing, and many. many standards, personally, I'd go for an IEC 60950-1 certified power supply, as these have some of the most stringent (Medical 3rd edition aside) requirements for circuit separation.

I could now waffle on that beyond this, you then have flammability ratings (UL94 V-) of components, tested by needle flame, enclosures flammability ratings tested by horizontal burning (HB) and Clever burning ratings of enclosures (VW).. materials supporting live parts in place, maximum Touch Temperature requirements, marking requirements, durabilty of markings, leakage currents (earth leakage, touch currents requirements..)

Don't get me started on requirements for VDRs (ANNEX Q of IEC 60950-1)... Even that VDR sat across live and neutral - one of the first components before you've even started worrying about might not even meet the required climatic category, have at least 125% working voltage of the, meet specific 8/20uS pulse tests either...

April 10, 2014 at 1:19 PM

Any one please help me to decide original one, also safety level.
I bought them from seller claiming original apple, but teardown and tried to compare with ken shirriff picture, but failed.
below are picture of both....
front view image web link:-

http://oi60.tinypic.com/jkhkwz.jpg

back view image web link:-

http://oi57.tinypic.com/6olls0.jpg

package view image web link:-

http://i.ebayimg.com/00/s/NTAwWDUwMA==/z/1ZAAAOxy2CZTXGw6/$_12.JPG

April 26, 2014 at 9:43 PM

This comment has been removed by the author.

May 1, 2014 at 4:07 AM

Just to get in on the 'flyback' thing. Indeed the original term 'flyback' did refer to the the line output transformer, where the HF was derived from the point flying back to start another line, but now seems to have been re-appropriated to mean 'any HF ferrite transformer'. In absolute technical terms, the anonymous guy was right, it's NOT a flyback, but... for tact, he gets a zero ;)

June 19, 2014 at 12:27 PM

Damn it why didnt i read this before i bought a charger? I should have understood that a charger for only a little over 100kr was way to cheap and now my 1000 dollar iphone is dead ):

July 3, 2014 at 12:44 PM

Given the millions of cheap Chinese chargers bought each year I would have expected a large number of annual deaths from them. Instead there are a large number of reports of fried devices. I thought Apple stuff was made in China like everything else. I wouldn't trust that a US built charger correctly coped with 230v.

August 16, 2014 at 10:05 PM

Can a RCCB/ELCB trip due to a faulty charger and save from lethal shock ?

September 9, 2014 at 11:13 PM

I was looking into a USB charging solution for a DIY project.

I'd like to connect to the back of a wall socket (so no visible connections from the front) and run a cable up the inside of my wall to an in wall ipad holder.

I only have a thin gap to work with.

Any ideas on the best solution?

October 14, 2014 at 4:04 AM

Dear Ken,
WOW! the technical expertise/precision of your blog is, in its rarity, refreshing! I'm a teacher trying to get 11th graders excited about science and have hit upon a good carrot--maybe. Solar-powered cell phone charger. We're using an old 60W roof-mount solar panel to charge cute little 6V, 4.5 AHr Pb-acid batteries which, with a 1N4003 diode delive3r a 5.3V output, via USB connector, to cell phone. This is NOT a constant current, then constant voltage charging system, which is recommended for charging Li-ion batteries. Is the regulating circuitry in a cell phone (both smart phone and cheap phone .e. Go Phone) sufficient protection when charged by my charger?
Thanks,
Bruce Ratcliffe, Edison High School, Fresno, CA

October 23, 2014 at 8:27 PM

My iPhone 5 dead when my cheap charger blown up. Please help what can I do.. do I need to replace the battery by my self? Is the explosion cause a big damage on my iPhone? or shall I bring it to Apple shop or high St. repair shop? How much it cost me? please help!!!

November 5, 2014 at 6:04 PM

Thank you so much! for this blog Really,Its very nice & interesting Blog. I found this page after my mate bought me a crappy blackberry charger and it blew up, but luckily it triggered the circuit breaker in my office.

November 21, 2014 at 12:16 AM

What about the "clearance items" from the chains like Best Buy or Staples? These have what I consider to be absurdly high "regular" prices, but seem to go on "clearance" sales like clockwork for about $3-$5, to be replaced by new models that look the same and have the same specs.

December 23, 2014 at 4:59 AM

I came THIS close to buying a (believe it or not)$1.79 fake iPhone charger.

December 25, 2014 at 11:36 PM

Thanks for this info. I reposted it to my blog at www.riceisfordinner.com A PSA/info blog on the silliness that is, "Put your wet phone in rice".

February 3, 2015 at 1:05 PM

So they are cheap AND explode!? And yet you are tellng me not to buy one? I am confused, good sir.

February 5, 2015 at 6:00 AM

You are right. I got mine with the RC Copter same design like yours. I connected the battery and within 3 minutes my charger blew up. Since then I am afraid to connect my copter battery to USB charger but after reading your article, I understand it was due to charger not the battery. Thanks

February 25, 2015 at 11:47 PM

Great Post, very useful, and thanks very much for the links about TDK.

Everything was a joy to read,

Kind Regards
Heider Sati

May 31, 2015 at 1:40 PM

Very nice post Thanks!!!!!

May 31, 2015 at 4:01 PM

China dumps a lot of "sheet" into the USA and eBay is fill of sellers from China!

July 19, 2015 at 8:54 AM

This is very true! I once received one of these fake chargers for free when I bought a phone case on eBay. The adapter caught fire when I plugged it into the wall! Meanwhile, the charging cable made my phone freak-out and go into a restart loop. Needless to say, these Chinese products are dangerous and worthless.

August 31, 2015 at 4:53 PM

http://i.imgur.com/hu0ULDQ.jpg
http://i.imgur.com/IjRD53H.jpg

My made-in-china no-brand usb charger plug ejected from socket when I was using it to charge a mp3 player. It had worked over an year without problems. Also threw few spark on the carpet which didn't ignite anything, luckily. The adapter was 5V 1A one with input power of 100-240V 50/60Hz 0.15A with CE marking.......

January 2, 2016 at 12:36 AM

The worrying thing is, although I am not challenging anything technical, in the article is that the emphasis was on cheap. I have noticed recently that the price has increased and there is little price differential and so that is not a guide.
The CE Mark is a nonsense as it is often just applied by anyone and means little.

So the question, which I can't answer is how do you know a dud one before it is too late without opening it up to look and then it is ruined as they are not intended to be taken apart.

Also what about those that come included with gadgets where there is a non standard low voltage plug and not 5v there is little you can do.

SO

What do I do.
I stick an oscilloscope across the output and look at the waveform it picks up dodgy ones in an instant. Including an odd Apple one bought from an Apple shop.

January 23, 2016 at 8:53 AM

Woooow, cool article for all the iOS geeks and Android haters

November 16, 2016 at 7:24 AM

Thank you for the info! =)

April 9, 2017 at 8:44 PM

They have probably sold millions of these cheap chargers.
One woman was electrocuted. Under unknown circumstances.
OK.

June 16, 2018 at 9:35 PM

most of the charger are fake in Condition because customer do not known the feature of charger.so most company sell out charger in the market.so we are provided best laptop charger in Dubai.if you face any issue regarding your charger.then you can Buy Apple laptop Charger in UAE. you may visit our website.
https://laptopcharger.ae/apple.html

August 11, 2018 at 2:16 AM

That’s a good post and hope it helps other peoples.
Best quality wall to wall carpets in dubai

December 2, 2018 at 11:08 PM