This is why iPads say "Charging is not supported with this accessory" with some chargers. Through these resistors the genuine charger indicates that it is an Apple 2A charger, while the counterfeit indicates that it is an Apple 1A charger. This shows that the counterfeit is really a 5W charger packaged as a 10W charger.
When looking at these circuits up close, it's easy to forget just how small the components are. The picture below shows one of the surface-mount components a 0-ohm resistor [13] from the iPad charger. It is just to the left of Roosevelt's chin on the dime. A zero-ohm resistor Safety, or lack thereof Safety probably isn't something you think about when you plug in your charger, but it's important. Inside the charger is volts or more with very little separating it from your iPad and you.
If something goes wrong, the charger can burn up below , injure you , or even kill you. Devices such as chargers have strict safety standards [14] - if you get a charger from a reputable manufacturer.
If you buy a cheap counterfeit charger, these safety standards are ignored. You can't see the safety risks from the outside, but by taking the chargers apart, I can show you the dangers of the counterfeit.
Counterfeit iPhone A Counterfeit iPhone charger that burned up. Photo by Anool Mahidharia. Used with permission Creepage and clearance The UL regulations [14] require safe separation between the high voltage and the low voltage. This is measured by creepage - the distance between them along the circuit board, and clearance - the distance between them through air. The regulations are complex, but in general there should be at least 4mm between high-voltage circuitry and low-voltage circuitry.
The image above shows how the genuine iPad charger's circuit board separates the high voltage bottom from the low voltage top. The happy face on the right marks an empty region that provides a safety gap between the primary and secondary.
This is a contrast with the rest of the circuit board, which is crammed full of components. This gap of 5. The happy face on the left marks a slot in the board that separates the low voltage and high voltage. The photo below shows how an insulating fin is built into the case and through this slot to protect the USB connector. Additional reddish-brown insulating tape goes through this slot, and the whole high-voltage section is wrapped in yellow insulating tape. The result is multiple layers of protection.
The creepage distance on the counterfeit charger board below is scary - only 0. The sad face on the right shows where a low-voltage trace is nearly touching the high-voltage trace below. The ruler on the right indicates millimeters. The board isn't as bad as it could be: the happy face on the left marks a slot cut in the circuit board under the transformer to increase the creepage distance. But overall, this board is unsafe. If you use the charger in a humid bathroom and a drop of water condenses across the 0.
Counterfeit Dangerous creepage in a counterfeit iPad charger. Safety in the transformer For safety, the high-voltage and low-voltage sides of the charger must be electrically isolated.
The flyback transformer accomplishes this task by using magnetic fields to transfer the power without a dangerous direct connection. Because the transformer is a large and relatively expensive component, it is tempting to take safety and quality short cuts here.
The genuine transformer left is considerably larger than the counterfeit right , which is a hint of better quality and more power capacity. Disassembling the transformers shows that this is the case. Dime and banana are for scale. The key safety requirement of the transformer is to separate the high-voltage windings from the low-voltage secondary winding, and the counterfeit charger fails here. The pictures below show the transformers after removing primary windings and insulating tape, revealing the secondary winding.
The wires look similar at first glance, but the the genuine charger left has triple-insulated wire while the counterfeit right is uninsulated except for a thin varnish. The triple-insulated wire is an important safety feature that keeps the high voltage out even if there is a flaw in the insulating tape and in the wire's insulation.
Also note the additional black and white insulation on the wires where they leave the transformer. In the counterfeit charger, the only thing separating the secondary winding from high voltage is the insulating tape. If there is a flaw in the tape or the wires shift too far, then zap! First, the counterfeit turns out to provide at most 5.
Second, the output voltage is extremely noisy and full of spikes. The following voltage-vs-current graphs show the performance of the iPad charger left and counterfeit charger right under increasing load. The line for the real charger goes much farther to the right, showing that the real charger provides much more current.
By my measurements, the real charger provides a maximum of The consequence is the real charger will charge your iPad almost twice as fast. For details on these graphs, see my article testing a dozen chargers. The other thing to note is the line for the Apple charger is smooth and thin, while the counterfeit charger's line is all over the place. This indicates that the power provided by the counterfeit charger is noisy and low quality.
The yellow line shows the voltage. The real charger has a stable yellow thin line, while the counterfeit charger's output has large voltage spikes. I had to change the scale to get the output to fit on the screen, so the counterfeit charger is actually twice as bad as it appears here. The bottom of the counterfeit charger's yellow line is wavy, due to Hz ripple appearing in the output voltage. The counterfeit spectrum is much higher in general, with a large spike at the switching frequency.
This shows that the counterfeit charger's power is worse across the frequency spectrum. You might wonder if the power quality actually matters. The biggest impact it has is on touchscreen performance. The interference from bad power supplies is known to cause the touchscreen to behave erratically. Inside the real charger's transformer There's more inside the transformer that you'd expect. This section does a full teardown of the transformer from the genuine charger.
Next, removing the ferrite core and more insulation reveals the double-stranded primary winding. The high-voltage input is fed into this winding. In the photo, this winding has been removed and is surrounding the transformer. After removing more insulating tape, the secondary winding of the transformer is visible.
As discussed in the safety section, the secondary winding has triple-insulated wires and extra insulation where the wires leave the transformer. The next layer of insulation right contains copper foil.
This helps reduce interference. Splitting the primary winding into two layers is more expensive, but results in a better transformer due to better coupling of the magnetic fields. In comparison, the transformer of the counterfeit charger is much lower quality. I haven't included the pictures for reasons of space; click through to see them. It simply has the bias winding pic , secondary winding pic , and primary winding pic , separated by insulating tape.
Unlike the genuine transformer, the counterfeit saves cost by omitting the copper foil layers. The counterfeit also doesn't use the more expensive split, multi-stranded windings that the genuine charger uses. As discussed earlier, the secondary winding is plain copper wire, not triple-insulated wire, which is a significant safety flaw. How does the iPad charger compare to the iPhone charger?
The iPad charger is considerably larger than the iPhone charger and provides twice the power. In my detailed iPhone charger teardown I looked at the internals of the iPhone charger.
The iPhone charger below uses two circuit boards that combine to form a one inch cube, which is impressive engineering. The iPhone and iPad chargers are both flyback switching power supplies, but the feedback mechanisms are very different. The genuine iPad charger is almost identical [18] to the reference design schematic provided by iWatt. The counterfeit charger is almost identical to the schematic in the DB02A controller datasheet.
You can see from the schematics that the genuine charger has a much more complex circuit than the counterfeit. Click the thumbnails below to get to the datasheets. Apple's charger is expensive compared to other chargers, but is a high quality product. You should definitely stay away from the cheap counterfeit chargers, as they are low quality and dangerous.
Non-Apple name brand chargers are generally good quality according to my tests , with some better than Apple.
If you want to get an Apple charger without the high price, the best way I've found is to buy a used one on eBay from a US source. I've bought several for testing, and they have always been genuine. I wrote earlier about Apple's huge profit margins on chargers. The counterfeit charger is also impressive in its own way - it's amazing that a charger can be manufactured and sold for such a low price if you don't care about safety and quality.
Overall, you mostly get what you pay for; even if you can't tell from the outside, there are big differences inside the case. Notes and references [1] Foxlink Taiwan , Foxconn Taiwan , and Flextronics Singapore are all manufacturers for Apple with confusingly similar names. Foxconn is the company with controversy over employee treatment; this charger is made by Foxlink, a different company.
Interestingly, the chairmen of both companies are brothers and the companies do a lot of business with each other. The companies state that they are entirely independent, though statement , Foxlink annual report. Foxconn and Flextronics are the world's 1 and 3 largest electronics manufacturing companies according to the MMI top 50 for , while Foxlink is smaller.
When a voltage pulse is sent into the transformer, the output diode blocks the output so there is no output - instead a magnetic field builds up in the transformer. The transformer core has a tiny air gap to help store this field.
When the voltage input stops, the magnetic field collapses, transferring power to the output winding. Flyback power supplies are very common for low-wattage power supplies. The DC voltage is approximately sqrt 2 times the AC voltage, since the diode charges the capacitor to the peak of the AC signal.
Thus, the input of to volts AC is converted to a DC voltage of to volts internally. This isn't enough to be officially high voltage but I'll call it high voltage for convenience. According to standards, anything under 50 volts AC or V dc is considered extra-low voltage and is considered safe under normal conditions.
But I'll refer to the 5V output as low voltage for convenience. It's a puzzle why some companies use TO to describe 4-pin inline packages. According to the datasheet Chinese , the chip is for mAmA chargers, which explains why the counterfeit charger only produces 5 watts, instead of the 10 watts an iPad charger is supposed to produce.
I couldn't find any US chips similar to this chip, even after a lot of searching; it appears to be a Chinese design with datasheets only in Chinese, manufactured by "Fine Made" Shenzhen Fuman Electronics. Since the chip only has four pins, I expected it to be a trivial Ringing Choke Converter RCC circuit with just a couple transistors inside the chip - but I cracked it open with Vise-Grips and it turns out to be a fairly complex chip.
I took a picture through a microscope of the IC die, which is about 1 mm across. One interesting feature is the many white pads around the outside of the die, which are used to blow fuses to trim various resistances in the chip. I wasn't expecting to see this level of quality and sophistication.
The die has the label "N " at the right; I don't know what this indicates. Three of the four wires connect in the lower left, and the fourth in the lower right.
This transistor is a version of Motorola's MJE switchmode transistor which was introduced in MJE indicates power device in a plastic package. The bridge rectifier is a B6M datasheet.
The output diode is a SR Schottky barrier rectifier. This capacitor helps reduce EMI interference, and is specially designed to avoid any safety hazard. It does, however, pass a tiny amount of electricity - if you feel a tingle from your charger, these capacitors are probably the cause. I had some an eletronics lab where we designed basic linear sources, very nice to have a look at real world! Thanks for the comments. LeMadChef: 12V converters would be interesting to examine; perhaps a future article.
Waskita: to measure the power curve, I used a power mosfet as a variable load, and plotted the voltage and current with an oscilloscope as I changed the load. See footnote 16 for more details. Is it dangerous to use a high output power charger, like the HP TouchPad one, with a low consumption device, like a phone?
Thanks :. Be curious how they rate in your tests. The blackberry playbook charger would be a good one to check out as well. I've been using one of those to charge everything recently. Thanks for the well explained walk through! I recently purchased one of these on eBay, and it actually blew up when I dropped it! Thank you for an informative read. Can you do this comparison for genuine original laptop AC adapters and a cheap aftermarket one? Perhaps you can do a test based on your current laptop so only need to spent a few dollars on a cheap one to compare it with?
Thank you! Hi Ken, Interesting article. At the beginning, you mentioned "noisy power that cause touchscreen malfunctions". I'm going through the source you linked to, but I have had this question in my head for a while now, so I'll just put it here. For some reason, Indian Railways has V power sockets in trains. When charging phones in the train, it always happens that the touchscreen goes wonky. Different phones show different behaviour, from totally non-responsiveness to very heavy lag or some offset in the touch location.
So that would mean that the power coming in from the train sockets is very noisy. In that case, how much blame do we assign to the charger for not filtering it out? Great post. Please analyze more chargers, like the Amazon Kindle PowerFast. Also, it would be good to understand the Android situation, where I understand the data pins have to be shorted together in the charger or cable?
My guess is the voltage sag is intentional and helps to reduce the power dissipated in the wall charger itself. There is no need to maintain exactly 5V at the charger output when the battery is at a low charger level. As along as the sag does not extend lower than 4. I have a suggestion for an article topic..
I was totally surprised that various cables I have around the house have totally different charge rates. U R Clueless. Thereafter it wont charge Apple of course, but who cares. So the author should have tested first if the charger was a standard USB-charger or Apple-crapped.
Because now the test results are useless, because non-standard charger can deliver only max mA to a standard device. Interesting that the HP touchpad charger won - it's the charger we can't stand to have in the bedroom. When not under load, ours gives off a high-pitched like 10khz whine that drives us crazy.
Fascinating article. One thing I'd be interested to see would be how this maps on to the European insistence that everything use a micro-usb cable, so that people can minimise the number of charges they own.
It seems to me from your article that phone manufacturers are still only paying lip-service to such a standard, if the charging voltages are being provided on distinct pins.
Have you ever come across the Momax brand of chargers. It's a fairly well-known brand of third-party chargers in Hong Kong and Mainland China.
Their chargers seem to have a fairly solid build, just from the looks. I would love to see an analysis, especially one of the BS ones. Iwould love to see a similar set of tests that included some wall sockets with built in USB chargers.
It is really tempting to be able to plug a usb cable right into the wall rather than having to use a bulky adapter. Author Please report the items with fake UL livery. Was an eye opener and brought up a lot of good points that I never considered. Would it be possible to do the same thing with Car Chargers? As most of the time I have to charge my phone in the car. There is no reason for a powersupply to HAVE a constant-current mode.
A charger rated at say 1. The problem is, you'll never supply the startup-current of a few capacitors on the output this way. But a powersupply could be designed to provide say 1. From then on it will shutdown when 1.
Anyway, in practice you're right, most have a constant-current phase leading up to the "overcurrent shutdown". Ken, do you know what the max draw is for an iPhone 4 or 5? Would they benefit from using the 2. Does it really use 0 vampire power when not plugged into the phone? Do other chargers shut off when unplugged? What is the quality of the power? You seem overly concerned with the voltage of the Apple adapters. The USB spec allows the supply voltage to vary between 4. So the iPad power supply drooping down to 4.
Also the iPad supply is advertised as a 10W adapter and that's exactly what it delivers. It seems perverse to mark it down for living up to its specification. The power supplied is a USB nominal 5V, which is allowed to be as low as 4.
Great article! I have a general question: I have moved to India and am using my US chargers at v. I also have some stepdown transformers for the things that require v. In general, would it be better to charge through the transformers--IOW, do they help to prevent surges and spikes? Since HTC is doing well with their phones these days, why not review it. A teardown would be nice too. Oh, and the Apple MagSafe chargers too! That was an awesome article, I have been buying some of that junk, no more.
I put in a few Leviton ones and now I only need chargers when I travel. Great article, I never knew there was so much to tell about USB chargers. Like a couple of others, I would also like a test of an HTC charger.
As a matter of interest how was the fake UK charger connected to the the presumably US power supply? Was any attempt made to separate the effect if any of the socket adaptor from the device performance? Also looking at the oscilloscope traces I suspect that not only was this tested only for V but also only at 50Hz. Thank you so much for the fascinating article! I really enjoyed it and certainly learned a few things. Great article. It's marketed as a premium usb charger and seems to be pretty nicely made.
Thank you so much for posting your findings! I'd bet it probably took you a long time to buy the charges, evaluate all the different measurements and present your findings. I am grateful for your hard work. Can you test some Scosche chargers.
They seem to be a very popular aftermarket choice for chargers, making single usb, multiple usb, car chargers, 1A and 2A chargers. Great analysis and data!
The reason that holograms aren't used is that they only add a few cents to the cost of counterfeiting an item. Holograms are old news; you can buy stacks and stacks of "authentication holograms" in shenzhen. Great article, i was looking for some more information around these chargers. Is there any chance there is a car USB charger variant in the planning?
Question: if you've been using generic cheapo chargers with no ill effects does that mean they're okay or I should stop using them because they will damage the phone over time?
Nice work. This is interesting. In light of the capacitor plague please see Wikipedia. Do you have any intentions of testing older power supplies. In my experience Apple power supplies, at least until , suffered terribly from that. Also, could you make one graph that shows the voltage output, versus amp draw, of all the power supplies. The votes are all in and "car charger" won for the charger that people are most interested in. Kindle narrowly edged out iPhone 5 at the end. Thanks to everyone who voted; stay tuned for more teardowns.
Anonymous who asked about the oscilloscope probes I used: they are surprisingly expensive Tek P and PA probes. Many people asked about cables. I found an article where someone tested cabled. The quick summary is cheap cables have higher resistance which makes charging slower. Akshay: sounds like Indian trains have bad quality power.
Why V in trains and V normally? It would be interesting to see if higher quality chargers do a better job filtering the power on Indian trains. Next time I visit India I'll bring a bunch of chargers, an oscilloscope, and a train ticket :- Anonymous with the step-down transformer: My guess is that using the step-down transformer provides a bit of filtering if the input power is bad due to its inductance , but it wastes some power in the process.
In India, I just plug US chargers into V after carefully reading the label to make sure it will take the voltage. I use a Kensington travel adapter , which converts the plug format, not the voltage. Andrew S: thanks for the info on holograms. Andsetinn: I probably won't be testing computer power supplies as tomshardware and jonnyGURU cover them extensively. There are lots of comments about testing brand Bb and aaaa.
I think the only way the author can test is to send him two units! I would like some clarification about the "Indicated charger type" test. What is used as a load? An iDevice? A resistor? Various device depending on the charger? Thank you for a thorough and informative testing effort and write up. I would be interested to see a wider range of chargers tested, as manufacturers even the good ones seem to provide little information on their products beyond nominal input and output figures.
In the meantime I'm investigating getting hold of a Touchpad charger to replace a Chinese generic that I bought before from a well-known internet auction site. Would be interested to send it to you for testing, but it seems you're on the other side of the pond for that to be easy. Regards from the UK, Rob. They all say genuine, and have pictures if what appears to be the real charger, but I'm skeptical that they are fakes. Anyone order one? There are most definitely fakes of the hp charger out there.
Be skeptical of any shipping from china. They are most likely the Kmashi charger that looks identical in the listing. Some listings go out and say it isn't the official one, while others say it is official. This is a great review, I'll be picking up another touchpad charger. Are you going to do a car charger review? I want to buy one of the dual 2A units, but I'll wait if you are going to review them.
Great job. You spoiled the review for me ;- by your misuse of "eschew". Angus, thanks for your comment. What I mean is that chargers such as Apple have a minimalist cube design, while the Belkin charger adds multiple non-functional design elements such as ridges, swoops, and an oval shape to make the charger more interesting.
The HP touchpad charger looks like a slightly larger version of my old Palm Pre charger. I checked, the prongs twist off in the same way, had that for years, never knew.
It would be nice to see it tested too. Per your recommendations and data I purchased an HP Touchpad charger. When I connect it to my Ipad 3, the battery status indicates "Not Charging". My initial thought is that Apple "programmed" it that way to discourage 3rd party accessories.
Hi Donnie! I'm sorry to hear that your charger isn't working. The problem is probably explained in the "Indicated charger type" section of the article, and footnote 6. Apple uses proprietary voltages on the middle two pins to indicate that it's an Apple charger, and HP uses different voltages to indicate that it's an HP charger. So the iPad can tell that it's not an Apple charger.
One thing to check: does it still charge, even though the device says it isn't? I agree that noisy, spiky output can lead to instability and undesirable behaviour in sensitive electronics, such as the aforementioned touch-screens, while charging Batteries will happily accept any electrons that come by. In fact, a battery should act as a great big smoothing capacitor. I'm not defending the junky Chinese chargers that might zap you, burn your house down, or simply don't work, but lets not get carried away and pretend like we're performing high precision experiments in a research lab.
Most of us just want to charge a device, and you don't need to shell out a day's wages for a shiny crApple branded premium charger to get the job done. I still have an adapter from a Pong game console. It consists of a transformer, a single diode and an electrolytic capacitor. Ken, thanks very much for such an informative post.
If you are at all inclined to test any of the additional devices people have asked for, perhaps you should set up an Amazon wishlist with them on and the people who want you to test them can buy them for you. Hi Ken Great work! But my experience of switch-mode wall-warts is that too many of them die, almost invariably because of inadequate ripple-rating of either the mains-side electrolytic capacitor or else the first electrolytic after the secondary-side rectifier.
The equivalent components in the Standby-supply section of a desktop-PC PSU account for nearly all dead ones of those too. BTW For live-side measurements I use a Tektronix P HV Differential probe - this has been an expensive but most-useful accessory and is good at rejecting stray-fields around switching supplies!
Great article, and long overdue. If you redo the AC chargers in the future, could you see if you can do a conducted emissions test on the AC side? As that would interest a lot of Ham Radio guys and gals out here.
Some of these things can be very noisy when left powered, but not connected to anything. I have some very noisy car 12V DC powered phone chargers too, the worst being a branded product that came with a phone!
As someone else said, after market laptop chargers vs originals would be an interesting comparison too. Keep up the great work. This is a great post. Very helpful. So, for some questions: 1 Would this be a good idea? You say your previous teardowns where "surprisingly popular", considering that your writing is a surprisingly good read for such a boring subject, and not only a good read, but a very thorough investigation of this important subject.
Nobody -not on the web- has better consumer advice in this particular area than you have here on this blog. Keep on Hey Ken - this was super informative and I wanted to thank you for it. A charger is just some normal, every day piece of technology that people pay little to no attention to at all but as you've found out, they are not created equal and vary wildly in terms of performance.
Furthermore, if you have a watt adapter, the compatibility page for the watt adapter states it is compatible with the iPhone 8 and newer. If you charge your iPhone with your iPad charger, your iPhone will charge as normal, and once fully charged, it will stop charging because iPhones have battery technology that stops charging once completely full.
You may get some fast-charging benefits from charging your iPhone with your iPad charger. You should see no differences other than the length of time it takes to charge your iPhone when you're using your iPad charger for your iPhone. However, note that if you try to charge your iPad with the lower wattage iPhone charger, it will still charge, but it will take longer. If your iPhone is charging slowly or not charging at all, examine the charging cable and USB adapter for signs of damage or debris.
Try replacing the cable and see if this solves the problem. If you're still having problems, force-restart your iPhone , then let it charge for another 30 minutes. If the iPhone still won't charge, contact Apple support. If you don't have access to an AC adapter and wall outlet, you have a few options. Try using a car charger or charge your phone wirelessly with a compatible Qi-certified wireless charger.
You can also use a USB cable to charge the iPhone via your laptop, use a portable charger , or try a charging case. There are even hand-cranked and solar chargers out there for when you're really off the grid. Actively scan device characteristics for identification. Reply I have this question too I have this question too Me too Me too.
Answer: A: Answer: A: The iPad charger has two pieces, the charger itself and a plug "duckbill" that slides on the charger block. View answer in context. All replies Drop Down menu. Loading page content.
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