On the other extreme, the fake iPhone charger used mW. The Apple iPhone charger performed surprisingly badly at mW. If plugged in for a year, this would cost you about 21 cents in electricity, so it's probably not worth worrying about. The HP charger was the winner here. If you look closely, the genuine one says "Designed by Apple in California", while the counterfeit has the puzzling text "Designed by California".
The counterfeit also removed the "Apple Japan" text below the plug. I've seen another counterfeit that says "Designed by Abble" not Apple. I assume the word "Apple" is removed for legal or trademark reasons, since the word "Apple" is often but not always missing from counterfeits. Samsung oblong I call this charger the Samsung oblong charger, to distinguish it from the Samsung cube charger.
Samsung cube The Samsung cube charger is shaped very similarly to the Apple iPhone charger.
Internally, however, it turns out to be entirely different. Apple iPad and counterfeit The photo above shows a real iPad charger left and a counterfeit right. The counterfeit has almost identical text, but without "Designed by Apple in California. The above photo shows a real iPad charger on the left and a fake iPad charger on the right, with the plug removed. The most visible difference is the real charger has a round metal grounding post, while the fake has plastic.
The US plug isn't grounded, but in other countries the lack of ground in the counterfeit could pose a safety hazard. The charger twists apart, allowing the plug to be replaced for different countries. It took me weeks to discover this feature.
It is a relatively large charger. They've removed Apple from the text, but left Emerson Network Power, which I'm sure is not the actual manufacturer. Belkin The Belkin charger eschews the minimal design styling of most chargers, with a roughly oval cross section, curves and ribs, and a cover over the USB port. It also gives off a blue glow while in use. The plug can be removed and replaced for use in different countries, similar to the iPad and HP TouchPad chargers. I couldn't find any UL safety approval on this charger, but I did find a report of one catching fire. Motorola The Motorola charger has the lowest listed power output, mA.
The back of it has a holographic sticker like a credit card , which may ward off counterfeiters, even though it's unlikely for anyone to counterfeit this charger. I wonder though why Apple doesn't use holograms or other anti-counterfeiting techniques, given the large number of counterfeit Apple chargers being sold. Delivery of advertised power Each charger has an advertised power output, but some chargers produce considerably more and some produce much less.
Your device will take longer to charge, if the charger can't put out enough power. This table shows each charger's ability to deliver the rated power, based on my measurements of maximum power. While most chargers meet or exceed the power rating, there are some exceptions. The counterfeit chargers perform extremely poorly, putting out a fraction of the expected power.
Charging your device with one of these chargers will be a slow, frustrating experience. In particular, the counterfeit UK charger only produces a third of the expected power. Although the label claims the charger works on volts, it's clearly not designed to work on US power.
The iPad is a surprise, putting out less power than expected. Despite being nominally a 10 watt charger, the label says it provides 5. However, the maximum power I measured is Since the measured power is slightly less than advertised, it only gets four bolts. I analyze it for voltage spikes, high frequency noise, and line-frequency ripple. The following table summarizes the results in three categories.
Spikes indicates extremely brief large voltage spikes in the output, while Noise indicates high-frequency noise in the output, and Ripple indicates low-frequency Hz fluctuations in the output. The left images provide high-frequency information on the output voltage. The right images show the low-frequency information on the output voltage. However, some factors mess this up.
First, any ripple from the power line will show up as 5 sinusoidal peaks in the first high-frequency yellow line. High-frequency noise will widen the yellow line. Voltage spikes will appear as vertical spikes in the yellow line. The plots also show the frequency spectrum in orange, from 0 at the left to kHz at the right. The desired graph would have the orange spectrum near the bottom of the screen.
Thus, the power quality exponentially gets worse as the orange line gets higher. The left high frequency spectrum generally shows noise at the switching frequency of the charger and harmonics. The right low frequency spectrum typically shows spikes at multiples of Hz, caused by ripple from the 60 Hz power. The iPhone charger performs extremely well at filtering out spikes and noise, the best of the chargers I measured.
Apart from the Hz spikes, the noise spectrum orange is flat and very low. The power quality is so good, I checked the results several times to make sure I wasn't missing something. Samsung oblong The Samsung charger's output has a lot more noise than the iPhone charger. This is visible in the thickness and jaggedness of the yellow output curves. The orange frequency spectrum on the left shows large peaks at harmonics of the switching frequency. The Hz spike on the right is a bit lower than the iPhone charger, so the ripple filtering is a bit better.
Samsung cube The Samsung cube charger shows some noise in the output yellow. The frequency spectrum shows wide peaks at multiples of the the switching frequency, about 90kHz. There's some ripple. Apple iPad The iPad charger almost eliminates the ripple; only a small blip is visible in the orange spectrum on the right. The noise level is low, although appreciably worse than the iPhone. The overall noise level is good.
Counterfeit iPhone The output from this counterfeit charger is a wall of noise. In order to fit the waveform in the display, I had to double the scale on the left and increase it by a factor of 5 on the right, so the yellow curve is actually much worse than it appears. On the left, note the huge ripple with massive high-frequency noise on top. This output is not something you want to feed into your phone. Monoprice The output from this charger is very noisy, as you can see from the thickness of the yellow line. Note that the frequency spectrum left has very tall but narrow spikes at harmonics of the 28kHz switching frequency, showing a lot of high-frequency noise.
On the positive side, there is hardly any ripple. Counterfeit UK This charger has very bad output. The large degree of ripple is visible in the waveform yellow, left and the very large spikes in the spectrum orange, right. The thickness of the yellow waveform shows the large amount of high-frequency noise, which is also visible in the very high peaks in the spectrum orange, left.
Counterfeit iPad This counterfeit charger has so much noise in the output that I had to double the scale on the left to get it to fit. Note the very large spikes in the output yellow. The spectrum orange, left is much higher everywhere, indicating noise at all frequencies. Surprisingly, it has only a moderate amount of ripple; the manufacturer seems to have done at least one thing right.
Belkin The Belkin charger does well at eliminating ripple, but has a lot of noise otherwise. The spectrum orange, left shows large peaks. KMS The KMS charger has fairly good output, with a small peak in the spectrum orange, left at the switching frequency. It has no detectable ripple.
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However, it has many large voltage spikes in the output, over half a volt, as can be seen on the right. Motorola The Motorola charger has a lot of spikes in the output yellow. The spectrum orange, left shows high frequency noise at the switching frequencies. There's a moderate amount of ripple yellow, left and orange, right. Summary The quality of the output power is radically different between chargers. The counterfeit chargers are uniformly bad, with hardly any effort at filtering the output. The other chargers vary in quality with the iPhone charger setting the standard for noise-free power, but surprisingly poor filtering of ripple.
The power quality is a key factor that affects the performance of chargers; spikes and noise are known to interfere with touchscreens. The first rating is Voltage Sag , which is the undesired drop in output voltage as the load increases. The second rating is Current Sag , which shows how the current fluctuates as load increases. Finally, Regulation shows the overall stability of the output from the charger.
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Each point on the curve shows the current X axis and voltage Y axis produced by the charger under a particular load condition. Follow the yellow curve clockwise from the upper left to the lower left to see the effect of increasing load. The upper left point of the curve shows the voltage produced by the charger when there is no load on the charger. As the load increases, the charger is supposed to keep a constant voltage and increase the current i. If the load continues increasing, the charger switches to a constant current mode, dropping the voltage while continuing to provide the maximum current i.
The charger starts off with 5. As the load increases, the current keeps increasing, resulting in the slope of the right yellow line. Note however that the yellow line is relatively thin, so the regulation is pretty good at each point. Note that because this charger has a high current output, this chart has a different current horizontal scale than most of the charts to fit the whole trace in the image.
Stretch it horizontally to compare with other graphs. Samsung oblong For this charger, the voltage is approximately flat, except for a bump under no load upper left which is probably a measurement artifact. The vertical yellow line shows the current stays nearly constant as the load increases. The charger shows good voltage and current stability under changing load.
The yellow line is a bit wider than the iPhone charger, showing a bit less regulation for a fixed load. Samsung cube The voltage curve sags slightly under load. The right hand curve shows the current stays stable, but the line is moderately wide, showing a bit of weakness in regulation. Apple iPad Similar to the iPhone charger, the iPad charger shows a lot of voltage sag. The voltage is about 5. Unlike the iPhone charger, the iPad charger has pretty good current stability. The regulation is solid, as shown by the narrowness of the yellow trace.
Note the scale change due to the high current output. I'm puzzled by the steep voltage sag on both the iPhone and iPad charger. Since the designers of the Apple charger went to a great deal of effort to build a high quality charger, I conclude they must not consider voltage sag worth worrying about. Or, more interestingly, maybe they built this sag as a feature for some reason.
In any case, the chargers lose points on this. HP TouchPad The charger has some voltage sag, but the current vertical is nice and constant. The yellow line is relatively thin, showing good regulation. Counterfeit iPhone This counterfeit charger shows extremely poor regulation, as shown by the very wide yellow line.
It's hard to fit a voltage-current curve to this picture. The amount of power supplied by this charger seems almost random. Monoprice The Monoprice charger shows reasonably straight voltage and current lines showing good constant voltage and current outputs. The vertical line shows some width and noise, suggesting the regulation isn't totally stable. Counterfeit UK For this charger, the upper line doesn't get very far, showing that this charger doesn't output much current. My suspicion is that it was only tested with volts so it performs poorly with volts, even though the label says it takes to volts.
The width of the yellow line shows very poor regulation. Counterfeit iPad The output of this counterfeit charger is so poorly regulated that it's hard to tell exactly what's happening with the voltage and current. It looks like the voltage is roughly constant underneath all the noise. Belkin The Belkin charger shows voltage sag as the current increases.
In addition, the output is fairly noisy. In addition, the output is all over the place, showing very poor regulation, more like what I'd expect from a counterfeit charger. Motorola The Motorola charger shows a bit of voltage sag, but good current stability. The regulation is good but not perfect, as shown by the width of the yellow line. The gaps in the vertical line are just measurement artifacts.
Note that the maximum current output of this charger is fairly low as advertised. Conclusions So what charger should you spend your hard-earned money on? First, make sure the charger will work with your phone - for instance, newer iPhones only work with certain chargers. Second, don't buy a counterfeit charger; the price is great, but it's not worth risking your expensive device or your safety. Beyond that, it's your decision on how much quality is worth versus price, and I hope the data here helps you make a decision.
How about some teardowns? My previous iPhone charger and fake charger teardowns were surprisingly popular, but if you were hoping for teardowns on the full set of chargers, you'll need to wait for a future blog post. I haven't torn the chargers apart yet; if I need to take more measurements, I don't want to have just a pile of parts. But I do have some preview pictures to hold you over until my teardown article. The above picture shows the internals of a counterfeit Apple iPhone cube charger. The two boards stack to form the compact cube shape. This charger blatantly tries to pass as a genuine Apple charger; unlike the "Designed by California" charger, this one exactly copies the "Designed by Apple in California" text from the real charger.
Note the very simple circuitry  - there are no components on the other side of the board, no controller IC, and very little filtering. Also look at the terrible mounting of the transistor on the front right; clearly the build quality of this charger is poor. Finally, note the overall lack of insulation; this charger wouldn't meet UL safety standards and could easily short out. But on the plus side, this charger only cost a couple dollars.
The transformer is very short to fit into this charger. Like the previous charger, it uses a very simple circuit,  has little filtering, and almost no safety insulation. Finally, the above pictures show the internals of the Samsung cube charger, which has circuit boards packed with tiny components and is much more advanced than the counterfeits although slightly less complex than the Apple charger.
Despite being very similar to the Apple charger on the outside, the Samsung charger uses an entirely different design and circuitry internally. One interesting design feature is the filter capacitors fit through the cut-out holes in the secondary circuit board, allowing the large filter capacitors to fit in the charger. More comments on this article are at Hacker News and reddit.
Thanks for visiting! Notes and references  For an explanation of how the noisy output from cheap chargers messes up touchscreens, see Noise Wars: Projected Capacitance Strikes Back. With this design a tablet charger could be as small as the iPhone charger. These chargers use an extremely simple feedback mechanism in place of the control IC in higher-quality chargers.
See a comic-book explanation or a technical explanation for details. The pulses are smoothed out with filter capacitors before being fed into the switching circuit, but if the filtering isn't sufficient the output may show some Hz ripple. Because of this, an "incorrect" charger may be rejected by an iPhone with the message "Charging is not supported with this accessory". However, companies such as Apple, HP, and Sony have their own proprietary nonstandard techniques.
The Apple 2A i. For details on USB charging protocols, see my references in my earlier posting. Amusingly, semiconductor manufacturers have recently introduced chips that allow chargers to sequentially pretend to be different proprietary chargers until they trick the device into accepting the charger. It seems crazy that companies such as Apple design incompatible chargers, and then chip companies invent schemes to work around these incompatibilities in order to build universally compatible chargers. For Energy Star ratings, a 5W charger must have under.
A 10W charger must have under. I measured the AC input voltage and current with an oscilloscope. The oscilloscope's math functions multiplied the voltage and current at each instant to compute the instantaneous power, and then computed the average power over time. For safety and to avoid vaporizing the oscilloscope I used an isolation transformer.
My measurements are fairly close to Apple's  , which is reassuring. Unfortunately it doesn't have the resolution for the small power consumptions I'm measuring: it reports 0. Ironically, after computing these detailed power measurements, I simply measured the input current with a multimeter, multiplied by volts, and got almost exactly the same results for vampire power.
The Spikes measurement is based on the maximum peak-to-peak voltage on the high frequency trace the low frequency trace yields almost identical results. The Noise measurement is based on the RMS voltage on the high-frequency trace, and Ripple is based on the maximum dB measured in the low-frequency spectrum. These measurements appear on the right in the traces. The low-frequency right images show 1 second of the output voltage in yellow and the frequency spectrum up to Hz in orange.
Because the frequency spectrum is measured in dBm, it is logarithmic; every division higher indicates 20 dB which is 10 times the voltage and times the power. It lists 0. These values are reasonably close to my measurements of 0. The transistor needed a large heat sink to dissipate 10 watts. A more complex dynamic load circuit is described here , but the simple circuit was sufficient for me. The graphs were generated using the X-Y mode on the oscilloscope, with the load voltage as Y and the current as X.
I used a. Note that increasing load corresponds to a decreasing resistance across the output: the upper left has infinite resistance no load , the lower left has zero resistance short circuit , and the resistance decreases in between. The load resistance can be computed by Ohm's law, e. Middle of the right hand curve: 2. The manufacturers of the chargers can be looked up from the UL certification number.
The counterfeit chargers are made by anonymous Chinese manufacturers, despite what they claim on the labels.
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The Belkin charger is manufactured by the obscure company Mobiletec of Taiwan. Apple uses a dizzying variety of manufacturers for their chargers. The A iPhone charger often comes with the iPhone 5 and looks identical to the A I measured, but is manufactured by Emerson Network Power instead of Flextronics. I am told that by using multiple manufacturers, Apple has more negotiating leverage, since they can easily switch manufacturers at any time if they're not happy with the price or quality. Foxlink the name for Cheng Uei Precision Industry and Foxconn the name for Hon Hai Precision Industry are entirely independent companies aside from the fact that the chairmen of both companies are brothers and the companies do a lot of business with each other statement , Foxlink annual report.
Foxconn is the company with continuing controversy over employee treatment. Foxconn and Flextronics are the world's 1 and 2 largest electronics manufacturing companies according to the Circuits Assembly Top Email This BlogThis! What model of scope and probes are you using? Thank you for the great article on usb power supply. I'm surprised to learn how bad the fake power supplies are. Be careful when shopping for usb chargers or batteries over Ebay. I've been burned with few bad batteries as well. Does using a chinese iPhone charging cable matter than the original one? Thanks for a detailed article.
Hi Anonymous! Instead of buying the Tektronix, you might want to get a Rigol and a new car :- I'm not sure what probes were attached. Anonymous 2: the charging cable shouldn't matter, unless it's really bad. Would that be possible? Very cool! 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. And the iPhone 5s and 5c work perfectly well with these these accessories. However, iOS 7 brings some bad and some good when it comes to using an external keyboard. On the bad side, if your external keyboard has a dedicated Spotlight-search key, that key no longer brings up a Spotlight search under iOS 7.
From a gesture standpoint, Apple changed the way you access Spotlight in iOS 7: Instead of pressing the Home button or swiping to the right when on the first Home screen, in iOS 7 you swipe down on any Home screen. On the good side, iOS 7 has added support for a few new shortcuts when using an external keyboard thanks to Tao of Mac for the tip. Third-party Lightning-connector accessories The other iOS 7-related issue relates to third-party Lightning-connector accessories. Apple has long recommended that people use only officially licensed accessories—those displaying the Made for iPhone, Made for iPad, or Made for iPod badge—with their iOS devices.
However, licensed gear tends to be more expensive than unlicensed, both because Apple charges a fee for licensing and because most licensed gear comes from name brands. So unlicensed gear, which tends to be cheaper, has become quite popular. The same thing happens with my new iPhone 5s. A couple of the cables still allow charging and syncing, despite the warning, but two others no longer function at all. Licensing the Lightning connector gets a vendor more than just a badge for its packaging.
It also provides access to special authentication circuitry inside the connector itself. Some companies have attempted to reverse-engineer the circuitry, some more successfully than others, but the risk to buying unlicensed gear is now greater than before. The iPad Pro just got a massive discount at Amazon.
If you need to charge more than two devices at once, this is the car charger to get. Each of its ports can put out 12 watts, and one supports Quick Charge 3. Previously, for three years I was the accessories editor at iLounge , where I reviewed more than 1, products, including numerous charging options. This step allows us to definitively say that our picks work exactly as advertised, putting out the right levels of power and adhering to safety standards. Good USB-A chargers can charge more than twice as fast 12 watts , and the latest USB-C chargers can charge modern smartphones at up to 18 watts as long as you use a cable that plugs into the smaller port instead of the USB-A cable that probably came with your device.
This is our favorite cable for iPhones. All of our picks let you charge two or more devices from a single accessory outlet—something your family and friends will appreciate. Over the past few years, these models have become significantly smaller, more powerful, and less expensive—just like USB wall chargers.
These days, a good USB charger for the car should offer the following:. To find the top options in each category, we put the finalists through a number of tests. Once we had these results, the Wirecutter team had a spirited discussion about the pros and cons of different physical sizes: Is smaller always better, or can a charger be too small? Other USB-C car chargers with 18 W output— we tested four others —can charge a phone just as quickly, but few pair that capability with a quality USB-A port, and none do so for such a good price.
Since many compact laptops charge at 30 or 45 W, you can even use this Nekteck charger to quickly fill them up on the go. In our tests, its USB-C port charged the and The larger iPad reached 33 percent charge in half an hour and 65 percent in one hour. The body of the Nekteck PD 45W combines glossy black plastic and matte metal elements. It sticks out 1. You can keep this cable in your car to charge your Android phone, computer, or iPad Pro without having to buy a separate accessory.
Android phones, including the Google Pixel family and the latest generations of the Samsung Galaxy line, would see similar gains compared with using USB-A chargers. The Scosche also performed as expected when we ran it through the Total Phase test, showing the proper power rates and no errors, so it should be compatible with any device that charges on the USB-C standard.