If the output voltage is not filtered well, there will be noise and spikes due to the high-frequency switching. Ī poor design can suffer several problems. Name-brand chargers use a specialized control IC to run the charger, while cheap chargers cut corners by replacing the IC with a cheap, low-quality feedback circuit.
A feedback mechanism regulates the chopping frequency to keep the output voltage stable. The output of the transformer is converted to low-voltage DC, filtered, and provided as the 5 volt output through the USB port. The DC is chopped up tens of thousands of times a second and fed into a tiny flyback transformer. The input AC is first converted to high-voltage DC. Internally a charger is an amazingly compact switching power supply that efficiently converts line AC into 5 volt DC output. The result is a wide variation in the quality of the chargers, most of which is invisible to the user, who may believe "a charger is a charger". The small size makes it challenging to make an efficient, high-quality charger, while the commoditization of chargers and the demand for low prices pressure manufacturers to make the circuit as simple as possible and exclude expensive components, even if the power quality is worse. (See my iPhone charger teardown for more details.) These chargers cram a lot of complex circuitry into a small package, as you can see from the iPhone charger below. Monoprice Switching Mode Power Supply MIPTC1A Hewlett Packard LPS AC/DC Adaptor P/N 157-10157-00įake Apple A1265 "Designed by California" The counterfeit iPhone charger set a new low for bad quality, strikingly worse than the other two counterfeits. Much to my surprise, the HP TouchPad charger (which isn't sold any more) turned out to have the best overall score. The quick summary is that phone manufacturers provide pretty good chargers, the aftermarket chargers are worse, and $2 counterfeit chargers are pretty much junk. The overall rating below is the average of the ratings in nine different categories, based on my measurements of efficiency, power stability, power quality, and power output. The chargers are rated from 1 to 5 energy bolts, with 5 bolts the best. KMS power supply provides four USB ports.
Next is a counterfeit iPad charger that looks just like the real one.
The colorful orange charger is a counterfeit of the Apple UK iPhone charger. In the upper right, the Monoprice iPhone charger has a 30-pin dock connector, not USB. Next is a counterfeit iPhone charger, which appears identical to the real thing but only costs a couple dollars. The HP TouchPad power charger has an unusual cylindrical shape.
The Apple iPad power adapter is substantially larger than the iPhone charger but provides twice the power. The charger in the upper-left is the cube-shaped The above picture shows the twelve chargers I analyzed. In this article, I carefully measure the performance of a dozen different chargers, rate their performance in multiple categories, and determine the winners and losers. When you buy a USB charger, how do you know if you're getting a safe, high-quality charger for your money? You can't tell from the outside if a charger provides silky-smooth power or if it is a dangerous charger that emits noisy power that cause touchscreen malfunctions and could self-destruct.
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