First, voltage stability is different
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USB voltage relative to the charger, the error is small, but also very stable, in this respect, the voltage error and stability is much better than the charger.
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Second, different currents
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USB voltage is DC 5V, but the computer in front of the use of small wire power supply, if the use of inferior wire, sometimes afraid of insufficient current, not enough voltage, resulting in heat. The back of the computer is led from the motherboard, the copper will be thicker, no heat concerns. For charging, a slight fluctuation in voltage will not have any effect on charging, precisely speaking, a certain period of pulse fluctuation charging is very good for the battery, especially for lead-acid batteries and nickel-hydrogen-nickel-cadmium batteries.
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Third, the difference in charging speed
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Charging through the USB interface, the maximum current to supply the computer can only be 500mA, and charging through the charger, often more than 500mA, many chargers tend to 800-1200mA. That is to say, charging through the USB interface of the computer, charging time is longer, if your charger provides current greater than 500 mA, charging time is shorter.
General USB charging only 5 volt ampere of current, the USB on the laptop and the USB on the board are relatively small, which will lead to the mobile phone charging speed is relatively slow.
Now the general mobile phone is standard, fast charge function. The use of the original charging plug will support Qualcomm's QC4.0 fast charge protocol, and the power can reach 60 watts, generally a 5000 mah battery will be full in one and a half hours, and the speed is quite fast!
As for the two charging methods, the difference is not big, the difference in speed. However, the plug charging speed is generally faster, because the current is larger, my mobile phone plug current is 1A, and the USB2.0 fixed is 500mA, that is, 0.5A, the voltage is 5V, so the speed is different, of course, it is recommended that you use the plug to charge, but if the phone and the computer exchange data at the same time charging, it does not matter.