Is there anything wrong with mixing iPad chargers to charge iPhone?

I don't know if you often mix charging cable with me. One day, when I borrowed his flat charging cable from another AI to charge my mobile phone, he just refused!

In the non fast charging mode, although the two charging lines are the same in length and the voltage is 5V, the charging current of iPhone is 1a, while that of iPad is 2.1a. According to P = UI, the power of iPhone charger is 5W, while that of iPad is 10.2w. The consequence of this is to hurt both the iPhone and the iPad charger (high current may cause breakdown of key capacitors!)


It's frightening, really?

I believe there are many people who often mix charging wires. After reading the title of this article, do you feel nervous? You don't have to worry about it at all. The author of the above "popular science knowledge" probably does not really understand the electronic knowledge, but just based on the parameters of the charger, he came to such a wrong conclusion.

To figure out why the iPad charger can charge the iPhone, you need to really understand how the charger works.
What is the charging process like
One end of the charger plug is connected to a 220 V AC socket, and the other end is connected to the iPhone / iPad with a dedicated Apple data cable. The 220 V alternating current is first converted into high-voltage direct current through the rectifier circuit, then into high-frequency high-voltage pulse through the switch tube, and then converted into low-voltage (such as 5 V) pulse through the transformer. The low voltage pulse of 5V passes through a rectifier and voltage stabilizing circuit to become a stable DC of 5V. In the whole process of changing from 220 V AC to 5 V DC, transformer, rectifier circuit and voltage stabilizing circuit only play a role in changing the form of electric energy (from high voltage AC to low voltage DC).

In the matter of charging, only the charger can't make a sound. If the 5V output end of the regulator circuit (USB interface) is not connected to the iPad or iPhone (term: load), there will be no current flow and no power consumption. After the load is connected, the charger starts to work. The current flowing through the charger depends on the state of the load: as long as the load (i.e. iPad or iPhone) needs as much current as it can, the charger will provide as much current as it can. If the current required by the load exceeds the upper limit of the current that the charger can provide, the charger will always output the maximum current. This is because the internal protection circuit of the charger is usually designed. Once the output current is too large, the protection mechanism will be triggered and the current output will be suspended.

However, in order to make all its chargers and digital products mix as much as possible, Apple has come up with a trick:

If you look closely at the USB interface, you'll find that there are four narrow metal strips, called four pins. These four pins are respectively connected with 5V power supply, GND ground, D + data line positive signal and d-data line negative signal.

Generally, the D + and D - pins of a charger compatible with USB interface are suspended. As long as any device is plugged into such a charger, it will get power from the 5V and GND pins. Apple's charger adds a voltage divider on the D + and D - data pins, so that the charging device can read two voltages from the two data lines during charging.

Makers on the Internet have proved through practice that the voltage of 5v1a charger corresponding to iPhone or iPod is 2V on D + and 2V on D -, while the voltage of 5v2.1a charger used by iPad is 2.7V on D + and 2V on D -. When the iPad or iPhone is connected with a charger, the different voltages on the two pins can distinguish which charger is currently used, and the load can be adjusted accordingly, so as to charge safely.
Charge your iPhone with an iPad charger,
What will happen?
There's a reason the design of the iPad and iPhone chargers is different. IPhone Battery capacity is small, only need 1A charging current can be completed in a reasonable time. Although a larger charging current can greatly shorten the charging time, it will bring more heat. High temperature is the number one killer of lithium battery life reduction, so the maximum output current of iPhone charger is designed as 1a.
The charger of iPad is marked with 5V 2.1a, which means that the charger of iPad can only output 2.1a current at most. When you use the iPad charger to charge the iPhone, although the iPad charger can provide a maximum current of 2.1a, because the iPhone can only accept 1a of current, the iPad charger has to accommodate it. It's like driving on a 4-lane highway. When you encounter a toll booth, only one toll booth is open, and then there is only one car passing through the toll booth at the most.

The iPad battery is designed to charge at 2.1a for the best time. If you use the iPhone charger to charge the iPad, because the iPhone charger can only provide 1A current output at most, the whole charging time will be about 2.1 times of the original. Because of Apple's tricks on the USB interface data pin, the iPad knows that this is the iPhone charger, so it will not "require" more than 1a of charging current, and will not overload the iPhone charger and cause damage. It's also like on the highway, although there are four toll booths in the toll station, due to road construction, there is only one lane actually open to traffic, so there is still only one car passing through the toll station at the most.

As mentioned at the end of this rumor, excessive current may lead to breakdown of key capacitors, which is totally illogical. It also shows that microblog authors lack knowledge of electrical physics. The most basic function of capacitor is to connect AC and isolate DC. Charger output is DC, and no matter how much DC current, are unable to pass through the capacitor, and can not lead to capacitor "breakdown". It is the high DC voltage that can breakdown the capacitor, that is "breakdown voltage".
So it's completely feasible to charge the iPhone with an iPad charger, and it won't damage the iPhone and the charger. The iPhone charger can charge the iPad, but it takes longer to charge.
Anyway, if this cross charging is dangerous, take Apple's urine
They don't make the same charging cable for iPad and iPhone!