Can the iPad charger replace the iPhone charger?

Anyone who has read the official data knows that the iPad charger parameters are 2.1A/12W, and the iPhone charger parameters are 1A/5W. It seems that the chargers of the two devices are not compatible according to the parameters, but is this really the case?

       
If one end of the power adapter is connected to the 220V/110V AC outlet and the other end is connected to the iPhone/iPad through the Lightning cable, the AC power is first converted to high voltage DC through the rectifier circuit. It is then converted into a high-frequency high-voltage pulse through a switching tube, and then converted into a low-voltage pulse through a transformer.

The 5V low voltage pulse is converted into a 5V stable DC power through a rectification and voltage stabilization circuit. In the process of converting 220V/110V AC to 5V DC, the transformer, rectifier circuit and voltage regulator circuit only play a role in changing the computer form.

If the end of the 5V output of the regulator circuit (USB terminal) is not connected to the iPad or iPhone, no current will flow through and no power will be consumed. Once the device is connected, the power adapter will not start working. The amount of current depends on the load state: how much current the load (iPhone or iPad) requires, and how much current the power adapter supplies.

       
In order to make all of its power adapters and digital products compatible, Apple has designed a complex design on the Lightning data line: the USB interface of the data line has a total of four narrow metal strips connected to the 5V power supply and GND ground. The D+ data line positive signal and the D-data line negative signal, Apple’s power adapter adds a voltage divider resistor to the D+ and D- pins, allowing the device to read both voltages while charging.

The 5V1A charger that comes with the iPhone, D+ and D- are both 2V; and the 5V 2.1A charger used by the iPad has D+ voltage of 2.7V and D-voltage of 2V. By different voltages on these two pins, it is possible to distinguish which charger is currently being used, and the load can be adjusted accordingly to safely charge.

The iPhone and iPad are designed differently because of the different battery capacity. The iPhone has a small battery capacity and requires only 1A of current to complete charging in a reasonable period of time. Although a larger charging current can shorten the charging time, it will take To generate more heat, and high temperatures will lead to a shorter lithium battery life, so the maximum output current of the iPhone charger is set to 1A.

       
When using the iPad charger to charge the iPhone, if the iPhone can only receive 1A of current, the iPad charger will only provide 1A of current output. However, starting from the model after the iPhone 6, the iPhone’s charging profile is the same as that of the iPad, which means that the device can also be charged with 2.1A current, up to 12W. The iPad charger can be used to some extent. Reduce the charging time of your iPhone.
       
So it’s perfectly feasible to charge the iPhone with the iPad charger, and it won’t hurt the iPhone and charger.