146 views Yuda Electronic (HK) Technology Co.,Limited. 2018-12-18
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 cannot be mixed according to the parameters, but is this really the case?
If the power adapter is connected to a 220V/110V AC outlet and the other end is connected to the iPhone/iPad via a Lightning cable, the AC power is first converted to high voltage DC through the rectifier circuit. It is 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 AC to 5V DC, the transformer, rectifier circuit and voltage regulator circuit only play a role in changing the shape of the device.
If the 5V USB port of the regulator circuit is not connected to an iPad or iPhone, no current will pass 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 made a complicated design on the Lightning data cable: the USB interface of the data cable has a total of four narrow metal strips connected to the 5V power supply and GND ground. The D+ data cable positive signal and the D-data cable 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 iPhone’s own 5V/1A charger, D+ and D- are both 2V; and the 5V/2.1A charger used by the iPad has a D+ voltage of 2.7V and a 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 only needs 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 iPhone 6 model, the iPhone’s charging profile is the same as the iPad, which means that the device can also use 2.1A current charging, up to 12W power, iPad charger can shorten the iPhone charging time.
So it’s perfectly feasible to charge the iPhone with the iPad charger, and it won’t hurt the iPhone and charger.
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