How does iPhones or Google's phone recognize its original charger vs other companies’ chargers?

The power adapter/brick — the thing everyone calls a charger but isn’t a charger — is just a power supply. For simple USB charging, all the power brick has to communicate to the phone is its type: is the phone plugged into a simple USB data port or a charger that follows the USB Battery Charging specification. So that’s either +5Vdc@500mA or +5Vdc@1500mA.

adapter-charger

For more recent phones, there’s a more sophisticated “conversation” or “handshake” between the power dongle and the phone. This is done in Qualcomm’s Quick Charge protocol and the USB standard Power Deliver (PD) standard. In both cases, the phone and the power brick exchange capabilities, decided on one, and then it’s up to the phone to worry about charging. These protocols allow voltages above the USB +5V standard to be used, which means less loss in the cable, faster charging.

Apple has long had their own proprietary ways to detect a higher power output. In fact, if you back some years, you’ll note that many off-the-shelf power dongles had two USB jacks, one for Apple, one for everyone else.

Apple can actually tell something about the cable, though not necessarily the power dongle, plugged into an iPhone. In order to enforce their licensing rules, every Lighting cable is digitally “tagged” with a memory chip that identifies the cable for what it is. So your iPhone knows when you have plugged in a charging cable.

But the other end of that cable probably obeys normal USB charging rules, with perhaps support for the older Apple proprietary higher power mode. And iPhones since, I believe, the iPhone 8, also use the USB Power Delivery protocol to allow faster charging. Apple was already using that for MacBooks, so while it’s rare for Apple to use an industry standard when they can just “roll their own,” the whole point of power charging standards are to make it easy and simple to charge you phone. Apple gets their 30% royalty from the cable, they don’t have to control the power supply, too.

Post a Comment

Previous Post Next Post