What is Qi Charging? The standard for wireless charging in detail

The Qi technology is used, among other things, in the current iPhone generations and in the AirPods charging case, so that the respective batteries can be charged wirelessly. But how does the wireless energy transfer work in detail and what is behind the name “Qi”? In this guide you will find the most important details about the technological standard Qi wireless charging and its backgrounds. Do you have any questions or would you like to contribute some more information on the topic? Then please leave a comment.

What is Qi Charging? How does the wireless charging of Apple iPhone, AirPods charging case and other devices work? Here you will find the answers to these and other questions!
What is Qi Charging? How does the wireless charging of Apple iPhone, AirPods charging case and other devices work? Here you will find the answers to these and other questions!

Qi Charging - charging the battery through resonant inductive coupling

For Qi technology, which Apple has been using since 2017 (iPhone X and iPhone 8), a so-called resonance transformer is used to transfer energy from the transmitter (charger) to the receiver (end device). This type of circuit is also called "Boucherot circuit" and is loud Wikipedia "A circuit similar to an oscillating circuit consisting of a capacitor and a coil". 

When the individual components in the charger and smartphone or charging case interact, not only is electricity generated, there is also an exchange of information. This guarantees an optimal transmission of energy and ensures that the highest supported performance is achieved in the respective connection. The technology for data exchange can be compared with RFID.

How does Qi wireless charging work? The infographic explains

I could throw around some technical terms that I find on Wikipedia on the subject. But a picture is sometimes worth a thousand words - and pictures can also be found on Wiki: D Therefore, in the following, I will simply include an infographic that shows you how the electricity gets from the charging station (below) to the mobile phone (above). 

As you can see on the overview, controllers and drivers ensure that, after a corresponding data exchange, a service is negotiated with which the cell phone battery is then charged safely but as quickly as possible. Both sender and receiver use a space-saving coil for the exchange (source: MakeMagazinDE at Wikimedia under CC BY-SA 4.0 License).

How does Qi wireless charging work? Which components are responsible for communication and performance? This infographic shows you how.
How does Qi wireless charging work? Which components are responsible for communication and performance? This infographic shows you how.

Technical data of inductive energy transfer via Qi

Here are some technical data and further information about Qi technology:

  • Sender and receiver exchange data at a data rate of 2 kBit / s
  • Achieving high performance without exceeding EMC limit values ​​thanks to high magnetic coupling 
  • Long wave transmission frequencies between 87 kHz and 205 kHz
  • Power with current devices from 5 watts (Baseline Power Profile) to 15 watts (Extended Power Profile)
  • Already in use since 2008, made better known by Samsung since 2012 and Apple in 2017

Qi Charging - advantages and disadvantages at a glance

As you can see in the list of technical data for Qi Wireless Charging, wireless charging of batteries is currently not the fastest way to get power into the device. If you want, you can see that as a disadvantage. What else belongs in an overview of advantages and disadvantages, you can see in the following table.

Qi benefits Qi disadvantages
No cable required, the device is placed on the loading surface Use during charging is severely restricted as the device has to lie / lean on the charging mat
Less wear on the interface or cable, as no USB or Lightning is used Low efficiency
Standardization of “Qi” chargers ensures a free choice of manufacturer Currently still quite high price for comparatively little performance
A Qi charger can charge a wide variety of devices from Apple, Samsung, Huawei, Google, Nokia, Xiaomi, Sony, etc. (one after the other) Currently only up to 15 watts of charging power, while USB-C chargers create 60 watts and more
Allows higher protection against water and dust for devices that can only be charged wirelessly Possibility of high heat generation and long-wave radio interference

Information as of June 24.06.2020th, XNUMX

History of technology

The Qi standard for wireless charging of device batteries was founded in 2008 by the Wireless Power Consortium (WPC). The standard for wireless energy transmission, which is implemented via electromagnetic induction, is to be used by more than 200 companies for more than 1.000 device models - there is information on this as well as other backgrounds and news on the official website of the WPC.

In Germany, the charging standard was not particularly well known in 2008 or in the following years. It was only through some IKEA products that he started talking. After the manufacturer Palm Pre offered a mobile phone with Qi charging technology in 2009, Samsung came around the corner in 2012 with the Galaxy S III and Nokia with the Lumia 820 and Lumia 920. The iPhone 2017 and iPhone X again attracted great global attention in 8 - the Qi standard has been an integral part of Apple ever since.

Charge iPhone wirelessly: Apple support document

No compatibility with competing products

The name “Qi” should be remembered when using the appropriate devices so that when looking for wireless chargers, you don't accidentally reach for a competitor product that is not compatible with your own technology. The AirFuel products with the Powermat or Rezence standard, for example, follow a similar approach of inductive coupling or resonant magnetic coupling. More information on the different standards can be found in the Wiki articles to "Wireless Energy Transmission", where you can also see how a light bulb was lit up wirelessly as early as 1910.

Where does the name "Qi" come from?

Now that we know everything important about functionality, technology, data and competition, let's finally take a look at the name. This is not only the combination of two random letters, but is the conversion of a Chinese word and character into Latin characters. Qi is pronounced here according to Duden [tʃiː] and is therefore also spelled “Chi” as an alternative (but not regarding the charging standard). 

Qi (氣 or 气 in Chinese, 気 or き in Japanese, and 氣 or 기 in Korean) can have different meanings depending on the context. For example “energy” or “breath”. But it can also be used as “air”, “gas”, “ether” or “force”. A meaningful, but extensively usable word that, with its various interpretations, is well suited for the wireless charging standard;)

Qi chargers - The bestsellers on Amazon

Here you can find the current bestsellers in the field of Qi chargers for iPhone, AirPods and more on Amazon:

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The page contains affiliate links / images: Amazon.de

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