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The Qi (pronounced chee) standard is a inductive power transfer (IPT) technology. The standard is developed for smartphones and other mobile devices. Therefore, Qi is considered a low-power and static WPT charging standard. Transmitter and receiver are placed in close proximity to each other (mm-cm). This close coupling is essential for maximising efficiency. To further enhance efficiency, the Qi standard incorporates technology-specific features. These features are discussed in detail later in this article. Today, there are more than 11,000 Qi Certified products on the market (Qi Wireless Charging, n.d.).

The Qi standard was developed by the Wireless Power Consortium (WPC) and was first introduced in July 2010 with Version 1.0. WPC is an open standards development group that collaborates with electronics and technology companies. Today, the consortium consists of over 300 member companies worldwide, including major technology firms such as Apple, Samsung, Google, and Meta (Membership Directory, n.d.; Qi2’s Wireless Charging Benefits Spurring Continued Expansion Consumers’ Appetite for Wireless Charging Devices Fueling Demand, n.d., p. 2).

The Qi standard has been updated several times over the years to improve performance, compatibility, and efficiency. A brief summary of the change in technology is given:

In 2010 the WPC launched Qi Version 1.0. This version supported three transmitter types: single coil, coil arrays, and moving coils. The coils allowed power transmission of up to 5W. However, its design flexibility was limited, meaning manufacturers could only optimise charging performance by tweaking receiver designs rather than the transmitters themselves.

Two years later, Qi Version 1.1 expanded the standard by introducing 12 transmitter types. This gave manufacturers more room for innovation. This version also improved Foreign Object Detection (FOD). Another key upgrade was the ability to power Qi transmitters using USB chargers.

The release of Qi Version 1.2 in 2015 marked a significant step forward. The introduction of the Extended Power Profile (EPP) increased charging speeds to 15W. This version also included thermal testing to improve heat management and unique IDs for power receivers, hence boosting efficiency and compatibility.

By 2021, Qi Version 1.3 further enhanced the standard by focusing on security. One of the major improvements was authentication features, ensuring safer and more reliable wireless charging.

In 2023, WPC unveiled Qi2, a next-generation standard featuring the Magnetic Power Profile (MPP). Inspired by Apple's MagSafe technology, it introduces magnetic alignment of the transmitter and receiver. This increases charging efficiency and user-friendliness. To ensure compatibility with earlier Qi devices, traditional BPP and EPP were updated with Qi2.

(Evolution of Qi Wireless Charging Standard & What’s New With Qi2, n.d.; History of the Qi Specifications, n.d.)

All previous improvements of the Qi standard resulted in several key advantages. The updated list of these technology-specific features are:

• Transmitter can deliver up to 15W
• Operating frequency of 360kHz
• Magnetic Power Profile (MPP)
• Foreign Object Detection (FOD)
• Universal compatibility
• Bidirectional in-band communication

References

• Evolution of Qi Wireless Charging Standard & What’s New With Qi2. (n.d.). Https://Www.Graniteriverlabs.Com/En-Us/Technical-Blog/Qi2-Wireless-Charging-Standards-Evolution.
• History of the Qi Specifications. (n.d.). Https://Www.Wirelesspowerconsortium.Com/Knowledge-Base/Specifications/History-of-the-Qi-Specifications/.
• Membership Directory. (n.d.). Https://Www.Wirelesspowerconsortium.Com/Membership-Directory-Bak/.
• Qi Wireless charging. (n.d.). Https://Www.Wirelesspowerconsortium.Com/Standards/Qi-Wireless-Charging/.
• Qi2’s Wireless Charging Benefits Spurring Continued Expansion Consumers’ Appetite for Wireless Charging Devices Fueling Demand. (n.d.).