page_title: Qi (standard)
section_title: Features and specifications
hierarchical_section_title: Qi (standard) / Features and specifications
caption_attribution_description: English: Nokia DT-900 Qi charger rated 12 V, 750 mA DC input power, with the top cover removed. The longest dimension is 116.6 mm.
context_page_description: Qi is an open interface standard that defines wireless power transfer using inductive charging over distances of up to 4 cm, developed by the Wireless Power Consortium. The system uses a charging pad and a compatible device, which is placed on top of the pad, charging via resonant inductive coupling.
  Mobile device manufacturers that are working with the standard include Apple, Asus, Google, HTC, Huawei, LG Electronics, Motorola Mobility, Nokia, Samsung, BlackBerry, Xiaomi, and Sony.
  First released in 2008, the Qi standard had by 2019 been incorporated into more than 160 smartphones, tablets and other devices.
context_section_description: The WPC published the Qi low-power specification in August 2009. The Qi specification can be downloaded freely after registration. Under the Qi specification, "low power" inductive transfers deliver power below 5 W using inductive coupling between two planar coils. These coils are typically 5 mm apart but can be up to 40 mm and possibly farther apart. The Qi low-power specification has been renamed to the Qi Baseline Power Profile (BPP).
  
  Regulation of the output voltage is provided by a digital control loop where the power receiver communicates with the power transmitter and requests more or less power. Communication is unidirectional from the power receiver to the power transmitter via backscatter modulation. In backscatter modulation, the power-receiver coil is loaded, changing the current draw at the power transmitter. These current changes are monitored and demodulated into the information required for the two devices to work together.
  In 2011, the Wireless Power Consortium began to extend the Qi specification to medium power. As of 2019, the Medium Power standard currently delivers 30 to 65 W, it is expected to eventually support up to 200 W (typically used for portable power tools, robotic vacuum cleaners, drones and e-bikes).
  In 2015, the WPC also demonstrated a high-power specification "Ki" that will deliver up to 1 kW, allowing the powering of kitchen appliances among other high-power utilities.
caption: Opened Nokia DT-900 Qi charger
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