Introduction to the
Power Class 0 Specification
Version 1.2.3
February 2017
WIRELESS POWER
C O N S O R T I U M
Introduction to the
Power Class 0 Specification
Version 1.2.3 Copyright
Wireless Power Consortium
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WIRELESS POWER
C O N S O R T I U M
COPYRIGHT
© 2017 by the Wireless Power Consortium. All rights reserved.
Photos of the TYLT Vu wireless charger are copyrighted by Technocel and are reprinted by permission.
The Introduction to the Power Class 0 Specification is published by the Wireless Power Consortium, and has
been prepared by the members of the Wireless Power Consortium. Reproduction in whole or in part is
prohibited without express and prior written permission of the Wireless Power Consortium.
DISCLAIMER
The information contained herein is believed to be accurate as of the date of publication. However, neither
the Wireless Power Consortium, nor any member of the Wireless Power Consortium will be liable for any
damages, including indirect or consequential, from use of or reliance on the accuracy of this document. For
any further explanation of the contents of this document, or in case of any perceived inconsistency or
ambiguity of interpretation, or for any information regarding the associated patent license program,
contact info@wirelesspowerconsortium.com.
RELEASE HISTORY
Specification Version
Release Date
Description
1.2.3
February 2017
Initial release of this document.
Introduction to the
Power Class 0 Specification
Version 1.2.3 Contents
Wireless Power Consortium
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Contents
1 About the Wireless Power Consortium .............................................................. 4
2 What is the Qi wireless power transfer system? ................................................ 5
3 How Qi wireless power transfer works .............................................................. 8
3.1 Examples of Qi wireless products ........................................................................................................... 10
3.1.1 Mobile devices ................................................................................................................................. 10
3.1.2 Chargers........................................................................................................................................... 10
4 Qi wireless power transfer features ................................................................ 11
4.1 Power levels ............................................................................................................................................ 11
4.2 Operating frequency ............................................................................................................................... 11
4.3 Charging area .......................................................................................................................................... 11
4.4 Coupling requirements ........................................................................................................................... 12
4.5 PTx and PRx communication protocol .................................................................................................... 12
4.6 Foreign object handling .......................................................................................................................... 12
5 The Qi specification ......................................................................................... 13
5.1 Parts 1 and 2: Interface Definitions ........................................................................................................ 14
5.2 Part 3: Compliance Testing ..................................................................................................................... 15
5.3 Part 4: Reference Designs ....................................................................................................................... 15
6 Product registration ........................................................................................ 16
Introduction to the
Power Class 0 Specification
Version 1.2.3 About the Wireless Power Consortium
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1 About the Wireless Power Consortium
The Wireless Power Consortium (WPC) is a worldwide organization that develops and promotes the global
interface standard for wireless power transfer called Qi.
1
Interface standards ensure the interoperability
of devices that conform to that standard. Supported by more than 200 companies and with over 1000
registered products, Qi has become the international wireless-charging standard for hand-held consumer
electronics.
This document introduces the Power Class 0 specification, which includes flat surface devices such as
mobile phones and tablets that use up to 15 W of power.
2
The WPC actively investigates new applications for wireless power transfer, such as a cordless kitchen
solution that uses power transmitters installed underneath countertops and tables that enable a variety of
kitchen appliances and smart cookware to operate without power cords.
The Qi logo is a registered trademark of the Wireless Power Consortium, and is made available to members
of the consortium to display on their products after successfully completing the Power Class 0 test and
registration procedure outlined in section 6 of this document. A database of registered Qi products is
maintained on the WPC’s public Web site where consumers can look up products to see whether they have
been tested for compliance with the Qi standard and for interoperability with all other Qi wireless products.
1
Qi (氣; qì) is pronounced “chee,” and is the Chinese word for energy flow or life force.
2
Version 1.2 of the Qi specification introduced fast charging, which covers transmitter and receiver products that use
up to 15 W of power. However, the architectural limit of the extended power profile is 30 W, which will
accommodate a growing family of product designs in the Power Class 0 category.
Introduction to the
Power Class 0 Specification
Version 1.2.3 What is the Qi wireless power transfer system?
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2 What is the Qi wireless power transfer system?
The powering of hand-held devices is continuing to evolve. Originally, electrical devices had to be plugged
directly into outlets, and the range of operation was limited by the length of the power cord. Next came
disposable batteries that severed the power cord’s range restriction.
Figure 1. Corded appliance (c. 1950) to battery-powered consumer electronics (c. 1955)
In recent years, rechargeable batteries have all but replaced disposable batteries, eliminating the need to
purchase, store, and throw large quantities of these batteries into landfills. But for frequently-used
devices—smartphones in particular—recharging became a daily ritual of plugging and unplugging
charging cables.
A new era of convenience emerged in 2011 when the first Qi wireless smartphone case was introduced,
followed shortly thereafter by smartphones with built-in Qi wireless support. Qi wireless devices need only
to be set down on a Qi wireless charger for recharging to occur. The device remains unplugged and ready
to be picked up and used at any moment. With the deployment of Qi chargers in cars, enterprises, and public
locations, it becomes possible to no longer worry about running out of charge or carrying charger cables.
Figure 1 and Figure 2 show the evolution of corded power to wirelessly-charged portable devices.
