A4WP Wireless Charging Tutorial
- details and specifics about the A4WP Wireless Charging system developed and promoted by the Alliance for Wireless Power.
A4WP is a wireless charging and transfer technology that has been developed to enable the efficient transfer of power to devices without the use of wires.
In this way A4WP allows wire less charging for many devices from mobile phones to music devices and much more.
Alliance For Wireless Power, A4WP
The Alliance for Wireless Power is an independent industry body that was set up to develop and maintain the standards for a form of wireless power that allowed additional spatial freedom over the standards that already existed.
The aim was to develop a standard that would address simultaneous charging of multiple devices ranging from very low power products, such as Bluetooth headsets, to today's most power hungry tablets.
Beyond the development of their standards, the organisation seeks to promote the use of wire-less charging, and in particular its own standard.
A4WP wireless charging basics
The A4WP standard is used to deliver power, typically for wireless charging.
At the core of its technology is the inductive power transfer techniques used by other competing standards.
A4WP uses a large area for the magnetic field, and this enables the device positioning requirements to be less critical, and it also allows a single power transmitter to charge multiple devices at any one time.
A4WP states that it uses magnetic resonance charging. Essentially it uses the same magnetic inductive techniques, but using this approach it allows devices placed within the inductor ring to be charged without having to line-up perfectly with the coil.
A further advantage of A4WP is that it enables the possibility of Z axis charging placement. This means that chargers can be built deeper into other objects, like a desk for example, whilst still allowing the electromagnetic fields to permeate the material.
The A4WP standard differs from other wireless charging techniques in a number of ways. Being more recent in its development it has looked at some of the issues with wireless charging and adopted a slightly different approach.
There are several features to the development:
- Wireless Power Transfer: This uses a relatively high frequency of 6.78 MHz. This is a frequency that is internationally available for this type of application, and using one as high means that it avoids inductive heating issues seen with tightly-coupled inductive systems using much lower frequencies.
- Control / management protocol: The frequency used for control and management is within the 2.4 GHz ISM (Industrial Scientific and Medial) band. It is internationally available and is ideal for use with smartphones and other electronic items. Read more about the control and management protocols and signalling.
- Power Transmitter Unit, PTU: This is the unit that transmits the power to the unit requiring charging. Read more about the power transmitting unit.
- Power Receiving Unit, PRU: This unit takes the power from the transmitter and uses it, often for charging a battery. There are several classes of PRU dependent upon the application envisaged. Read more about the power receiving unit.
A4WP PRU Categories PRU Category Power Output Anticipated Applications Category 1 On roadmap Headset Category 2 3.5 W Feature phone Category 3 6.5 W Smart phone Category 4 On roadmap Tablet Category 5 On roadmap Laptop
Key A4WP specification highlights
|A4WP Technology Highlights|
|Power transfer frequency||6.78 MHz (ISM band)|
|Protocol / control signal frequency||2.4 GHz|
By Ian Poole
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