Introduction to the A4WP Loosely-Coupled Wireless Power Transfer System Specification Version 1.0 - Embedded.com

Introduction to the A4WP Loosely-Coupled Wireless Power Transfer System Specification Version 1.0

The vision of ubiquitous power is to meet portable, hand- held, consumer electronic device (e.g., smartphone) energy demands in a “consumer friendly” manner within a wireless power transfer (WPT) source-rich environment.

In this paper we focus on loosely-coupled (LC), or non- radiative, near-field magnetic resonance WPT defined as “… resonant wireless transfer of power… through magnetic induction between… coil(s) where the coupling factor (k) can be less than 0.1, though values up to 1 may also be supported, and where the system requires [coupled] magnetic resonance.

LC WPT attributes include, power transfer efficiency that is (roughly) rotationally and translationally invariant in the horizontal (x-y) plane, and tolerant of angular and vertical (z- direction) displacement, for example, with respect to a horizontal WPT source planar surface. LC WPT supports the simultaneous charging of a multiplicity of devices, each with possibly different power requirements [e.g., Bluetooth headset (~1W), feature phone (~3.5W), smartphone (~6.5W), tablets and laptops (10-30W)].

The focus of this paper is to survey the Version 1.0 Baseline System Specification (BSS) approved by the A4WP in January, 2013.

The A4WP WPT basic architecture is a star topology network, in which a single power transmitting unit (PTU) interacts with one or more power receiving units (PRU) for simultaneous charging. There is a functional and physical separation between the wireless power transfer (strictly from PTU to PRU) and session and power control management (from PTU to PRU and PRU to PTU).

This survey of the A4WP Version 1.0 BSS reviews an LC WPT reference model, power transmitting and power receiving unit device classification, power system interfaces and key parameters, the power control specification, the signaling specification, and the framework for certification and acceptance testing based on reference power transmitting and power receiving resonators.

The selection of ISM band (6.78MHz) as the WPT operating frequency and ISM band (2.4GHz) for WPT management protocol via BluetoothLE is discussed.

To read more of this external content, download the complete paper from the author archives at the A4WP website.

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