Design of Wireless Power Applications with Moving Receivers

Speaker: Nobby Stevens and Bart Thoen

Company/ Institute: KU Leuven – KAHo Sint-Lieven

Event: 16th work meeting

Date: 16 October

Abstract:

Wireless power systems based on inductive coupling gained significance over the past years. As a consequence, standards and regulations were developed, such as the Qi-standard of the wireless power consortium and Rezence from the alliance for wireless power. All these commercial systems are designed for stationary charging devices with batteries, like smartphones and tablets. Communication is required for device detection and power regulation. The Qi-standard uses one way communication from the power receiver to the power transmitter. This is achieved by modulating the inductive link using load modulation. The Rezence standard on the other hand uses a two way Bluetooth connection. Because all these systems are designed with a stationary battery powered receiver as boundary condition, none of these is suitable to power a constantly moving device. This is due to the long time it takes to activate the power transmitter when the power receiver is detected. For this kind of systems, a new and dedicated communication and power transfer system has been developed. Were have implemented this protocol in the representative example of a wireless computer mouse. The wireless mouse that we have chosen is the M705 wireless mouse from Logitech, which is normally powered by two AA-batteries. The available amount of space for the receiver circuitry is created by removing the two AA-batteries. The average power consumption of the mouse under normal working load is 10 mW. With the choice of dedicated components and the implementation of the new communication protocol, presence of the receiver for less than 12~s above the transmitter guarantees autonomous functionality for more than 15 minutes. Remark that these 12 s must not be contiguous, short presence for less than half a second is sufficient to load the on-board energy buffer.

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