Large Area Wireless Power Transfer with Coupled Relay Resonators PDF Download

Author: Xingyi Shi
Publisher:
ISBN:
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Languages : en
Pages : 138

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Book Description
Emerging wireless charging technologies will become essential for medical implants, which currently require cables passing through patients' skin in order to provide power, or force the patient to undergo costly surgery operations to replace dead batteries. Likewise, makers of sensors and devices used on the factory floor are increasingly looking towards wireless power to eliminate the need for battery changes and eliminate downtime. Even the ever-increasing number and diversity of consumer electronics, such as smartphones, laptops, wearables, and VR headsets, will benefit from wireless power solutions that make battery charging more convenient. Commercially available wireless chargers, such as those implementing the Qi standard, partially address the problem. Qi chargers can typically charge only one device at a time and require precise alignment of transmitter and receiver, and so are not effective as the number of electronics that need to be charged increases. Magnetic resonance wireless power transfer systems, which use resonant coils as transmitters, have greater range and tolerance to misalignment. However, the size of the transmitter cannot be arbitrarily increased to fit any large area because large transmitter-to-receiver size ratios result in extreme inefficiency. As an enhancement on magnetic resonance, phased array transmitters explored in academic research can extend transmission range. However, they have the tradeoff of increased cost and complexity, because each array element requires an independent RF source. Non-magnetic methods of wireless power transfer, such as radiative ultra-high frequency beaming and tracking laser systems, have more extended power transfer range but much less efficiency, and they both have lower output power limits due to safety regulations. So whereas these methods may be useful for devices that only need small amount of energy and require long separation distances, they cannot be used for systems that require high power output while still being safe for use near humans and animals. This dissertation focuses on the design of a wireless power transfer solution that can provide efficient wireless charging over a large area, can tolerate some amount of separation and misalignment, can charge multiple devices at the same time, at a reasonable complexity and cost, and can do all of this while staying well within safety regulations. To achieve this, we introduce an adaptive, passive wireless relay system to extend power transfer range. A prototype of a centrally controlled array of reconfigurable relays (CARR) is implemented that can deliver power to multiple moving receivers. We show that the relay system is much more efficient at delivering power to small receivers over a large area than a single transmitter system, and has better uniformity of coverage. The CARR prototype can identify and adaptively route power to a new or moving receiver in as little as 120 microseconds. Additionally, a method for enabling large area power transfer without a large transmitter is introduced, which proposes to use receivers themselves as relays when many receivers are in close proximity. We demonstrate a key step towards realizing this receivers-as-relay system by showing that a suitable routing configuration for delivering power to receivers can be identified using a load modulation technique. Finally, in evaluating the safety of magnetic resonance systems, we conclude an interesting feature of coupled resonator systems which reduces safety concerns by reducing the SAR, a measure of the energy absorbed by biological tissue.