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TMCNet:  Wireless Charging: Almost Ready For Prime Time

[November 28, 2012]

Wireless Charging: Almost Ready For Prime Time

(Mobile Development and Design Via Acquire Media NewsEdge) How many chargers do you own If you have a cell phone, laptop, tablet, camera, GPS, and other portable devices, you probably have quite a few and have even lost some of them. Still, you may want to add one more to the list. Wireless chargers have been around for a little while now, but the technology is starting to take off.



Wireless chargers plug into the ac outlet, but you don’t plug your device into them. Instead, you simply put your device on top of the flat surface. The charger has a coil that acts as a transformer primary winding and generates a magnetic field. The device that’s getting charged also has a built-in coil that becomes the transformer’s secondary winding. The magnetic field induces a voltage into the secondary winding, and that voltage is then rectified into dc and used to charge the device’s battery.

The wireless chargers on the market so far aren’t too popular. Most mobile devices don’t have a built-in secondary coil, so you have to put them into a special sleeve that has one so much for the convenience and low cost of wireless charging. In addition, you have to carefully align the coils to get maximum coupling between them to get enough transferred power for charging. It’s a nuisance at best. Is this any more convenient than just plugging in a charger The Industry Investigates Still, the industry is moving to adopt some form of wireless charging for cell phones. Three groups have released specifications and standards: The Power Matters Alliance, including AT&T, Google, Starbucks, and others              The Wireless Power Consortium, including LG, Motorola, Nokia, Energizer, and othersThe Alliance for Wireless Power, including Samsung and others         With no industry agreement on one approach, it’s difficult to see where this will end up. All the approaches are different and incompatible. My guess is that we will see multiple standards coexist unless the industry suddenly decides to coalesce around one of them. What will Apple do We shall see.

The biggest issue is spatial freedom, or not having to precisely align the phone and the charger coils. They need to be close but not so perfectly aligned, which is hard to do magnetically. I saw a capacitive coupling method developed by Murata at last year’s CES that is better in that regard, but none of the standards are using it.

Intel is also working on wireless charging, enabling you charge your cell phone from your laptop. It uses resonance at higher frequencies in the inductive coils to boost the range and power of the magnetic fields. Integrated Device Technology (IDT) has developed a chipset for this technology, but it is incompatible with all the other standards.

Power by Proxi, a New Zealand company, is trying to develop patents from the University of Auckland. It owns 125 patents in this field as well as more than 900 claims developed over years of research and development. The company’s first developments involved charging electrical vehicles like forklifts, golf carts, and other industrial and construction equipment. It also developed wireless couplings that go between the rotating joints of blade motors on wind generators and the generator itself without slip rings.

Recently, Power by Proxi turned its attention to cell phones. So far, it has developed a wirelessly chargeable AA cell. The cell phone can be oriented in any position inside the charging box (see the figure). It operates at 500 kHz and is loosely coupled, probably using resonance. It’s one more technology to deal with, but Power by Proxi could be a major player with its killer IP portfolio.

I’m not sure this format fits everyone. You have to have the charger pad, which is likely larger than your regular charger.

Furthermore, unless airports, hotels, restaurants and other places install them, you still need an ac outlet. Hopefully, phones with wireless chargers also will still be able to plug into standard chargers.

© 2012 Penton Media

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