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HOME REVIEWS CONTACT ABOUT January 14, 2010
Wireless Power for Small
Appliances
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WiFi and Bluetooth are wonderful technologies for freeing
our portable devices from cables, except for the power cable, right? Some vendors are ready with a new technology
that will allow the 
charging of cell phones or other small appliances without
wires.
Is that "Buck Rogers" or what?
Powercast Wireless Power
Powercast (
Powercast uses a signal in the 900
Megahertz band for moving the energy to the unit being charged. Other devices
on the same band will not interfere with the operation; in fact, the Powercast receiver will consume any power near this
frequency that enters its perimeter.
However, this technology cannot fully replace a conventional charger for
most appliances. It is able to "trickle charge" over a period of time
so that the energy depletion rate is slowed dramatically for low power
devices.
The idea behind the Powercast
product isn't a new idea. The problem is that power transmitted in this way
reflects off different surfaces, and modifies the signal. The Powercast
solution is a receiver that acts like a radio tuned to many frequencies at the
same time.
The maximum power transmission is a few milliwatts at distance of 3 feet. That should be sufficient to recharge most
cell phones to a 50% level in 12 hours.
This rate is ideal for cell phones, wireless keyboards/mice, medical implants
like pacemakers, and other small appliances.
The technology is not currently capable of supporting higher electricity
consuming devices such as laptop computers, which currently use more than an
order of magnitude more power than the Powercast
system can supply.
Phillips to Market Powercast System
Phillips will be the first to market with a product
utilizing the Powercast system. The first product will be a light stick for
low power lighting application. For this
application, the device will not have a battery on-board, but will receive
power continuously from the Powercast system. "If you had asked me seven months ago if
this was possible, I would have said, are you dreaming? Have you been smoking
something?" says Govi Rao,
vice president of solid-state lighting at Phillips.
A Powercast system currently
cost less that $10 to manufacture. In
many devices, implementing a Powercast solution is
less expensive than implementing a battery, and in addition, is more
environmentally "green".
An alternative to the Powercast
technology is inductive charging. If you
have a Sonicare electric toothbrush, you already have
an inductive charging system. An
inductive system is effectively a transformer, but inductive charging is more
"connector less" rather than wireless. This system requires a very close proximity
between charger and device, because the efficiency drops precipitously at
anything other than very short distances.
Powermat is one of several companies
developing a system in the form a pad that you would put underneath the device
to be charged, and that would be capable of supporting higher power devices
like laptop computers. The system is
currently capable of power outputs of about 90 watts.
The Wireless Power Consortium was launched to develop
standards so that charging systems and consuming devices will be able to
communicate. This is important so that
the transmitter only emits power when a consuming device is present, and at the
appropriate output power. This will
improve safety and efficiency. Founding
members of the consortium include Logitech, National Semiconductor, Philips
Electronics, Sanyo, Shenzhen Sang Fei Consumer
Communications, and Texas Instruments.