Inductive charging
From Wikipedia, the free encyclopedia
Inductive charging charges electrical batteries using electromagnetic induction. A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries. Because there is a small gap between the two coils, inductive charging is one kind of short-distance wireless energy transfer.
The other kind of charging, direct wired contact (also known as conductive charging or direct coupling) requires direct electrical contact between the batteries and the charger. Conductive charging is normally achieved by moving batteries from a device to charger, or connecting a device to a power source with plug-in wires.
Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in proximity combine to form an electrical transformer.[1][2]
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[edit] Advantages and disadvantages
The major advantage of the inductive approach over conductive charging is that there is no possibility of electrocution as there are no exposed conductors. This advantage also makes the approach attractive for implanted medical devices that require periodic or even constant external power.
Prior technologies for inductive charging have used lower frequencies and older drive technologies, and generally charge slowly and generate heat for most portable electronics,[citation needed] though the technology is used in some electric toothbrushes and wet/dry electric shavers, partly for the advantage that the battery contacts can be completely sealed to prevent exposure to water.[1][2]
Newer approaches with ultra thin coils, higher frequencies and optimized drive electronics provide chargers and receivers that are compact, efficient[citation needed] and can be integrated into mobile devices or batteries with minimal change.[3]. These technologies provide charging time that are the same as wired approaches and are finding their way into mobile devices rapidly.
[edit] Examples
- April 28, 2009: An Energizer inductive charging station for the Wii remote is reported on IGN. [4]
- In November of 2008, Mojo Mobility Inc.[5] announced their high efficiency, compact modules for wireless charging of mobile devices.
- At CES in January of 2009, Palm, Inc. announced their new Pre smartphone would be available with an inductive charger, though the charger itself will be sold as a separate accessory.[6] The charger is known as the "Touchstone", and a special backplate must be fitted to the Pre in order to be compatible with it.
- The electric toothbrush battery charger
- Transcutaneous energy transfer (TET) systems in artificial hearts and other surgically implanted devices.
- Devices using induction to charge portable consumer electronics such as cell phones.[7][8] unveiled their own take on inductive coupling, which will soon be used on Herman Miller desks to recharge devices wirelessly.
- General Motors' (GM) discontinued EV-1 electric car was charged with an inductive charging paddle, which was inserted into a receptacle on the vehicle. GM and Toyota agreed on a standard inductive charging interface, called Magne Charge, though GM was to abandon its support in 2002 when the California Air Resources Board settled on a conductive charging interface for electric vehicles in California.[9]
- In 2006, researchers at the Massachusetts Institute of Technology reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin Soljačić, theorized that they could extend the distance between the coils by adding resonance to the equation. The MIT wireless power project, called WiTricity, uses a curved coil and capacitive plates.[10][11]
[edit] See also
[edit] References
- ^ a b "How can an electric toothbrush recharge its batteries when there are no metal contacts between the toothbrush and the base?" (Commercial website). HowStuffWorks, Inc., via howstuffworks.com. Retrieved on 2007-08-23.
- ^ a b US patent 6972543 "Series resonant inductive charging circuit"
- ^ "Non-contact Charging System Simultaneously Charges Multiple Mobile Devices"
- ^ "Energizer Induction Charger for Wii Preview". IGN.com. 2009-04-28. http://gear.ign.com/articles/977/977418p1.html.
- ^ "Mojo Mobility Inc.". http://mojomobility.com/. Company web page.
- ^ Miller, Paul (2009-01-08). "Palm Pre's wireless charger, the Touchstone". Engadget. http://www.engadget.com/2009/01/08/palm-pres-wireless-charger.
- ^ "SplashPower". http://www.splashpower.com/. Battery powered devices can be charged by placing them on an induction mat.
- ^ "eCoupled". http://www.ecoupled.com. Company web page.
- ^ "GM Pulls the Plug on Inductive Charging: Letter from General Motors Advanced Technology Vehicles". EV1 Club. 2002-03-15. http://ev1-club.power.net/archive/020315/index.htm. Retrieved on 2007-08-23.
- ^ Hadley, Franklin (2007-06-07). "Goodbye wires…". MIT News. Massachusetts Institute of Technology. http://web.mit.edu/newsoffice/2007/wireless-0607.html. Retrieved on 2007-08-23. MIT team experimentally demonstrates wireless power transfer, potentially useful for powering laptops, cell phones without cords.
- ^ Castelvecchi, Davide (2006-11-15). "Wireless energy may power electronics: Dead cell phone inspired research innovation" (pdf). TechTalk (Massachusetts Institute of Technology) 51 (9). http://web.mit.edu/newsoffice/2006/techtalk51-9.pdf. Retrieved on 2007-08-23.
