Appliance Design - March 2009 - (Page 14)

POWER inductive field induces current into the secondary coil in the toothbrush and this power is passed on to the rechargeable battery in the toothbrush. In the toothbrush example, the goal is to create a sealed unit and eliminate exposed electrical contacts in a potentially wet environment, since an electric toothbrush typically sits near a sink. The new twist on such technologies is the use of microprocessors and control programs that enable sophisticated monitoring and management of the process. There are three basic approaches to wireless power transfer. In near-field or closeproximity applications, where the electronic device is situated close to the charging apparatus, companies have developed inductive and conductive technologies. In the third method, broadcast, a transmitter sends RF energy through the air to the receiving device, permitting a greater degree of separation between the two. With wireless power transfer, there is generally a tradeoff between distance and efficiency. If the distance between the transmitter and receiver is small, transfer efficiency will be high. Efficiency levels drop if power is sent over a distance of just a few feet, especially if the distance is greater than the diameter of the transmitting and receiving coils. As the distance expands, more of the transmitted power dissipates into space. This is true even for systems that have developed methods to better target power transmission. A near-field inductive coupling charging system can achieve power efficiency of around 100 percent, while a highly efficient broadcast system can generally do no better than about 75 to 80 percent efficiency. (This assumes that the two coils are not right next to each other when the power is transferred, which would improve transfer efficiency.) Not only is inductive charging almost totally efficient, it is also the most developed of wireless technologies. Like the toothbrush example, the method uses two coils, one in the transmitting device, and one in the receiving device. To begin charging, an electric current runs through the emitting coil to induce a current in the nearby receiving coil. Fulton Innovation, developers of eCoupled Intelligent Wireless Technology, is one of the more mature technologies and has been one of the most successful developers and marketers of wireless power transfer using inductive coupling. The technology has been used in some 1.5-million eSpring water purification units made by Fulton, and its use in other devices is growing. Some of Fulton’s technology licensing contracts include deals with Motorola, Visteon, and Herman Miller. Recently, it has contracted with Bosch, regarding the charging of power tools; Energizer, to develop commercial lighting products; and Texas Instruments, to develop integrated circuitry to support eCoupled technology. Fulton’s technology uses adaptive inductive coupling. Embedded integrated circuits sense changes in the positioning of the primary, or transmitting coil, in relation to the secondary, or receiving coil to determine the best orientation for that configuration. A digital-control loop constantly monitors load requirements and responds to changes in power needs. This control allows for power transfer levels to be maintained even if the device moves several inches, up or down, or less than an inch off of the transmitter surface. SETTING POWER STaNDaRDS Current wireless charging technology prevents different brands of power sources from charging the same portable device or different portable devices by a common power source. A new organization wants to change that. The Wireless Power Consortium was formed to develop a wireless power standard to solve the compatibility problem. The Consortium’s initial eight members include ConvenientPower Limited, Fulton Innovation, Logitech SA, National Semiconductor, Royal Philips Electronics N.V., Sanyo Electric, Shenzhen Sang Fei Consumer Communications, and Texas Instruments. As the consortium works to develop a single standard, Menno Treffers, senior director of standardization at Royal Philips Electronics, Sweden, and chairman of the Wireless Power Consortium, calls this time a crucial moment in the development of wireless power. He points to the number of users who own more than one electronic device, which results in a tangle of wires and bulky chargers that is ugly, frustrating, and inconvenient to use. And, that problem is going to continue to grow. With a universal wireless power charging standard, electronic products and charging stations using the same standard would recognize each other and charge. Different brands and different devices could then re-charge using the same battery and charging station. The consortium will first establish a standard for low-power electronic devices using 5 W and below, such as mobile phones, music and video players, and computer and game accessories. The range can be less than 1 cm. and allows the transmitter to focus energy on the receiver safely, with high efficiency. The standard will relate only to close proximity wireless power transmission and is based on the principle of magnetic induction. The group believes this is the most efficient, safest, and reliable transfer method. The wireless power standard will require that compliant technology have the same charging time as the current technology of wired chargers and will meet the major regulatory international safety radiation and emissions standards. Other issues that will be considered include the potential for corrosion and breakage when using traditional connectors, and the environmental impact of the wide variety of chargers already in the field. < 14 applianceDESIGN March 2009 www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - March 2009

Appliance Design - March 2009 Contents Editorial Shipments/Forecasts News Watch Transmitting Power Wirelessly Promises to Reduce the Ever-Growing Tangle of Cords and Cables Found in the Modern Home. There Are Different Technological Approaches for Achieving this Goal, and Some Are Already on the Market. Electrochemical Capacitors Can Provide an Extra Peak-Power Boost in Battery-Operated Appliances, Allowing Product Designs to Have Smaller Battery Packs. Metallic Foams Put the Properties of Metals into Lightweight Packages. Applications for this Emerging Technology Include Gas Burners, Heat Exchangers, and Electronics Housings. Hall-Effect Switches Are Compact and Provide a High Degree of Reliability and Durability as They Virtually Eliminate Mechanical Wear, Shock, and Contact Oxidation. Blowing Agents for Polyurethane Foam Insulation Face Increased Scrutiny Due to Global Warming Concerns, but Alternatives with Lower GWP Values May Provide Solutions to Meet These Challenges. Design Marts Association Report: AHAM Advertisers' Index

Appliance Design - March 2009

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