无线充电技术的发展趋势en.doc

Startup Beams Wireless Power to Charge DevicesBy Bryan GardinerCords and cables have been a reality for consumer devices since the advent of home electronics. That reality may be changing very soon, however, as a number of companies continue to make inroads into eliminating the wires that keep our gadgets tethered to a walland to one another. Powercast, a new Pennsylvania-based startup says its solution for wireless power harvesting is not only reliable, FCC-approved, and safe, but is also ready to debut in millions of small devices by the end of 2008, according to John Shearer, Powercasts founder and chief executive. The technology? Radio waves, the same technology driving cellular phones and your FM dial.Whether its the promise of short-range wireless technologies like ultra wideband (UWB), wireless USB, and the wireless high-definition interface (WHDI) that transmit data from one device to another, or methods for supplying those devices with power, such as induction - or now, RF - the future home looks to be increasingly cordless. Basically, weve developed a chip on the transceiver and receiver side that efficiently transmits RF energy, said Keith Kressin, executive vice president of sales and marketing for Powercast. While Kressin admits that using RF energy to power electronic devices isnt a particularly new idea, he says his companys patented approach is unique in that it can harvest much more of that energy (50-70 percent) than traditional methods, typically 10 percent, according to the company. Its extreme PC power: read about ThermalTakes 1.2-kW power supply. Because radio waves are in fact energy, they are already used to send and receive cell phone, television, radio, and Wi-Fi signals every day, he explained. Those waves spread out in all directions until they reach an antenna that is tuned to the appropriate frequency. Powercasts wireless power platform uses a Powercaster transmitter circuit running on conventional current to broadcast a low-power radio signal at a predetermined frequency. The smaller Powerharvester receiver circuitwhich can be embedded in any low-power devicethen uses that energy to recharge or can even replace the devices battery, according to Kressin. The Powercast solution is able to maximize power transfer by using a much broader area of the RF spectrum, the 900-MHz band. While not necessarily a replacement for a conventional charger, the technology will be able to trickle charge a variety of electronics over a period of time so that their energy is never fully depleted. As with a traditional AM/FM radio, the closer one is to the tower transmitting the signal, the better the reception. Powercasts wireless platform operates using a similar principle. According to the company, the wireless power platform can harvest a few milliwatts of energy within a meter of the source, in this case the transmitter. That is enough energy to charge a single depleted cell phone battery about half way overnight, according to Kressin. The solution will also be ideal for devices with small batteries such as watches, hearing aids, wireless keyboards and mice, and game controllers, said Kressin, all of which could be continuously charged. But there are limits to the charging capabilities the Powercast platform. Larger devices such as laptops will not be able to make use of the companys solution simply because they require too much power. In fact, the size limit for now seems to be at the cell phone level for effective charging, company executives said. During Powercasts demo at this years CES, two prototype light sticks equipped with LEDs from Philips were shown using the companys new technology. According to Kressin, Philips will be the first company to ship products using the wireless power platform later this year. Theyre developing a lighting application, something you can do with small LEDs, he said. In this form, youre just powering, though, and not charging. But Im tracking about 20 major categories of devices where our solution would be viable. Were also talking to many companies that are now interested in developing prototypes. While a spokesman from Philips was not immediately available to comment on the forthcoming lighting product, Govi Rao, the companys vice president and general manager of solid-state lighting, said the technology could revolutionize what we know about power in a recent interview with Business 2.0 magazine. Of course, Powercast isnt the only company working on wireless energy transfer. Arizona-based WildCharger, who also demonstrated its technology at this years CES, is currently developing a line of charging pads that can wirelessly transfer power via direct contact between a smaller adapter fitted on a device and the pad itself, using whats known as direct induction. Induction is basically the same technology that charges your electric toothbrush, and inductive coupling, as its known, uses the magnetic fields that are an innate part of any currents movement through wire. When a current moves through a wire, it creates a circular magnetic field around the wire. By bending the wire into a coil, this can amplify these magnetic fields. The more loops the coil makes, the bigger the field will be. And while the pad itself has to be plugged into a wall socket, it will supply a steady stream of power to devices placed anywhere on top of it. WildCharger says its 15 x 40 cm pads will come in 90-watt capacities and will be able to charge large devices like laptops, BlackBerries, and cell phones simultaneously. Another solution comes from Fulton Innovation and its new eCoupled technology. eCoupled also makes use of intelligent induction, but is designed to be embedded in circuitry in common household and everyday objects like countertops, cabinets, carrying bags, car dashboards, and consoles, the company says. The circuitry will then communicate with the receiving coil that can be built into common consumer electronics devices like laptops, cell phones, music players, and gaming devices. When someone places an eCoupled device on an eCoupled-ready surface, the base will automatically recognize the relationship between the device itself and base and will compensate and adapt based on its charging needs. As with all wireless communication technologies, consumers can expect to see a variety of complimentary wireless charging solutions emerge onto the market in the next few years. Kressin says that in all likelih