Wireless charging for mobile devices

Philips research, June 17, 2008
People today own and use an increasing number of portable electronic devices such as mobile phones, digital cameras, MP3 players or handheld computers. Each with its own battery and adaptor for recharging. How much more convenient would it be if you didn’t have to deal with all those different adaptors, connectors and cables? But instead have a single wireless charging unit that would keep all your portables powered up, so that you never miss an important call on your mobile phone or that perfect shot with your digital camera?
Wireless charging pad
Philips Research is working on a wireless power system that is very intuitive and convenient in use for charging mobile electronic devices. It consists of a tablet, the size of a mouse pad, which allows you to simply place your mobile device on it to charge it –hassle-free with no cables or plugs to contend with. The wireless charging pad can be used in the home or office but also in the likes of hotel rooms or on trains and airplanes.







How does it work?
The charging pad uses the principle of magnetic induction, which is also used for the current Philips electronic toothbrush. It consists of a matrix of charger coils that can generate an alternating magnetic field. The mobile devices contain a receiver coil in which a voltage is induced. This voltage is used to power the device and its battery. The transmitter and the receiver coil basically consist of planar, spiral windings, typically made of printed circuit boards (PCB) tracks.
High efficiency and low emission
To enhance the efficiency of the system and to reduce the emission of the magnetic field to a minimum, the transmitter coils in the charging pad can be switched locally so that only those close to a device on the charging pad are active. A sensor circuit is used to detect where the device is placed on the charging pad. This means that the charging pad can be scaled to any size, without loss of efficiency.



Standardization
To ensure that the power pad can charge all kind of portable electronic devices from different brands, both the portable devices as well as the charging pads have to comply with a universal interface. For this reason, Philips is initiating cooperation with other companies to develop a standard for this technology.