Friday, December 14, 2012

Getting Power Without A Plug :Concept of Wireless Charging

Qi standard and Future of interoperable wireless charging
The Power Consortium is a business alliance of more than 80 companies that are working on similar technology. The list of the member countries include: Convenient Power, Fulton Innovation, National Semiconductor, Nokia, Philips, Sang Fei, Sanyo and Texas Instruments etc. The organization started in 1998 with the aim of creating a Wireless power charging standard so that the charging station and the electronic product recognize each other and charge automatically.

The consortium has already proved that the electric power can be transmitted without wires and over limited distance this process is pretty simple as well. The company has worked on developing a pretty simple mechanism using which they can develop a platform that could recognize the device that is kept on it and keep it fully charged all the time. The technology that they use is pretty simple and pretty effective one as well in simple words it is called the Electromagnetic Induction and the phenomenon is known as Inductive charging, In this method there exists a charging station that sends power to the device kept on top with the help of a inductive coupling the induced charge on the other device is stored on separate batteries.

Qi wireless charging standard basics.

The Qi standard has been developed by the Wireless Power Consortium and is applicable for electrical power transfer over distances of up to 40 millimetres (1.6 inches).
The Qi wireless charging standard uses a power transmission pad that is akin to the charger that would be used in a normal wired system, and a compatible wireless power receiver that is located in the device to be charged. The power transfer then takes place using magnetic induction.
The way in which the wireless power charging is achieved conforms to the standard and allows a single Qi wireless charger from any supplier to be used to charge any Qi compatible device. As most wireless charging systems now conform to this standard, it means that only one charger pad is required to charge all devices.
There are two categories for Qi wireless chargers:
  • Low power:   The low power category covers chargers that can deliver power in the range 0 - 5 watts. This will cover most of the domestic portable devices like mobile phones, music players, Bluetooth earpieces, etc..
  • Medium power:   Chargers in the medium power category can deliver power up to 120 watts.
Within any Qi wireless charging system, there are two main elements:
  • Base Stations:   The Qi base station is the device that provides inductive power for the wireless transmission. As such it contains a power transmitter of which a major element is the transmitting coil. The overall Qi charger typically has a flat surface. This is normally referred to as the Interface Surface. The mobile device or devices may be placed on top of this surface.
  • Mobile Devices:   The Qi mobile devices are those which consume the wirelessly transmitted power. This is typically used to charge the battery contained within the mobile device.
To keep the efficiency as high as possible, it is necessary to ensure that he coupling between the transmit and receive coils is as high as possible. To achieve this the mobile device must be placed in the position where this can be achieved. The Qi standard defines two ways of achieving this:
  • Guided positioning:   This form of placement on a Qi charger involves the use of means to guide the user to place the mobile in the correct place on the Qi base station for charging.
  • Placement anywhere:   The second form of Qi charger placement does not require the user to accurately place the mobile device on a particular area of the charging surface. Instead a wider area is usable. This can be achieved by using more than one transmitter coil.
The frequency used for Qi chargers is located between about 110 and 205 kHz for the low power Qi chargers up to 5 watts and 80-300 kHz for the medium power Qi chargers.
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