An induction charger replenishes power to an electronic device but does not require a direct connection between metallic parts of the charger and the device. Proximity charging is a more descriptive name for this type of charging. In the beginning of the 21st century, induction charging was on the rise in popularity for mobile phones, laptops, and other hand-held devices. This type of power source is especially popular in charging low-voltage appliances or items that must be operated around or stored near water. Wireless induction is also useful for implanted medical devices that must be charged externally, such as an artificial heart.
Most small mobile devices – such as MP3 players, cell phones, and digital cameras – come with power cords. Those cords feature little boxes that function as transformers. The domestic voltage necessary to operate the dishwasher, vacuum, or television would fry these types of small low-voltage devices. These little boxes scale back the domestic voltage to appropriate levels to charge the small appliances.
By making creative use of the electric process of energy transfer that occurs in a transformer, an induction charger can transfer energy into a portable device without requiring metallic contact. All transformers contain a primary coil, an iron core, and a secondary coil. The power travels from the primary coil through the iron core to charge the secondary coil. With an induction charger, the secondary coil resides within the device and not within the transformer. When the secondary coil within that device comes in proximity to the primary coil, the iron core links the two coils electromagnetically and transfers power to the secondary coil, even if those two parts are not physically connected.
The advantages of an induction charger are that it can be operated safely in situations where traditional transformers would be dangerous – such as near water or with internal medical devices – power can be transferred across short distances without direct connection, and that small, portable devices can be liberated. Some studies, however, show that wireless induction is less efficient than traditional charging options and that this type of charging often leaves portable devices hot. In addition, until induction chargers can sense when to stop charging a device, the devices continue to draw power, resulting in the use of more fossil fuels than traditional powering devices.
Toothbrushes and electric razors commonly feature an induction charger. In 2009, Dell® released a laptop featuring an induction charger. That same year, several companies released induction chargers for phones, Wii™ remotes, and MP3 players. Technology for powering blenders, mixers, and food processors via induction chargers stored on kitchen countertops and for charging power tools via induction chargers built into workbenches is on the horizon.