Introduction of Inductive charging coil

Introduction of Inductive charging coil

Inductive charging (also known as wireless charging or cordless charging) is a type of wireless power transfer. It uses electromagnetic induction to provide electricity to portable devices. The most common application is the Qi wireless charging standard for smartphones, smartwatches and tablets. Inductive charging is also used in vehicles, power tools, electric toothbrushes and medical devices. The portable equipment can be placed near a charging station or inductive pad without needing to be precisely aligned or make electrical contact with a dock or plug.

Energy is transferred through inductive coupling. An alternating current is run through an induction coil in the charging station or pad (the primary or transmission coil.) Any moving electric charge creates a magnetic field, as stated by Oersted's law. The magnetic field fluctuates in strength as the AC current is continually changing amplitude. A changing magnetic field generates an electromotive force otherwise known as Faraday's law of induction. This makes an alternating electric current in a second induction coil (the receiving, or secondary coil) in the portable device. It is then converted to direct current with a rectifier and used to charge a battery or provide operating power.

Greater distances between sender and receiver coils can be achieved when the inductive charging system uses resonant inductive coupling, where a capacitor is added to each induction coil to create two LC circuits with a specific resonance frequency. The frequency of the alternating current is matched with the resonance frequency, and the frequency chosen depending on the distance desired for peak efficiency. Recent improvements to this resonant system include using a movable transmission coil (i.e., mounted on an elevating platform or arm) and the use of other materials for the receiver coil such as silver-plated copper or sometimes aluminum to minimize weight and decrease resistance due to the skin effect.

Many manufacturers of smartphones have started adding this technology into their devices, the majority adopting the Qi wireless charging standard. Major manufacturers such as Apple and Samsung produce many models of their phones in high volume with Qi capabilities. The popularity of the Qi standard has driven other manufacturers to adopt this as their own standard. Smartphones have become the driving force of this technology entering consumers’ homes, where many household technologies have been developed to utilize this technology.

Samsung and other companies have begun exploring the idea of "surface charging", building an inductive charging station into an entire surface such as a desk or table. Contrarily, Apple and Anker are pushing a dock-based charging platform. This includes charging pads and disks that have a much smaller footprint. These are geared for consumers who wish to have smaller chargers that would be located in common areas and blend in with the current décor of their home. Due to the adoption of the Qi standard of wireless charging, any of these chargers will work with any phone as long as the phone is Qi capable.

Another developement is reverse wireless charging, which allows a mobile phone to wirelessly discharge its own battery into another device.

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