Everyone of us own one or more portable smart electronic gadgets - be it Smartphone, Tablet, Laptop, Music Player, Camera etc. And everyone of us will agree that putting our portable device for charging is a hassle, we don't like it! Because during charging over device doesn't remain portable! Moreover we have to look for a wired charger, plug it into our gadget whose other end goes to the switchboard. We don't enjoy the whole experience. If our devices are becoming smarter day by day why not charging them also transforms! Wireless charging technology is something that most smart phones manufactures are coming up with. Recently there was a TV commercial of a Samsung high end smart phone where they beautifully demonstrated their wireless charging feature. This article is going to talk about how wireless charging technology works.

Wireless charging is, without any physical connection through a conductor (wire) a power source transfers the electrical power to the load or receiving device (for example smart phone). The power is transmitted through time varying electromagnetic fields, the power source or transmitter is connected to a main power line (switch board) and transmits power through space in the form of electromagnetic field which is converted back to electrical power and utilized by the receiving device.

There are two main categories of wireless power transmission - non-radiative or near field which uses magnetic field by inductive coupling for transfer of power at short distance and radiative or far-field where power is transmitted over long distance using beam of electromagnetic radiation.

In our case of wireless charging that we are discussing, it is surely non-radiative based on the principle of magnetic resonance or Inductive Power Transfer (IPT) where power is transmitted by magnetic field using coils of wire. The mechanism is quite simple. Power Source (that is connected to the main line) converts the AC voltage from the mains to high frequency AC and high frequency AC in the transmitter coil of the power source creates magnetic field. This magnetic field extends to the receiver coil (for example wireless charging circuitry in your smartphone) and creates a resonant magnetic field in the receiver (with the help of resonant circuit both at transmitter & receiver) . Magnetic field in the receiver induce AC current in the receiver which is converted into DC current by receiver circuit and is used to charge the battery. The transfer of power takes place through space or it may also take place through any non conductive material like wood, plastic etc. The transfer of power can take place at normal AC frequency 50/60Hz also but high frequency is desirable because it increases transmission efficiency. Furthermore the resonance between the transmitter and receiver coils also improves transmission efficiency. Inductive coupling is the oldest and the most widely used technology for wireless power transfer. It first featured in electric toothbrush, electric shavers. It also finds use in biomedical applications like recharging prosthetic devices. But today the use of wireless charging is growing fast in smart phones, tablets, laptops and other smart portable electronic gadgets.

There are numerous advantages associated with wireless charging like hassle free charging, reduce risk of getting electric shock, ease of use, high power efficiency and short charging time, cost effective, safe as you don't have to fiddle with wires or direct power contacts, offers ease of use and ubiquitous charging.

By Aarti Bansal - Asst. Prof., Simran Bhalla - 2nd year ECE student Chitkara University Punjab

References:
https://en.wikipedia.org/wiki/Wireless_power