Wireless chargers

Wireless charging is set to be a major theme at this year's Mobile World Congress (MWC) in Barcelona, with many of the big smartphone manufacturers including Samsung, LG, Motorola, Nokia and Apple investing in the technology. But what is it and how does it work?

Wireless charging (also known as inductive charging) uses an electromagnetic field to transfer energy between two objects. Inventor Nikola Tesla was the first to demonstrate wireless power transmission in 1891, when he succeeded in lighting electric lamps without wires.

It took over a century for the technology to find its way into the mainstream, but over the past few years wireless charging has finally emerged onto the consumer electronics market.

Some smartphones and smartphone accessories now have wireless charging capabilities built-in, and the technology is being integrated into all sorts of devices, appliances, public spaces and even vehicles, as companies look to make power cords obsolete.

For example, wireless charging pads can already be seen at around 50 McDonald’s locations in the UK, thanks to a deal between the fast food chain and Air-charge, and Starbucks also offers free wireless charging stations in 10 cafes in the UK.


Wireless Charging Guide: What is it and which phones are supported?

What is Qi?


Wireless charging is a new technology that allows charging over (very) short distances without cables.The advantage of wireless charging is that charging is quicker and easier, as you don’t have to plug and unplug each time – you just place your device on top of your wireless charging pad It also looks neater.

There are various competing standards for wireless charging. The most popular is Qi (pronounced ‘chee’), which has been supported by companies like Samsung, Google and Nokia however more and more manufacturers are taking advantage in some form or another

Phones and tablets with built-in Qi wireless charging


If your phone appears here, you just need to buy a wireless charger such as a wireless charging dock.

Wireless chargers

Once you’ve determined your phone has wireless charging built in or you’ve added it with an accessory, you just need a wireless charger.

There are plenty of Qi wireless chargers available, in different sizes, shapes and colours. You can get Qi chargers for your desk, for your car, or even portable Qi



Wireless Battery Charger Circuit Principle:


This circuit mainly works on the principle of mutual inductance. Power is transferred from transmitter to the receiver wirelessly based on the principle of “inductive coupling”.



Inductance is the property of the conductor, in which the current flowing in a conductor induces a voltage or electromotive force in it or in another nearby conductor. There are two types inductance. 1) Self inductance, 2)Mutual Inductance.



“Mutual inductance” is the phenomena in which, when a current carrying conductor is placed near another conductor voltage is induced in that conductor. This is because, as the current is flowing in the conductor, a magnetic flux is induced in it. This induced magnetic flux links with another conductor and this flux induces voltage in the second conductor. Thus two conductors are said to be inductively coupled.



Wireless Power Transfer Circuit Diagram:


Wireless Mobile Charger Circuit Design: 


Wireless battery charger circuit design is very simple and easy. These circuits require only resistors, capacitors, diodes, Voltage regulator, copper coils and Transformer.



In our Wireless battery charger, we use two circuits. The first circuit is transmitter circuit used to produce voltage wirelessly. The transmitter circuit consists of DC source, oscillator circuit and a transmitter coil. oscillator circuit consists of two n channel MOSFETS  IRF 540 , 4148 diodes. When the DC power is given to the oscillator, current starts flowing through the two coils L1, L2 and drain terminal of the transistor. At the same time some voltage is appeared at the gate terminals of the transistors. One of the transistors is in on state while the other is in off state. Thus voltage at drain of transistor which is in off state raises and it fall through the tank circuit made of 6.8nf capacitors and transmitter coil of 0.674. Thus operating frequency is determined by using formula F=1/[2π√(LC)].