Wireless phone charger

Wireless phone chargers are devices which utilizes the principle of electromagnetic power transfer to charge smartphones wirelessly over a short distance.

In the previous chapters we have learnt about how electromagnetic induction can be used to transfer energy, so in this tutorial we will learn about wireless phone chargers; how they works, basic parts,  technology, ,behind it and how you can build yours. So let's get started!

Wireless phone chargers have been in the market for a very long time. Since the 1890s, it's no more a novejlholty that devices can be powered wirelessly. An example of devices which uses the technology of wireless power transfer are electric tooth brush, wireless phone chargers, laptop chargers, electric cars etc.

Short distance wireless power transfer can be used to charge batteries  and power loads. 

Basic parts of a wireless phone charger.

1.Transmitter coil.

Electricity is transmitted from a 5v adapter by the transmmiter coil. It receives oscillating high frequency  current from the oscillator and then creates a varying magnetic field.

2. Receiver coil.

Varying electromagnetic field from the transmmiter coil is recieved by the receiver coil when it is placed in near the transmmiter.

The reciever coil is usually connected to a diode rectifier to rectify the alternating current induced into the coil into direct current.

  

4. Oscillator circuit.

The oscilator circuit is usually connected directly to the transmitter coil and the oscilator circuit is connected to a 5v DC power supply from an adapter. The oscilator is responsible for convertion of DC into high frequency alternating current.

The oscilator circuit consists of transistors and integrated circuits. The input DC is first amplified and switched on and off rapidly at high frequency. 

How the wireless phone charger works.

Wireless charging has been around since the late 19th century, when electricity pioneer Nikola Tesla demonstrated magnetic resonant coupling (the ability to transmit electricity through the air by creating a magnetic field between two coils (a transmitter and a receiver). But for about 100 years it was a technology without many practical applications, except,  for a few electric toothbrush models. 

The wireless phone charger works based on the principle of electromagnetic induction. Energy is transferred from the transmmiter coil to the receiver coil when an oscilator changes the input 5v DC from the adapater to a high frequency alternating current and then feed it to the transmitter coil. When the alternating current gloee through the transmitter coil, electromagnetic field is produced around it.The receiver coil is placed in the phones casing and then connect to the charging point. Anytime the smartphone is placed over the transmmiter, the receiver coil converts the electromagnetic field around the coil into direct current much enough to charge your phone.

The wattage or power of the wireless phone charger depends on the design such as the size  of the transmitter coil, the frequency of the oscilating current and the amount of input current.

The bigger the coils, the greater the distance between the receiver and the transmitter.

The larger the input voltage, the greater the magnetic field of the coil.

Also the higher the frequency of oscillation the more the wattage.

Some wireless charger are made to produce a power of 10 ampere while some can dissipate more than 15A.