In recent years, wireless charging has become more commonly available in our daily lives. Already over 500 types of devices, including phones, are in the market which can be charged wirelessly. You may have been using wireless charging for many years already if you possess an electrical toothbrush: you just put it on the holder and it starts charging.
The principle to charge your smartphone or smartwatch wirelessly is the same: just put your phone on a charging pad or wireless charging sweet spot and it starts charging. Very convenient, no need to connect a cable first. But how does wireless charging actually work?
How wireless charging works
How can energy be transferred through air from one part to the other? The way wireless charging works is by something which is called magnetic induction. Firstly discovered in the 1830’s by Michael Faraday, he discovered that when you move a permanent magnet in and out of a single loop of wire, it induces a voltage. Linking electricity with magnetism. Let’s explain by conducting an experiment:
DIY experiment: how wireless charging works
Seeing is believing, do try this at home:
Take a permanent magnet – like the ones you stick on your fridge;
Connect a light bulb to a simple loop of copper wire;
Move the magnet quickly back and forth, bringing it closer and further away from the loop;
The bulb will start lighting up a little!
So what just happened? Why did the bulb light up? By bringing the magnet back and forth, you change the magnetic field experienced by the loop, which induces a voltage in the loop. The voltage created is in some way comparable to the voltage of a battery.
How does wireless charing work with induction?
Induction coils inside a wireless charger
Basically, wireless charging your toothbrush, smartphone or any other device works similar as we just showed with the light bulb. In practice, we don’t have a moving magnet but we do have another loop of copper wire, a so-called induction coil, which will carry a changing current at high frequency.
This changing current generates the changing magnetic field. This part of the wireless charging system is called the “transmitter”. The part inside your phone, smartwatch or toothbrush is called the “receiver” and is charged in the same way as the light bulb.
Is wireless charging safe?
Magnetism or magnetic fields are always perceived as being a bit mysterious because you can’t see them, you can’t feel them and you can’t smell them. To build an efficient wireless charging system, you need to limit the magnetic field closely around the copper wire loops.
This is done by special materials, called ferrites, which are conducting the magnetic field very well, much better than air does. Therefore, the magnetic field has a preference to flow though the ferrite instead of through the air. Because of that, hardly any field comes out of the wireless charging system and is therefore inherently safe.
And what if I put a piece of metal on the transmitter?
Magnetic fields can heat up metals just like an induction cooker heats a pan. However, the transmitter of a wireless charging system can detect if a piece of metal is located on its surface. In case it does, the transmitter either does not start at all or shuts down. So apart from power transfer, there is communication between the transmitter and receiver. Among others, the communication ensures that wireless charging will only take place if the right receiver is put on the transmitter. The magnetic field is present only then.
Furthermore, wireless charging systems must obey a set of rules and regulations related to electromagnetic interference (EMI/EMC), sometimes also called “radio disturbance”, and magnetic fields. All products of course meet these rules and regulations. So, is wireless power safe? Yes, all kinds of precautions have been taken to make sure that it is.
Wireless charging versus cabled charging
Is wireless power just as fast as power through wires? Well, it’s all about power. A 5W wireless charging system can deliver up to 5W of power to your phone battery. This is like a 5V/1A USB outlet and therefore it’s just as fast as wired charging.
Latest developments in wireless charging enable to charge even faster: up to 15W of power can be delivered to your phone. This will significantly reduce charging time and “battery anxiety”.
Can I charge my smartphone wirelessly?
Today, over a 100 models of phones with wireless charging compatibility are in the market. If you want to find out if your phone has wireless charging included, first check to see if your phone supports the Qi technology.
You can also check out the list of Qi enabled phones on our website. If your phone does not have wireless charging included, you might enable wireless charging by an add-on like a case or a sleeve.
Smartphones with Qi technology integrated (no sleeve needed)