The new wireless charging system can charge devices located anywhere around it.

Existing systems transmit energy in a certain direction or at a certain position of the gadget. The new device has a donut-shaped charging field, so the design works more conveniently and more reliably.

The main problem with creating an omnidirectional charger is that the strength of the charging field varies depending on the location of the gadget. This means that devices will charge inefficiently if they are in the wrong place or facing the wrong way.

One approach to solving this problem is to create a charging field using multiple transmitter coils that are connected to multiple power supplies. But in this case, the design of the transmitter will be very complex – this is impractical. Other systems use feedback to correctly orient the charge field, but the control system, in this case, also turns out to be complex and expensive.

Researchers at Aalto University have come up with a solution to this problem:

We set out to create a simple, low cost system using only one power supply.

Nam Ha-Wan, Research Fellow and Head of Research

The authors decided to make a new design in the form of a cylinder. The wire at the top of the coil is wound in the opposite direction from the wire at the bottom of the coil: they are connected by a z-bridge.

Current flows through the wires in opposite directions, so additional magnetic fields are created. One field is formed from the middle of the cylindrical coil, around the top wire and back, the other is formed from the middle, around the bottom coil and goes back through the bottom one.

This creates a uniform magnetic field around the middle of the charging coil. Gadgets placed anywhere in this area charge efficiently, regardless of their position.

It was just a proof of concept. Now we can work on improving efficiency – perhaps up to about 90% – as well as power.

Yining Liu, Dr.