Recently you might have heard of Qi Wireless charging, thanks to Apple and IKEA releasing new products that support it.

QI is an open interface standard for wireless charging developed by the Wireless Power Consortium (WPC) in 2008. Yep it is not new, however has only recently become mainstream. “Qi” is the Chinese word for “energy flow“, pronounced like the “chee“in “cheese“.

It is wireless power transfer using inductive charging.

You just just places your device on a base station where only the base is connected by a wire to the power supply. Currently a number mobile companies are working with this standard. These include market leaders like Apple, Samsung, LG, HTC, Sony and many more.

The principle behind this is very simple.

The system consists of two devices, the charging base station (Qi sender) and the mobile phone (Qi receiver) where both should be Qi standard compatible.

The base station activates only when the device is placed on it. To check this the base station sends an intermittent signal to which the mobile responds by communicating the received signal strength. Once a device replies the required energy is calculated and the wireless charging process begins.

In this process the energy transferred wirelessly through electromagnetic waves. For this we require two coils; one transmitter coil for the base station and one receiver coil for the device.

The transmitter coil generates an oscillating magnetic field which in turn based on the fardays law of induction induces an alternating current in the receiver’s coil.

Efficiency of the inductive power transfer relies on close spacing of the two coils, as well as shielding on their surfaces.

In 2009, WPC published the Qi low-power specification which delivers up to 5W which is usually used for charging mobile phones.

In 2009 the Qi specification was extended to medium power which will deliver up to 120 W, to power displays and laptops.

By 2015, a high-power specification was developed to deliver up to 1 kW to power high power utilities.

The advantage to the Qi standard is that once a device is Qi compatible it can be charged on any Qi charging transmitter, regardless of the manufacturer, make of the device. For example an Apple user can use IKEA’s Qi Wireless Charging table to charge their compatible iPhone.

Recently even McDonalds in the UK have introduced wireless charging points in their restaurants.