Inductive charging and the Qi standard

how does inductive charging work

Inductive charging is the most commonly used method of wireless charging available today. Through electromagnetic induction, inductive charging uses an electromagnetic field to transfer energy between two objects. As a wireless power expert, we like to explain how inductive charging works exactly.

How does inductive charging work?

In inductive charging systems, energy is transferred between coils by a magnetic field via inductive coupling. The alternating magnetic field is generated by the transmitter coil. This coil induces an alternating voltage in the receiving coil. By connecting a load to the receiving coil, power is transferred.

Inductive charging vs. resonant inductive coupling

Inductive charging is often associated with resonant inductive coupling. If the transmitter and receiver coils are close together and tightly coupled, efficient power transfer can be realised with ordinary inductive coupling. If the coils are further away from each other and are loosely coupled a resonant system is preferred. A resonant system enhances power transfer significantly.

In a resonant system, power is transferred between resonant circuits that are driven at the resonance frequency. Additional components – called capacitors – are added to compensate for the effects of stray and or magnetizing inductances of the wireless power transformer which consists out of the transmitter and the receiver coils.

Alternative ways to transfer power wirelessly

Next to inductive power transfer via magnetic induction, there are other technologies to transfer power wirelessly. The best known are RF (far field), ultrasound and power transfer through light (e.g. laser). These technologies have been presented and demonstrated frequently for many years already on the internet and at fairs as a wireless power solution. However no commercial products made it to the market today. Issues blocking market introduction are mostly related to safety issues, like the maximum exposure to electromagnetic fields according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP), Electro-magnetic Interference (EMC) or a simple lack of efficiency in wireless power transfer.

Qi wireless power standard

In 2008 the Wireless Power Consortium (WPC) was founded and they introduced the first wireless power “Qi” standard. Today there are over 220 companies member of the Wireless Power Consortium, including ZENS. The Qi standard is the most widely adopted global wireless power standard. More than 1300 Qi types of devices, including phones, are in the market which can be charged wirelessly. The consortium continuously defines new parts of, maintains and develops the Qi standard.

The name “Qi” comes from the Asian philosophy and means vital energy, an intangible flow of power. If a mobile device carries the Qi logo it is an official tested and registered device meeting all the requirements imposed by the Qi standard.  The benefit of having such a standard is that any mobile device can be charged on any Qi charger. This is not only convenient at home but for sure also in public spaces. New chargers must be backwards compatible meaning that also older types of phones still work with a new charger.

Qi developments

The first Qi standard was the low power standard up to 5W, introduced by the WPC  in 2008. The 15W standard, enabling fast charging of smartphones and charging of tablets, has been introduced in 2015. The standards of the 60W – 200W and the 200W – 2400W power ranges are still in development.

About ZENS | your wireless power expert

ZENS is your innovative wireless charging expert. From the heart of one of Europe’s most prominent high-tech centres, we develop state-of-the-art wireless charging solutions that aim to improve quality of life. ZENS is not limited to Qi only. As a wireless charging expert we offer customized wireless power designs for you as well. Check out our wireless power business solutionswireless chargers for consumers or if you’re thinking about applying the technology to your business environment, do not hesitate to contact us.

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