Wireless Charging

Wireless charging is essentially the transmission of an electrical current from a power source to a receiving device without the use of a physical connection. The electrical current is then used to charge or re-charge the battery of the receiving device. In this circumstance the receiving device can be anything from a smart phone or wearable, to a large industrial forklift.

How does wireless charging work?

Wireless charging is based on the principle of magnetic resonance or inductive power transfer (IPT) – the process whereby electricity is transferred between two objects through coils.

5 key steps of wireless power transfer:

Step 1. Mains voltage is converted into high frequency alternating current (AC).

Step 2. The alternating current (AC) is sent to the transmitter coil by the transmitter circuit.  The alternating current then induces a time varying magnetic field in the transmitter coil.

Step 3. Alternating current flowing within the transmitter coil induces a magnetic field which extends to the receiver coil (when within a specified distance).

Step 4. The magnetic field generates current within the receiver coil of the device.  The process whereby energy is transmitted between the transmitter and receiver coil is also referred to as magnetic or resonant coupling and is achieved by both coils resonating at the same frequency.

Step 5. Current flowing within the receiver coil is converted into direct current (DC) by the receiver circuit, which can then be used to charge the battery.



As illustrated, power can be transferred safely over an air gap and also through any non-metal object which might exist between the coils i.e. wood, plastic, granite. The addition of extra (or larger) transmitter coils can also extend the range at which the power can be transferred.

Wireless charging pad for smartphones & tablets

Current options for wireless charging of smart phones and tablets involve the use of a charging pad which acts as the transmitter, transferring power to a miniaturized wireless receiver integrated into the smartphone or tablet.

Three teams are competing in wireless charging technology

The consumer tech marketplace offers a range of pad-based charging systems, to create a wireless in-room network is what people are advancing towards. A San Jose-based company Energous is busy creating WattUp, a wire-free charging system that can power gadgets up to 15 feet away using a combination of RF (radio frequency), Bluetooth and other imperceptible tech. Even sooner is the XE (from TechNovator), which is a tower that communicates via electromagnetic resonance with a smartphone case that then safely translates those energy waves into electricity. TechNovator plans to launch with a Kickstarter campaign in November focusing on iPhone 6 and 6 Plus cases. And uBeam is aiming for a base station taking the form of a wafer-thin ceiling tile and embedding small chips into handsets.