Inductor and coils in wireless charging technology

Wireless power transfer (WPT) applications

involve transferring power from a source to a load without a physical connection. Such applications typically use technologies such as inductive coupling to transfer power through electromagnetic fields. The power source plays a key role in ensuring efficient and safe power transfer.

WPT is a popular choice in many application areas.

It has been widely used in consumer electronics ranging from smartphones to electric toothbrushes. In addition, in the medical field, WPT plays a vital role in powering implantable devices such as pacemakers and insulin pumps. In the industrial field, WPT technology has been integrated into products such as power tools and automatic guided vehicles (AGVs), bringing benefits to the field.

WPT designs require a transmitting coil and a receiving coil.

Power is transferred wirelessly via a magnetic field between the transmitter and receiver. On the transmitting side, the DC input power is typically fed into a half-bridge or full-bridge topology, which powers a DC to AC power inverter

The inverter uses an LC series resonant tank to generate an alternating magnetic field to transfer power to the receiver.

On the receiving end, the series resonant element converts the received magnetic field into a current, which is then converted to a DC voltage by a high-power rectifier. An output regulator is used to provide a stable DC voltage to the load. The coil configuration varies greatly depending on the application and the type of power coupling; resonant and non-resonant inductive coupling are commonly used.

WPT technology used in consumer electronics should comply with relevant industry standards for inductive charging.

The Qi (pronounced "chee") system launched by the Wireless Power Consortium (WPC) is very efficient, but requires the position of the transmitting and receiving coils to be aligned. Its competitor, the AirFuel Alliance, uses magnetic resonance power transfer technology, whose tuned coils are less sensitive to misalignment and can support long-distance transmission of up to several meters.