1. What Is Wireless Power Transfer?

Wireless power transfer refers to the transmission of electrical power from a power source to a receiver without the need for physical wires. It has become a commonplace technology, widely adopted in various applications such as electric toothbrushes, smartphones, and in automated guided vehicles used in factories.
While it is currently being used for relatively low-power applications, in the near future, it is expected to be utilized in high-power applications for electric vehicles and trains.

Application example of wireless power transfer


2. Representative Wireless Power Transfer Technologies

There are multiple wireless power transfer methods, but broadly categorized, there are two types: the “coupling method” for power transmission at relatively short distances and the “radiation method” for power transmission at relatively long distances.
The different attributes of these methods are shown in the table below.

Classification Coupling method Radiation method
Electromagnetic induction Electric field coupling Microwave
Magnetic coupling
(Magnetic field coupling)
Magnetic field resonance
Image Magnetic coupling Magnetic field resonance Electric field coupling Microwave
Advantage – High efficiency in power transmission
– Stable transmission
– Allows relatively long-distance transmission – Enables high power transmission
– High efficiency in power transmission
– Allows long-distance transmission
– Supports multiple receivers
Drawback – Limited distance – Sensitive to circuit constants – Requires high voltage
– Very limited distance
Low efficiency in power transmission
Use case – Electric toothbrushes
– Qi standard
– ABLIC’s wireless power transfer
– AGV (Automated guided vehicle)
– EV charging
  – IoT sensors

Currently, magnetic coupling, which is a coupling method with a relatively short distance, is primarily utilized for various applications.
A brief description of each method is listed below.

Magnetic coupling
(Magnetic field coupling)
Power is transmitted by generating a magnetic field with a transmitter coil and inducing electric power in the receiver coil.
Magnetic resonance Power is transmitted by electrically resonating the transmission resonant circuit and the reception resonant circuit, both of which have the same resonant frequency, inducing electric power in the receiver coil.
Electric field coupling Power is transmitted to the receiver by applying a high-frequency current through a capacitor formed by placing the transmitter and receiver electrodes facing each other.
Microwave Power is transmitted by converting power into electromagnetic waves at the transmitter side and then receiving and rectifying the electromagnetic waves with a receiver antenna.

Across the globe, companies and universities are currently engaged in various undertakings in order to harness the advantages of these methods.

– Resonance: The physical phenomenon of an object vibrating at the same frequency as its natural frequency when subjected to an external force, even if the force is small.
– Electrical resonance: Sometimes considered synonymous with “resonance,” but refers specifically to the case of electrical oscillations.


3. Benefits of Wireless Power Transfer

A wireless power transfer offers various advantages compared to a traditional cable-based power transfer. In addition to eliminating the hassle of plugging and unplugging cables, it improves design aesthetics by removing the need for connectors and enables waterproofing without the use of specialized waterproof connectors.
Moreover, switching devices that currently use disposable batteries to wireless power transfer brings many benefits beyond just eliminating the need for battery replacement. It enables prolonged device usage without disposable batteries, contributing to the realization of a more sustainable society.


4. ABLIC’s Wireless Power Transfer

ABLIC’s wireless power ICs implement the widely adopted magnetic coupling method, which is a type of electromagnetic induction. The application can be used in many countries without the need for special approvals or licenses.
Finally, as our ICs are designed specifically for low-power wireless power transfer, they can easily build highly compact systems.