Until a few years ago, many people were arguing about whether a smartphone battery was removable or integrated. But that has completely disappeared. Did someone dissolve the detergent? No. It started after even Samsung Electronics, the leader in removable batteries, released the Galaxy S6 with an integrated battery. Currently, smartphones with removable batteries have almost disappeared from the market.


The advantages of the integrated type are evident in product design. First, there is no need to consider the battery cover, so a simple design is possible. The same applies to design. The battery package can be further reduced, and less space needs to be secured between the battery and other parts, making it easy to secure space.

The changing smartphone usage patterns of consumers have further enhanced the market dominance of integrated devices. This is due to the spread of auxiliary batteries and wireless charging. There are almost no smartphone users without auxiliary batteries, and even low-priced Chinese smartphones support wireless charging. Although it may vary from person to person, it has become more convenient to carry auxiliary batteries or use wireless charging than to have spare batteries.

Unlike auxiliary batteries, which are already sufficiently developed, wireless charging is a field with infinite potential for development. Accordingly, research and development of related products are also active. However, in order to release a product to the world, a certification process must be followed. There is a place that helps these companies develop wireless charging products. It is the Wireless Power Transmission Technology Center.
We met with Senior Researcher Hyungjun Kim of the Wireless Power Transmission Technology Center at Gyeongbuk Technopark located in Gyeongsan, Gyeongbuk, and asked him about the present and future of wireless charging.


The term wireless power transfer sounds unfamiliar. Isn't wireless charging the same as wireless power transfer?
Wireless charging is one of the concepts of wireless power transfer, and it is not completely the same. Wireless power transfer is not an independent technology. For example, in the case of self-driving cars, they can be called truly self-driving only when they can drive on the road, park themselves, and even charge.

Currently commercialized wireless power transmission technology is an offline wireless charging technology for small devices, but in the near future, it will include not only wireless charging but also online wireless power transmission technology that transmits power in real time.

In addition, as radiant technology is developed, it will be possible to receive power from distant satellites and use it on Earth, creating an eco-friendly power generation system that is different from conventional power generation methods.


Please explain what wireless power transfer technologies are available.
There are three main types of wireless power transfer methods.

There are three types of methods: the magnetic resonance method led by AirFuel, the magnetic induction method led by WPC, and the radiative method that uses electromagnetic waves.

The magnetic resonance method is a method in which a transmitter and receiver wirelessly transmit power using the same resonant frequency. Compared to the magnetic induction method that uses the magnetic induction phenomenon between the primary and secondary coils of a transformer, the transmission and reception distance is long, and wireless power transmission to multiple receivers is possible with one transmitter and receiver. The disadvantage is lower efficiency compared to the induction method.

The radial method uses electromagnetic waves using antennas and rectennas. Compared to resonance and induction methods, it allows for long-distance wireless charging. It can send signals to remote islands or even space. However, since it uses a lot of electricity, it has low efficiency and is harmful to the human body.

More than 90% of wireless charging products on the market are of the inductive type.


So what does the Center for Wireless Power Transmission Technology do?
The Wireless Power Transmission Technology Center (hereinafter referred to as the Center) was established here in May 2018 as part of the national industrial convergence infrastructure construction project.
The center is Korea's only specialized wireless power transmission technology center that conducts testing research and corporate support related to wireless power transmission, a fundamental technology of the 4th industrial revolution.

The center supports the development of related original technologies, global certification exam services, pre-tests, and resolution of technical difficulties to help companies gain global competitiveness along with the revitalization of the domestic wireless power transmission industry.
Gyeongbuk Technopark Wireless Power Transmission Center was designated as the world's 6th Qi 15W standard certification testing agency in November 2017. In April 2018, it was designated as the world's first international standards market monitoring organization for wireless chargers, and in October, it was designated as a Qi 5W standard certification organization.


What are the hottest issues in the industry related to wireless power transfer technology?
The most widely used technology at present is mobile phone charging technology. Since it is low-power, there is no major issue at present, but the power transmitted wirelessly is gradually increasing. Since wireless power transmission is a method of transmitting power by frequency, the industry is greatly concerned about the human body harm caused by electromagnetic waves generated during wireless charging, as well as electromagnetic interference (EMI) and electromagnetic compatibility (EMC).


What is the certification process that companies are having difficulty with?
In the case of wireless chargers, the voltage and current transmitted and received change depending on the resistance value of the load, that is, the environmental changes of the receiver. Therefore, it is not easy to stabilize the target rectified voltage during the product certification test.

The most difficult certification process for companies is the foreign substance detection function. The foreign substance detection function is a function that prevents the risk of fire due to the heat generated by the power transmitted and received when a conductive object such as a coin or ring is inserted between the transmitter and receiver during wireless charging operation. When a foreign substance is detected, the wireless charging operation must be stopped or the temperature of the foreign substance must be maintained below 60 degrees for 10 minutes.


I heard that the center not only conducts product certification tests but also conducts surveillance activities. What kind of surveillance activities related to wireless power transmission technology are carried out at the center?
In April 2018, WPC became the first in the world to designate our center and NTS in the United States as Market Surveillance Labs. Since then, the center has been randomly purchasing products that have received QI certification from WPC and re-conducting a simple certification test. After the test, the results are reported to WPC, and management is conducted after obtaining certification based on this.


Certification tests, pre-tests, and even surveillance activities. It seems like you'll need a lot of measuring equipment to do all of this.
The center is building many measuring instruments for certification and pre-testing and corporate support. There are many factors to measure when taking a certification test. There are also more than 6 channels.
Tektronix products help expedite certification exams by providing faster calculation and analysis speeds when measuring multiple channels and multiple factors compared to existing products. This is a strong selling point for companies that want to obtain certification quickly.


Please tell us about the center's vision.
The center is the only specialized center for wireless power transmission technology in Korea. The center has medium- and large-sized shielded rooms to support the development and certification of not only low-power products but also high-power products. Even large bus charging systems can be easily tested.
The biggest goal of the Wireless Power Transmission Center is to support businesses. The center is working to build a one-stop test system to save time and money for businesses, especially small and medium-sized businesses. The center is continuously recruiting personnel. Based on this, we will conduct related research and contribute to alleviating the suffering of related businesses.


This interview showed that the potential of wireless power transmission technology is not limited to low-power products. It is no longer a fantasy to dream of a future where solar power satellites transmit power to the ground or where power transmitters installed under roads charge electric vehicles running on the road.