On September 12, Apple's keynote event for new products took place at Steve Jobs Theater. At this event, as anticipated, Apple announced a new iPhone 8, iPhone 8 Plus, and iPhone X with a wireless charging feature, suggesting that wireless charging technology became a new trend in the smartphone industry.

 Since the second half of 2016, there were many speculations on the next-generation iPhone; many people anticipated that the new iPhone will adopt wireless charging technology. Furthermore, we could easily predict that the new iPhone will adopt wireless charging technology from the fact that Apple joined Wireless Power Consortium (WPC), an international organization for standardization of wireless charging, in February. The design drawing leaked recently showed that there is a large coil at the back of the product. Looking back at it, it was maybe a drawing for adopting wireless charging technology. In this event, the speculation turned out to be true, indicating that wireless charging technology is to be widely used.

 In fact, in addition to the Apple iPhone, wireless charging technology has been already used in smartphones released by Samsung, Blackberry, and Motorola. However, wireless charging technology has not been adopted very actively, leaving the technology in the gray zone. So, where is this awesome technology coming from? And how does wireless charging work? What's been the progress to date? Will this technology innovate the smartphone industry in the future? We will talk about these questions.

 The origin of wireless charging technology goes back to the late 19th century. As the distance between an area producing electricity and an area using it were too long, people had difficulty establishing wired power transmission and distribution systems. Therefore, scientists at that time wished to wirelessly transmit power, and that's when wireless power transmission technology came to life. In fact, many scientists studied this technology. The most famous scientist among them is Nikola Tesla. He was an electrical engineer and a physicist, after whose name Elon Musk established the Tesla company. Although he made a big contribution to wireless power transmission technology, he is not that well publicly known.

 Tesla invented direct current and alternating current. A rumor has it that he caused the Tunguska explosion in Siberia. That's why some people think he was transcendent. However, only few people know about his achievements because many people didn't want him to be known to public. These days, however, the social shifts such as widespread use of the Internet and aggravating environmental pollution are yet again bringing considerable public attention to Tesla's name and achievements. Tesla wanted to build a 187-foot-high steel tower, which has a dome with a diameter of 68 feet, on Long Island in the US. He thought that he could produce ultra-high voltage using a resonant transformer on the roof, turn atmosphere into a conductor through a high voltage effect, and thus create artificial lightning between the power transmission terminal and the power consumption terminal to enable power transmission. However, Tesla went bankrupt before the tower could be completed and the dream of global wireless power transmission vanished.

 Since Tesla, many scientists have tried to realize wireless power transmission, but most ended in failure. However, studies on fundamental theory are still being conducted. After more than a century, the idea of wireless power transmission still seems unlikely; however, the concept of near-field wireless charging is widespread.

 Since the modern era, the demand for wireless power transmission is being replaced by the demand for wireless charging that requires near-field power transmission. A few conditions need to be met for advancing recent wireless charging technology.

 Power grids, which are a vital infrastructure of modern city life, have improved over the decades, or even centuries, in most countries in the world. Today, electricity is not rare and is essentially supplied to every inhabited area. Therefore, while the demand for far-field wireless power transmission is decreasing, the demand for near-field power transmission is emerging.

 Power electronics emerged in the form of electrical engineering in 1960s. Power supply technology has since seen a big advancement as the space race caused high demand for aero/space power supply technology. In turn, this resulted in the advancement of power switch theory and semiconductor part production in recent decades. Recently, it is easier to use a power supply unit with a high frequency power switch with much higher power density and efficiency.

 The rapid growth of mobile Internet has seen surging demand for a variety of smart terminals. While diversified customer demand for smart products regarding speed, design, screen, and features have led to an increase in the demand for smart product chargers, short battery life remains an issue that needs to be resolved.

 So, we're missing the feature phone era when we could use the phone with no battery problem while charging it once a week. Although the battery capacity of smart devices has increased three-fold, battery life is rather worse than before. Thus, wireless charging technology is receiving attention as an easy way of charging smart devices.

 At present, wireless charging technology is realized in many forms, including magnetic induction, magnetic resonance, electric induction, electromagnetic wave, and optical transmission, with magnetic induction and magnetic resonance being the most widely used.

 Magnetic induction is a common wireless charging technology — you may have heard of it in your high school physics class. Its most common application in daily life is for transformers. A typical transformer has a magnet with magnetic flux direction induced by the primary coil. However, a transformer without a magnet is useless. Planar primary and secondary coils can serve as two key parts in wireless charging, wireless charging transmitter and receiver. As such, the principle of magnetic inductive wireless charging is very simple, and it's essentially no different from a transformer.

 In an effort to disseminate and unify magnetic inductive wireless charging technology, City University of Hong Kong established Wireless Power Consortium (WPC), an international organization for the standardization of wireless charging technology, for exchanging and sharing technologies used in devices produced in many countries. By the end of 2012, WPC announced 'Qi,' which is the first standard for wireless power transmission. The name originates from the Chinese character '气 (qi),' which means intangible energy. After the announcement of the standard, it received worldwide attention and many companies expressed an intention to join the organization. In fact, there were as many as 217 WPC members as of September 2015. Apple joined WPC in February 2017.

 However, the first magnetic inductive technology encountered many problems. For example, there were spatial restrictions for charging, the device needs to be standing upright, and the vertical gap between the device and the charger shouldn't be too long. Therefore, a device couldn't be charged oftentimes as the device was not in place. This caused serious damage to the customer experience. An expensive learning cost was an obstacle to the advancement of the technology.

 So, next-generation magnetic resonant wireless charging technology was developed to improve customer experience by reducing spatial restrictions. Using this technology, a coil creates a magnetic field by converting direct current to an alternating current, or alternating current is generated within the coil. Compared to the first magnetic inductive wireless charging technology, the key difference is that magnetic resonant wireless charging technology controls the energy path better by using a resonator placed at the opposite side. Essentially, this technology relies on the physical principle of 'electromagnetic induction' and merely a small improvement based on the existing design.

 As wireless charging technology has advanced, the possibility of smart devices has increased. As wireless charging technology is so significant to smart devices, we will see a big improvement in the technology in the future. Even a few years ago, however, when companies like Samsung and several Chinese companies started using wireless charging technology, they couldn't realize a major improvement. That is because although wireless charging technology has many advantages, there are many problems lurking in the industry.

 First, there is no organization for standardization of wireless charging technology. Even though organizations such as PMA, Qi, and A4WP tried to develop universal standards, they couldn't achieve much. We talked about Qi earlier. Since its establishment in 2012 led by Samsung, Qualcomm, Broadcom, and Intel, A4WP had 150 members as of September 2015 and merged with PMA in the same year. Given such trends, it's not unlikely that standardization can be achieved. In either case, it will certainly be a gradual process.

 Second, because wireless charging technology consumes almost half of the energy to generate magnetic fields, and supply and receive power, its efficiency is low and it takes too long to charge. This is why wireless charging is not as fast as wired charging.

 Third, it costs much to realize wireless charging technology. This cost includes financial cost and psychological cost. As wireless charging technology is not widespread yet, only a few people understand the concept of wireless charging. Most users will be disappointed when they find out that 'A USB cable needs to be connected to the wireless charger to wirelessly charge a smartphone.' While excessive expectation can be an obstacle for widespread use of the technology, users are concerned about the radiation created by wireless charging technology.

 Of course, wireless charging technology has been advanced and improved over a long time. Wireless charging technology has more potential in today's overall mobile device market. In order to create a mature environment, however, existing problems need to be resolved before improving the technology. Only then can the new technology be improved in a better environment. The industry leader, Apple, adopted wireless charging technology for the first time, and, hopefully, it will transform the market in diverse ways. Early in 2014, a company named Energous developed a technology called WattUp, which is a sort of wireless charging technology, using above mentioned magnetic resonance.

 When equipped with the dedicated wireless charging module, an iPhone can be charged within a four-meter range. Energous developed an energy receiver chip that is smaller than a coin, which can be integrated with iPhone very easily. More importantly, at The International Consumer Electronics Show (CES) 2017 the CEO of Energous gave us a hint that they are partnering with Apple.

 If other Apple devices adopt similar wireless charging technology in the future, we may be able to charge an iPhone, iPad, Mac, and Apple Watch with just one charger under the TV.

 I'd like to close this column with a phrase used in a promotional video for Apple's AirPods.

 "We believe in a wireless future, a future where all of your devices intuitively connect."