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Breakthrough technology in wireless power transfer

Mar 4, 2015

Prof. Ron Hui, Department of Electrical and Electronic Engineering, and the Wireless Domino Power Transfer Systems.
Prof. Ron Hui, Department of Electrical and Electronic Engineering, and the Wireless Domino Power Transfer Systems.

Prof. Ron Hui’s latest breakthrough on wireless charging technology has been widely reported by the media. SCMP on March 11 covered Prof. Hui’s research and development process; Apple Daily on March 4 covered the introduction and adaptation of the new invention.

Below is a brief summary of Prof. Hui’s research process of the Wireless Domino Power Transfer Systems developed here at HKU.

With the announcement by the Swedish furniture company, IKEA, to launch a new series of furniture and products with wireless charging pads embedded, wireless charging has gained new momentum in its course to reach globalization. The Wireless Power Consortium (WPC), an international organization formed in 2008 to promote a global wireless power standard launched the world’s first wireless power standard “Qi” in 2010 for charging portable consumer electronics such as mobile phones. By 2015, over 210 companies worldwide would have joined the WPC and over 800 Qi-compatible products have been registered.

The basic principles of wireless power transfer (WPT) were pioneered by Nicola Tesla in late 19th century.  However, there were not many WPT applications in the first half of the 20th century, because several key technologies such as power electronics (with fast switching capability to form high-frequency power supplies), Litz wire (to reduce winding resistance) and high-frequency magnetics were not available. Such situation changed in 1980 when these three elements have reached their mature stages for mass production. 

Prof. Andrew Green and Prof. John Boys (Auckland University) started to study WPT for mobile robots up to several kilowatts in 1980s. With the dawn of the mobile phone era in the same time, Prof. Hui (HKU since 2011) and his team members have systematically developed a series of technologies for planar wireless charging systems since the late 1980s. Such technologies underpin key features of the Qi standard with free-positioning, localized charging and compatibility check features.

Prof. Hui’s contributions focused on the user-friendliness and technologies that can meet the safety and international regulations. He developed a multilayer planar coil array structure that can generate magnetic field uniformly over a flat surface, making it possible and easy to place and charge several electronic devices on the surface simultaneously regardless of their orientations. The localized charging principle and compatibility check technique ensure that energy flow only occurs to compatible electronic devices within the covered areas between the electronic devices (being charged) and the charging surface. Since the magnetic flux is totally enclosed, there is no magnetic flux leakage. Consequently, incompatible items such as credit cards, smart cards and cigarette lighters will not be affected.

Prof. Hui’s latest series of technologies underpin key features of the Qi standard with free-positioning, localized charging and compatibility check features.
Prof. Hui’s latest series of technologies underpin key features of the Qi standard with free-positioning, localized charging and compatibility check features.

The challenges that Prof. Hui faced in the R&D process were both financial and technical. He was partially supported by small RGC funds and partially supported by Philips Electronics in the early stage of this R&D work. In the first few years, there was virtually no interest from local industry. Despite the fact that his first research publication on the wireless charging pad technology was largely ignored by the research community in the first two years after its publication in 2005, this invention caught the attention of a senior management member of a major European electronics company, who eventually formed a start-up company named Convenientpower Ltd. with several local partners in the Science Park to develop and market this planar wireless charging technology. With their business visions and skills, they managed to gather many major electronics companies to form the WPC in 2008 and launched the Qi standard in 2010.
The technical challenges were rather different. The initial obstacles were the lack of electronics components that are of planar or flat shape.  As the awareness of wireless power research increased, component manufacturers were willing to produce planar components and control integrated circuits for such applications. Despite some initial difficulties, Prof. Hui enjoyed good partnership with his former research students, who are in senior positions in wireless power industry.

Since joining HKU in 2011, Prof. Hui has led a research team conducting new research in WPT. They have developed the wireless domino power transfer techniques which can substantially increase the transmission distance without compromising energy efficiency. Wireless domino power transfer systems can be formed in various forms. Currently, he and his team are extending the traditional “directional” WPT methods to “omni-directional” WPT systems.  Several patent applications on this topic have been filed through the Technology Transfer Office of HKU. In addition, the HKU team has been working on new wireless charging techniques for electric vehicles. Despite the severe lack of large research funds in HK, his team has been focusing on new WPT technologies that have the potential to make global impacts. It is envisaged that such technologies will attract the attention of industry worldwide, as the planar wireless charging pad technologies did in the past.

The WPT research at HKU has received international attention. In 2014, Prof. Hui was invited to give plenary speeches on WPT in two IEEE conferences. He will be the plenary speaker for two more IEEE conferences in 2015. For his contributions to planar wireless charging technologies, he has been selected to be the recipient of the IEEE William E. Newell Power Electronics Award in 2015. He is the first recipient of Chinese origin to receive this award since it was elevated to the IEEE Technical Field Award status in 2006 by the Institute of Electrical and Electronic Engineers (IEEE).

Click here for this piece of online news on SCMP.
Click here for this piece of online news on Apple Daily.