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How to Charge Your Phone while Saving Energy



Last year alone, more than 1.4 billion smartphones were shipped around the world. Their performance improves constantly as they become more widely used.


But not everyone is completely happy with the technology, one concern being the amount of time it takes to charge the batteries. But Fujitsu has succeeded in developing the world’s smallest and most efficient AC adapter that will allow smartphones to be charged in one-third of the conventional time by reducing the current loss during conversion from alternating current from the household socket to direct current. The new adapter is smaller than conventional adapters and looks like a 25mm dice. While charging a smartphone can usually take up to an average of about 3 hours, it only takes one hour with the new adapter.


Developed by Fujitsu in December 2015. GaN-based semiconductors were used as main components. The company achieved the world’s most efficient 5V type power supply at 87 percent, a great improvement from the conventional 70 percent.


The new adapter was developed by Tatsuya Hirose of Fujitsu Laboratories Ltd. together with his subordinate Miki Imai. They began their project in early 2014 when Hirose was considering making an AC adapter for laptops. The reason they changed to adapters for smartphones was because “smartphones were becoming more popular and could make a bigger impact.” What we aimed to achieve was a smaller adapter that allowed phones to be charged faster. “If there was such a thing, I’d buy one for myself,” laughs Hirose.


They found it was difficult to simultaneously reduce the charge time while also them smaller, but they persisted. Imai agreed that “if we’re aiming for the best in the world, the smaller the better.”


Inside AC adapters, there are semiconductors called transistors which control the voltage and can switch a current output “on” and “off.” There are also electrical devices called transformers that can transfer or switch electrical energy from one circuit to another. The faster the switch, the better the conversion efficiency but the conventional transistors that used silicon had its limitations when trying to shorten the battery charge time.


That is when they decided to use gallium nitride (GaN) as their transistor material. It is a high-efficiency material that is even used for blue LED and is known for its rapid on/off switching. But it’s expensive and not used for conventional smartphones. Fujitsu was able to reduce the cost by combining gallium nitride with more affordable silicon. The company had already developed its own technology for their switching element called “High Electron Mobility Transistors” (HEMT) in 1980. This was a then- revolutionary invention since electrons flowed more easily in HEMT than in conventional transistors. Hirose and his team thought that combining GaN with HEMT would enable electrons to move faster at a higher frequency, thereby increasing the power output and would also make the adapter more compact.



But it wasn’t quite so simple. Operating at a higher frequency meant that there would be more high-frequency “noise” which made them more susceptible to malfunction. In fact, many of their prototypes did not work as intended.


(Tatsuya Hirose, left, with Miki Imai, right)


Hirose would design the circuit and Imai would build the circuit board prototypes. It was a repetition of trial and error, changing the structure, adding parts to the circuitry, that lead to their success a year-and-a-half later.


Assuming that there are 7.2 billion smartphones in use around the world, Fujitsu estimates the total electricity saved by this new AC adapter can amount to 16.74 billion watt-hours per day, or 1.2 million households-worth of electricity consumption and will enable carbon dioxide emission to be reduced by 3.24 million tons a year.


Fujitsu is already getting offers from many manufacturers and the new adapter is soon to be made available on the market within the year at the earliest. “We want to show not only its convenience but also its eco-friendliness,” stresses Hirose.


For this new invention, Fujitsu has been awarded the grand prize of the 26th annual Global Environment Award, sponsored by the Fujisankei Communications Group, that recognizes companies and organizations undertaking initiatives to preserve the environment such as global warming.


Michito Ida is an economics staff writer for the Sankei Shimbun



(Learn more about the Global Environment Awards here)


(Click here to read the original in Japanese)

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