OREANDA-NEWS. Fujitsu Laboratories Ltd. today announced the development of the world's smallest, most efficient AC adapter, which uses gallium nitride (GaN) high electron-mobility transistor (HEMT) power devices for super-fast charging of smartphones and other mobile electronics.

As mobile devices using AC adapters to recharge such as smartphones, tablets, and other electronics powered by rechargeable batteries have become more and more prevalent, charger efficiency has become an issue in reducing the total amount of power consumed and reducing society's environmental footprint. As mobile devices are built with increasing battery capacity, charging those batteries quickly becomes an issue, creating a demand for compact, high-output AC adapters.

Fujitsu Laboratories has now used low dynamic resistance GaN-HEMT as the switching element, which is heavily by low-loss, to develop the world's smallest and most efficient AC adapter. New circuitry that precisely controls switching timing reduces current loss, allowing for the world's smallest 12-W AC adapter (15.6-cc) and the world's most efficient power supply at 87%. Using GaN-HEMPT has made it possible to have small, high-speed switching as well as achieve low-resistance and improved energy efficiency. With this technology, AC adapters charging mobile electronics will consume half the power and will be able to charge in one-third of the time. Widespread use of this AC adapter will help reduce CO2 emissions and reduce burden on the environment.

The prototype AC adapter will be exhibited at Eco-Products 2015, from December 10 at Tokyo Big Sight.

 

The has been an rapid increase in prevalence of cellphones, smartphones, tablets, and other mobile electronics powered by rechargeable batteries and there are pressing needs for high-capacity battery-equipped mobile electronics with long run times, and to charge such devices quickly, making smaller and higher-output AC adapters even more desirable. In addressing their environmental impact, reducing power consumption has become an issue. In February 2016, the U.S. Department of Energy will be putting into effect revised "Level-VI" efficiency standards for external power supplies, calling for power supplies operating at 6-V or less to increase their efficiency by as much as 5.46%. Meeting this higher efficiency level has been a significant undertaking.

AC adapters today use a switching-based approach with field-effect transistors (FET) as the switching elements, which repeatedly turn on and off to convert and thereby control the voltage.

The most effective means of improving the size, efficiency, and output of AC adapters is to use switching that increases the frequency of the on/off cycling action. GaN-HEMT, which can run at megahertz rates with a low threshold voltage to determine on/off switching, is considered the ideal technology for that switching element for its extremely high performance. It can be run at ten times the frequency of the Si-MOSFET silicon semiconductor devices that are currently widely used switching elements, and with one-tenth the dynamic resistance. But today's control ICs, which control the operation of the switching elements and stabilize voltage, are slower even than current switching actions, and would make it impossible to fully take advantage of GaN-HEMT performance. Furthermore, timing delays in the switching can cause the current to flow backwards through the circuit, creating considerable loss.