Batteries and Portable Power

GaN enables Wide-Input and Compact 12W DC-DCs

In the last couple of years, a team of researchers at DTU Electrical Engineering have worked to develop the world’s smallest power supply unit called TinyPower together with a number of companies. The initial purpose was to produce a power supply unit which could be used in LED light bulbs or light sensors. The development of the TinyPower power supply unit will mean an expected improvement in service life, cost, size, and weight. In future, wireless energy harvested from renewable energy sources is to run the world’s smallest power supply unit, making it possible to use it for small new devices sewn into clothes and other wearable and IoT applications.

"The efficiency depends on Input and output voltage ratio and output power. But it is above 84%," commented Yasser Nour, who is a PhD student and member of DTU's team of researchers together with fellow PhD student Lin Fan and associate professors Arnold Knott and Ivan Jørgensen.

Some technical details about this specific prototype include: 4- to 80-Vdc input range; Output voltage can be 20% to 80% of the input voltage (from as low as 0.8Vdc for a 4Vdc input up to 64Vdc with an input voltage of 80Vdc); 12W maximum output power; Switching frequency up to 12MHz; Air-core magnetics; and Soft-switching step-down topology (a buck topology and can be modified externally to operate as a resonant converter).

"There are many benefits associated with the tiny power supply unit that we have developed. In addition to the size, which also means that the weight has been greatly reduced, this tiny power supply unit is less expensive, lasts longer, and has higher output than a conventional power supply unit," commented Nour.

It almost sounds too good to be true, but the fact is that the researchers have succeeded in creating a power supply unit in which the classic passive components (electrolytic capacitors and magnetic coil) have been replaced with small ceramic capacitors and an air-core coil. The researchers' objective is that these will be removed completely, so that the power supply unit will consist of fewer components and become even smaller than the current 1 x 1 cm, which is the result achieved so far. The omission of components will also eliminate the need to use rare earths in the power supply production, thus also benefiting the environment.

"We can do this, because TinyPower uses modern semiconductors and a much higher frequency than the one usually used in power supply units. Figuratively speaking, you could say that our power supply unit delivers energy faster, but in minor volumes at a time. This corresponds to having only a small cup for emptying a swimming pool, where you previously used a large bucket. This requires that you run faster and go back and forth more times. At the higher speed, there is consequently no longer a need for, for example, a large coil, and we can thus reduce components and the size of the power supply unit," explains Nour.

“TinyPower uses modern semiconductors and a much higher frequency than the one usually used in power supply units. Figuratively speaking, you could say that our power supply unit delivers energy faster, but in minor volumes at a time.”

The small power supply unit has been developed in collaboration with the four Danish companies, which, among other things, will use it in their development of intelligent products such as LED-based lighting systems, motion sensors, alarm systems, thermostats, pumps, wall sockets, and door locks.

“We will use the new power supply units in our already very compact products for, for example, intelligent lighting control. The development in this field is progressing rapidly, and it will not be long before consumers will take it for granted that they can control the lighting and other installations in their home from their mobile phones. We need to be ready to supply this in a design that does not comprise expensive and big, clumsy power supply units," explains Tommy Bjerre, CTO, Niko-Servodan, in Sønderborg.

Also other companies participate in the development, including Nordic Power Converters, which currently uses the first generation of fast-switching power supply units in their LED lighting products.

While the researchers have worked on TinyPower, the Internet of Things has also developed substantially. This means that there are now both interest in and demand for further developing the power supply unit, so that it will be able to harvest energy, for example from vibrations produced when walking.

"The Internet of Things is no longer a distant future vision. Before long, there will be a need for small units, which can, for example, be mounted on the body or in clothing to monitor pulse, temperature or heart rhythm. The power for this must come from a renewable energy source and be wirelessly transferable," says Nour.

He and his colleagues at DTU expect that a wireless power supply unit can be developed and be ready for commercialization in the next couple of years if funding can be found for the researchers' ongoing work.

Technical University of Denmark
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