Technology Radiative solution keeps wearables cool, even in sunlight


A team of Korean and American scientists has developed an innovative solution to combat heat in wearable sensors. Led by Professor Young Min Song from Gwangju Institute of Science and Technology (GIST) in Korea, the team produced a flexible and non-metallic cooler made from perforated polymers. Te resulting material reflects nearly all sunlight and has high emissivity in the range of frequencies known as the atmospheric window, allowing it to radiate excess heat into the atmosphere, keeping it cool. In addition, its mechanical properties make it perfect for outdoor wearable devices. Wearable electronic devices, like fitness


trackers and biosensors, are very promising for healthcare applications and research. Tey can be used to measure relevant biosignals in real time and send gathered data wirelessly, opening up new ways to study how our bodies react to different types of activities


Keeping it cool – new approach to thermal protection in outdoor wearable electronics


and exercise. However, heat accumulates in these devices for various reasons: operation in close contact with the user’s skin and from other sources. When these combine, the temperature of wearable devices can rise to uncomfortable levels, and may even cause erroneous measurements. Heat sinks and


dissipators for wearable devices have metallic layers, which block electromagnetic signals, hindering wireless communications. Tis new radiative cooler using perforated


polymers promises to keep the gadgets cool and functional under heat, paving the way for thermally-protected wearable devices.


Pulsiv moves on to next stages of development with £1.5m funding


Plymouth University spin-off Pulsiv has received £1.5m funding to accelerate the development of its power-conversion technology and prepare its growth. Initially known as Pulsiv Solar, Pulsiv has confirmed its goal to “make the most efficient use of electricity wherever it is converted” with economic and environmentally- friendly power supply solutions. Its technology aims to improve the power output and efficiency of electricity conversion, which should lead to reduced bills and efficient products. A latest example is its cooperation with Bosch on a new microinverter to enhance the efficiency of photovoltaic solar cells. Calls for sustainable electronic systems and


devices are driving the trend for smarter and more energy-efficient products; consumers also want faster battery charging, longer battery life, and energy-efficient and cheaper domestic appliances. Pulsiv promises to deliver all these with smaller, lighter and more cost-effective designs through “fundamentally new power- conversion techniques”. Power supply topologies have evolved over


the years, especially in specific applications, with the semiconductor industry keeping pace with


tailored solutions for improved performance and lower costs. Now, Pulsiv offers a series of reference designs


to improve the power factor in commodity power supplies of < 65W, to deliver 65W-250W power supplies for OEMs with high power density or lowest cost per watt, and for a new power-balancing mode in consumer products. “To deliver 65W-250W power supplies for


OEMs requiring high power density, even in modest volumes, COTS power supplies can be expensive. Many companies design their own or employ third parties to create bespoke solutions,” wrote the company in a statement. Pulsiv claims to provide an alternative.


Patented power factor correction techniques and proprietary microcontroller algorithms are used to optimise circuit designs. Te company has also replaced expensive capacitors in its designs with commodity parts, and completely removed large magnetic components, which has translated into simpler, smaller, lighter and lower-cost OEM products. “Electronic devices have traditionally


consumed whatever they require with little or no consideration for the power source. Standby,


low-power and eco modes are now a feature of many home appliances, but none of these address underlying supply limitations,” said Dr Zaki Ahmed, Pulsiv founder and Chief Strategy Officer. “Our low-cost integrated circuit detects grid over/under supply on each AC cycle, enabling consumer products to intelligently adjust consumption in real time. Widespread adoption could eliminate demand surges, blackouts, bottlenecks and reliability issues in the power network.” He continued: “Phone chargers, generic


USB adaptors, Wi-Fi boxes, Chromebook power bricks and many other high- volume devices typically exhibit a power factor in the 30-50% range. National grid infrastructure and local renewable sources must therefore provide 2-3 times more power than is actually used. Typical peak and inrush currents are far higher than they need to be; both put unnecessary stress on transmission systems and cause losses throughout the network.” Early prototypes of the Pulsiv design


have exhibited a power factor of 90% and over.


www.electronicsworld.co.uk June 2021 05


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