{"id":11600,"date":"2017-02-19T09:01:26","date_gmt":"2017-02-19T09:01:26","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=11600"},"modified":"2017-02-19T09:01:26","modified_gmt":"2017-02-19T09:01:26","slug":"researchers-devise-efficient-power-converter-internet-things","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/researchers-devise-efficient-power-converter-internet-things\/","title":{"rendered":"Researchers devise efficient power converter for internet of things"},"content":{"rendered":"

Design reduces converter\u2019s resting power consumption by 50 percent.<\/strong><\/em><\/span><\/p>\n

\"\"
Researchers from MIT\u2019s Microsystems Technologies Laboratories (MTL) have designed a new power converter that maintains its efficiency at currents ranging from 100 picoamps to 1 milliamp, a span that encompasses a millionfold increase in current levels.<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0The \u201cinternet of things\u201d is the idea that vehicles, appliances, civil structures, manufacturing equipment, and even livestock will soon have sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks.<\/span><\/p>\n

Those sensors will have to operate at very low powers, in order to extend battery life for months or make do with energy harvested from the environment. But that means that they\u2019ll need to draw a wide range of electrical currents. A sensor might, for instance, wake up every so often, take a measurement, and perform a small calculation to see whether that measurement crosses some threshold. Those operations require relatively little current, but occasionally, the sensor might need to transmit an alert to a distant radio receiver. That requires much larger currents.<\/span><\/p>\n

Generally, power converters, which take an input voltage and convert it to a steady output voltage, are efficient only within a narrow range of currents. But at the International Solid-State Circuits Conference last week, researchers from MIT\u2019s Microsystems Technologies Laboratories (MTL) presented a new power converter that maintains its efficiency at currents ranging from 500 picoamps to 1 milliamp, a span that encompasses a 200,000-fold increase in current levels.<\/span><\/p>\n

\u201cTypically, converters have a quiescent power, which is the power that they consume even when they\u2019re not providing any current to the load,\u201d says Arun Paidimarri, who was a postdoc at MTL when the work was done and is now at IBM Research. \u201cSo, for example, if the quiescent power is a microamp, then even if the load pulls only a nanoamp, it\u2019s still going to consume a microamp of current. My converter is something that can maintain efficiency over a wide range of currents.\u201d<\/span><\/p>\n

Paidimarri, who also earned doctoral and master\u2019s degrees from MIT, is first author on the conference paper. He\u2019s joined by his thesis advisor, Anantha Chandrakasan, the Vannevar Bush Professor of Electrical Engineering and Computer Science at MIT.<\/span><\/p>\n

Packet perspective<\/strong><\/span><\/p>\n

The researchers\u2019 converter is a step-down converter, meaning that its output voltage is lower than its input voltage. In particular, it takes input voltages ranging from 1.2 to 3.3 volts and reduces them to between 0.7 and 0.9 volts.<\/span><\/p>\n

\u201cIn the low-power regime, the way these power converters work, it\u2019s not based on a continuous flow of energy,\u201d Paidimarri says. \u201cIt\u2019s based on these packets of energy. You have these switches, and an inductor, and a capacitor in the power converter, and you basically turn on and off these switches.\u201d<\/span><\/p>\n

The control circuitry for the switches includes a circuit that measures the output voltage of the converter. If the output voltage is below some threshold \u2014 in this case, 0.9 volts \u2014 the controllers throw a switch and release a packet of energy. Then they perform another measurement and, if necessary, release another packet.<\/span><\/p>\n

If no device is drawing current from the converter, or if the current is going only to a simple, local circuit, the controllers might release between 1 and a couple hundred packets per second. But if the converter is feeding power to a radio, it might need to release a million packets a second.<\/span><\/p>\n

To accommodate that range of outputs, a typical converter \u2014 even a low-power one \u2014 will simply perform 1 million voltage measurements a second; on that basis, it will release anywhere from 1 to 1 million packets. Each measurement consumes energy, but for most existing applications, the power drain is negligible. For the internet of things, however, it\u2019s intolerable.<\/span><\/p>\n

Clocking down<\/strong><\/span><\/p>\n

Paidimarri and Chandrakasan\u2019s converter thus features a variable clock, which can run the switch controllers at a wide range of rates. That, however, requires more complex control circuits. The circuit that monitors the converter\u2019s output voltage, for instance, contains an element called a voltage divider, which siphons off a little current from the output for measurement. In a typical converter, the voltage divider is just another element in the circuit path; it is, in effect, always on.<\/span><\/p>\n

But siphoning current lowers the converter\u2019s efficiency, so in the MIT researchers\u2019 chip, the divider is surrounded by a block of additional circuit elements, which grant access to the divider only for the fraction of a second that a measurement requires. The result is a 50 percent reduction in quiescent power over even the best previously reported experimental low-power, step-down converter and a tenfold expansion of the current-handling range.<\/span><\/p>\n

\u201cThis opens up exciting new opportunities to operate these circuits from new types of energy-harvesting sources, such as body-powered electronics,\u201d Chandrakasan says.<\/span><\/p>\n

The work was funded by Shell and Texas Instruments, and the prototype chips were built by the Taiwan Semiconductor Manufacturing Corporation, through its University Shuttle Program.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Design reduces converter\u2019s resting power consumption by 50 percent. CAMBRIDGE, Mass. —\u00a0The \u201cinternet of things\u201d is the idea that vehicles, appliances, civil structures, manufacturing equipment, and even livestock will soon have sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks. Those sensors will have to operate at very […]<\/p>\n","protected":false},"author":6,"featured_media":11601,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,28],"tags":[],"class_list":["post-11600","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research","category-techbiz"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/02\/MIT-Power-Harvest_0.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a> Tech<\/a>","tag_info":"Tech","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/11600","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=11600"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/11600\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/11601"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=11600"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=11600"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=11600"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}