It may seem impossible that a sensor, RFID module, small display or microcontroller could operate on 20millivolts. Yet engineers at the Fraunhofer Institute for Integrated Circuits IIS have achieved precisely this by developing a novel voltage converter which has been miniaturized into an ASIC. With the aid of this voltage converter, tiny amounts of energy, such as can be extracted from the environment, for instance, can be utilized to power small electrical loads.
Eliminating the need for batteries, the new voltage converter makes it possible to considerably reduce the size of sensors such as pulse oximeters and EEG devices to make them wearable. It also enables self-powered thermostats that can transmit measured data to an air conditioning system. These are only a few potential applications of this novel voltage converter IC, which measures only 1.5 mm by 1.5 mm.
The IC can, for example, supply 3.3 volts to electronic components such as sensors, wireless transceivers and displays. Depending on the difference between the input and output voltages, its efficiency varies between 30 and 80 percent. This is the first solution worldwide that operates on supply voltages as low as 20 millivolts. Besides the ASIC, all that is needed is a small transformer and two capacitors.
It is possible to use a 2 cm x 2 cm thermoelectric generator which in conjunction with the microchip can produce up to 4 milliwatts from a 2°C temperature gradient. This is equivalent to the difference between the surface temperature of a human hand and room temperature, for example. If the energy produced is collected over a prolonged period and stored in a battery, it becomes possible to power larger loads such as MP3 players or PDAs.
The voltage converter is the result of collaboration between Fraunhofer IIS (Erlangen), Fraunhofer IFAM (Dresden) and Fraunhofer IPM (Freiburg) in the context of an ongoing Fraunhofer project on thermoelectric nanocomposites. The project is aimed at developing thermoelectric generators specially geared to distributed power generation for self powered sensor/actuator networks. For this purpose, various approaches to creating highly efficient polycrystalline thermoelectric materials and components are being pursued, and highly integrated electronic circuits are being created that are essential for use in a thermoelectric generator.
Located in Nuremberg, Fraunhofer IIS's Power-Optimized Systems Department develops, among other things, integrated circuits and systems for integrated power supplies, power and battery management, energy harvesting and wireless energy transmission. The department provides customer specific solutions, for instance for facilities management and automation as well as for medical and automotive engineering.
Founded in 1985 the Fraunhofer Institute for Integrated Circuits IIS in Erlangen, today with 585 staff members, ranks first among the Fraunhofer Institutes concerning headcount and revenues. As the inventor of mp3 and co-inventor of the MPEG 4 AAC audio coding standard, Fraunhofer IIS has reached worldwide recognition.
It provides research services on contract basis and technology licensing. The research topics are: Audio and video source coding, multimedia realtime systems, digital radio broadcasting and digital cinema systems, integrated circuits and sensor systems, design automation, wireless, wired and optical networks, localization and navigation, imaging systems and nanofocus X-ray technology, high-speed cameras, medical sensor solutions and communications technology in transport and logistics.
The budget of 72 million Euros is mainly financed by projects from industry, the service sector and public authorities. Less than 25 percent of the budget is subsidized by federal and state funds.
Top Image: the diminutive size of the unique voltage converter which is able to handle input voltages as low as 20 millivolts. (Source: Fraunhofer IIS)
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