Fraunhofer Institute for Integrated Circuits IIS announced that, although it may seem impossible that a sensor, RFID module, small display or microcontroller could operate on 20mV, its engineers 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.
Said to eliminate 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 voltage converter IC, which measures only 1.5 by 1.5mm.
The IC can, for example, supply 3.3V 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%. Fraunhofer claims that this is the first solution worldwide that operates on supply voltages as low as 20mV. Besides the ASIC, all that is needed is a small transformer and two capacitors.
It is possible to use a 2 x 2cm thermoelectric generator which in conjunction with the microchip can produce up to 4mW 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 selfpowered 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.
