Proc. SPIE. 7268, Smart Structures, Devices, and Systems IV
KEYWORDS: Electronics, Microsystems, Signal processing, Structural health monitoring, Smart structures, Thermoelectric materials, Chemical elements, Aircraft structures, Instrument modeling, Current controlled current source
Vibration harvesting has been intensively developed recently and systems have been simulated and realized, but real-life situations (including aircraft Structure Health Monitoring (SHM)involve uneven, low amplitude, low frequency vibrations. In such an unfavorable case, it is very likely that no power can be harvested for a long time. To overcome this, multi-source harvesting is a relevant solution, and in our application both solar and thermal gradient sources are available. We propose in this paper a complete Microsystem including a piezoelectric vibration harvesting module, thermoelectric conversion module, signal processing electronics and supercapacitor. A model is proposed for these elements and a VHDL-AMS simulation of the whole system is presented, showing that the vibration harvesting device alone cannot supply properly a SHM wireless node. Its role is nevertheless important since it is a more reliable source than thermoelectric (which depends on climatic conditions). Moreover, synergies between vibration harvesting and thermoelectric scavenging circuits are presented.
For applications such as computers, cellular telephones and Microsystems, it is essential to reduce the size and the
weight of DC-DC converters. To miniaturize passive components, micromachining techniques provide solutions based
on low-temperature process compatible with active part of the converter. This paper deals with the integration on silicon
of "spiral-type" inductor topology. Electroplating techniques are used to achieve the copper conductor and the CoNiFe
laminated magnetic core and several investigations on the electroplating bath's parameters have been realized in order to
obtain the adequate magnetic properties. Finally, a 1μH micro-inductor prototype has been characterized.
In portable electronic equipments, miniaturisation, cost, multi-functionalities and reliability are the main factors driving the power electronics industry. In this context, the realisation of all integrated high performance DC-DC micro-converters working at high frequencies (few MHz) is necessary. The passive components such as inductors, transformers and capacitors, are for the moment the bulkiest components and their integration on silicon substrate would constitute a real improvement in term of compactness and reliability of power converters. This paper deals with the fabrication of integrated capacitors realised on silicon using MEMS-type techniques. High capacitance density, low series resistance and inductance are sought. Structures using deep cavities etched in silicon were realised in order to increase the effective area of the capacitor's electrodes while minimising the area on the substrate. The development of micro-fabrication techniques such as Deep Reactive Ion Etching (DRIE) and doped-polysilicon deep trenches filling are presented. Some preliminary measurement on the fabricated capacitors with the developed processes show that high capacitance density (36 nF/mm<sup>2</sup>) can be obtained.