In recent years, low-powered short-distance wireless communication techniques typified by ZigBee have been developed, and wireless sensor networks that employ such short-distance wireless communication techniques have been built. However, using batteries as power supplies in the wireless sensor networks leads to problems of the lifetime of batteries, environmental burdens due to battery disposal, and the like. Accordingly, attentions have been drawn to energy harvesting techniques which harvest various types of energy existing in the environment, such as heat, vibration, light, and radio waves and convert the energy into electricity.
One of the energy harvesting techniques having been proposed so far is a power generation device which includes a pair of beams made of a magnetostrictive material, a coil wound around each beam, and a magnet producing a magnetic flux. In this type of power generation device, the beams are bent by vibration, and the magnetic flux passing through the beams changes in density to induce current in the coils. The induced current is extracted from the coils and may be used as power for driving an electronic device.    Patent Literature 1: WO2011/158473