High efficiency piezoelectric energy harvester with synchronized switching interface circuit

A new vibration driven energy harvesting device with an additional synchronized switching interface for optimizing the power transfer from the energy harvester to a storage element is presented. The new type of piezoelectric energy transducer consists of 2 piezoelectric coupled generator structures. One of these structures acts as main generator. The other structure acts as injection generator, which provides the energy for an energy injection process. Both structures are realized on the same substrate and are therefore exposed to the same mechanical excitation. The transducer uses a four-point-bending principle. Both ends of the piezoelectric beam are pivot-mounted on the housing. Thus a uniform stress distribution over the whole generator structure is achieved. A novel interface circuitry, based on the initial energy injection described by Lallart et al. [1], is added to the system. It enables a harvesting process that is almost independent of the load and allows an almost ideal energy storage process. The results of parameter studies for an optimal generator design as well as measurement results obtained with the direct initial energy injection circuitry are presented and discussed in the presentation. The results show that an efficiency benefit by a factor of 3, compared to standard devices can be achieved by the presented device.