Implementation of a Single Supply Pre-biasing Circuit for Piezoelectric Energy Harvesters

AbstractIncreased output power can be obtained from piezoelectric energy harvesters by using switching circuits that modify the charge on the material at the extremes of cantilever travel. Here we present an implementation of the most efficient of these charge modification techniques, single-supply piezoelectric pre-biasing. We describe practical results from this scheme and circuit details, including power processing components and control circuits. The power circuit current paths are synchronously commutated with MOSFETs, removing inefficient diode voltage drops. The control circuit is implemented using low power discretes. A useful output power of 2.6 mW was achieved after a 400μW reduction required for the control circuitry. This is a factor of 4.3 greater than when the harvester was connected to a passive diode bridge and is greater than can be achieved by other piezoelectric interface circuits using an inductor with the same Q-factor

Maximum performance of piezoelectric energy harvesters when coupled to interface circuits

This paper presents a complete optimization of a piezoelectric vibration energy harvesting system, including a piezoelectric transducer, a power conditioning circuit with full semiconductor device models, a battery and passive components. To the authors awareness, this is the first time and all of these elements have been integrated into one optimization. The optimization is done within a framework, which models the combined mechanical and electrical elements of a complete piezoelectric vibration energy harvesting system. To realize the optimization, an optimal electrical damping is achieved using a single-supply pre-biasing circuit with a buck converter to charge the battery. The model is implemented in MATLAB and verified in SPICE. The results of the full system model are used to find the mechanical and electrical system parameters required to maximize the power output. The model, therefore, yields the upper bound of the output power and the system effectiveness of complete piezoelectric energy harvesting systems and, hence, provides both a benchmark for assessing the effectiveness of existing harvesters and a framework to design the optimized harvesters. It is also shown that the increased acceleration does not always result in increased power generation as a larger damping force is required, forcing a geometry change of the harvester to avoid exceeding the piezoelectric breakdown voltage. Similarly, increasing available volume may not result in the increased power generation because of the difficulty of resonating the beam at certain frequencies whilst utilizing the entire volume. A maximum system effectiveness of 48% is shown to be achievable at 100 Hz for a 3.38-cm3 generator

Co-design/simulation of flip-chip assembly for high voltage IGBT packages

This paper details a co-design and modelling methodology to optimise the flip-chip assembly parameters so that the overall package and system meets performance and reliability specifications for LED lighting applications. A co-design methodology is employed between device level modelling and package level modelling in order enhance the flow of information. As part of this methodology, coupled electrical, thermal and mechniacal predictions are made in order to mitigate underfill dielectric breakdown failure and solder interconnect fatigue failure. Five commercial underfills were selected for investigating the trade-off in materials properties that mitigate underfill electrical breakdown and solder joint fatigue

Orthobunyaviruses: recent genetic and structural insights

Orthobunyaviruses, which have small, tripartite, negative-sense RNA genomes and structurally simple virions composed of just four proteins, can have devastating effects on human health and well-being, either by causing disease in humans or by causing disease in livestock and crops. In this Review, I describe the recent genetic and structural advances that have revealed important insights into the composition of orthobunyavirus virions, viral transcription and replication and viral interactions with the host innate immune response. Lastly, I highlight outstanding questions and areas of future research