Interleaved Switch Harvesting on Inductor: Non-linear extraction, action and reaction

The circuit presented in this paper provides increased transfer efficiency for the electric charge generated by a piezoelectric element to the storage device, it also enables a simplified active control circuitry required for switched harvesting solutions as the control transistors are referenced to ground. This is achieved by inverting the voltage potential across the piezoelectric element and thereby maintaining a higher voltage while extracting energy. The increased potential allows vibration harvesters to operate over a broader frequency range. For weakly coupled piezoelectric harvesters, the increased potential allows the electrical power output to be increased. In this paper, the circuit is simulated in SPICE using existing models of discrete components in conjunction with a model of a piezoelectric vibration harvester. The power output and mechanical behavior of the harvester using the presented circuit are compared to two existing technologies: Synchronous Switch Harvesting on Inductor (SSHI) and a full-wave rectifying bridge. The comparison demonstrates that the novel Interleaved Switch Harvesting on Inductor (ISHI) circuit outperforms state-of-the-art active harvesting solutions, e.g., SSHI, as a result of the decreased energy losses from diodes. In addition, the ISHI circuit requires fewer components than does the SSHI circuit and solves the floating transistor source issue that arises in SSHI implementations. To achieve the maximum power conversion efficiency, impedance matching is required, which can be achieved by controlling the voltage of the storage device.