The synchronized multiple bias-flip (SMBF) interface circuits enhance the piezoelectric energy harvesting (PEH) capability by maximizing the extracted energy from the piezoelectric source and simultaneously minimizing the dissipated energy in the power conditioning circuit. They provide the most energy-economic solution for piezoelectric energy harvesting enhancement. However, the growing scale of switches network and the increasing number of bias voltages have added much complexity to the circuit design and control. In this paper, we reduce the number of passive components to the biggest extent by maximizing the usage of a single capacitor, which simultaneously acts as energy storage and provides two non-zero bias voltages. Together with the free zero-volt bias, triple bias-flip actions (S3BF) are realized in the new design. Compared with other single-capacitor designs, it makes the best energy harvesting capability so far. Moreover, the proposed series S3BF circuit can automatically shift among single, double, and triple bias-flip operations under heavy, medium, and light load conditions, respectively, which is unprecedented in the previous designs. Theoretical and experimental results show that the harvested power can always follow the maximum power envelope of the single, double, or triple bias-flip operations.

The emerging energy harvesting technology facilitates the development of ubiquitous and everlasting battery-free motion detectors. This article introduces a robust design of the transient-motion-powered motion detector, which is called ViPSN-pluck. “ViPSN” is the acronym for the vibration-powered sensing node while “pluck” stands for the plucking-motion energy harvester. By using a piezo-magneto-elastic structure, ViPSN-pluck can efficiently harvest energy from a transient motion. By properly making good use of this tiny harvested energy, ViPSN-pluck can effectively carry out motion detection and Bluetooth low-energy (BLE) wireless communication. Given the concurrency of mechanical potential energy precharging and motion detection, the transient-motion plucking energy harvester used in ViPSN-pluck has the merit of high energy reliability. This unique feature is unprecedented in the solar and radio-frequency (RF) energy harvesting cases, which might suffer from energy outages under fluctuating irradiance or RF signal strength, respectively. The working principle of ViPSN-pluck, in particular, the dynamic characteristics of the plucking energy harvester and the energy matching between generation and utilization, are discussed in detail to demonstrate the robustness in operation. The cyber-electromechanical synergy among the mechanical dynamics, power conditioning circuit, and low-power embedded system is highlighted. The design methodology of ViPSN-pluck provides a valuable reference for the developments of future motion-powered Internet of Things devices.

Piezoelectric energy harvesting (PEH) systems convert ambient vibration energy into useful electricity. An interface circuit intervenes the electromechanical energy conversion; it has a significant effect on the electromechanical joint dynamics and harvested power. Among the existing interface circuits, the synchronized electric charge extraction (SECE) solution was known for its unique feature of load independence. However, the actual harvested power was usually shown to be lower than the previous theoretical predictions. The reason is that the energy dissipation in power conditioning, e.g. the diode dissipation in the rectifier and the switching dissipation in each energy extraction, have not received sufficient consideration. This paper revisits the joint dynamics and harvested power of PEH systems with a SECE interface circuit by using the energy flow analysis and impedance modeling. By qualitatively scrutinizing the energy cycle of SECE, the electrically induced dynamic characteristics are broken down into three components: the equivalent capacitance, dissipative resistance, and harvesting resistance, which have the same effects but different values, like those in other PEH interface circuits. The three components are equivalent to an additional stiffness, a dissipative damper, and a regenerative damper in the mechanical domain. The theoretical harvested power, which is estimated based on the impedance modeling, shows good agreement with the experimental results under different loading conditions and operating frequencies. Owing to its modular way of thinking, the impedance modeling technique once again shows its effectiveness and efficiency towards the analyses of joint dynamics and harvested power in PEH systems using different power conditioning interface circuits.