Improved Design and Analysis of Self-Powered Synchronized Switch Interface Circuit for Piezoelectric Energy Harvesting Systems

In piezoelectric energy harvesting (PEH), with the use of the technique named synchronized switch harvesting on inductor (SSHI), the harvesting efficiency can be greatly enhanced. Furthermore, the introduction of its self-powered feature makes this technique more applicable for stand-alone systems. In this paper, a modified circuit and an improved analysis for the self-powered SSHI (SP-SSHI) are proposed. With the modified circuit, direct peak detection and better isolation among different units within the circuit are achieved, both of which result in the further removal on the dissipative components. In the improved analysis, details in the open circuit voltage, switching phase lag, and intermediate voltages among different phases are discussed, all of which lead to a better understanding on the working principle of SP-SSHI. The total power dissipation from the piezoelectric source is also investigated. It is of concern but has not been considered in the previous literatures. Both analyses and experiments show that, in terms of the harvested power, the higher the excitation level, the closer between SP-SSHI and ideal (externally powered) SSHI; at the same time, the more beneficial the adoption of SP-SSHI treatment in PEH, compared to the standard energy harvesting (SEH) technique. Under the four excitation levels investigated, the SP-SSHI can harvest up to 200% more power than the SEH interface circuit.