**5. Conclusions**

A highly efficient active CMOS rectifier suitable to be applied to vibrational energy harvesters was presented in this work. The proposed structure was designed in 130 nm CMOS technology, and the results showed a VCE of 99% and a PCE of 80–90% for a low operation voltage from 0.45 V to 1 V and for an operating frequency of 3.2 kHz, which proves the value of this work for a practical energy harvesting application. These features were achieved by combining an NVC with an active diode biased by a threshold cancellation circuit, which dynamically reduces the threshold voltage effect. Moreover, this structure avoids the reverse leakage current due to the use of a no-delay comparator, which was vital to reduce the power losses.

The research work focused on developing a highly efficient rectifier to be integrated into a PMC. It is believed that this structure will efficiently contribute to solving the battery limitation problems of the WSNs for an environmental monitoring application. Further work should focus on integrating the proposed structure in the PMC and respective testing in real environmental conditions.

**Author Contributions:** A.G. was responsible for the investigation, design of the proposed circuit, simulations, respective validation, and the writing of the original draft. Z.Y. was involved in the investigation, simulations, respective validation, and in the writing revision and editing. T.D. supervised the research, administrated the project, and acquired the project funding. L.G. and P.M. were involved in the research supervision and validation of the simulation. Y.W. and P.L. were responsible for the conceptualization of the research and the administration of the project. Z.J. was also involved in the conceptualization of the research. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the National Natural Science Foundation of China under Project 61531008; by the "Praktisk og effektiv oppfølging av KOLS-pasienter i kommunene" from RFF Forskningsfond Oslofjordfondet under Project 285575; by the RFF Forskningsfond Agder under Project 321343; by the Chongqing Research Program of Basic and Frontier Technology under Project Cstc2018jcyjA3877, Project cstc2018jcyjAX0474, and Project cstc2019jcyj-msxmX0776; and by the Chongqing Education Commission–Science and Technology Research Program under Grant KJZD-K201800802, Grant KJZDK201900802, and Grant KLZD-K202000805.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
