Contents lists available at ScienceDirect Nano Energy journal homepage: www.elsevier.com/locate/nanoen Full paper A conditioning circuit with exponential enhancement of output energy for triboelectric nanogenerator Ali Ghaffarinejad a,b , Javad Yavand Hasani b, ⁎ , Ronan Hinchet c , Yingxian Lu a , Hemin Zhang a , Armine Karami d , Dimitri Galayko d , Sang-Woo Kim c , Philippe Basset a, ⁎ a Université Paris-Est, ESYCOM, ESIEE Paris-CNAM-UPEM, Noisy-le-Grand 93162, France b School of Electrical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran c School of Advanced Materials Science and Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Republic of Korea d Sorbonne Universités, F-75005 Paris, France ARTICLE INFO Keywords: Triboelectric-electret (triboelectret) nanogenerator Bennet’s doubler Power management circuit Conditioning circuit Kinetic energy harvester T-ENG ABSTRACT Triboelectric-electret nanogenerators (T-ENG) are characterized by their high output voltage and small current and therefore a relatively low output power, making them limited to small power consuming electronics. Here we report a self-enhancing conditioning circuit (CC) that exponentially amplifies the output electrical energy converted from the mechanical domain of a T-ENG, in orders of magnitude compared to traditional CC. The circuit, working on the principles of Bennet’s doubler device, is inductorless and uses only diodes as automatic switches to reconfigure the charge storing capacitors between series and parallel modes. We previously reported this circuit in saturation and stable mode for T-ENG and compared the performances with half-wave rectifier. Here we investigate the circuit performance in exponential and unstable mode in comparison with half-wave and full-wave rectifiers. Theoretical analysis is presented to study the operation of the circuit and to find out the required conditions for the Bennet’s doubler to work in exponential boosting mode. Output performance of half and full wave rectifiers are compared theoretically. Simulations and experiments are performed to verify the theoretical discussions and to present the effect of non-ideal circuit elements on the output performance of the T- ENG. 1. Introduction With the development of Internet of things (IOT) and portable de- vices, a vast variety of small electronic instruments are becoming parts of our daily life. Powering such devices is a challenge that is to be overcome, either by using rechargeable batteries or harvesting elec- trical energy from ambient energy. Electrostatic kinetic energy har- vesters (e-KEH) convert the kinetic energy of mechanical vibrations into electrical energy by varying the capacitance of an electromechanical transducer [1]. These transducers require an initial bias to work prop- erly, which is provided either by an external power source [2], an electret layer embedded in the variable capacitor of the device [3,4] or a triboelectric contact between the capacitor’s electrodes [5]. Although electrets are preferable to a battery, they can lose charge over the time and render the harvester useless. Triboelectric charge generation can be a solution to this problem, since successive contacts continuously ac- cumulates triboelecric charge on the surface of dielectric materials [5]. Such e-KEH are called Triboelectric-Electret Nano Generator (T-ENG) [6], and the initial bias comes from the charge transfer between the materials covering the electrodes of the harvester with different elec- tronegativity conditions. T-ENG is a promising technology to provide the power for small electronic tools, however there are still several challenges on the way to practical applications. Unlike non-contact electret-based e-KEHs, tribo- based e-KEHs do not carry a pre-imposed charge and the surface density of tribo-charges depends on many parameters like contact force, hu- midity, coefficient of friction, surface energy, surface roughness or electron affinity of the contacting surfaces [7–10]. Thus, the generated charges are not uniformly distributed on the surface and the charge density changes from one point to another point. Due to the nature of triboelectric contact and charge generation, the tribo-charge density hardly reaches the theoretical maximum as with corona-charged elec- tret [11]. As a result, e-KEH’s that rely only on triboelectricity usually produce less energy per cycle compared to other electret-based e-KEH’s. Therefore, the biggest challenge is to manage the relatively small quantity of charges produced by T-ENG in a way that increases the total https://doi.org/10.1016/j.nanoen.2018.06.034 Received 8 May 2018; Received in revised form 9 June 2018; Accepted 9 June 2018 ⁎ Corresponding author. E-mail addresses: yavand@iust.ac.ir (J.Y. Hasani), philippe.basset@esiee.fr (P. Basset). Nano Energy 51 (2018) 173–184 Available online 18 June 2018 2211-2855/ © 2018 Elsevier Ltd. All rights reserved. T