Abstract
Owing to the advantages of integration and being magnet-free and light-weight, the switched-capacitor-convertor plays an increasing role compared to traditional transformer in some specific power supply systems. However, the high output impedance and switching loss largely reduces its power efficiency, due to imperfect topology and transistors. Herein, we propose a fractal-design based switched-capacitor-convertors with characteristics including high conversion efficiency, minimum output impedance, and electrostatic voltage applicability. As a double-function output power management system for triboelectric nanogenerators, it delivers over 67 times charge boosting and 954 W m−2 power density in pulse mode, and achieves over 94% total energy transfer efficiency in constant mode. The establishment of the fractal-design switched-capacitor-convertors provides significant guidance for the development of power management toward multi-functional output for numerous applications. The successful demonstration in triboelectric nanogenerators also declares its great potential in electric vehicles, DC micro-grids etc.
Highlights
Owing to the advantages of integration and being magnet-free and light-weight, the switched-capacitor-convertor plays an increasing role compared to traditional transformer in some specific power supply systems
Over 94% total energy transfer efficiency is realized with output power of 37.09 mW m−2, and mobile electric devices like digital vernier caliper and temperature hygrometer can be driven continuously by the triboelectric nanogenerator (TENG) with fractal design based switched-capacitor-convertors (FSCC) power management system as well
We introduce the name rules of FSCC to understand it better
Summary
The basic series-parallel SCCs can form a FSCC by fractal design, which can achieve better step-down/up by more effectively switching the connection mode of capacitors. We chose a 4 = 2 × 2 (2nd order 4-unit) FSCC that consists of nine diodes and four identical charge storage capacitors to illustrate its step-down mechanism. Compared with basic SCC (1st order FSCC), the capacitors in multi-order FSCC can have minimum total output voltage drop Vd,t (charge flowing through the least diodes) due to the 2D diodes network based on fractal design during the discharging process.
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