Inductive
transformer for TENG. (a)-(i) Schematic illustrations
of the radial-arrayed rotary TENG. (a)-(ii) Circuit diagram of the
complete power-supplying system that consists of a triboelectric generator
and a power management circuit. (a)-(iii) Output voltage of the system
reaches a constant value of 5 V in less than 0.5 s as the triboelectric
generator starts to rotate at 3,000 r/min. Reprinted with permission
from ref (555). Copyright
2014 Springer Nature. (b)-(i) The equivalent circuit of battery charging
by the TENG with the aid of a transformer and a rectifier. (b)-(ii)
Rectified currents of the TENG at the same rotating speed (250 rpm)
but with different transformers (n = 1, 6, 12, 24,
and 36). (b)-(iii) The effect of the transformer coil ratio on matched
impedances of the TENG, and the power utilization efficiency of the
TENG at 250 rpm when charging an LFP–LTO full cell. Reprinted
with permission under a Creative Commons CC BY license from ref (558), Copyright 2015, John
Wiley and Sons.