  Triboelectric nanogenerator (TENG), a class of mechanical to electrical
energy transducers, has emerged as a promising solution to self-power Internet
of Things (IoT) sensors, wearable electronics, etc. The use of synchronous
switched energy extraction circuits (EECs) as an interface between TENG and
battery load can deliver multi-fold energy gain over simple minded Full Wave
Rectification (FWR). This paper presents a detailed analysis of Parallel and
Series Synchronous Switched Harvesting on Inductor (P-SSHI and S-SSHI) EECs to
derive the energy delivered to the battery load and compare it with the
standard FWR (a 3rd circuit) in a common analytical framework, under both
realistic conditions, and also ideal conditions. Further, the optimal value of
battery load to maximize output and upper bound beyond which charging is not
feasible are derived for all the three considered circuits. These closed-form
results derived with general TENG electrical parameters and first-order circuit
non-idealities shed light on the physics of the modeling and guide the choice
and design of EECs for any given TENG. The derived analytical results are
verified against PSpice based simulation results as well as the experimentally
measured values.
