Optimal control applied to TEG harvesting: The necessity of a ring oscillator

Abstract

In this article, unlike the available literature, an optimal theorem is presented to design conditioning circuits for thermoelectric generator (TEG) energy harvesting without previous ad-hoc assumptions about the electric/electronic structure. The results show that simple linear time-invariant (LTI) conditioning circuits plus an extra non-linear element transforming the TEG's constant voltage into a square wave (ring oscillator) are in fact the optimal choice to pick up the biggest output's energy. This research opens the door to new developments: ring oscillators with ultra-low voltages (less than 1 mV) and nonlinear optimal control techniques applied to micro energy harvesting. Real measurement along with LT-Spice simulations is presented to validate the theoretical results, presenting transfer functions for simulation and modeling purposes.

Design of high precision ring ICO circuit with power supply voltage of 0.77V in 0.18µm CMOS process

“…Oscillator (OSC) is an important part of many electronic systems and is widely used in various electronic devices 1,2 . With the expansion of application scope and the development of integrated circuit, the demand for high-performance OSC circuit is higher and higher, which has also become an important research topic 3 .…”