Analysis and design of ultra low power thermoelectric energy harvesting systems

Thermal energy harvesting using micro-scale thermoelectric generators is a promising approach to alleviate the power supply challenge in ultra low power systems. In thermal energy harvesting systems, energy is extracted from the transducer using an interface circuitry, which plays a key role in the determining the energy extraction efficiency. This paper presents techniques for the systematic modeling, analysis, and design of interface circuitry used in micro-scale thermoelectric energy harvesting systems. We characterize the electrical behavior of a micro-scale thermoelectric transducer connected to a step-up charge pump based power converter and model the relationship between the transducer output voltage and the charge pump switching frequency. We model various power loss components inside the interface circuitry and present an analytical design methodology that estimates optimal parameter values for the interface circuitry. These parameter values lead to maximum net output power being delivered to the energy buffer. We have implemented various interface circuitries using IBM 65nm technology to verify our proposed models and methodology. Circuit simulation results show that the proposed methodology accurately estimates the maximum power point voltage of the system with an error of 3%.