Design Of Thermoelectric Energy Harvesting Circuit Based On Human Body Temperature

Wearable devices are usually powered by batteries and are very sensitive to power consumption.While reducing device power consumption,obtaining energy from the environment to supplement battery consumption has become an effective means to prolong working time.Human thermal energy has high energy density and stability.However,a very low voltage generated by the Thermoelectric Generator is resulted by a small temperature difference with the environment and human.How to realize the self-starting of the thermoelectric energy harvesting circuit at a small input voltage and maintain a high energy conversion efficiency after the startup is completed are two major problems.In view of these problems,a thermoelectric energy harvester based on human body temperature is designed by adopting the on-chip integrated cold-start method and the strategy of modeling the overall circuit power consumption according to the application scenario.The whole thermoelectric energy harvesting circuit is divided into two parts:cold start circuit and Boost DC-DC(Direct Current-Direct Current)boost converter.The cold-start circuit is integrated on-chip,reducing the number of off-chip components.The load of the cold-start circuit is reduced to a switch gate capacitor of the DC-DC boost converter,and the cold-start voltage of the circuit is reduced and the cold-start time of the circuit is shortened by one-time start-up.Focusing on the goal of high energy conversion efficiency,a method to model the power consumption of the overall circuit is proposed,and the relevant parameters corresponding to the maximum end-to-end efficiency of the circuit is determined.Then,the reference current source,Voltage controlled oscillator,power-on reset module,maximum power point tracking module and zero current switching module were designed respectively,which improved the energy of the overall circuit.conversion efficiency.The thermoelectric energy harvester is designed based on the TSMC 40nm process,with a layout area of 0.29mm~2.The simulation results show that the thermoelectric energy harvester can achieve cold start at a minimum input voltage of 60m V.After the circuit is started,the output voltage is 800m V,and the input voltage can be further reduced to 7m V.Under the condition of 30m V input voltage and 12μA load current,the maximum end-to-end conversion efficiency of 82.35%is reached by the circuit.