An Integrated System For Cooperative Harvester Of Light And Thermal Energy

With the development of 5G technology and Internet of things technology,the relationship between things and people is more and more close,which requires a large number of sensors to get information between objects and wireless sensor networks.The traditional battery supplies power to electronic devices such as sensors,which is limited by the volume and endurance time.The complexity and cost of replacing batteries seriously restrict the further development of wireless sensor networks.Environmental energy harvester provides an effective solution for the application of wireless sensor.But the single energy source harvester system is restricted by environmental conditions,and the output power of single energy source is limited.The multi energy harvester system has been widely concerned by researchers recently.The existing multi energy harvester technology is difficult to achieve the cooperative acquisition of multiple energy sources at the maximum power point(MPP),and the acquisition of each energy source does not interfere with each other.In this paper,an integrated system for cooperative harvester of light and thermal energy is studied.The purposed system is used to explore an efficient environment energy harvester system and realize the self-power supply of wireless sensor networks.In this paper,the simultaneous harvester technology of light energy and thermal energy is studied.Firstly,the photoelectric device and thermoelectric device,their corresponding equivalent circuits and output power characteristics are analyzed.Then according to the output power characteristic curve of the energy sources,the maximum power point tracking theory and the relationship between energy acquisition efficiency are studied.In order to realize the cooperative acquisition of light energy and heat energy,an energy acquisition interface circuit with single inductor,double input and maximum power point tracking function is proposed;in order to improve the influence of the comparator's offset and delay on the active diode,an improved offset calibration comparator is proposed;in order to realize the cold-start and self-power of the system,a three-stage cold start circuit is proposed.This paper proposed an integrated system for collaborative acquisition of light energy and thermal energy applied to wireless sensor nodes,and the simulation verification and layout implementation of the design are carried out.The proposed system includes BOOST power circuit,maximum power point tracking circuit and cold start-up circuit.The BOOST power stage uses the idle time of DCM mode to combine the working periods of two input energy sources,and only one inductance is needed to realize the simultaneous harvester of two input sources in one period;the sampling and hold circuit with different voltage division ratio and the open-circuit voltage algorithm are used to realize the maximum power point tracking of the two energy sources;the low-voltage starting circuit ensures that the system realizes the cold start and self-powered.The proposed circuit is designed in a SMIC 0.18?m standard CMOS technology and simulated under Cadence platform.The simulation results show that the design can achieve the optimal operation with light and thermal energy in a cycle.The open-circuit voltage range of light energy is 0.2V-1V,and the open-circuit voltage range of thermal energy is 0.1V-0.4V.Thermal energy path takes about 50% of the cycle,and photovoltaic energy path takes about 5% of the cycle.Among them,the peak tracking efficiency of light energy is 98.9%,the peak tracking efficiency of thermal energy is 99%,and the peak power conversion efficiency of the system is 89%.Low power design and intermittent operation are adopted in the circuit design.The static power consumption of the control circuit is 1.8?W.At the same time,the proposed circuit realizes the functions of cold start and self-power supply.