Design Of Efficient Indoor Light Energy And Thermal Energy Cooperative Harvesting Circuit

With the high-speed development of integrated circuit technology,sensorand communication technology,the wireless sensor network(WSN)has been gradually coming into people's sight,and they are widely used in military,industry,environmental monitoring system,consumer electronics,implantable medical devices and smart home.However,there are many defects that use traditional batteries to power WSN,such as large size,poor battery life and inconvenience of regular replacement.In recent years,powering WSN nodes by harvesting energy from the work environment has become the hot spot in current research.And with further research,the design of multi-source energy harvesting circuit has gradually become a new direction in current research.Among the environmental energy harvesting technologies,photoelectric energy harvesting technology and thermoelectric energy harvesting technology are favored for their advantages such as more environmentally friendly energy forms,simple structure,and low operating noise.There are various kinds of light energy and thermal energy in indoor environment.And by using photovoltaic(PV)cell and thermoelectric generator(TEG),the DC power can be obtained.However,the thermal energy is difficult to harvest due to the low open-circuit voltage and low light energy density resulting in inefficient indoor light energy harvesting.Therefore,for the indoor environment,the design of an efficient energy harvesting circuit to achieve the fusion harvesting of indoor light and thermal energy has become the main research direction of this thesis.This thesis aims at indoor light energy and thermal energy,and analyzes the photovoltaic system and the thermoelectric generator system,establishes equivalent models respectively.The maximum power point tracking techniques are compared and analyzed,which are suitable for the indoor light energy harvesting system,an efficient cooperative harvesting circuit is proposed.The main research contents of thisthesis are as follows:1.Aiming at the problem that the change of lighting conditions has a large impact on the efficiency of indoor light energy harvesting,a maximum power tracking circuit suitable for indoor environment is proposed.The circuit is composed of capacitors,MOS transistors and comparator,charge and discharge capacitors by switching on and off,sample the maximum power point voltage according to the charge redistribution principle of the capacitor s,and compare it to the current working voltage of the photovoltaic cell with a comparator to control the main circuit,as to achieve the purpose of tracking the maximum power point of photovoltaic cells.2.For indoor light and thermal energy,a dual-source energy cooperative harvesting circuit(DCHC)is proposed.By tracking the maximum power point of photovoltaic cells,the proposed DCHC enables extraction of power from both a photovoltaic(PV)cell under indoor faint light and two thermoelectric generators(TEG)in one inductor charge and discharge cycle,it increases the total harvested energy.At the same time,the introduction of thermal energy has a cooperative effect on the harvest of light energy.The results show that the highest efficiency of light energy harvest can reach to 86%.Besides,it can also harvest the weak thermal energy in the environment with the ignorance of the threshold voltage of the circui t components,the average conversion rate of thermal energy can reach 58%.