Design Of Photoelectric Energy Harvesting Chip Based On Reconfigurable Photovoltaic Cells Network

With the rapid development of Internet of Things technology(IoT),some technologies necessary for the development of the IoT is gradually mastered.However,in the application of the IoT,the key factors limiting sensor performance and life cycle are energy supply and battery life.Because solar energy has the advantages of wide resources and easy access,the use of solar photovoltaic cells to achieve energy self-supply of sensor nodes to effectively extend the life cycle of sensor nodes is the focus of current research in the direction of the IoT.Among them,the design and research of power management chip based on photovoltaic cells for photoelectric energy harvesting has very important research and application value.The photoelectric energy harvesting chip based on reconfigurable photovoltaic cells network,a novel maximum power point tracking(MPPT)method is used to design the photovoltaic energy harvesting chip.According to the current-voltage and power-voltage characteristics of photovoltaic cells,the discrete photovoltaic cells are connected in series or in parallel to form different network connection modes.Thus,the working voltage of each discrete photovoltaic cell can be adjusted to work at the corresponding voltage of the maximum power point,and the efficiency of charging process can be dynamically optimized.Then the positive end of the photovoltaic cell connect directly to the super capacitor for charging.This chip eliminates the capacitors required for switched capacitor DC-DC converters or the inductors occupying a large area in the switched inductor circuit to achieve the goal of keeping maximum output power of photovoltaic cells charging super capacitors.Under the same power(1mW),the chip power loss and chip area characteristics are better.The photoelectric energy harvesting chip based on the reconfigurable photovoltaic cells network is mainly designed by analog circuit.Under the Silterra 0.18μm CMOS process,the circuit design,circuit simulation,layout design and post-simulation verification are completed based on the Cadence software platform.The chip has been taped out.The main research contents include establishing photovoltaic cell model and simulation under Cadence software,drawing its I-V and P-V curve,and exploring the relationship between maximum output power and light intensity and load size.Use the transmission gate to connect discrete 3×5,1×5,1×4,3×1,2×1 five units and 7 unit photovoltaic cells into 3×12,4×9,5×7,6×6 and 7×5 five network modes by series/parallel.Explore the maximum output power point of each combined network.Through the simulation data,the maximum power point range of different combined networks is obtained,the mode conversion threshold is determined,and the arbitration logic circuit for controlling the conduction and disconduction of the transmission gate is designed to realize the conversion between different combined networks.The circuit mainly includes hysteresis comparator module,arbitration logic module,photovoltaic cells connection module,current bias module,bandgap reference module,and operational amplifier module,start circuit and super capacitor anti-overcharge module.The photovoltaic cell operates at 50μA-100μA current and is controlled by MPPT to convert the connection network mode.It charges 1F-5V supercapacitor with the highest efficiency of 94% and the lowest efficiency of 80%.