Research And Design Of Energy Harvesting System With Real-Time Maximum Power Point Tracking Function

With the rapid development of the Internet of Things technology,battery-based power supply systems are increasingly unable to meet the requirements of IoT smart nodes for low cost,small size,and low replacement frequency.The rapid development of micro-nano technology and system-on-chip technology makes energy harvesting and related application possible.This paper mainly focuses on the research and implementation of energy harvesting systems with the real-time maximum power point tracking function.An open-circuit voltage scheme and a simplified ripple correlation scheme that track the maximum power point on a cycle-by-cycle basis are built.The implementation of the former scheme is given in this paper.The traditional open-circuit voltage method usually performs an open-circuit voltage sampling every several hundred milliseconds or seconds.Therefore,the required sampling capacitor and the open-circuit voltage storage capacitor are usually large,and they cannot achieve rapid response to changing environments.Because the cycle-by-cycle open-circuit voltage method proposed in this paper will update the input port voltage value corresponding to the maximum power point every cycle,a smaller sampling capacitor and storage capacitor can be used,so that the energy source is only disconnected from the energy harvesting system for less time.The timing of sampling the open circuit voltage in each cycle is arranged at the time when the input port is just at the maximum power point,which improves the charging speed of the sampling capacitor.Futhermore,at this time,the inductor current is zero,so the impact of open circuit voltage sampling on the input capacitor voltage and the normal operation of the converter can be reduced.The design of the sub-module circuits avoids the use of high-power-consumption circuits such as amplifiers,current sampling circuits,and multipliers.Circuit design mainly focuses on the improvement of low-voltage and low-power consumption.Only when the function is enabled,the corresponding module is opened,so as to achieve the purpose of reducing system power consumption and improving system efficiency.The circuit implementation in this paper is based on the 180 nm BCD process.The overall simulation of the system verifies the power-on,stable input optical power state and input optical power transient process.The verification results show that the system is suitable for input light of 1 mW ~ 10 mW.The power range covers indoor to outdoor lighting conditions.The maximum power point tracking accuracy of the energy harvesting system peaks at 99.94%,and the overall efficiency peaks at 88.37%,and can quickly respond to changes in input optical power.