High Efficiency And High Stability DC-DC Polarity Reversal Buck-boost Converter For Energy Harvesting System

The output voltage of the thermoelectric battery(TEG)is proportional to the temperature difference between the two ends of the battery,which results in the voltage generated by the TEG in a wide range.To solve this problem,an array thermoelectric battery is used to limit the output voltage to a certain range.But this also brings a new problem,that is,the maximum power tracking(MPPT)circuit of the traditional single comparator structure cannot track the changing input impedance.This paper proposes a voltage resistance adaptive MPPT circuit through the analysis of the boost circuit loss.Tracking the changing input impedance and input voltage adaptive generation delay time to complete the maximum power tracking and improve the conversion efficiency.In order to ensure the uninterrupted operation of the equipment powered by the energy harvesting circuit,an electrical energy storage element(rechargeable lithium battery or super capacitor)can be added to the energy harvesting circuit.When the collected energy is greater than the load consumption,the storage element is used to store energy,and When the energy required by the load is greater than the energy collected,the electrical energy in the storage element is used.To this end,an energy harvesting control circuit and a DC-DC converter with reconfigurable working modes are proposed.Aiming at the problem of low conversion efficiency of traditional buck-boost circuits at low input power,a high-efficiency and high-stability DC-DC polarity-reversing buck-boost converter for energy harvesting systems is proposed.This circuit uses extremely high energy storage capacitors.The way of sex reversal stores the excess energy,and the inductor uses integral multiplexing to improve the conversion efficiency by reducing the switching loss.At the same time,in order to further improve the conversion efficiency,the adopted adaptive zero-crossing comparator can adaptively match the mismatch resistance according to the inductor current to reduce the transmission loss on the inductor.The designed voltage resistance adaptive MPPT circuit is designed with TSMC 0.18μm CMOS process,and the simulation results of Cadence software show that the input resistance is between 5Ω-2.7KΩ,the input power is between12μW-50m W,and the conversion efficiency is higher than 46%(R_S=5Ω,V_S=0.03V),its peak conversion efficiency is 95.52%(R_S=100Ω,V_S=1V).Compared with the traditional comparator-based MPPT circuit,the conversion efficiency can be increased by 23.23%(R_S=2.7KΩ,V_S=0.6V).The designed high-efficiency and high-stability DC-DC polarity reversal buck-boost converter for energy harvesting systems has higher conversion efficiency,and the output voltage ripple is less than 10m V.Mathematical analysis and simulation results show that the designed energy harvesting system can be well applied to the power management system of portable medical equipment.