Key Technology Research And Design Of Power Management Circuit For Low-Voltage Piezoelectric Energy Harvesting

With the development of 5G and artificial intelligence technologies,the application area and scale of wireless sensor networks in the Internet of Things are rapidly expanding.However,the single-battery-powered scheme of intelligent node has problems such as limited battery life,periodic replacement and potential environmental pollution,which restricts its deployment in certain scenarios.Based on self-powered approach,the energy harvesting system collects energy from the environment and convert it into electrical energy,providing better endurance for powering wireless sensor networks.In this thesis,a power management circuit is designed to convert and regulate the electrical energy generated by single or continuous vibrations of piezoelectric materials as energy conversion devices.Considering the low AC voltage amplitude under weak vibration,the power management circuit includes a rectifier circuit and a Boost converter,which perform AC-DC conversion on the piezoelectric output signal and DC-DC conversion on the rectified signal,respectively.A rectification architecture that operates at lower AC voltage amplitude and with low losses is proposed.The passive rectifier circuit is used to assist the fast establishment of the input voltage at low AC voltage amplitudes,and the active rectifier circuit is used to reduce conduction loss subsequently.The Boost converter utilizes a cold start-up circuit when the input and output voltages are not high enough.The designed cold start-up circuit limits the peak current of the inductor during the switching process and generates a higher voltage power rail to drive the asynchronous Boost to complete energy transfer.Furthermore,a maximum power point tracking circuit is proposed to improve the input power of the Boost converter.Based on the impedance matching strategy,the maximum power point tracking circuit can adaptively adjust the peak current of the inductor and the switching frequency when the vibration frequency and output voltage are fixed,and the reconfiguration of tracking parameters can be performed off-chip for changes in input source characteristics and output voltage.A hysteresis architecture for the Boost converter is proposed to balance maximum power point tracking and output voltage regulation.The partial modules and switching actions can be disabled under light loads to reduce static power consumption of the circuits,and load control is achieved through mode switching under heavy loads.The pre-regulator and bandgap REFerence circuit form a coupled architecture at steady state,ensuring the low-noise characteristics of the REFerence voltage.The circuit design and layout of this thesis are based on 0.25 μm BCD process,and the submodules and overall circuit were simulated.The simulation results demonstrate that the minimum AC voltage amplitude input to the rectifier is 320 m V,and the cold start-up threshold is 650 m V.When the output voltage is 4.2V,the peak conversion efficiency of the Boost converter can reach 96%.Based on the maximum power point tracking circuit,the closeness to maximum power can achieve over 98.1%.The power management circuit designed in this thesis can meet the load requirements of microjoule magnitude.