Research And Design Of AC-DC Booster Usedin Energy Harvesting

With the development of sensing technology,sensing system is becoming very important in monitoring different physical parameters like temperature,humidity,or mechanical stress.Energy autonomous operation is required if the system is difficult to access.Self-powered devices harvest the ambient energies by micro generators and can perform their operations without any continuous external power supply.The inertial micro generators,which harvest mechanical energy from the ambient vibrations,are currently the focus of many research groups.The electromagnetic micro generators have the highest energy density.However,the output power and voltage of the electromagnetic micro generator which harvest vibration energy from the surrounding environment is very small,which can not be directly applied.An ultra low input voltage,low power consumption and high efficiency AC-DC boost converter circuit is designed.The converter consists of two parts,the front part is an active rectifier based on the substrate drive comparator structure,and the back part is a DC-DC boost circuit.The active rectifier consists of two stages,a first passive stage and only one active diode as second stage.A bulk-input comparator working in the subthreshold region is used to drive the switch of the active diode.The voltage drop over the rectifier is some tens of millivolt,which results in voltage and power efficiencies of over 90%,the minimum operating voltage is 300 mV.DC-DC boost circuit using the boost converter,working in the discontinuous conduction mode,the use of pulse frequency modulation.In order to improve the energy conversion efficiency of the boost converter,we monitor the voltage switch node,feedback to the frequency controller,adjusting the switch time,the inductor current is zero,the switch can be disconnected,so as to improve the energy conversion efficiency of boost converter.The implementation of the design of 0.18 um based on standard CMOS process,using Spectre simulation.The results show that when the input voltage equals 0.5V@100Hz with a load resistance of 50 K ?.The boost converter power efficiencies of 73.8%,and the output voltage ripple is only 26 mV.