Research And Design Of Solar Energy Harvester With MPPT

In the area of IoT applications and portable devices,energy harvesting systems(EH)are key to improve the time of endurance.Specifically,solar collection systems are widely used because of the its universality.In order to increase the efficiency of the solar energy collection system,a system which automatically adjusts the equvalent input resistance of EH to make it equal to the internal output resistance of solar energy source is need.This system is called maximum power point tracking system(MPPT system).The common method is to use a microcontroller and on-chip current sampling circuit to achieve this function,but this method is not suitable for micro-power IoT applications and portable devices,such as field detectors,termite detection points,solar watches,and so on.A fully integrated MPPT system can solve this problem,and the power consumption of the entire system is limited to the microwatt level.Fully integrated MPPT systems are generally divided into BOOST systems and charge pump systems,but BOOST systems cannot be implemented in small spaces due to the need for off-chip inductors.On the other hand,the fully integrated charge pump MPPT system is often faced with a tracking range problem because of the small range of parameters that can be adjusted in a fully integrated system.In order to solve this problem,a proposed 3-D MPPT method based on the hillclimbing algorithm,which adjusts charge pump gain,inter-stage capacitance and working frequency is designed to expand the tracking range of MPPT system.In order to ensure the normal operation of the load circuit,two loops are designed in this system-MPPT system loop and output voltage regulation loop.In this way,while the solar energy collection system realizes the MPPT function,the output voltage is regulated to be about 3.3V,which can be directly supplied to the load circuit.Because the micropower system of IoT applications often has the characteristics of large instantaneous power consumption and low average power consumption,a storage capacitor is added to the system design to ensure the stability of the output voltage under transient large load conditions.At the same time,in order to reduce the power consumption of the solar energy collection system and improve the overall energy collection efficiency,no power-hungry operational amplifier is used in the overall system.A low power reference,a low power oscillator and a low power compactor is designed to support the system.Spectre is used to support designing the whole system and key sub-modules based on smic 0.18?m BCD process,and the system has been verified by cold start power-on,MPPT tracking and load transient step.The simulation results show that the proposed solar energy harvester with MPPT function can achieve maximum power point tracking in a wide illumination range,and the output voltage is held at about 3.3 V as a standard CMOS operation voltage.