Design Of A Self-startup Ultra-low Voltage Solar Energy Harvester With MPPT

With the rapid development of integrated circuit technology,the miniaturization,low power consumption,and high stability of integrated circuits have promoted the wide application of Io T devices.At the same time,it is the low power consumption,small size,and low maintenance cost of smart devices of the Io T that puts forward new requirements for lowvoltage and low-power integrated circuits,such as power management modules especially.The battery-powered method needs to be replaced or recharged to maintain long-term use and requires a long-term power supply to support.But an energy harvesting circuit can harvest environmental energy,being a potential solution for power supply of Io T.This thesis focuses on the realization of an energy harvesting IC chip,aiming at indoor photovoltaic energy harvesting.This chip can operate under ultra-low voltage conditions of only a few hundred millivolts.Key modules of this IC include an ultra-low voltage start-up circuit,an ultra-low voltage clock drive circuit,a boost converter circuit,and maximum power point tracking(MPPT)circuit.Because of much weaker indoor lighting conditions,and the small size of Io T devices,photovoltaic cells can provide is only about 100-300 mV voltage,which is lower than the threshold voltage of the MOS transistors.Such ultra-low voltage requires a start-up circuit to boost the voltage to meet the requirements of normal circuit operation.In this thesis,a low-voltage start-up circuit is realized by a low-voltage clock generating circuit,a low-voltage clock driving circuit and a cross-coupled charge pump,and a voltage of 500 mV is obtained.And 500 mV voltage supply provides power for generating the boost converter control clock,frequency divider circuit,and maximum power point tracking circuit,and forms a low-voltage negative feedback loop to achieve maximum power point tracking(MPPT).Simulated in 130 nm process with Cadence Virtuoso,operating at 150 mV ultra-low voltage,the proposed circuit focuses on the realization of ring oscillator under ultra-low voltage conditions,ultra-low voltage inverter drive circuit,ultra-low voltage start-up boost circuit and boosted clock generation circuit.Due to the limitation of ultra-low voltage,MOS transistors generally work in the sub-threshold area.Under the condition of lower than threshold voltage300 mV,a 150 mV clock is generated and then boosted to 230 mV.A start-up charge pump increases the 150 mV voltage of energy source to 500 mV in 25 ms.After startup,the main circuit is powered by 500 mV voltage supply,to further boost the source voltage for the normal operation under extremely low voltage conditions with energy source voltage locked at the maximum power point of 150 mV.