Design And Research Of Ultra Low Power Boost Converter For Energy Harvesting Systems

The new energy scavenging devices like solar cell has a bright prospect in the wireless sensor network and other emerging areas. Since these energy transducers have relatively low output voltage and limited output power, an ultra-low start-up voltage low-power switch-inductor power supply module for energy harvesting system is designed in this thesis, which can provide a stable supply voltage and preserve high energy transfer efficiency at the same time.After discussing and analyzing the output characteristic of photovoltaic cell or thermoelectric generator and the load characteristic of the wireless sensor network, this thesis provides a model to select an optimal specification for the dc-dc converter. Moreover, some methods to reduce the power dissipation of the switch-inductor power supplier are also proposed in this thesis.In order to kick up the whole system when its output capacitor is deeply discharged, a charge-pump based startup circuit without any external auxiliary devices is proposed in this paper. Furthermore, burst-mode constant-on-time control method is adopted in this system to reduce the operation period so as to improve the power efficiency. Meanwhile, this paper proposed a temperature insensitive and process independent low power consumption output voltage detector which consumes only800nW, costs50um*75um chip area and reduces the detected error within±3%. In order to further improve the power efficiency, a constant on time based maximum power point tracking (MPPT) technique for energy harvesting system is proposed.The whole system is fabricated in SMIC0.18um CMOS process. The simulation results show that the whole system can start up by itself when its input voltage is above300mV and provide a stable1.8V output voltage, and the power efficiency can reach84%(or65%) at the load of180uW (or9uW), which achieved the expectative design objectives.