Research And Design Of Multi-Source Energy Harvesting System Based On Switched Capacitor Converter

In modern society,wireless sensors are widely used in various applications ranging from factories and homes to fitness trackers,implanted medical devices,and outdoor weather stations.It is impractical to power these devices using wired connections,and relying on battery power requires frequent battery replacements,resulting in high long-term costs.Therefore,the use of reliable and highly integrated energy harvesting systems to power these sensor nodes has become a viable solution,leading to extensive research on energy harvesting systems.However,the current energy harvesting systems mostly suffer from issues such as a single energy source,short effective energy harvesting time,limited applicability,the need for battery backup power,and lack of internal integrated voltage regulation.This thesis presents a multi-input energy harvesting system based on a switched capacitor converter,which replaces the commonly used inductor-based DC-DC boost module in traditional energy harvesting systems.This substitution allows for higher integration and broader applicability of the energy harvesting system.The proposed system utilizes a self-starting circuit based on gate-cross-coupled charge pumps,which can select the input source with the highest voltage among four input sources for self-starting.To ensure proper circuit operation,the minimum self-starting voltage is set to be no less than300 m V.When the self-starting circuit boosts the input voltage to 1.5 V,the voltage detection module enables maximum power point tracking(MPPT),combiner,switched capacitor converter,and digital low-dropout regulator(DLDO)modules,initiating the overall operation of the energy harvesting system.The system employs an open-circuit voltage method to perform maximum power point tracking for each of the four input sources independently.Based on the maximum power point tracking,PWM pulse signals are generated to control the combiner,integrating the four input sources to increase the input power of the energy harvesting system.To address the issue of fixed boosting ratios in switched capacitor converters,the system incorporates a self-adaptive boosting ratio adjustment mechanism,which selects an appropriate boosting ratio based on the input voltage,thereby reducing unnecessary energy losses.Furthermore,to further reduce output voltage ripple and achieve stable voltage regulation with a smaller voltage difference,a three-loop structure DLDO circuit is designed to stabilize the output voltage,with a maximum conversion efficiency of up to 94.1%.The energy harvesting system presented in this paper is implemented using 180 nm CMOS technology.The final simulation verification confirms that the system supports normal startup under multiple-source or single-source input,with an input voltage range of0.45 V to 2.0 V.After passing through the DLDO,the system can stabilize the output voltage at 1.6 V.The overall conversion efficiency of the system can reach a maximum of76.2%,and the system layout occupies an area of 0.686 mm * 0.456 mm.