Vibration Energy Scavenging System With Maximum Power Tracking for Micropower Applications

In this work, we present a vibration-based energy scavenging system based on piezoelectric conversion for micropower applications. A novel maximum power point (MPP) tracking scheme is proposed to harvest the maximum power from the vibration system. A time-multiplexing mechanism is employed to perform energy harvesting and MPP tracking alternately. In the MPP tracking mode, a voltage reference that represents the optimal output voltage at the MPP is generated. A control unit then uses this reference to track the system operation around the MPP. The proposed system is capable of self-starting up without the help of an energy buffer. As a result, it is suitable for battery-less applications or when the energy buffer is completely drained. This tracking scheme has very small power overhead and is simple to implement in VLSI. Hence, it is especially applicable for micropower systems. The entire design was fabricated in a 0.35-μ m CMOS process. Experimental results verified the proposed MPP tracking scheme and demonstrated the system operation. Measurement results show that the power harvesting efficiency of the electrical circuitry is higher than 90%.