Piezoelectric Micro-power Generation to Charge Supercapacitor with Optimized Duty Cycle

Energy harvesting has been proved to be a novel solution to replace the batteries in remote power supply applications. Unfortunately, the limited capacity and low efficiency of output power constraint the practical applications of energy harvesting in daily life. After a systematic review of previous researches about energy harvesting in power management perspective, a circuit design, which focuses on low-frequency mechanical vibration, is introduced. With classical piezoelectric cantilever configuration, the maximum charging current of a supercapacitor can be obtained by optimizing the duty cycle of a buck regulator through software implemented pulse width modulation. The results of experiments prove the capacitive electric model of the piezo, the existence of maximum charging current of the supercapacitor, and the adaptive control of the designed circuits. With the duty cycle optimized to 2.17%, the maximum charging current of 17.36mA is measured, which is approximately four times fold of previous researches in similar vibration conditions. An active RFID application is proposed to utilize the harvested power of 67.2 mW.