Energy harvesting has been proved to be an innovative solution to replace the batteries in remote power supply applications. Unfortunately, the limited capacity aucl low efficiency of power conversion restrict the practical applications of energy harvesting in daily-life. After a systematic review of research on energy harvesting iu power management perspective, a circuit design, which targets low-frequency mechanical vibrations, is presented. With the classical piezoelectric cantilever setup, the maximum charging current of a supercapacitor can be obtained by optimizing the duty-cycle of a buck converter through software implemented pulse width modulation. The results of experiments prove the capacitive electric model of the piezoelectric element, 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%, a maximum charging current of 17.36 mA is measured, which is approximately 4 times that obtained in related researches. An active radio frequency identification (RFID) application is proposed to utilize the harvested power of 67.2 µW. In addition, the digital design in field programmable gate array (FPGA) is integrated using AMIS 0.5 µrn CMOS process technology to reduce system power dissipation.