Achieving maximum power efficiency of a novel rectifier charge pump by impedance matching in an energy harvester suited for self-powered sensors

Abstract

A new rectifier (AC-DC) charge pump with impedance matching is proposed in this study for maximizing power transfer efficiency in an energy harvester circuitry equipping self-powered sensors. In addition to the rectifier charge pump, there are power management circuits, a low dropout regulator and a battery charger to complete the energy harvester circuitry module for self-power sensors. The proposed circuit is suitable for harvesting the low-frequency vibration energy in portable medical sensors or low-power high-frequency RFID sensors. In the harvester circuit, the rectifier charge pump operated in dual phase is proposed to preform efficient conversion of vibratory AC powers to DC by means of automatic switchings and capacitors. To optimize the charge pump circuit, a charging equivalent model is first derived, where all capacitances are optimized to derive maximum average energy stored in capacitors and then transferred to loadings. The design rules are distilled based on rigorous analysis, and the capacitances are optimized based on the relation between the energy stored in capacitances and inherent electronic properties of the harvester. The chips with optimized capacitances are fabricated by the TSMC 0.35um process for verification. It is shown theoretically and experimentally that implementation of the proposed optimized circuit is able to harvest more power than un-optimized.