An Ultra-Low Power Fully Integrated Energy Harvester Based on Self-Oscillating Switched-Capacitor V oltage Doubler Wanyeong Jung, Student Member , IEEE , Sechang Oh , Student Member , IEEE , Suyoung Bang, Student Member , IEEE , Y

Abstract

This paper presents a fully integrated energy harvester that maintains 35% end-to-end ef ficiency when harvesting from a 0.84 mm solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V. Newly proposed self-oscillating switched-capacitor (SC) DC-DC voltage doublers are cascaded to form a complete harvester, with configurable overall conversion ratio from 9× to 23×. In each voltage doubler, the oscillator is completely internalized within the SC network, eliminating clock generation and level shifting power overheads. A single doubler has 70% measured efficiency a c r o s s1n At o0 . 3 5m Ao u t p u tc u r r e n t(10 range) with low idle power consumption of 170 pW. In the harvester, each doubler has independent frequency modulation to maintain its optimum conversion ef ficiency, enabling optimization of harvester overall conversion ef ficiency. A leakage-based delay element provides energy-efficient frequency control over a wide range, enabling low idle power consumption and a wide load range with optimum conversion ef ficiency. The harvester delivers 5 nW–5 µW output power with 40% ef ficiency and has an idle power consumption 3 nW, in test chip fabricated in 0.18 µm CMOS technology.