Resistor emulation approach to low-power energy harvesting

This paper presents an approach and associated circuitry for harvesting near maximum output from low power sources in the 100 mu W range for miniature wireless devices. A set of converter topologies and control approaches are presented together with detailed efficiency analysis and a design example for a buck-boost based energy harvesting converter using commercially available discrete circuitry. Experimental results are presented for harvesting energy from miniature RF and wind power sources operating over a 10:1 input power range from 500 mu W to 50 mu W. A closed-system efficiency of 65% at 50 gW output power is achieved, including all control and converter losses. The results demonstrate that useful energy, sufficient to power typical wireless sensors, can be harvested from miniature sources that output less than 100 law at a few hundred mV.