With the ever-growing energy demands, the focus towards efficient energy conversion systems has been increasing. Whether it is for wireless sensor nodes, hand-held battery-operated portable devices, consumer electronics, the lighting industry or high performance computing and mission critical applications, high efficiency and small form factor power converters are required by all conceivable electronics around us. High efficiency translates to lower cost, better reliability and increased lifetime.
Low power electronics has enabled us to design wireless sensors and low power implantable electronics that work off minuscule amounts of energy harvested from the ambient energy (light, heat differentials, vibrations, RF, etc.) (Annala et al., 2002; Finkenzeller, 2003; and Chao et al., 2007). These systems can be used in applications that require sensing (or actuation) along with communication with a central base station that may not be energy constrained. For these devices, the cost of replacing the battery may be too high, thus making energy harvesting a viable solution. The main challenge in such converters is maintaining high efficiencies even for low power levels since the harvested power is in the nW to 100ís of pW range. In the portable devices regime, recent advances in battery technology have led to higher battery capacities. However, with the mobile revolution, higher integration and increasing functionalities have made it necessary for designers to adopt low power design techniques like dynamic voltage-frequency scaling, parallelism, clock and power gating. It must be noted that the efficacy of dynamic voltage scaling relies heavily on the DC-DC converters that have to provide power to the load circuits with a fast loop response. Further, the DC-DC converters powered by batteries for portable applications need to handle a wide load range efficiently, thereby making the power management circuit and control design extremely critical. To achieve this, it requires good application knowledge and well-designed energy harvester to enable an optimal balance between power and resolution.