In what way is a DC/DC converter for energy harvesters different from other converters?

DC/DC Switching RegulatorsHow to use

Energy harvesting (environmental power generation) sometimes deals with considerably small current, and ICs which extract the power are required to be as low power consuming as possible and to operate efficiently at light load.
Other differences are, for instance, that DC/DC converters for photovoltaic harvesters like solar batteries have a function to extract the maximum power from the harvester by biasing the maximum power point.

If a harvesting system is designed for outdoor harvesters, most DC/DC converters adopt a method called Maximum Power Point Tracking (MPPT) which tracks the maximum power point of the harvester. On the other hand, the maximum power point of harvesters for indoor use tends hardly to change even though illuminance varies. So, there are also DC/DC converters which have one bias point optimised for the harvester and conduct operation at the point.

The R18xx series, our DC/DC converter series for energy harvesters, adopts the MPPC method. The graph below describes the maximum power point control method adopted to the R18xx series.