Photovoltaic energy harvester for micro-scale applications

New micro-systems like ad-hoc wireless transceiver micro-sensors continue to integrate more and more functionalities in smaller packaging size. This size reduction has many benefits and opens new application areas but it deeply constrains the amount of power embedded and tends to require a smart power management unit. One issue to achieve longer life time is the use of renewable energy sources (solar, thermal, or kinetic). Number of challenges need to be overcome in order to convert efficiently the energy harvested. This paper proposes a novel photovoltaic DCDC converter circuit with two feedback loops. It harvests energy from various solar conditions (indoor and outdoor) by imposing the harvester to work close to its maximum power point. Furthermore when the solar harvester is activated, the load can directly be supplied by solar energy through a new regulated power path, otherwise the energy go through the accumulator. Simulations in the UMC 180nm technology process show that the circuit can harvest energy from indoor to outdoor conditions, with a power consumption below 10μW, equivalent to an efficiency rising up to 82%.