A Reconfigurable Dual-Output Energy Harvesting System with MPPT and Storage Capability

In this paper, a fully-integrated reconfigurable dual-output energy harvesting system is introduced. The proposed energy harvesting system provides two outputs V
_out
and V
_SC
. The first output (V
_out
) is regulated at 1.6 V and delivers the load power in the primary mode. It is generated by the primary path of the system that is implemented using a 5-stage reconfigurable boosting charge pump. In case of having more available power than the load demand, the other output (V
_SC
) is used to charge a supercapacitor up to 3.2 V through a secondary path. The secondary path ensures both V
_out
regulation and maximum power point tracking of the input source to optimize end-to-end efficiency of the system. The optimization algorithm used to reconfigure the system in response to the expected variations of the input available power and the load power is also presented. The proposed system is implemented in a 0.18 μm CMOS technology and uses a total on-chip flying capacitance of 2.22 nF. It achieves a maximum end-to-end efficiency of 77.3% at a total output power of 773 μW and input available power of 1 mW.