Maximum Energy Efficiency Tracking Circuits for Converter-Less Energy Harvesting Sensor Nodes

Abstract

Converter-less supply architecture is promising for energy harvesting sensor nodes, due to their high conversion efficiency, low cost, and easy integration. However, lack of a dc-dc converter precludes the electronic load operating under the voltage for optimal energy efficiency, since the output voltage of the energy harvester is set as the maximum power point tracking (MPPT) voltage. To mitigate efficiency loss of workload, we propose an architecture to achieve maximum energy efficiency tracking for the overall sensor node. A theoretical analysis is given for the architecture and an efficiency-driven frequency controller is fabricated to validate the design methodology. Measured results demonstrate that up to 162% performance gain of the overall sensor node is achieved compared with the existing systems with MPPT.