A 3.5 mV Input Single-Inductor Self-Starting Boost Converter with Loss-Aware MPPT for Efficient Autonomous Body-Heat Energy Harvesting.

A single-inductor self-starting boost converter is presented suitable for thermoelectric energy harvesting from human body heat. In order to extract maximum energy from a thermoelectric generator (TEG) at small temperature gradients, a loss-aware maximum power point tracking (MPPT) scheme was developed that enables the harvester to achieve high end-to-end efficiency at low input voltages. The boost converter is implemented in a 0.18 µm CMOS technology and is more than 75% efficient for a matched input voltage range of 15 mV-100 mV, with a peak efficiency of 82%. Enhanced power extraction enables the converter to sustain operation at an input voltage as low as 3.5 mV. In addition, the boost converter self-starts with a minimum TEG voltage of 50 mV leveraging a dual-path architecture without using additional off-chip components.

Integrated Cold-Start of a Boost Converter at 57mV using Cross-Coupled Complementary Charge Pumps and Ultra-Low-Voltage Ring Oscillator.

This paper demonstrates an on-chip electrical cold-start technique to achieve low-voltage and fast start up of a boost converter for autonomous thermal energy harvesting from human body heat. An improved charge transfer through high gate-boosted switches by means of cross-coupled complementary charge pumps enables voltage multiplication of the low input voltage during cold start. The start-up voltage multiplier operates with an on-chip clock generated by an ultra-low-voltage ring oscillator. The proposed cold-start scheme implemented in a general purpose 0.18µm CMOS process assists an inductive boost converter to start operation with a minimum input voltage of 57mV in 135 ms while consuming only 90 nJ of energy from the harvesting source, without using additional sources of energy or additional off-chip components.