Fully Integrated Autonomous Interface With Maximum Power Point Tracking for Energy Harvesting TEGs With High Power Capacity

In this article, a novel fully autonomous and integrated power management interface circuit is introduced for energy harvesting using thermoelectric generators (TEGs) to supply power to Internet of Thing nodes. The circuit consists of a self-starting dc-dc converter based on a dual-phase charge pump with LC-tank oscillator, a digital MPPT unit, and a 1-V LDO regulator. The novel maximum power point tracking (MPPT) algorithm avoids open-circuit state, and accommodates varying input power and ultra-low voltage conditions. Validation data from the fabricated test-chip in 180 nm standard CMOS technology indicates the circuit start-up voltage is as low as 170 mV. The maximum output power capacity is 0.5 mW, which is the highest noted in the literature for a fully integrated solution. The high output power at low cost is achieved with a peak system efficiency of 30%. The relatively low efficiency is expected, since the focus of the design is high power capacity at low cost. The MPPT algorithm reaches 98% maximum accuracy for a source output resistance of 40 Ω, which is typical for wearable TEG modules.