Fast Energy-Harvesting TEG-Supplied Charging Regulator Microsystem

Abstract

This paper presents a fast hysteretic switched-inductor charging regulator (SLCR) microsystem. It is powered by on-chip thermoelectric generators (TEGs) to supply Internet-of-Things (IoT) wireless microsensors. On-chip TEGs are appealing because they are 12–1400× smaller than off-chip ones. IoT sensors mostly idle in low-power mode and transmit data wirelessly only in high-power mode on demand. This requires CMOS SLCRs to respond quickly to abrupt load dumps caused by IoT sensors. State-of-the-art (SoA) SLCRs respond to load dumps in 100 μs–2.5 ms. This time duration amounts to a significant portion of the IoT sensor's data transmission time (500 μs–7 ms). This slow response time jeopardizes the quality of data transmission. This paper presents a fast hysteretic control that responds in 9.6 μs. This control adopts nested hysteretic architecture and requires only three comparators and simple combinational logics, which is appealing, considering the low power budget limited by on-chip TEGs. Moreover, this paper contributes detailed stability analysis, derives response time and accuracy and provides intuitive and accurate system design equations. Measured results of a 180-nm CMOS prototype validate that the proposed system shortens response time by 10–260× compared to the SoA.