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Title:	Architecture of an optimal power management circuit with sub-threshold start-up for thermoelectric energy harvesting
Authors:	Michelle Lim Sern Mi (P69658)
Supervisor:	Md. Shabiul, Prof. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Power management circuit Thermoelectric energy harvesting
Issue Date:	18-Jan-2022
Description:	Emerging low voltage (< 3 V) and low power (..100 ..W) wearable/ wireless sensor nodes in internet-of-things (IoT) applications motivates ambient energy sources as battery replacements. Among others, the thermoelectric generators (TEGs) are promising to convert temperature gradient (1-10 K) from body heat to useful voltage levels. However, the immediate challenge is its characteristically low output voltage (50-300 mV) in portable sized TEGs. These voltages cannot overcome typical CMOS threshold beyond 500 mV. Although new solutions have improved efficiencies, most reported works emphasizes on maximum power point (MPP) extraction rather than the effective power transfer. Also, literatures rarely provide overall evaluation involving different goals. Hence, the aim here is to modularly design an energy-autonomous power management circuit (PMC) capable of optimal power delivery between TEG source and sensor load at low voltage (LV) levels evaluated with an overall comparison metrics. First, LV start-up is achieved with a dynamic CMOS structure to reduce sub-threshold leakages during off-state and increase conduction during on-state. Therefore, this PMC employs optimum power point (OPP) instead of MPP extraction on the TEG and a sub-threshold cold-start below 300 mV to seamlessly manage the PMC for efficient source to load energy transfer. Based on post-layout verification of the TSMC 180 nm model, the PMC generates above 100 𝜇W of power with a regulated output of 2.5 V within 40 ms from 285 mV cold-start. The significant contribution here is the dynamic cold-start and the constant time OPP extraction technique at 125.33 𝜇s. Also, the PMC is almost fully on-chip with layout area of 3.8 mm by 3.25 mm for RTEG between 0.29 to 4.17 Ω. OPP can be achieved by matching these RTEG values to the corresponding off-chip inductor, L. Using an overall figure-of-merit (FOM) to evaluate different design goals results in PMC's dynamic cold-start charge pump achieving 1.64 to 15.59 times better FOM compared to conventional structures while the overall OPP-based PMC has at least 2.91 times superior FOM compared to prior arts with MPP-based schemes. This overall improvement in speed, power and pumping efficiency facilitates battery-less solutions in TEG based wearable sensor applications.,Ph.D.
Pages:	198
Publisher:	UKM, Bangi
Appears in Collections:	Institute of Microengineering and Nanoelectronics / Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN)

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