This paper presents a step-up DC-DC converter that uses a stepwise gate-drive technique to reduce the power FET gate-drive energy by 82%, allowing positive efficiency down to an input voltage of ±0.5 mV—the lowest input voltage ever achieved for a DC-DC converter as far as we know. Below ±0.5 mV the converter automatically hibernates, reducing quiescent power consumption to just 255 pW. The converter has an efficiency of 63% at ±1 mV and 84% at ±6 mV. The input impedance is programmable from 1 Ω to 600 Ω to achieve maximum power extraction. A novel delay line circuit controls the stepwise gatedrive timing, programmable input impedance, and hibernation behavior. Bipolar input voltage is supported by using a flyback converter topology with two secondary windings. A generated power good signal enables the load when the output voltage has charged above 2.7 V and disables when the output voltage has discharged below 2.5 V. The DC-DC converter was used in a thermoelectric energy harvesting system that effectively harvests energy from small indoor temperature fluctuations of less than 1°C. Also, an analytical model with unprecedented accuracy of the stepwise gate-drive energy is presented.
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Thermoelectric Effect of Ca2Fe2O5 at Low Temperatures
This study investigates the thermoelectric properties of Ca2Fe2O5 over a temperature range of 7˚C to 50˚C. The experiment measured the voltage generated by temperature differences across two sides of the material, with a focus on the voltage response at temperatures both below and above room temperature. Results indicate that at lower temperatures (7˚C to 15˚C), the voltage generated by the temperature difference was higher, though not directly proportional to the magnitude of the temperature gradient. The highest voltage recorded for the smallest temperature difference in this range was 109 mV, observed between 14.6˚C and 17.6˚C (smallest temperature difference, 3˚C). Similarly, at temperatures above room temperature, the voltage generated was relatively lower, peaking at 125 mV between 9˚C and 44˚C (higher temperature difference). These results suggest complex behavior of Ca2Fe2O5’s thermoelectric response, with non-linear relationships between voltage and temperature differences at both low and high temperatures.
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- PAR ID:
- 10649598
- Publisher / Repository:
- Scientific Research Publishing
- Date Published:
- Journal Name:
- Journal of Materials Science and Chemical Engineering
- Volume:
- 13
- Issue:
- 06
- ISSN:
- 2327-6045
- Page Range / eLocation ID:
- 1 to 9
- Subject(s) / Keyword(s):
- XRD, Solid-State Reaction, Perovskite Oxides, Oxygen Deficiency, Thermoelectric
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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