In comparison to the other energy harvesting sources mentioned previously, thermoelectric generators (TEGs)
seem to be suitable for wearable applications because the harvested power is only dependent on temperature conditions. Based on the Seebeck effect, the output voltage from TEGs is proportional to the temperature gradient between the hot and cold sides. For the wearable applications, the hot and cold sides can be the surface of the skin and ambient environment, respectively. It should be noted that the voltage level harvested from TEG devices is not high enough to power any digital circuitry. Therefore, a dc-dc converter is very essential to boost the low voltage level generated by TEGs up to a useful voltage level for powering CMOS operations. In this project, the harvesting circuit is optimized to make the conversion ratio between the harvested power and the delivered power as high as possible. Therefore, power efficiency can be improved significantly if the power losses in the energy harvesting
system are taken into account. To do so, switching signals need to be controlled properly to minimize
synchronization losses. Also, it is very essential to utilize pure and simple digital circuits in implementing the dc-dc boost controller. This project aims to investigate the impacts of switching powers and synchronization losses and propose a high efficient power dc-dc boost converter in which the switching signals for both the low-side and high-side switches are controlled accurately to extract maximum input power from TEGs and minimize synchronization losses.

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Khoa Pham

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Self-power technique is a vital key for stand-alone applications whereas battery replacement may be impossible. For wearable applications, extracting energy from the ambient temperature is one of the best solutions among the other energy harvesting methods such as solar, wireless waves, and temperature. In this paper, a high-efficient power dc-dc converter with maximum power point tracking (MPPT) and zero-current switching (ZCS) based on digital counters is proposed for thermoelectric energy harvesting. The proposed technique is able to adapt to a wide range of temperature differences. The integrated ZCS module plays an essential role in reducing the loss induced by inaccurately controlling the high-side switch. Besides, the maximum power extracted from the thermal energy source is monitored with the MPPT module. The power converter was simulated using CMOS 600nm Nuvoton technology. From the simulation results, it shows that when employing a thermoelectric generator with a temperature gradient of 3 Celsius degrees, the converter is capable of providing a maximum power of 112µW with a high-efficient of 66%.





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