DC-DC Buck Converter with Inrush Current Limiter
E. Manousaka
A. van Wijk – Mentor
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Abstract
The Green Village envisions a sustainable, energy autarkic environment realized at the heart of the TU Delft campus. This environment will implement a DC electricity infrastructure with the main voltage level inside the buildings, being 380V. This innovative power system requires the development of new power electronics that can be used to such a grid and contribute to its high performance and reliability. The first test container is meant for testing this electricity system and the relative equipment. This project proposes a buck conversion method with inrush current limiting circuit designed for connecting the test container’s energy consumers to the 380V DC main bus, in order to achieve optimum operation, in terms of near peak efficiency and safety. Within the framework of this study, the “Femtogrid” system, which is the electricity system used by the test container, is explained and simulated. Additionally, the operation of the buck (step-down) converter and the boost (step-up) converter, that are the main elements of “Femtogrid” system, are studied and their control methods are analyzed. Moreover, some common electronic devices are tested with DC and AC input voltage, revealing important information regarding their behavior in normal and standby mode. An even better performance of some devices when running on DC is observed. The experiments showed high inrush currents due to the charging of the input capacitors during turn-on. Therefore, an inrush current limiter (ICL) is necessary in order to protect the system components from damage. The buck converter topology proposed in this project is the LLC resonant buck converter topology, which holds features like very high efficiency, isolation and small number of components. The ICL consists of a MOSFET in combination with some passive elements that can drive the MOSFET in such a way that the inrush current of the circuit can be limited by controlling the gate charge characteristic of the MOSFET. A prototype was simulated, built and tested. The simulations showed that the ICL should be able to limit the inrush current at a very low level.