Abstract
The purpose of the present paper is to analyze the input inductor design and to establish the relationship between the capacitance of the flying capacitor and the output voltage ripple in order to reduce the size and weight of the flying capacitor DC-DC boost converter (FCBC). The inductance of the input inductor is designed by considering the maximum input current ripple, and the experimental results are used to confirm that the input current ripple is within the designed value. Furthermore, according to the design specifications, the required inductance of an input inductor is approximately 25% of that of a conventional two-level DC-DC boost converter, and the required inductor core volume is approximately 35% of that of a conventional two-level DC-DC boost converter. Moreover, the capacitance of the flying capacitor and the output voltage ripple are confirmed to be independent of each other. Theoretically, this is because the time constant of the output capacitance and the output resistance of the FCBC is larger than the switching period of the switching frequency. This finding is confirmed by the simulation and experimental results of the present study. On the basis of this finding, the capacitance of the flying capacitor can be estimated and designed without considering the output voltage ripple. Moreover, the achieved maximum efficiency of the designed FCBC is 98.5% of the output power at 1kW.
