Investigation on silicon carbide mosfet based positive output superlift luo converter

Abstract

In today s world, boosting a low input DC source to a high output DC with less ripples has become essential. Voltage lifting of the DC-DC converter depends upon the duty ratio and pump circuit in the topology. By increasing the energy storage elements in the pump circuit, the voltage gain of the converter is increased at a low duty ratio with increased filtering effect. This research focuses on one such DC-DC converter topology-- Positive Output Super-Lift Luo Converter (POSLLC), having high voltage gain and reduced inductor current and capacitor voltage ripple. But the efficiency of the converter and power density is limited due to the internal cascading arrangement of the energy storage element. The essential requirement is to improve the efficiency of the converter by reducing the losses associated with the passive and active components. Active component losses comprise the conduction and switching losses. Both the losses, depend on the device used in realizing a converter. In order to minimize the losses and improve the performance of the POSLLC a silicon carbide (SiC) MOSFET is used in this research work. The characterization of the SiC MOSFET and its equivalent silicon (Si) IGBT at elevated operating conditions are addressed in this thesis with parameter extraction and comparison. The superlift Luo converter is classified into an elementary, relift and triplelift circuit. This research focuses on the relift type superlift Luo converter with detailed explanation on the operation and design equations. The converter performance is studied with different switching combinations such as all-SiC, Si-SiC and all-Si, and the results are compared. It is identified that the Si-SiC combination shows improved performance. LTspice simulation software is used for simulating the converter. The experimental setup of the Si-SiC combination is carried out and simulation results are validated experimentally. Performance parameters such as efficiency, ripple in the input current and output voltage ripple are evaluated under different operating conditions and the results are compared with those of the Si IGBT converter. In this work, the parasitic effects of the passive and active components are taken into account and their influence on the voltage gain and output voltage of the converter is addressed. Energy related parameters such as pumping energy, stored energy and energy factor are computed for the SiC MOSFET based POSLLC and compared with those of the Si IGBT based POSLLC. newline