Design Methodology and Analysis of Five-Level LLC Resonant Converter for Battery Chargers

This paper presents proposal of a five-level LLC resonant DC–DC converter design procedure for battery chargers. The five-level inverter side of the proposed converter is connected to a transform-less LLC resonant tank to ensure operating at high frequency and achieve soft switching. The proposed converter has less weight, size, and cost. It is also much simpler in terms of implementation, and has smooth energy conversion to the load. The proposed converter is designed to work within the range close to the resonant frequency, to ensure higher power density and efficiency. Thus, the range of operating frequency is set to be (91 kHz < fsw < 110 kHz), while the LLC parameters is designed to achieve resonant frequency fr = 100 kHz. Therefore, it is designed to achieve zero voltage switching (ZVS) for all switches, which enhances the efficiency as well. The theoretical analysis outcomes were confirmed by simulation studies conducted using MATLAB/SIMULINK. An experimental model was also developed and validated with 100 VDC input voltage, which delivered output power of 100 W, 48 V, with efficiency around 96.9%. Selected findings are presented to confirm the effectiveness of the suggested converter.