DC-DC converter with large step-down voltage conversion ratio

An improved non-isolated coupled-inductor-based high-step-down converter is presented in this paper. Compared with other coupled-inductor-based high-step-down converters, the proposed converter features zero DC-offset current and non-pulsating output current. In the proposed converter, one of the DC-blocking capacitors is connected between the input voltage and the coupled inductor. Therefore, the step-down voltage conversion ratio can be much higher than those of the traditional SR buck converter and the tapped-inductor buck converter. Furthermore, its voltage conversion ratio is linear, which makes control easier. Moreover, due to the DC-blocking capacitors, the DC magnetizing inductance current can be reduced to zero. Thus, the magnetizing current can be positive and negative, and the entire core B-H loop can be used, ranging from the first quadrant to the third quadrant. That is, the utilization of the coupled inductor can be upgraded. Also, due to a discrete output inductor, the proposed converter features non-pulsating output current. In this study, detailed theoretical analyses and experimental results are offered to demonstrate the feasibility and effectiveness of the proposed converter.