A Nonisolated Ultrahigh Step Down DC-DC Converter with Low Voltage Stress

In this paper, a new nonisolated interleaved dc-dc converter with ultrahigh step down conversion ratio is proposed. The proposed converter has several main advantages such as extremely low voltage gain, extended duty cycle, automatic current sharing, low voltage and current stress on active switches, and low output current ripple. To achieve these advantages, several techniques are combined. The interleaved method is applied to reduce the current stress and decrease the output current ripple due to the phase shift between two modules. The series capacitors are used to improve the step down conversion ratio and clamp the voltage stress across the active switches due to the capacitive voltage division characteristic. Thus, the conduction losses of the proposed converter are reduced because of using MOSFETs with lower voltage rating. In addition, the coupled inductors are used to reduce the voltage gain and extend the duty cycle without imposing extra voltage stress across the active switches. Hence, the overall efficiency of the proposed converter is improved. A prototype of the proposed converter is implemented to verify the converter operation and the theoretical analysis.