A Transformerless Noncascaded Quadratic-based Step-down Converter Without Pulsating Input Current for Automotive Applications

In many applications, it is necessary to use a dc-dc converter with a wide step-down range of conversion and small ripple in the input. The electrical automotive system based on 48 V/12 V to improve the distribution of energy is a typical case. In this paper, a transformerless converter with wide step-down conversion ratio is designed and analyzed. This converter is a quadratic step-down converter based on reduced redundant energy, which includes a low-pass filter in the input stage. The steady state conditions and the analysis of the dynamic behavior with an input filter are given. The space state switched and linear models are derived as well as the transfer functions of possible variables to be used for control purposes. Experimental results including frequency response analysis for a 300 W prototype are given to verify the proposed design expressions and models. The measured efficiency of the prototype results in 92.3% at the nominal output power.