Abstract -This paper presents a novel modified prototype topology of step-up and down non-isolated DC-DC power converter with a magnetically-coupled reactors，which provides dual balanced DC outputs with a single active switch. This DC-DC converter which is derived systematically from circuit topologies of reverse polarity type step-up and down converters due to a variety of active switch and passive switch arrangements can operate under the condition of heavy load range design with excellent voltage balance state for only one feedback voltage controller. On the other hand this converter causes dual voltage output unbalances under the conditions of extremely-unbalance loads over specific light load operation with one-loop voltage feedback control scheme. The operating analysis of this converter under dual voltage unbalance states is successfully performed with both experimental and theoretical data in order to achieve converter design criteria. The effectiveness of this converter is proven on the basis of experimental and theoretical considerations.