2015 IEEE International Telecommunications Energy Conference (INTELEC) 10.1109/INTLEC.2015.7572421 A Novel High Step-Down Interleaved Converter with Coupled Inductor Wilmar Martinez, Jun Imaoka, Yuki Itoh and Masayoshi Yamamoto Shimane University Matsue, Japan yamamoto@ecs.shimane-uc.jp Kazuhiro Umetani Okayama University Okayama, Japan umetani@okayama-u.ac.jp Abstract—Nowadays, high power density has become essential in networking, telecommunications and computing applications. Additionally, the electronic equipment used in these applications requires a very-low voltage feeding even when its power supply has a much higher voltage rating. Therefore, high step-down converters with high power density performance are required for these applications. Consequently, a novel two-phase interleaved high step-down converter is proposed in order to fulfill the requirements of high power density and high step-down conversion ratio of these applications. The proposed converter addresses the objective by a particular coupled inductor where three windings are only installed in one core. As a result, the proposed converter can achieve higher step-down ratio than the conventional topologies by adding a winding and two switches to the interleaved two phase buck converter, besides the coupled- inductor configuration. In this paper, the novel topology is introduced and analyzed in order to find its conversion ratio operation. Then, the proposed topology is compared to conventional topologies and some improved high step-down converters recently proposed. Finally, the proposed converter is experimentally validated and the results revealed that the proposed converter shows higher step-down conversion ratio than the conventional buck converter with a further increment of 40% in the conversion ratio when the converter is operating at a duty cycle of 30% and ratio of turns of 2. Keywords—Coupled-Inductor; High Step-Down Converter; Power Density; Step-Down Conversion Ratio. I. INTRODUCTION High power density DC-DC converters have become important components in networking, telecommunications, and computing applications where the supply voltage is higher than the required by the load [1]-[5]. Moreover, digital equipment such as, inter alia, MCUs (Micro Controller Unit), FPGAs (Field Programmable Gate Array) and ASICs (Application Specific Integrated Circuit) on mother boards, usually requires a very low feeding voltage with the purpose of increasing the efficiency and the power consumption of these devices [6]-[7]. Therefore, step-down converters with a high step-down conversion ratio have gained attention to interface the power supply with the digital equipment that requires a much lower voltage [8]-[10]. Nevertheless, conventional topologies present some drawbacks when a high step-down ratio is required. These drawbacks are mainly produced by three reasons: 1. A very small duty cycle is required to achieve the required output voltage which produces extremely high losses in the components due to the parasitic effects; 2. Usually, conventional converters cannot achieve high step-down conversion ratio because of the presence of parasitic resistances, capacitances and inductances in the components; and 3. Conventional converters have low power density because they need to use bulky components to achieve the required voltage and current ripples [11]-[14]. Consequently, the demand of high step-down conversion techniques has gradually increased according to the downsizing and low-voltage requirements of digital equipment [15]-[17]. Currently, there are several step-down topologies with high conversion ratio performance. However, most of them show the drawback of low power density because they need because they need many additional passive components to achieve a high conversion ratio. Therefore, this study is focused on the use of interleaving phases and magnetic coupling, which are well- known techniques reported as effective to increase the power density and downsize magnetic components [18]-[20]. Interleaving phases is effective because the input current is divided into the number of phases. Therefore, a reduction in the power ratings of the components is generated, as well as, a size miniaturization of the capacitive components because of the high frequency operation. Additionally, magnetic coupling is effective because a size reduction of the magnetic components can be achieved as a result of the integration of several windings into only one core. Using the magnetic coupling technique may reduce the input current ripple of the converter as well [21]-[23]. These outstanding techniques are used in order to propose a novel and improved high step-down power converter with high power density that use a novel coupled-inductor. Fig. 1 shows the proposed high step-down interleaved converter with integrated coupled inductor. Fig. 1. Proposed high step-down two-phase interleaved converter.