The DC-DC converter using integrated magnetic components that may achieve high power density has gained attention in environmentally-friendly cars such as electric vehicles (EV) and plug-in hybrid electric vehicle (PHEV). This paper focused on this circuit types using coupled indictors and close-coupled inductors that are the integrated magnetic components. In order to realize further high power density, calculation methods for the allowable power of the coupled indictors and close-coupled inductors are presented. The calculation method is based on detailed analysis of the characteristics of ripple current and magnetic flux. From the allowable power viewpoint, the volumes of the inductors are compared to a conventional interleaved boost chopper circuit in the same conditions. As a result, CCM operation is effective for downsizing of the magnetic components in case of the interleaved boost chopper circuit using coupled inductors. On the other hand, the interleaved boost converter using close-coupled inductors is effective for downsizing of the magnetic components with CRM operation.