Power electronic circuits are a key player in many essential electrical systems and applications, e.g., power converters. For computational and battery-powered consumer products, the desire for higher power densities and longer battery life increases the requirement for smaller, more power-efficient devices. Therefore, these requirements drive the research towards exploring different areas to improve the power converters like circuit topologies, integration, and technologies of the semiconductor devices and passive components. One of the main challenges in the power converter is the significant contribution of the passive components, particularly magnetics, to the overall solution losses and size. Understanding the different topologies requirement of the passive components for a given load requirement can lead to better utilisation of the passive components, hence, to optimise the passive components, particularly inductors from the circuit perspective, which can reduce the manufacturing materials consumption. This study proposes design procedures to optimise the utilisation of passive components in DC-DC power converters, particularly inductors. It presents a detailed analysis of passive components in the converter topologies of multiphase buck, multiphase 3-level and single-phase buck with 4th order resonance output filter. This study emphasises the passive components’ performance in terms of size and efficiency, besides considering the utilisation of coupled inductors in these circuits and the selection of coupling factor. Air-core PCB integrated inductors are considered in this study for fast prototyping and testing. However, this study is also applicable for inductors with the magnetic core. This study addresses the impact of the number of phases in multiphase interleaved buck and 3-level topologies on the passive components’ energies in wide input voltage converters, in addition to the impact of the PCB design rules on the manufactured inductors’ performance, which all combines for better utilisation of the passive components. The study also provides a detailed analysis and selection procedure of passive components in a buck converter with 4th order and 4th order resonance (4thRes) filters for a given converter specification. The novel 4thRes analysis presents its potential in reducing the size of the passive components and the converter’s full load efficiency. These contributions help improve the passive components, particularly the inductors, in terms of power density and performance in low power converters with a wide input voltage range. These contributions help improve the passive components, particularly inductor, power density and performance in low power converters with wide input voltage.