PCB Winding-Based Coupled Inductor for a High-Frequency DC/DC Converter with 99% Efficiency

For wide band-gap device based non-isolated DC/DC converters, operating in critical conduction mode (CRM) is deemed desirable for realizing soft-switching and enabling a high frequency operation. With a significant higher switching frequency compared to the current practice using silicon counterparts, integration of inductors with embedded windings in printed-circuit board (PCB) is feasible. However, for applications with wide input and output voltage ranges, switching frequency of a CRM DC/DC converter varies in a large range, which is undesirable in terms of efficiency and electromagnetic interference. Moreover, the large current ripple associated with CRM operation increases inductor loss compared to continuous conduction mode operation. This issue is more severe for a PCB winding-based planar inductor due to the strong accumulation of magnetomotive force in windings and the non-uniform flux distribution in magnetic cores. In this paper, the large frequency range of a CRM DC/DC converter is minimized by taking advantage of the non-linear inductance for a positively coupled inductor. Furthermore, a high efficiency integrated PCB winding-based planar inductor structure is proposed. Its winding loss is minimized by interleaving windings of different phases. Core loss is reduced by a proposed double-PQ core structure that has less flux crowding compared to the conventional EI-shape core. A 1.8 kW buck converter with input voltage 220–450 V, output voltage 80–140 V, and a peak efficiency of 99% is presented as an example.