A device is provided that integrates a plurality of inductors in parallel. The device includes a plurality of windings and a magnetic core structure. A number of the windings corresponds to a number of the inductors. The magnetic core structure includes a plurality of windows, wherein each window includes at least two windings coupled with each other. When a phase difference of the voltage phases is smaller than a predetermined value, voltage phases of two terminals of any two of the windings within the same window are substantially the same.