Inductors are key components in various multiphase topologies. Basically discrete inductors can be used. However, coupled Inductors can help to significantly reduce the volume and improve the efficiency of the circuit. In a coupled inductor two windings are wound on a common core. Thus L1 and L2 are magnetically coupled which allows to transfer the energy stored in the core between both the coils. The efficiency of the magnetic coupling between the primary and secondary winding is defined by the coupling factor K.

Coupled inductors are used in different DC/DC converter topologies. The function of coupled inductors is to transfer energy from the primary to the secondary winding through a commonly used core. The efficiency of the magnetic coupling between both the windings is defined by the coupling factor k. The coupling coefficient k can be calculated by using the following equation.

Inductors are the key elements of multiphase voltage regulators such as SEPIC, ZETA or CuK converters. It is not mandatory that coupled inductors are used. Basically two single inductors can be used as well. However, if L1 and L2 are closely coupled, the ripple current is split between them. Thus the required inductance value is just the half. If a dual inductor is used instead of two single power inductors, potentially a smaller component can be used which is saving space on the board.