A new downsized large current choke coil with magnet bias method

We have developed a new downsized large current choke coil with a ferrite core combined with a magnet. The magnet is inserted in a gap of the core in the opposite direction of the magnetomotive force of the coil. The method can expand the magnetic flux density area of the core, and it introduces miniaturization and high-efficiency of coils and transformers. As a result, we have been able to miniaturize a surface mounted type choke coil for DC-DC converters in an application like laptop computers. The size of the coil is 7.5(L) x 7.5(W) x 5.5(H) mm, which is downsized about 30% compared with conventional coils.