Transformer types#Planar transformer

Design and function

Planar transformers are mainly used in power electronics for transmission services 200-5000 watts. They are very small because of the good dissipation of power loss. The windings usually but not necessarily made ​​from conductor tracks on a printed circuit board or of correspondingly shaped copper sheets separated by insulating spacers. This results in not only manufacturing advantages, but the flat head shape also accommodates the earnings at the usually high operating frequencies skin effect.

Planar transformers can also be manufactured as a single integrated component than on a printed circuit board. In such a built- in circuit board planar transformer windings are present as conductive tracks prior to or in the circuit board, the two-part ferrite transformer core is glued or clamped on both sides of the board, which has openings for this purpose. This construction is cheaper than conventional wound transformers, especially at high volumes. The development effort is higher, since prototypes are expensive to manufacture.

In addition to the already more suitable for heat dissipation large ratio of surface to volume, a further reduced thermal resistance can be achieved by attached heatsink, which fails in the other transformers to the low heat conduction through the volume.

Planar transformers are generally operated at frequencies of 0.1 to several megahertz, which requires as well as at other switching power supplies special precautions regarding electromagnetic compatibility (EMC). In addition to the skin effect and the proximity effect plays a role, which moderates the benefits of the design somewhat.

Often also be connected in several transformers as required in series or in parallel to better integrate or to achieve a certain ratio. Thereby be further improved, the thermal and high frequency characteristics. Using the same technology also chokes are manufactured.