Using Planar Transformers in DC-DC Converter Designs

In general, there is not a huge difference between implementing a planar transformer versus a comparable conventional transformer in a DC-DC converter design.  However, they don’t perform as well as conventional transformers when used in a flyback topology, and since they are relatively uncommon, finding one that meets your specifications can be difficult.

One method of evaluating a planar transformer would be to try simulating it in a software package such as LTspice. To get a decent approximation of the transformer’s performance, it is necessary to use the transformer’s equivalent circuit as shown in Figure 1 below.

Figure 1: Transformer equivalent circuit. 

While software simulation is valid, there’s nothing like real-world testing.  The best evaluation would be to breadboard two simple DC-DC converter circuits, one with the planar transformer and one with a conventional one, enabling direct comparison of the transformer’s performance.