PCB Winding Loss Model and Design for Push-pull Transformer

The winding AC loss behaviors of push-pull transformer with four windings and two central taps are much different from that of general two winding transformer because the windings conduct currents in different time intervals. The model was introduced by the winding current FFT decomposition and magnetic motive force (MMF) analysis and discloses that the odd harmonic MMF is balanced among the all windings and the even harmonic MMF is only balanced between the two primary windings. The model is very helpful in winding optimal design, central tap terminal consideration and winding loss measurement. Application in a 400 W push-pull transformer showed the effectiveness of the model.