Switching devices capable of handling more than 800 V exhibit relatively large switching loss. A new current feedback Bi-MOS consisting of a Bipolar Junction Transistor, MOS-FET and current transformer is proposed in this note. The new device reduces switching loss in 100 kHz operation and is expected to result in a DC-DC converter efficiency greater than 90%.

A new transformer with a Co-based amorphous core for use in the switching regulators of telecommunications systems is described. This transformer in fabricated by a two-step magnetic field annealing technique to decrease core loss. It is shown that this amorphous core reduces loss to 1/2 that of a conventional ferrite core. It is also shown that the weight and size of the new transformer are 3/5 and 1/2 those of a conventional transformer using the ferrite core. A 100 kHz series resonant converter with this transformer is 93% efficient with an output power level of 50% to 100%.