Analysis of Current-Surge Suppression by Magnetic Snubber

In switching power converters, there arises a surge current due to the minority-carrier storage effect in a diode. This results in an overvoltage across the diode and an output noise voltage. To suppress this surge current, a magnetic snubber is used which consists of a parallel circuit with a saturable reactor and a linear inductor connected in series with a small diode. This paper describes the analysis of the noise-suppression mechanism of the magnetic snubber. In the analysis, the saturable reactor is assumed to be a small inductance during saturation period, and to be an infinite inductance and an equivalent resistance to eddy current during unsaturation periods. Other parasitic parameters such as depletion capacitances and lead inductances are introduced. As a result, the effect of the parallel inductor and the above mentioned parameters on the surge and noise voltages are made clear quantitatively, and are confirmed experimentaly.