Design of a thyristor snubber circuit by considering the reverse recovery process

Design procedures are presented for the snubber circuit in power electronic circuits by considering the reverse recovery process of the thyristor. The thyristor turnoff model, whose parameters are determined for best fitting to the device characteristics given on the data sheets, is applied to analyze the behavior of the snubber circuit with and without a saturable reactor during the reverse recovery time of the power device. Based on the turnoff model, exact expressions are derived for various quantities of interest including the maximum device stress, maximum reverse dv/dt, the reverse energy loss of a power device, and the total turnoff loss in the device plus the associated snubber circuit. Utilizing the analysis results, a systematic approach to the snubber-circuit design with the stray inductance taken into account is described. It is concluded that the proposed approach is very useful in the simulation of turnoff characteristics of the power device, snubber-circuit designs, and loss calculations in power circuits. >