Referring now to FIG. 12?FIG. 19, FIG. 12?FIG. 19 show second?ninth schematic views of a soft-switching auxiliary circuit of the third embodiment in accordance with the present disclosure. FIG. 12?FIG. 19 illustrate the operation process of the soft-switching auxiliary circuit 1 of the embodiment; the operation process may be divided into 8 stages.
As shown in FIG. 12, during the first stage, the capacitor Cds1 is at the initial status; at this time, the voltage Vds1 of the capacitor Cds1 is the voltage Vin of the power source P.
As shown in FIG. 13, during the second stage, after the first transistor Sa1 is turned on, the voltage Vin is applied to the first inductor L1 and the first capacitor C1, which achieves series resonance; then, the current IL1 gradually increases; afterward, the body diode BD2 of the second main switch S2 is cut off until the current IL1 increases to be equal to the current ILf.
