5.6 Active Snubber Operation

Secondary side leakage inductance energy oscillates with the SR MOSFET drain-source parasitic capacitance and causes high drain-source voltage spikes and ringing. This voltage spike maybe snubbed using an RCD snubber. In this design, an RCD snubber is used in conjunction with an active lossless snubber. This additional circuit detects when the voltage on +VSNUB exceeds a certain threshold. When the limit is reached, Q700 is switched ON. This redirects the leakage energy into a small buck like LC stage connected to VOUT, decreasing losses because of the leakage energy.