A controlled recovery

In transformer isolated switching converters, the secondary side leakage inductance and the parasitic capacitance of the switches form a resonant RLC network with low damping. Without countermeasures, this will result in ringing (unwanted oscillations) during every switch transition and high amplitude voltage spikes on the switching nodes. Voltage clamps limit the amplitude of these spikes, either to protect the power devices or allow the use of cheaper, smaller, more efficient power transistors with lower voltage rating. For monolithic integration of DC-DC converters limiting the voltage stress can reduce the required silicon area through the required voltage rating of the power transistors.