Snubber Circuits

Snubber Circuits are circuits which are placed across thyristors to protect it from transient high voltages which may occur during switching off.  When the current flowing through a thyristor is interrupted, the voltage across the thyristor can increase rapidly according to Faraday's second law.  This high voltage can cause damage to the thyristor or to other components in the circuit.

The snubber circuit works by preventing the voltage from rising too high across the component to be protected.  The snubber is normally used in circuits with inductance.

The Basic Snubber Circuit is a capacitor and a resistor connected in series.  The Snubber works on the principle that the current across a capacitor cannot fall to zero instantly.  Hence, a small current keeps flowing through the capacitor.  This current is enough to prevent the voltage from rising to high levels.

The Flyback resistor is also another example of the snubber circuit.