Conclusion

AN437

14/18

3

Conclusion

An RC snubber circuit is often used with TRIACs and presents different functions:

●

Aid circuit for turn-off commutation

●

Fast transient voltage suppressor

●

Overvoltage limiter at turn-off commutation in case of inductive load with low rms

current

The RC snubber circuit drawback is the turn-on stress induced by the capacitor discharge.

Thanks to the high voltage capability of TRIACs, the snubber circuit design can be optimized

in order to reduce the capacitor value and, in the same way, reduce the snubber circuit cost.

Nevertheless, when low load inductances are controlled or, low damping factor or low slope

of reapplied voltage are considered, the snubber circuit design can lead to choose a low

snubber resistance value. To limit the snubber capacitor discharge through the TRIAC at

turn-on, the resistor value must be higher than a minimum value (typically 47

Ω for most

TRIACs and ACSTs).