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A Snubber Circuit is designed to counter/reduce EMI and switching transients, i.e., voltage and current spikes, produced by the rapid switch associated with a Triac or similar components:
Many switching components, like the Triac, used in power circuit designs now incorporate a Snubber Circuit. A component specified by its datasheet as Snubberless, simply indicates that the component does not incorporate a Snubber circuit. And depending on the circuit design an additional appropriate Snubber Cricuit will need to be included.
Snubbers can be clamp diodes or small RC spike suppressors like 10Ω + 100pF @ 100MHz.
If your driving impedance is lower, then you may need 1Ω 1000pF @ 100MHz.
The key is your driving/load impedance and the maximum dv/dvt your triac can handle before it is false triggered by coupling thru the Miller capacitance to the gate...
and the rated current translated into load impedance which may alter the RC equivalent circuit. Plastic caps are always used due to the self healing and very low ESR qualities rated at high voltage but in some cases for lower voltage parts, high insulated "zener" like diodes in reverse conduction mode can give the equivalent capacitance to snub reverse voltage spikes, and also protect the device if it is not a 4 quadrant triac. Otherwise an additional process for adding ceramic caps inside is used.
A component specified by its datasheet as Snubberless, simply indicates that the component does not incorporate a Snubber circuit. And depending on the circuit design an additional appropriate Snubber Cricuit will need to be included.
BigDog
Actually, Snubberless Triacs typically don't require a snubber circuit because of their enhanced commutation performance. See this application note on the ST web site for details:
Thomson Semiconductors were the first to market a three-quadrant TRIAC as the Alternators, later after the consolidation of Thomson Semiconductors into STMicroelectronics, the Alternators were marketed under the trademark Snubberless.
The term Snubberless when used in conjunction with TRAIC was trademarked by STMicroelectronics and therefore limited its use in reference to Alternators/TRIACs to STMicroelectronics manufactured Alternistors (three-quadrant TRIACs).
Although perhaps poorly worded, I was referring to the circuit incorporating the TRIAC as well as the example circuits typically provided in the devices datasheet.
While there are now other manufacturers of three-quadrant TRIAC and although they cannot be marketed as Snubberless TRIACs, their common design enhancements do offer many of the features which reduce the need of a Snubber Circuit in some applications.
However, stating categorically they don't require a Snubber Circuit would be incorrect as pointed in the appnote provide in the above reply:
Reference: , Section: IS IT ALWAYS POSSIBLE TO REMOVE THE SNUBBER CIRCUIT?, Page 4
IS IT ALWAYS POSSIBLE TO REMOVE THE
SNUBBER CIRCUIT ?
The answer is not in the affirmative because
sometimes it has other functions :
improvement of the triac immunity against transients
in the off state ;
compensation of latching current at turn on (not
dealt in this paper).
Switching on and voltage perturbations can
provoke overvoltages and fast voltage variations
across the triac :
this one could break over when the overvoltages
are higher than its repetitive peak off state voltage,
VDRM;
due to the junction capacitance fast voltage variations
create a gate current and could trigger the
triac; the device limit is the rate of rise of the offstate
voltage, dV/dt.
The snubber circuit can improve the triac behavior
in off-state. But its efficiency is linked to the values
of series inductance L at the oscillation frequency
of perturbations (typically higher than 100 kHz).
We could add a saturable inductor in series with
the triac when L is too low: particularly this is the
case of resistive load.
A three-quadrant TRIAC simply reduces the requirement for the implementation of a Snubber Circuit, however they do not alleviate the requirement of a Snubber Circuit in all applications.
With the advent of Sensitive Gate Triacs, you need a Snubber to prevent false triggering from dv/dt injection.
This means you can cheaply drive motors with logic level currents using snubberless-sensitive gate with phase angle control of AC.
Snubber-less designs have higher immunity to false triggering but still egress like crazy with reactive loads so snubbers may be needed for EMI egress and also possible high levels of ingress. but normal levels ,, not as advertised as moderate noise rejection is included by reducing bandwidth of noise ingress.
"The T series is the latest addition to Snubberless™ Triacs and provides enhanced commutation for a given current rating. Immunity is also improved up to 5 times for a given current rating."
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