Why We Need The Snubberless TRIAC Drive Optocouplers: Reduce Component Count:
Due to the FOD4xx’s high commutating and static dv/dt immunity (10kV/us minimum), its performance is such that additional noise filtering is not required. This allows the snubber across the TRIAC driver to be eliminated from the circuit. Since the snubber capacitor is across the mains, it must be safety certified. These special safety certified capacitors are very expensive, approximately $0.35 each in high volume! Those capacitors are also about four times the size of the optocoupler which makes removing them a significant space savings! Reducing Standby Power:
By eliminating the snubber network a significant reduction in standby power consumption can be realized. The snubber circuit consumes power even when the load is in the off-state. As an example, a 240V AC Mains application using a 0.1uF snubber capacitor conducts 10mA in the off-state translating to a power loss of 2W. With new directives for reducing standby power as energy costs skyrocket, the power savings offered by these devices can substantially help designers achieve their standby power targets. Ease of Design:
Aside from the cost savings of removing the RC snubber components, there’s another advantage. Selecting the values of the RC network is tedious. Often, designers don’t know the power factor of their load, what noise will come from the mains, the type of load being switched, or even what type of load will be connected to the circuit (e.g., in the case of hockey puck solid state relays). As a result, they are forced to estimate the values and then hand tune the circuit on the bench. For the case of the SSR, that’s impossible because they can’t simulate an undefined load. The FOD4xx eliminates this hassle by removing those components from the circuit.
Since these parts are roughly 3x to 4x more expensive than the MOC30xxM and FODM30xx optocouplers, desingers need to understand why these devices should be considered.
| ● || Superior commutating and static dv/dt performance eliminates expensive snubber capacitor. |
| ● || Low input drive current saves on power consumption. |
| ● || Elimination of R-C snubber reduces standby power consumption. |
| ● || Rated for a blocking voltage of 800V minimum while the equivalent monolithic zero-cross devices are limited to a 600V rating. |
This optoisolator should not be used to drive a load directly. It is intended to be a discrete triac driver device only.
For Your Knowledge:
The Snubberless TRIAC also called: Three-quadrant / 3Quad / 3Q / Snubberless / High commutating / Hi-Com / High dv/dt TRIAC