I got a problem with my light dimmer pet project using ST's snubberless triac, T435-800T. It's working fine (turning on and off based on the control input) with the positive going half cycle of AC main. But during negative going half cycle, I found a strange behavior. Traic failed to turn off during the negative going half cycle of AC main. I tried two separate rated incandescent lamp as a load. One rated at 25 W and another 60 W. What I found are, for 25 W lamp, turning off of Triac during negative half cycle not working at random intervals (please find the attachment) and for 60 W lamp, there is no turning off of Triac during negative going pulse. Please be noted that I checked control signal for both cased, and controller producing exact signal as the positive going half cycle.
Can you please share your experience if I got same problem earlier? Do I need a Triac with higher Irms (on-state) value to overcome the issue? T435-800T has a Irms (on-state) of 4A.
Thanking you.Benoit RENARD