Some years ago I designed a stage lighting dimmer (I still use them). I found that at the end and beginning of the mains cycle the load current was too low to hold the tric on there was also some problem with low current loads and the supressor cicit ringing. I fired the triac by discharging a 100nf capacitor thro a thyristor itno the primay of a 1:1 pulse transformer with a 100R resistor in series with the gate and the seconadry