Here's a silly question.. I had wondered if it would be possible to do the phase sync and timing in a different way.. by using a feedback system. Remember, I only know enough to be dangerous. I just don't see why dimmer circuits aren't.. "smarter".
What I mean is that in my mind, you could initially switch the TRIAC on at any point, and "place" in the timing of the phase could be determined with a (adding a zener? to shunt the voltage) diode feeding a voltage back. One half of the cycle, there's a voltage passed back, measure that duration and you know both the frequency and the phase timing. Since the frequency is calculated from the timing, and the phase switching is done scaled accordingly, wouldn't that remove line frequency as a variable? In addition, if you are able to monitor the voltage, you can measure the magnitude.. and therefore calculate desired output voltage switching.. removing source voltage as a variable (within reason). I guess I'm just describing a switching-regulated power supply aren't I.... but what exactly is the difference? It just seems to me that all these isolators and such ought not to be necessary, if the dimmer is capable of intelligently modifying the timing based on sensed output.. and the resulting device would be more flexible than a device which is locked in for a particular source voltage and frequency.
As I understand (and it's more than possible I misunderstand), dimmers function by switching the power off and on at appropriate times, effectively making them voltage regulators with a Bipolar PWM output of a sort. Other than finding the duration of the phase and the timing of the phase, I would think pretty much anything else is a matter of switching at the appropriate time. Am I off base?
I really haven't researched TRIACS all that well, and maybe have misinterpreted how these beasties are used. Seems like you have gotten a good grasp of how these work and what is required for them to do the job.. mainly a bit of me being too lazy at the moment to research why I ought to know better...